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rfc:rfc4171

Network Working Group J. Tseng Request for Comments: 4171 Riverbed Technology Category: Standards Track K. Gibbons

                                                    McDATA Corporation
                                                         F. Travostino
                                                                Nortel
                                                           C. Du Laney
                                           Rincon Research Corporation
                                                              J. Souza
                                                             Microsoft
                                                        September 2005
               Internet Storage Name Service (iSNS)

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2005).

Abstract

 This document specifies the Internet Storage Name Service (iSNS)
 protocol, used for interaction between iSNS servers and iSNS clients,
 which facilitates automated discovery, management, and configuration
 of iSCSI and Fibre Channel devices (using iFCP gateways) on a TCP/IP
 network.  iSNS provides intelligent storage discovery and management
 services comparable to those found in Fibre Channel networks,
 allowing a commodity IP network to function in a capacity similar to
 that of a storage area network.  iSNS facilitates a seamless
 integration of IP and Fibre Channel networks due to its ability to
 emulate Fibre Channel fabric services and to manage both iSCSI and
 Fibre Channel devices.  iSNS thereby provides value in any storage
 network comprised of iSCSI devices, Fibre Channel devices (using iFCP
 gateways), or any combination thereof.

Tseng, et al. Standards Track [Page 1] RFC 4171 Internet Storage Name Service (iSNS) September 2005

Table of Contents

 1.  Introduction................................................... 6
     1.1.  Conventions Used in This Document........................ 6
     1.2.  Purpose of This Document................................. 6
 2.  iSNS Overview.................................................. 6
     2.1.  iSNS Architectural Components ........................... 7
           2.1.1.  iSNS Protocol (iSNSP) ........................... 7
           2.1.2.  iSNS Client...................................... 7
           2.1.3.  iSNS Server...................................... 7
           2.1.4.  iSNS Database ................................... 7
           2.1.5.  iSCSI............................................ 7
           2.1.6.  iFCP............................................. 7
     2.2.  iSNS Functional Overview................................. 8
           2.2.1.  Name Registration Service........................ 8
           2.2.2.  Discovery Domain and Login Control Service....... 8
           2.2.3.  State Change Notification Service............... 10
           2.2.4.  Open Mapping between
                   Fibre Channel and iSCSI Devices................. 11
     2.3.  iSNS Usage Model........................................ 11
           2.3.1.  iSCSI Initiator................................. 12
           2.3.2.  iSCSI Target.................................... 12
           2.3.3.  iSCSI-FC Gateway................................ 12
           2.3.4.  iFCP Gateway.................................... 12
           2.3.5.  Management Station.............................. 12
     2.4.  Administratively Controlled iSNS Settings............... 13
     2.5.  iSNS Server Discovery .................................. 14
           2.5.1.  Service Location Protocol (SLP)................. 14
           2.5.2.  Dynamic Host Configuration Protocol (DHCP)...... 14
           2.5.3.  iSNS Heartbeat Message.......................... 14
     2.6.  iSNS and Network Address Translation (NAT).............. 14
     2.7.  Transfer of iSNS Database Records between iSNS Servers.. 15
     2.8.  Backup iSNS Servers..................................... 17
     2.9.  Transport Protocols..................................... 19
           2.9.1.  Use of TCP for iSNS Communication............... 19
           2.9.2.  Use of UDP for iSNS Communication............... 20
           2.9.3.  iSNS Multicast and Broadcast Messages........... 20
     2.10. Simple Network Management Protocol (SNMP) Requirements.. 21
 3.  iSNS Object Model............................................. 21
     3.1.  Network Entity Object .................................. 22
     3.2.  Portal Object .......................................... 22
     3.3.  Storage Node Object..................................... 22
     3.4.  Portal Group Object..................................... 23
     3.5.  FC Device Object........................................ 24
     3.6.  Discovery Domain Object................................. 24
     3.7.  Discovery Domain Set Object............................. 24
     3.8.  iSNS Database Model..................................... 24
 4.  iSNS Implementation Requirements.............................. 25

Tseng, et al. Standards Track [Page 2] RFC 4171 Internet Storage Name Service (iSNS) September 2005

     4.1.  iSCSI Requirements...................................... 25
           4.1.1.  Required Attributes for Support of iSCSI........ 26
           4.1.2.  Examples: iSCSI Object Model Diagrams........... 28
           4.1.3.  Required Commands and
                   Response Messages for Support of iSCSI.......... 30
     4.2.  iFCP Requirements....................................... 31
           4.2.1.  Required Attributes for Support of iFCP......... 31
           4.2.2.  Example: iFCP Object Model Diagram.............. 32
           4.2.3.  Required Commands and
                   Response Messages for Support of iFCP........... 34
 5.  iSNSP Message Format.......................................... 35
     5.1.  iSNSP PDU Header........................................ 35
           5.1.1.  iSNSP Version................................... 36
           5.1.2.  iSNSP Function ID............................... 36
           5.1.3.  iSNSP PDU Length................................ 36
           5.1.4.  iSNSP Flags..................................... 36
           5.1.5.  iSNSP Transaction ID............................ 36
           5.1.6.  iSNSP Sequence ID............................... 37
     5.2.  iSNSP Message Segmentation and Reassembly............... 37
     5.3.  iSNSP PDU Payload....................................... 37
           5.3.1.  Attribute Value 4-Byte Alignment................ 38
     5.4.  iSNSP Response Status Codes............................. 39
     5.5.  Authentication for iSNS Multicast and Broadcast Messages 39
     5.6.  Registration and Query Messages......................... 41
           5.6.1.  Source Attribute................................ 42
           5.6.2.  Message Key Attributes.......................... 42
           5.6.3.  Delimiter Attribute............................. 42
           5.6.4.  Operating Attributes............................ 43
           5.6.5.  Registration and Query Request Message Types ... 44
     5.7.  Response Messages....................................... 66
           5.7.1.  Status Code..................................... 66
           5.7.2.  Message Key Attributes in Response.............. 66
           5.7.3.  Delimiter Attribute in Response................. 67
           5.7.4.  Operating Attributes in Response................ 67
           5.7.5.  Registration and Query Response Message Type.... 67
     5.8.  Vendor-Specific Messages................................ 72
 6.  iSNS Attributes............................................... 73
     6.1.  iSNS Attribute Summary.................................. 73
     6.2.  Entity Identifier-Keyed Attributes...................... 76
           6.2.1.  Entity Identifier (EID)......................... 76
           6.2.2.  Entity Protocol................................. 76
           6.2.3.  Management IP Address .......................... 77
           6.2.4.  Entity Registration Timestamp .................. 77
           6.2.5.  Protocol Version Range.......................... 77
           6.2.6.  Registration Period............................. 78
           6.2.7.  Entity Index.................................... 78
           6.2.8.  Entity Next Index............................... 79
           6.2.9.  Entity ISAKMP Phase-1 Proposals................. 79

Tseng, et al. Standards Track [Page 3] RFC 4171 Internet Storage Name Service (iSNS) September 2005

           6.2.10. Entity Certificate.............................. 79
     6.3.  Portal-Keyed Attributes................................. 80
           6.3.1.  Portal IP Address............................... 80
           6.3.2.  Portal TCP/UDP Port............................. 80
           6.3.3.  Portal Symbolic Name............................ 80
           6.3.4.  Entity Status Inquiry Interval.................. 81
           6.3.5.  ESI Port........................................ 82
           6.3.6.  Portal Index.................................... 82
           6.3.7.  SCN Port........................................ 82
           6.3.8.  Portal Next Index............................... 83
           6.3.9.  Portal Security Bitmap.......................... 83
           6.3.10. Portal ISAKMP Phase-1 Proposals................. 84
           6.3.11. Portal ISAKMP Phase-2 Proposals................. 84
           6.3.12. Portal Certificate.............................. 84
     6.4.  iSCSI Node-Keyed Attributes............................. 84
           6.4.1.  iSCSI Name...................................... 85
           6.4.2.  iSCSI Node Type................................. 85
           6.4.3.  iSCSI Node Alias................................ 86
           6.4.4.  iSCSI Node SCN Bitmap .......................... 86
           6.4.5.  iSCSI Node Index................................ 87
           6.4.6.  WWNN Token...................................... 87
           6.4.7.  iSCSI Node Next Index .......................... 89
           6.4.8.  iSCSI AuthMethod................................ 89
     6.5.  Portal Group (PG) Object-Keyed Attributes............... 89
           6.5.1.  Portal Group iSCSI Name......................... 90
           6.5.2.  PG Portal IP Addr............................... 90
           6.5.3.  PG Portal TCP/UDP Port.......................... 90
           6.5.4.  Portal Group Tag (PGT).......................... 90
           6.5.5.  Portal Group Index.............................. 90
           6.5.6.  Portal Group Next Index......................... 91
     6.6.  FC Port Name-Keyed Attributes .......................... 91
           6.6.1.  FC Port Name (WWPN)............................. 91
           6.6.2.  Port ID (FC_ID)................................. 91
           6.6.3.  FC Port Type.................................... 92
           6.6.4.  Symbolic Port Name.............................. 92
           6.6.5.  Fabric Port Name (FWWN)......................... 92
           6.6.6.  Hard Address.................................... 92
           6.6.7.  Port IP Address................................. 92
           6.6.8.  Class of Service (COS).......................... 93
           6.6.9.  FC-4 Types...................................... 93
           6.6.10. FC-4 Descriptor................................. 93
           6.6.11. FC-4 Features .................................. 93
           6.6.12. iFCP SCN Bitmap................................. 93
           6.6.13. Port Role....................................... 94
           6.6.14. Permanent Port Name (PPN)....................... 95
     6.7.  Node-Keyed Attributes .................................. 95
           6.7.1.  FC Node Name (WWNN)............................. 95
           6.7.2.  Symbolic Node Name.............................. 95

Tseng, et al. Standards Track [Page 4] RFC 4171 Internet Storage Name Service (iSNS) September 2005

           6.7.3.  Node IP Address................................. 95
           6.7.4.  Node IPA........................................ 96
           6.7.5.  Proxy iSCSI Name................................ 96
     6.8.  Other Attributes........................................ 96
           6.8.1.  FC-4 Type Code.................................. 96
           6.8.2.  iFCP Switch Name................................ 96
           6.8.3.  iFCP Transparent Mode Commands.................. 97
     6.9.  iSNS Server-Specific Attributes......................... 97
           6.9.1.  iSNS Server Vendor OUI.......................... 98
     6.10. Vendor-Specific Attributes.............................. 98
           6.10.1. Vendor-Specific Server Attributes............... 98
           6.10.2. Vendor-Specific Entity Attributes............... 98
           6.10.3. Vendor-Specific Portal Attributes............... 99
           6.10.4. Vendor-Specific iSCSI Node Attributes........... 99
           6.10.5. Vendor-Specific FC Port Name Attributes......... 99
           6.10.6. Vendor-Specific FC Node Name Attributes......... 99
           6.10.7. Vendor-Specific Discovery Domain Attributes..... 99
           6.10.8. Vendor-Specific Discovery Domain Set Attributes. 99
           6.10.9. Other Vendor-Specific Attributes................ 99
     6.11. Discovery Domain Registration Attributes............... 100
           6.11.1. DD Set ID Keyed Attributes..................... 100
           6.11.2. DD ID Keyed Attributes......................... 101
 7.  Security Considerations...................................... 103
     7.1.  iSNS Security Threat Analysis ......................... 103
     7.2.  iSNS Security Implementation and Usage Requirements.... 104
     7.3.  Discovering Security Requirements of Peer Devices...... 105
     7.4.  Configuring Security Policies of iFCP/iSCSI Devices.... 106
     7.5.  Resource Issues........................................ 107
     7.6.  iSNS Interaction with IKE and IPSec.................... 107
 8.  IANA Considerations.......................................... 107
     8.1.  Registry of Block Storage Protocols.................... 107
     8.2.  Registry of Standard iSNS Attributes .................. 108
     8.3.  Block Structure Descriptor (BSD) Registry.............. 108
 9.  Normative References......................................... 109
 10. Informative References....................................... 110
 Appendix A: iSNS Examples........................................ 112
     A.1.  iSCSI Initialization Example........................... 112
           A.1.1.  Simple iSCSI Target Registration............... 112
           A.1.2.  Target Registration and DD Configuration....... 114
           A.1.3.  Initiator Registration and Target Discovery.... 117
 Acknowledgements................................................. 121

Tseng, et al. Standards Track [Page 5] RFC 4171 Internet Storage Name Service (iSNS) September 2005

1. Introduction

1.1. Conventions Used in This Document

 "iSNS" refers to the storage network model and associated services
 covered in the text of this document.
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].
 All frame formats are in big endian network byte order.
 All unused fields and bitmaps, including those that are RESERVED,
 SHOULD be set to zero when sending and ignored when receiving.

1.2. Purpose of This Document

 This is a standards track document containing normative text
 specifying the iSNS Protocol, used by iSCSI and iFCP devices to
 communicate with the iSNS server.  This document focuses on the
 interaction between iSNS servers and iSNS clients; interactions among
 multiple authoritative primary iSNS servers are a potential topic for
 future work.

2. iSNS Overview

 iSNS facilitates scalable configuration and management of iSCSI and
 Fibre Channel (FCP) storage devices in an IP network by providing a
 set of services comparable to that available in Fibre Channel
 networks.  iSNS thus allows a commodity IP network to function at a
 level of intelligence comparable to a Fibre Channel fabric.  iSNS
 allows the administrator to go beyond a simple device-by-device
 management model, where each storage device is manually and
 individually configured with its own list of known initiators and
 targets.  Using the iSNS, each storage device subordinates its
 discovery and management responsibilities to the iSNS server.  The
 iSNS server thereby serves as the consolidated configuration point
 through which management stations can configure and manage the entire
 storage network, including both iSCSI and Fibre Channel devices.
 iSNS can be implemented to support iSCSI and/or iFCP protocols as
 needed; an iSNS implementation MAY provide support for one or both of
 these protocols as desired by the implementor.  Implementation
 requirements within each of these protocols are further discussed in
 Section 5.  Use of iSNS is OPTIONAL for iSCSI and REQUIRED for iFCP.

Tseng, et al. Standards Track [Page 6] RFC 4171 Internet Storage Name Service (iSNS) September 2005

2.1. iSNS Architectural Components

2.1.1. iSNS Protocol (iSNSP)

 The iSNS Protocol (iSNSP) is a flexible and lightweight protocol that
 specifies how iSNS clients and servers communicate.  It is suitable
 for various platforms, including switches and targets as well as
 server hosts.

2.1.2. iSNS Client

 iSNS clients initiate transactions with iSNS servers using the iSNSP.
 iSNS clients are processes that are co-resident in the storage
 device, and that can register device attribute information, download
 information about other registered clients in a common Discovery
 Domain (DD), and receive asynchronous notification of events that
 occur in their DD(s).  Management stations are a special type of iSNS
 client that have access to all DDs stored in the iSNS.

2.1.3. iSNS Server

 iSNS servers respond to iSNS protocol queries and requests, and
 initiate iSNS protocol State Change Notifications.  Properly
 authenticated information submitted by a registration request is
 stored in an iSNS database.

2.1.4. iSNS Database

 The iSNS database is the information repository for the iSNS
 server(s).  It maintains information about iSNS client attributes.  A
 directory-enabled implementation of iSNS may store client attributes
 in an LDAP directory infrastructure.

2.1.5. iSCSI

 iSCSI (Internet SCSI) is an encapsulation of SCSI for a new
 generation of storage devices interconnected with TCP/IP [iSCSI].

2.1.6. iFCP

 iFCP (Internet FCP) is a gateway-to-gateway protocol designed to
 interconnect existing Fibre Channel and SCSI devices using TCP/IP.
 iFCP maps the existing FCP standard and associated Fibre Channel
 services to TCP/IP [iFCP].

Tseng, et al. Standards Track [Page 7] RFC 4171 Internet Storage Name Service (iSNS) September 2005

2.2. iSNS Functional Overview

 There are four main functions of the iSNS:
 1)  A Name Service Providing Storage Resource Discovery
 2)  Discovery Domain (DD) and Login Control Service
 3)  State Change Notification Service
 4)  Open Mapping of Fibre Channel and iSCSI Devices

2.2.1. Name Registration Service

 The iSNS provides a registration function to allow all entities in a
 storage network to register and query the iSNS database.  Both
 targets and initiators can register in the iSNS database, as well as
 query for information about other initiators and targets.  This
 allows, for example, a client initiator to obtain information about
 target devices from the iSNS server.  This service is modeled on the
 Fibre Channel Generic Services Name Server described in FC-GS-4, with
 extensions, operating within the context of an IP network.
 The naming registration service also provides the ability to obtain a
 network-unique Domain ID for iFCP gateways when one is required.

2.2.2. Discovery Domain and Login Control Service

 The Discovery Domain (DD) Service facilitates the partitioning of
 Storage Nodes into more manageable groupings for administrative and
 login control purposes.  It allows the administrator to limit the
 login process of each host to the more appropriate subset of targets
 registered in the iSNS.  This is particularly important for reducing
 the number of unnecessary logins (iSCSI logins or Fibre Channel Port
 Logins), and for limiting the amount of time that the host spends
 initializing login relationships as the size of the storage network
 scales up.  Storage Nodes must be in at least one common enabled DD
 in order to obtain information about each other.  Devices can be
 members of multiple DDs simultaneously.
 Login Control allows targets to delegate their access
 control/authorization policies to the iSNS server.  This is
 consistent with the goal of centralizing management of those storage
 devices using the iSNS server.  The target node or device downloads
 the list of authorized initiators from the iSNS.  Each node or device
 is uniquely identified by an iSCSI Name or FC Port Name.  Only

Tseng, et al. Standards Track [Page 8] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 initiators that match the required identification and authorization
 provided by the iSNS will be allowed access by that target Node
 during session establishment.
 Placing Portals of a Network Entity into Discovery Domains allows
 administrators to indicate the preferred IP Portal interface through
 which storage traffic should access specific Storage Nodes of that
 Network Entity.  If no Portals of a Network Entity have been placed
 into a DD, then queries scoped to that DD SHALL report all Portals of
 that Network Entity.  If one or more Portals of a Network Entity have
 been placed into a DD, then queries scoped to that DD SHALL report
 only those Portals that have been explicitly placed in the DD.
 DDs can be managed offline through a separate management workstation
 using the iSNSP or SNMP.  If the target opts to use the Login Control
 feature of the iSNS, the target delegates management of access
 control policy (i.e., the list of initiators allowed to log in to
 that target) to the management workstations that are managing the
 configuration in the iSNS database.
 If administratively authorized, a target can upload its own Login
 Control list.  This is accomplished using the DDReg message and
 listing the iSCSI name of each initiator to be registered in the
 target's DD.
 An implementation MAY decide that newly registered devices that have
 not explicitly been placed into a DD by the management station will
 be placed into a "default DD" contained in a "default DDS" whose
 initial DD Set Status value is "enabled".  This makes them visible to
 other devices in the default DD.  Other implementations MAY decide
 that they are registered with no DD, making them inaccessible to
 source-scoped iSNSP messages.
 The iSNS server uses the Source Attribute of each iSNSP message to
 determine the originator of the request and to scope the operation to
 a set of Discovery Domains.  In addition, the Node Type (specified in
 the iFCP or iSCSI Node Type bitmap field) may also be used to
 determine authorization for the specified iSNS operation.  For
 example, only Control Nodes are authorized to create or delete
 discovery domains.
 Valid and active Discovery Domains (DDs) belong to at least one
 active Discovery Domain Set (DDS).  Discovery Domains that do not
 belong to an activated DDS are not enabled.  The iSNS server MUST
 maintain the state of DD membership for all Storage Nodes, even for
 those that have been deregistered.  DD membership is persistent
 regardless of whether a Storage Node is actively registered in the
 iSNS database.

Tseng, et al. Standards Track [Page 9] RFC 4171 Internet Storage Name Service (iSNS) September 2005

2.2.3. State Change Notification Service

 The State Change Notification (SCN) service allows the iSNS Server to
 issue notifications about network events that affect the operational
 state of Storage Nodes.  The iSNS client may register for
 notifications on behalf of its Storage Nodes for notification of
 events detected by the iSNS Server.  SCNs notify iSNS clients of
 explicit or implicit changes to the iSNS database; they do not
 necessarily indicate the state of connectivity to peer storage
 devices in the network.  The response of a storage device to receipt
 of an SCN is implementation-specific; the policy for responding to
 SCNs is outside of the scope of this document.
 There are two types of SCN registrations: regular registrations and
 management registrations.  Management registrations result in
 management SCNs, whereas regular registrations result in regular
 SCNs.  The type of registration and SCN message is indicated in the
 SCN bitmap (see Sections 6.4.4 and 6.6.12).
 A regular SCN registration indicates that the Discovery Domain
 Service SHALL be used to control the distribution of SCN messages.
 Receipt of regular SCNs is limited to the discovery domains in which
 the SCN-triggering event takes place.  Regular SCNs do not contain
 information about discovery domains.
 A management SCN registration can only by requested by Control Nodes.
 Management SCNs resulting from management registrations are not bound
 by the Discovery Domain service.  Authorization to request management
 SCN registrations may be administratively controlled.
 The iSNS server SHOULD be implemented with hardware and software
 resources sufficient to support the expected number of iSNS clients.
 However, if resources are unexpectedly exhausted, then the iSNS
 server MAY refuse SCN service by returning an SCN Registration
 Rejected (Status Code 17).  The rejection might occur in situations
 where the network size or current number of SCN registrations has
 passed an implementation-specific threshold.  A client not allowed to
 register for SCNs may decide to monitor its sessions with other
 storage devices directly.
 The specific notification mechanism by which the iSNS server learns
 of the events that trigger SCNs is implementation-specific, but can
 include examples such as explicit notification messages from an iSNS
 client to the iSNS server, or a hardware interrupt to a switch-hosted
 iSNS server as a result of link failure.

Tseng, et al. Standards Track [Page 10] RFC 4171 Internet Storage Name Service (iSNS) September 2005

2.2.4. Open Mapping between Fibre Channel and iSCSI Devices

 The iSNS database stores naming and discovery information about both
 Fibre Channel and iSCSI devices.  This allows the iSNS server to
 store mappings of a Fibre Channel device to a proxy iSCSI device
 "image" in the IP network.  Similarly, mappings of an iSCSI device to
 a "proxy WWN" can be stored under the WWNN Token field for that iSCSI
 device.
 Furthermore, through use of iSCSI-FC gateways, Fibre Channel-aware
 management stations can interact with the iSNS server to retrieve
 information about Fibre Channel devices, and use this information to
 manage Fibre Channel and iSCSI devices.  This allows management
 functions such as Discovery Domains and State Change Notifications to
 be applied seamlessly to both iSCSI and Fibre Channel devices,
 facilitating integration of IP networks with Fibre Channel devices
 and fabrics.
 Note that Fibre Channel attributes are stored as iFCP attributes, and
 that the ability to store this information in the iSNS server is
 useful even if the iFCP protocol is not implemented.  In particular,
 tag 101 can be used to store a "Proxy iSCSI Name" for Fibre Channel
 devices registered in the iSNS server.  This field is used to
 associate the FC device with an iSCSI registration entry that is used
 for the Fibre Channel device to communicate with iSCSI devices in the
 IP network.  Conversely, tag 37 (see Section 6.1) contains a WWNN
 Token field, which can be used to store an FC Node Name (WWNN) value
 used by iSCSI-FC gateways to represent an iSCSI device in the Fibre
 Channel domain.
 By storing the mapping between Fibre Channel and iSCSI devices in the
 iSNS server, this information becomes open to any authorized iSNS
 client wishing to retrieve and use this information.  In many cases,
 this provides advantages over storing the information internally
 within an iSCSI-FC gateway, where the mapping is inaccessible to
 other devices except by proprietary mechanisms.

2.3. iSNS Usage Model

 The following is a high-level description of how each type of device
 in a storage network can utilize iSNS.  Each type of device interacts
 with the iSNS server as an iSNS client and must register itself in
 the iSNS database in order to access services provided by the iSNS.

Tseng, et al. Standards Track [Page 11] RFC 4171 Internet Storage Name Service (iSNS) September 2005

2.3.1. iSCSI Initiator

 An iSCSI initiator will query the iSNS server to discover the
 presence and location of iSCSI target devices.  It may also request
 state change notifications (SCNs) so that it can be notified of new
 targets that appear on the network after the initial bootup and
 discovery.  SCNs can also inform the iSCSI initiator of targets that
 have been removed from or no longer available in the storage network,
 so that incomplete storage sessions can be gracefully terminated and
 resources for non-existent targets can be reallocated.

2.3.2. iSCSI Target

 An iSCSI target allows itself to be discovered by iSCSI initiators by
 registering its presence in the iSNS server.  It may also register
 for SCNs in order to detect the addition or removal of initiators for
 resource allocation purposes.  The iSCSI target device may also
 register for Entity Status Inquiry (ESI) messages, which allow the
 iSNS to monitor the target device's availability in the storage
 network.

2.3.3. iSCSI-FC Gateway

 An iSCSI-FC gateway bridges devices in a Fibre Channel network to an
 iSCSI/IP network.  It may use the iSNS server to store FC device
 attributes discovered in the FC name server, as well as mappings of
 FC device identifiers to iSCSI device identifiers.  iSNS has the
 capability to store all attributes of both iSCSI and Fibre Channel
 devices; iSCSI devices are managed through direct interaction using
 iSNS, while FC devices can be indirectly managed through iSNS
 interactions with the iSCSI-FC gateway.  This allows both iSCSI and
 Fibre Channel devices to be managed in a seamless management
 framework.

2.3.4. iFCP Gateway

 An iFCP gateway uses iSNS to emulate the services provided by a Fibre
 Channel name server for FC devices in its gateway region.  iSNS
 provides basic discovery and zoning configuration information to be
 enforced by the iFCP gateway.  When queried, iSNS returns information
 on the N_Port network address used to establish iFCP sessions between
 FC devices supported by iFCP gateways.

2.3.5. Management Station

 A management station uses iSNS to monitor storage devices and to
 enable or disable storage sessions by configuring discovery domains.
 A management station usually interacts with the iSNS server as a

Tseng, et al. Standards Track [Page 12] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Control Node endowed with access to all iSNS database records and
 with special privileges to configure discovery domains.  Through
 manipulation of discovery domains, the management station controls
 the scope of device discovery for iSNS clients querying the iSNS
 server.

2.4. Administratively Controlled iSNS Settings

 Some important operational settings for the iSNS server are
 configured using administrative means, such as a configuration file,
 a console port, an SNMP, or another implementation-specific method.
 These administratively-controlled settings cannot be configured using
 the iSNS Protocol, and therefore the iSNS server implementation MUST
 provide for such an administrative control interface.
 The following is a list of parameters that are administratively
 controlled for the iSNS server.  In the absence of alternative
 settings provided by the administrator, the following specified
 default settings MUST be used.
 Setting                                  Default Setting
 -------                                  ---------------
 ESI Non-Response Threshold                     3     (see 5.6.5.13)
 Management SCNs (Control Nodes only)        enabled  (see 5.6.5.8)
 Default DD/DDS                              disabled
 DD/DDS Modification
    - Control Node                           enabled
    - iSCSI Target Node Type                 disabled
    - iSCSI Initiator Node Type              disabled
    - iFCP Target Port Role                  disabled
    - iFCP Initiator Port Role               disabled
 Authorized Control Nodes                      N/A
 ESI Non-Response Threshold: determines the number of ESI messages
                 sent without receiving a response before the network
                 entity is deregistered from the iSNS database.
 Management SCN for Control Node: determines whether a registered
                 Control Node is permitted to register to receive
                 Management SCNs.
 Default DD/DDS: determines whether a newly registered device not
                 explicitly placed into a discovery domain (DD) and
                 discovery domain set (DDS) is placed into a default
                 DD/DDS.
 DD/DDS Modification: determines whether the specified type of Node is
                 allowed to add, delete or update DDs and DDSs.

Tseng, et al. Standards Track [Page 13] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Authorized Control Nodes: a list of Nodes identified by iSCSI Name or
                 FC Port Name WWPN that are authorized to register as
                 Control Nodes.

2.5. iSNS Server Discovery

2.5.1. Service Location Protocol (SLP)

 The Service Location Protocol (SLP) provides a flexible and scalable
 framework for providing hosts with access to information about the
 existence, location, and configuration of networked services,
 including the iSNS server.  SLP can be used by iSNS clients to
 discover the IP address or FQDN of the iSNS server.  To implement
 discovery through SLP, a Service Agent (SA) should be cohosted in the
 iSNS server, and a User Agent (UA) should be in each iSNS client.
 Each client multicasts a discovery message requesting the IP address
 of the iSNS server(s).  The SA responds to this request.  Optionally,
 the location of the iSNS server can be stored in the SLP Directory
 Agent (DA).
 Note that a complete description and specification of SLP can be
 found in [RFC2608], and is beyond the scope of this document.  A
 service template for using SLP to locate iSNS servers can be found in
 [iSCSI-SLP].

2.5.2. Dynamic Host Configuration Protocol (DHCP)

 The IP address of the iSNS server can be stored in a DHCP server to
 be downloaded by iSNS clients using a DHCP option.  The DHCP option
 number to be used for distributing the iSNS server location is found
 in [iSNSOption].

2.5.3. iSNS Heartbeat Message

 The iSNS heartbeat message is described in Section 5.6.5.14.  It
 allows iSNS clients within the broadcast or multicast domain of the
 iSNS server to discover the location of the active iSNS server and
 any backup servers.

2.6. iSNS and Network Address Translation (NAT)

 The existence of NAT will have an impact upon information retrieved
 from the iSNS server.  If the iSNS client exists in an addressing
 domain different from that of the iSNS server, then IP address
 information stored in the iSNS server may not be correct when
 interpreted in the domain of the iSNS client.

Tseng, et al. Standards Track [Page 14] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 There are several possible approaches to allow operation of iSNS
 within a NAT network.  The first approach is to require use of the
 canonical TCP port number by both targets and initiators when
 addressing targets across a NAT boundary, and for the iSNS client not
 to query for nominal IP addresses.  Rather, the iSNS client queries
 for the DNS Fully Qualified Domain Name stored in the Entity
 Identifier field when seeking addressing information.  Once
 retrieved, the DNS name can be interpreted in each address domain and
 mapped to the appropriate IP address by local DNS servers.
 A second approach is to deploy a distributed network of iSNS servers.
 Local iSNS servers are deployed inside and outside NAT boundaries,
 with each local server storing relevant IP addresses for their
 respective NAT domains.  Updates among the network of decentralized,
 local iSNS servers are handled using LDAP and appropriate NAT
 translation rules implemented within the update mechanism in each
 server.
 Finally, note that it is possible for an iSNS server in the private
 addressing domain behind a NAT boundary to exclusively support iSNS
 clients that are operating in the global IP addressing domain.  If
 this is the case, the administrator only needs to ensure that the
 appropriate mappings are configured on the NAT gateways to allow the
 iSNS clients to initiate iSNSP sessions to the iSNS server.  All
 registered addresses contained in the iSNS server are thus public IP
 addresses for use outside the NAT boundary.  Care should be taken to
 ensure that there are no iSNS clients querying the server from inside
 the NAT boundary.

2.7. Transfer of iSNS Database Records between iSNS Servers

 Transfer of iSNS database records between iSNS servers has important
 applications, including the following:
 1)  An independent organization needs to transfer storage information
     to a different organization.  Each organization independently
     maintains its own iSNS infrastructure.  To facilitate discovery
     of storage assets of the peer organization using IP, iSNS
     database records can be transferred between authoritative iSNS
     servers from each organization.  This allows storage sessions to
     be established directly between devices residing in each
     organization's storage network infrastructure over a common IP
     network.
 2)  Multiple iSNS servers are desired for redundancy.  Backup servers
     need to maintain copies of the primary server's dynamically
     changing database.

Tseng, et al. Standards Track [Page 15] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 To support the above applications, information in an iSNS server can
 be distributed to other iSNS servers either using the iSNS protocol,
 or through out-of-band mechanisms using non-iSNS protocols.  The
 following examples illustrate possible methods for transferring data
 records between iSNS servers.  In the first example, a back-end LDAP
 information base is used to support the iSNS server, and the data is
 transferred using the LDAP protocol.  Once the record transfer of the
 remote device is completed, it becomes visible and accessible to
 local devices using the local iSNS server.  This allows local devices
 to establish sessions with remote devices (provided that firewall
 boundaries can be negotiated).
 +-------------------------+           +-------------------------+
 |+------+ iSNSP           |           |           iSNSP +-----+ |
 ||dev A |<----->+------+  |           |  +------+<----->|dev C| |
 |+------+       |      |  |           |  |      |       +-----+ |
 |+------+ iSNSP |local |  |           |  |remote| iSNSP +-----+ |
 ||dev B |<----->| iSNS |  |           |  | iSNS |<----->|dev D| |
 |+------+       |server|  |           |  |server|       +-----+ |
 |........       +--+---+  |   WAN     |  +---+--+               |
 |.dev C'.          |      |   Link    |      |                  |
 |........          |      =============      |                  |
 |                  |      |           |      |                  |
 |               +--+---+  |           |  +---+--+               |
 |               | local|<--- <--- <--- <-|remote|               |
 |               | LDAP |  |  LDAP:    |  | LDAP |               |
 |               +------+  Xfer "dev C"|  +------+               |
 +-------------------------+           +-------------------------+
        Enterprise                           Enterprise
        Network A                            Network B
 In the above diagram, two business partners wish to share storage
 "dev C".  Using LDAP, the record for "dev C" can be transferred from
 Network B to Network A.  Once accessible to the local iSNS server in
 Network A, local devices A and B can now discover and connect to "dev
 C".

Tseng, et al. Standards Track [Page 16] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 +-------------------------+           +-------------------------+
 |+------+ iSNSP           |           |           iSNSP +-----+ |
 ||dev A |<----->+------+  |           |  +------+<----->|dev C| |
 |+------+       |      |  |           |  |      |       +-----+ |
 |+------+ iSNSP |local |  |           |  |remote| iSNSP +-----+ |
 ||dev B |<----->| iSNS |  |           |  | iSNS |<----->|dev D| |
 |+------+       |server|  |           |  |server|       +-----+ |
 |........       +------+  |   WAN     |  +---+--+               |
 |.dev C'.          ^      |   Link    |      |                  |
 |........          |      =============      v                  |
 |                  |      |           |      |SNMP              |
 |                  |      |           |      |                  |
 |               +--+----+ |           |      v                  |
 |               | SNMP  |<--- <--- <--- <----                   |
 |               | Mgmt  | |  SNMP: Xfer "dev C"                 |
 |               |Station| |           |                         |
 |               +-------+ |           |                         |
 +-------------------------+           +-------------------------+
        Enterprise                           Enterprise
        Network A                            Network B
 The above diagram illustrates a second example of how iSNS records
 can be shared.  This method uses an SNMP-based management station to
 retrieve (GET) the desired record for "dev C" manually, and then to
 store (SET) it on the local iSNS server directly.  Once the record is
 transferred to the local iSNS server in Network A, "dev C" becomes
 visible and accessible (provided that firewall boundaries can be
 negotiated) to other devices in Network A.
 Other methods, including proprietary protocols, can be used to
 transfer device records between iSNS servers.  Further discussion and
 explanation of these methodologies is beyond the scope of this
 document.

2.8. Backup iSNS Servers

 This section offers a broad framework for implementation and
 deployment of iSNS backup servers.  Server failover and recovery are
 topics of continuing research, and adequate resolution of issues such
 as split brain and primary server selection is dependent on the
 specific implementation requirements and deployment needs.  The
 failover mechanisms discussed in this document focus on the
 interaction between iSNS clients and iSNS servers.  Specifically,
 what is covered in this document includes the following:
  1. iSNS client behavior and the iSNS protocol interaction between the

client and multiple iSNS servers, some of which are backup

    servers.

Tseng, et al. Standards Track [Page 17] RFC 4171 Internet Storage Name Service (iSNS) September 2005

  1. Required failover behaviors of the collection of iSNS servers that

includes active and backup servers.

 However, note that this document does not specify the complete
 functional failover requirements of each iSNS server.  In particular,
 it does not specify the complete set of protocol interactions among
 the iSNS servers that are required to achieve stable failover
 operation in an interoperable manner.
 For the purposes of this discussion, the specified backup mechanisms
 pertain to interaction among different logical iSNS servers.  Note
 that it is possible to create multiple physical iSNS servers to form
 a single logical iSNS server cluster, and thus to distribute iSNS
 transaction processing among multiple physical servers.  However, a
 more detailed discussion of the interactions between physical servers
 within a logical iSNS server cluster is beyond the scope of this
 document.
 Multiple logical iSNS servers can be used to provide redundancy in
 the event that the active iSNS server fails or is removed from the
 network.  The methods described in Section 2.7 above can be used to
 transfer name server records to backup iSNS servers.  Each backup
 server maintains a redundant copy of the name server database found
 in the primary iSNS server, and can respond to iSNS protocol messages
 in the same way as the active server.  Each backup server SHOULD
 monitor the health and status of the active iSNS server, including
 checking to make sure its own database is synchronized with the
 active server's database.  How each backup server accomplishes this
 is implementation-dependent, and may (or may not) include using the
 iSNS protocol.  If the iSNS protocol is used, then the backup server
 MAY register itself in the active server's iSNS database as a Control
 Node, allowing it to receive state-change notifications.
 Generally, the administrator or some automated election process is
 responsible for initial and subsequent designation of the primary
 server and each backup server.
 A maximum of one logical backup iSNS server SHALL exist at any
 individual IP address, in order to avoid conflicts from multiple
 servers listening on the same canonical iSNS TCP or UDP port number.
 The iSNS heartbeat can also be used to coordinate the designation and
 selection of primary and backup iSNS servers.
 Each backup server MUST note its relative precedence in the active
 server's list of backup servers.  If its precedence is not already
 known, each backup server MAY learn it from the iSNS heartbeat
 message, by noting the position of its IP address in the ordered list

Tseng, et al. Standards Track [Page 18] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 of backup server IP addresses.  For example, if it is the first
 backup listed in the heartbeat message, then its backup precedence is
 1.  If it is the third backup server listed, then its backup
 precedence is 3.
 If a backup server establishes that it has lost connectivity to the
 active server and other backup servers of higher precedence, then it
 SHOULD assume that it is the active server.  The method of
 determining whether connectivity has been lost is implementation-
 specific.  One possible approach is to assume that if the backup
 server does not receive iSNS heartbeat messages for a period of time,
 then connectivity to the active server has been lost.  Alternatively,
 the backup server may establish TCP connections to the active server
 and other backup servers, with loss of connectivity determined
 through non-response to periodic echo or polling messages (using
 iSNSP, SNMP, or other protocols).
 When a backup server becomes the active server, it SHALL assume all
 active server responsibilities, including (if used) transmission of
 the iSNS heartbeat message.  If transmitting the iSNS heartbeat, the
 backup server replaces the active Server IP Address and TCP/UDP Port
 entries with its own IP address and TCP/UDP Port, and begins
 incrementing the counter field from the last known value from the
 previously-active iSNS server.  However, it MUST NOT change the
 original ordered list of backup server IP Address and TCP/UDP Port
 entries.  If the primary backup server or other higher-precedence
 backup server returns, then the existing active server is responsible
 for ensuring that the new active server's database is up-to-date
 before demoting itself to its original status as backup.
 Since the primary and backup iSNS servers maintain a coordinated
 database, no re-registration by an iSNS Client is required when a
 backup server takes the active server role.  Likewise, no re-
 registration by an iSNS Client is required when the previous primary
 server returns to the active server role.

2.9. Transport Protocols

 The iSNS Protocol is transport-neutral.  Query and registration
 messages are transported over TCP or UDP.  iSNS heartbeat messages
 are transported using IP multicast or broadcast.

2.9.1. Use of TCP for iSNS Communication

 It MUST be possible to use TCP for iSNS communication.  The iSNS
 server MUST accept TCP connections for client registrations.  To
 receive Entity Status Inquiry (ESI) (see Section 5.6.5.13) monitoring
 the use of TCP, the client registers the Portal ESI Interval and the

Tseng, et al. Standards Track [Page 19] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 port number of the TCP port that will be used to receive ESI
 messages.  The iSNS server initiates the TCP connection used to
 deliver the ESI message.  This TCP connection does not need to be
 continuously open.
 To receive SCN notifications using TCP, the client registers the
 iSCSI or iFCP SCN Bitmap and the port number of the TCP port in the
 Portal used to receive SCNs.  The iSNS server initiates the TCP
 connection used to deliver the SCN message.  This TCP connection does
 not need to be continuously open.
 It is possible for an iSNS client to use the same TCP connection for
 SCN, ESI, and iSNS queries.  Alternatively, separate connections may
 be used.

2.9.2. Use of UDP for iSNS Communication

 The iSNS server MAY accept UDP messages for client registrations.
 The iSNS server MUST accept registrations from clients requesting
 UDP-based ESI and SCN messages.
 To receive UDP-based ESI monitoring messages, the client registers
 the port number of the UDP port in at least one Portal to be used to
 receive and respond to ESI messages from the iSNS server.  If a
 Network Entity has multiple Portals with registered ESI UDP Ports,
 then ESI messages SHALL be delivered to every Portal registered to
 receive such messages.
 To receive UDP-based SCN notification messages, the client registers
 the port number of the UDP port in at least one Portal to be used to
 receive SCN messages from the iSNS server.  If a Network Entity has
 multiple Portals with registered SCN UDP Ports, then SCN messages
 SHALL be delivered to each Portal registered to receive such
 messages.
 When using UDP to transport iSNS messages, each UDP datagram MUST
 contain exactly one iSNS PDU (see Section 5).

2.9.3. iSNS Multicast and Broadcast Messages

 iSNS multicast messages are transported using IP multicast or
 broadcast.  The iSNS heartbeat is the only iSNS multicast or
 broadcast message.  This message is originated by the iSNS server and
 sent to all iSNS clients that are listening on the IP multicast
 address allocated for the iSNS heartbeat.

Tseng, et al. Standards Track [Page 20] RFC 4171 Internet Storage Name Service (iSNS) September 2005

2.10. Simple Network Management Protocol (SNMP) Requirements

 The iSNS Server may be managed via the iSNS MIB [iSNSMIB] using an
 SNMP management framework [RFC3411].  For a detailed overview of the
 documents that describe the current Internet-Standard Management
 Framework, please refer to Section 7 of RFC 3410 [RFC3410].  The iSNS
 MIB provides the ability to configure and monitor an iSNS server
 without using the iSNS protocol directly.  SNMP management frameworks
 have several requirements for object indexing in order for objects to
 be accessed or added.
 SNMP uses an Object Identifier (OID) for object identification.  The
 size of each OID is restricted to a maximum of 128 sub-identifiers.
 Both the iSCSI and iFCP protocol contain identifiers, such as the
 iSCSI Name, that are greater the 128 characters in length.  Using
 such identifiers as an index would result in more than 128 sub-
 identifiers per OID.  In order to support objects that have key
 identifiers whose maximum length is longer than the maximum SNMP-
 supported length, the iSNS server provides secondary non-zero integer
 index identifiers.  These indexes SHALL be persistent for as long as
 the server is active.  Furthermore, index values for recently
 deregistered objects SHOULD NOT be reused in the short term.  Object
 attributes, including indexes, are described in detail in Section 6.
 For SNMP based management applications to create a new entry in a
 table of objects, a valid OID must be available to specify the table
 row.  The iSNS server supports this by providing, for each type of
 object that can be added via SNMP, an object attribute that returns
 the next available non-zero integer index.  This allows an SNMP
 client to request an OID to be used for registering a new object in
 the server.  Object attributes, including next available index
 attributes, are described in detail in Section 6.

3. iSNS Object Model

 iSNS provides the framework for the registration, discovery, and
 management of iSCSI devices and Fibre Channel-based devices (using
 iFCP).  This architecture framework provides elements needed to
 describe various storage device objects and attributes that may exist
 on an IP storage network.  Objects defined in this architecture
 framework include Network Entity, Portal, Storage Node, FC Device,
 Discovery Domain, and Discovery Domain Set.  Each of these objects is
 described in greater detail in the following sections.

Tseng, et al. Standards Track [Page 21] RFC 4171 Internet Storage Name Service (iSNS) September 2005

3.1. Network Entity Object

 The Network Entity object is a container of Storage Node objects and
 Portal objects.  It represents the infrastructure supporting access
 to a unique set of one or more Storage Nodes.  The Entity Identifier
 attribute uniquely distinguishes a Network Entity, and is the key
 used to register a Network Entity object in an iSNS server.  All
 Storage Nodes and Portals contained within a single Network Entity
 object operate as a cohesive unit.
 Note that it is possible for a single physical device or gateway to
 be represented by more than one logical Network Entity in the iSNS
 database.  For example, one of the Storage Nodes on a physical device
 may be accessible from only a subset of the network interfaces (i.e.,
 Portals) available on that device.  In this case, a logical network
 entity (i.e., a "shadow entity") is created and used to contain the
 Portals and Storage Nodes that can operate cooperatively.  No object
 (Portals, Storage Nodes, etc.) can be contained in more than one
 logical Network Entity.
 Similarly, it is possible for a logical Network Entity to be
 supported by more than one physical device or gateway.  For example,
 multiple FC-iSCSI gateways may be used to bridge FC devices in a
 single Fibre Channel network.  Collectively, the multiple gateways
 can be used to support a single logical Network Entity that is used
 to contain all the devices in that Fibre Channel network.

3.2. Portal Object

 The Portal object is an interface through which access to Storage
 Nodes within the Network Entity can be obtained.  The IP address and
 TCP/UDP Port number attributes uniquely distinguish a Portal object,
 and combined are the key used to register a Portal object in an iSNS
 server.  A Portal is contained in one and only one Network Entity,
 and may be contained in one or more DDs (see Section 3.6).

3.3. Storage Node Object

 The Storage Node object is the logical endpoint of an iSCSI or iFCP
 session.  In iFCP, the session endpoint is represented by the World
 Wide Port Name (WWPN).  In iSCSI, the session endpoint is represented
 by the iSCSI Name of the device.  For iSCSI, the iSCSI Name attribute
 uniquely distinguishes a Storage Node, and is the key used to
 register a Storage Node object in an iSNS Server.  For iFCP, the FC
 Port Name (WWPN) attribute uniquely distinguishes a Storage Node, and
 is the key used to register a Storage Node object in the iSNS Server.
 Storage Node is contained in only one Network Entity object and may
 be contained in one or more DDs (see Section 3.6).

Tseng, et al. Standards Track [Page 22] RFC 4171 Internet Storage Name Service (iSNS) September 2005

3.4. Portal Group Object

 The Portal Group (PG) object represents an association between a
 Portal and an iSCSI Node.  Each Portal and iSCSI Storage Node
 registered in an Entity can be associated using a Portal Group (PG)
 object.  The PG Tag (PGT), if non-NULL, indicates that the associated
 Portal provides access to the associated iSCSI Storage Node in the
 Entity.  All Portals that have the same PGT value for a specific
 iSCSI Storage Node allow coordinated access to that node.
 A PG object MAY be registered when a Portal or iSCSI Storage Node is
 registered.  Each Portal to iSCSI Node association is represented by
 one and only one PG object.  In order for a Portal to provide access
 to an iSCSI Node, the PGT of the PG object MUST be non-NULL.  If the
 PGT value registered for a specified Portal and iSCSI Node is NULL,
 or if no PGT value is registered, then the Portal does not provide
 access to that iSCSI Node in the Entity.
 The PGT value indicates whether access to an iSCSI Node can be
 coordinated across multiple Portals.  All Portals that have the same
 PGT value for a specific iSCSI Node can provide coordinated access to
 that iSCSI Node.  According to the iSCSI Specification, coordinated
 access to an iSCSI node indicates the capability of coordinating an
 iSCSI session with connections that span these Portals [iSCSI].
 The PG object is uniquely distinguished by the iSCSI Name, Portal IP
 Address, and Portal TCP Port values of the associated Storage Node
 and Portal objects.  These are represented in the iSNS Server by the
 PG iSCSI Name, PG Portal IP Address, and PG Portal TCP/UDP Port
 attributes, respectively.  The PG object is also uniquely
 distinguished in the iSNS Server by the PG Index value.
 A new PG object can only be registered by referencing its associated
 iSCSI Storage Node or Portal object.  A pre-existing PG object can be
 modified or queried by using its Portal Group Index as message key,
 or by referencing its associated iSCSI Storage Node or Portal object.
 A 0-length Tag, Length, Value TLV is used to register a PGT NULL
 value.
 The PG object is deregistered if and only if its associated iSCSI
 Node and Portal objects are both removed.

Tseng, et al. Standards Track [Page 23] RFC 4171 Internet Storage Name Service (iSNS) September 2005

3.5. Device Object

 The FC Device represents the Fibre Channel Node.  This object
 contains information that may be useful in the management of the
 Fibre Channel device.  The FC Node Name (WWNN) attribute uniquely
 distinguishes an FC Device, and is the key used to register an FC
 Device object in the iSNS Server.
 The FC Device is contained in one or more Storage Node objects.

3.6. Discovery Domain Object

 Discovery Domains (DD) are a security and management mechanism used
 to administer access and connectivity to storage devices.  For query
 and registration purposes, they are considered containers for Storage
 Node and Portal objects.  A query by an iSNS client that is not from
 a Control Node only returns information about objects with which it
 shares at least one active DD.  The only exception to this rule is
 with Portals; if Storage Nodes of a Network Entity are registered in
 the DD without Portals, then all Portals of that Network Entity are
 implicit members of that DD.  The Discovery Domain ID (DD_ID)
 attribute uniquely distinguishes a Discovery Domain object, and is
 the key used to register a Discovery Domain object in the iSNS
 Server.
 A DD is considered active if it is a member of at least one active DD
 Set.  DDs that are not members of at least one enabled DDS are
 considered disabled.  A Storage Node can be a member of one or more
 DDs.  An enabled DD establishes connectivity among the Storage Nodes
 in that DD.

3.7. Discovery Domain Set Object

 The Discovery Domain Set (DDS) is a container object for Discovery
 Domains (DDs).  DDSs may contain one or more DDs.  Similarly, each DD
 can be a member of one or more DDSs.  DDSs are a mechanism to store
 coordinated sets of DD mappings in the iSNS server.  Active DDs are
 members of at least one active DD Set.  Multiple DDSs may be
 considered active at the same time.  The Discovery Domain Set ID
 (DDS_ID) attribute uniquely distinguishes a Discovery Domain Set
 object, and is the key used to register a Discovery Domain Set object
 in the iSNS Server.

3.8. Database Model

 As presented to the iSNS client, each object of a specific type in
 the iSNS database MUST have an implicit internal linear ordering
 based on the key(s) for that object type.  This ordering provides the

Tseng, et al. Standards Track [Page 24] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 ability to respond to DevGetNext queries (see Section 5.6.5.3).  The
 ordering of objects in the iSNS database SHOULD NOT be changed with
 respect to that implied ordering, as a consequence of object
 insertions and deletions.  That is, the relative order of surviving
 object entries in the iSNS database SHOULD be preserved so that the
 DevGetNext message encounters generally reasonable behavior.
 The following diagram shows the various objects described above and
 their relationship to each other.
                  +--------------+    +-----------+
                  |    NETWORK   |1  *|           |
                  |    ENTITY    |----|  PORTAL   |
                  |              |    |           |
                  +--------------+    +-----------+
                          |1            |1  |*
                          |             |   |
                          |             |*  |
                          |   +----------+  |
                          |   |  PORTAL  |  |
                          |   |  GROUP   |  |
                          |   +----------+  |
                          |    |*           |
                          |    |            |
                          |*   |1           |*
 +-----------+    +--------------+    +-----------+    +-----------+
 |    FC     |1  *|   STORAGE    |*  *| DISCOVERY |*  *| DISCOVERY |
 |  DEVICE   |----|    NODE      |----|  DOMAIN   |----|  DOMAIN   |
 |           |    |              |    |           |    |    SET    |
 +-----------+    +--------------+    +-----------+    +-----------+
  • represents 0 to many possible relationships

4. iSNS Implementation Requirements

 This section details specific requirements for support of each of
 these IP storage protocols.  Implementation requirements for security
 are described in Section 7.

4.1. iSCSI Requirements

 Use of iSNS in support of iSCSI is OPTIONAL.  iSCSI devices MAY be
 manually configured with the iSCSI Name and IP address of peer
 devices, without the aid or intervention of iSNS.  iSCSI devices may
 also use SLP [RFC2608] to discover peer iSCSI devices.  However, iSNS
 is useful for scaling a storage network to a larger number of iSCSI
 devices.

Tseng, et al. Standards Track [Page 25] RFC 4171 Internet Storage Name Service (iSNS) September 2005

4.1.1. Required Attributes for Support of iSCSI

 The following attributes are available to support iSCSI.  Attributes
 indicated in the REQUIRED for Server column MUST be implemented by an
 iSNS server used to support iSCSI.  Attributes indicated in the
 REQUIRED for Client column MUST be implemented by an iSCSI device
 that elects to use the iSNS.  Attributes indicated in the K (Key)
 column uniquely identify the object type in the iSNS Server.  A more
 detailed description of each attribute is found in Section 6.
                                                      REQUIRED for:
 Object             Attribute                    K    Server  Client
 ------             ---------                    -    ------  ------
 NETWORK ENTITY     Entity Identifier            *      *        *
                    Entity Protocol                     *        *
                    Management IP Address               *
                    Timestamp                           *
                    Protocol Version Range              *
                    Registration Period                 *
                    Entity Index                        *
                    Entity IKE Phase-1 Proposal
                    Entity Certificate
 PORTAL             IP Address                   *      *        *
                    TCP/UDP Port                 *      *        *
                    Portal Symbolic Name                *
                    ESI Interval                        *
                    ESI Port                            *
                    Portal Index                        *
                    SCN Port                            *
                    Portal Security Bitmap              *
                    Portal IKE Phase-1 Proposal
                    Portal IKE Phase-2 Proposal
                    Portal Certificate
 PORTAL GROUP       PG iSCSI Name                *      *        *
                    PG IP Address                *      *        *
                    PG TCP/UDP Port              *      *        *
                    PG Tag                              *        *
                    PG Index                            *

Tseng, et al. Standards Track [Page 26] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 STORAGE NODE       iSCSI Name                   *      *        *
                    iSCSI Node Type                     *        *
                    Alias                               *
                    iSCSI SCN Bitmap                    *
                    iSCSI Node Index                    *
                    WWNN Token
                    iSCSI AuthMethod
                    iSCSI Node Certificate
 DISCOVERY DOMAIN   DD ID                        *      *        *
                    DD Symbolic Name                    *
                    DD Member iSCSI Node Index          *
                    DD Member iSCSI Name                *
                    DD Member Portal Index              *
                    DD Member Portal IP Addr            *
                    DD Member Portal TCP/UDP            *
                    DD Features                         *
 DISCOVERY DOMAIN   DDS Identifier                *     *
 SET                DDS Symbolic Name                   *
                    DDS Status                          *
 All iSCSI user-specified and vendor-specified attributes are OPTIONAL
 to implement and use.

Tseng, et al. Standards Track [Page 27] RFC 4171 Internet Storage Name Service (iSNS) September 2005

4.1.2. Examples: iSCSI Object Model Diagrams

 The following diagram models how a simple iSCSI-based initiator and
 target is represented using database objects stored in the iSNS
 server.  In this implementation, each target and initiator is
 attached to a single Portal.
 +----------------------------------------------------------------+
 |                         IP Network                             |
 +------------+--------------------------------------+------------+
              |                                      |
              |                                      |
 +-----+------+------+-----+            +-----+------+------+-----+
 |     | PORTAL      |     |            |     | PORTAL      |     |
 |     | -IP Addr 1  |     |            |     | -IP Addr 2  |     |
 |     | -TCP Port 1 |     |            |     | -TCP Port 2 |     |
 |     +-----+ +-----+     |            |     +-----+ +-----+     |
 |           | |           |            |           | |           |
 |     +-----+ +-----+     |            |     +-----+ +-----+     |
 |     | PORTAL GROUP|     |            |     | PORTAL GROUP|     |
 |     | -Prtl Tag 1 |     |            |     | -Prtl Tag 2 |     |
 |     +-----+ +-----+     |            |     +-----+ +-----+     |
 |           | |           |            |           | |           |
 |  +--------+ +--------+  |            |   +-------+ +--------+  |
 |  |                   |  |            |   |                  |  |
 |  |  STORAGE NODE     |  |            |   |  STORAGE NODE    |  |
 |  |  -iSCSI Name      |  |            |   |   -iSCSI Name    |  |
 |  |  -Alias: "server1"|  |            |   |   -Alias: "disk1"|  |
 |  |  -Type: initiator |  |            |   |   -Type: target  |  |
 |  |                   |  |            |   |                  |  |
 |  +-------------------+  |            |   +------------------+  |
 |                         |            |                         |
 |    NETWORK ENTITY       |            |    NETWORK ENTITY       |
 |   -Entity ID (FQDN):    |            |   -Entity ID (FQDN):    |
 |    "strg1.example.com"  |            |    "strg2.example.net"  |
 |   -Protocol: iSCSI      |            |   -Protocol: iSCSI      |
 |                         |            |                         |
 +-------------------------+            +-------------------------+
 The object model can be expanded to describe more complex devices,
 such as an iSCSI device with more than one storage controller, in
 which each controller is accessible through any of multiple Portal
 interfaces, possibly using multiple Portal Groups.  The storage
 controllers on this device can be accessed through alternate Portal
 interfaces if any original interface should fail.  The following
 diagram describes such a device:

Tseng, et al. Standards Track [Page 28] RFC 4171 Internet Storage Name Service (iSNS) September 2005

    +---------------------------------------------------------------+
    |                         IP Network                            |
    +-------------------+-----------------------+-------------------+
                        |                       |
                        |                       |
    +------------+------+------+---------+------+------+------------+
    |            | PORTAL 1    |         | PORTAL 2    |            |
    |            | -IP Addr 1  |         | -IP Addr 2  |            |
    |            | -TCP Port 1 |         | -TCP Port 2 |            |
    |            +-----+ +-----+         +-----+ +-----+            |
    |                  | |                     | |                  |
    |  +---------------+ +---------------------+ +---------------+  |
    |  +-------+ +----------------+ +-------------------+ +------+  |
    |          | |                | |                   | |         |
    |  +-------+ +-------+ +------+ +--------+ +--------+ +------+  |
    |  |                 | |                 | |                 |  |
    |  | STORAGE NODE 1  | | STORAGE NODE 2  | | STORAGE NODE 3  |  |
    |  |  -iSCSI Name 1  | |  -iSCSI Name 2  | |  -iSCSI Name 3  |  |
    |  |  -Alias: "disk1"| |  -Alias: "disk2"| |  -Alias: "disk3"|  |
    |  |  -Type: target  | |  -Type: target  | |  -Type: target  |  |
    |  |                 | |                 | |                 |  |
    |  +-----------------+ +-----------------+ +-----------------+  |
    |                                                               |
    |                         NETWORK ENTITY                        |
    |                    -Entity ID (FQDN): "dev1.example.com"      |
    |                    -Protocol: iSCSI                           |
    |                                                               |
    |                   Portal Group Object Table                   |
    |           Storage-Node Portal Portal-Group-Tag                |
    |                1         1           10                       |
    |                1         2         NULL (no access permitted) |
    |                2         1           20                       |
    |                2         2           20                       |
    |                3         1           30                       |
    |                3         2           10                       |
    |                                                               |
    +---------------------------------------------------------------+
 Storage Node 1 is accessible via Portal 1 with a PGT of 10.  It does
 not have a Portal Group Tag (PGT) assigned for Portal 2, so Storage
 Node 1 cannot be accessed via Portal 2.
 Storage Node 2 can be accessed via both Portal 1 and Portal 2.  Since
 Storage Node 2 has the same PGT value assigned to both Portal 1 and
 Portal 2, in this case 20, coordinated access via the Portals is
 available [iSCSI].

Tseng, et al. Standards Track [Page 29] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Storage Node 3 can be accessed via Portal 1 or Portal 2.  However,
 since Storage Node 3 has different PGT values assigned to each
 Portal, in this case 10 and 30, access is not coordinated [iSCSI].
 Because PGTs are assigned within the context of a Storage Node, the
 PGT value of 10 used for Storage Node 1 and Storage Node 3 are not
 interrelated.

4.1.3. Required Commands and Response Messages for Support of iSCSI

 The following iSNSP messages and responses are available in support
 of iSCSI.  Messages indicated in the REQUIRED for Server column MUST
 be implemented in iSNS servers used for iSCSI devices.  Messages
 indicated in the REQUIRED for Client column MUST be implemented in
 iSCSI devices that elect to use the iSNS server.
                                                   REQUIRED for:
 Message Description       Abbreviation  Func_ID   Server  Client
 -------------------       ------------  -------   ------  ------
 RESERVED                                0x0000
 Device Attr Reg Request   DevAttrReg    0x0001       *       *
 Dev Attr Query Request    DevAttrQry    0x0002       *       *
 Dev Get Next Request      DevGetNext    0x0003       *
 Deregister Dev Request    DevDereg      0x0004       *       *
 SCN Register Request      SCNReg        0x0005       *
 SCN Deregister Request    SCNDereg      0x0006       *
 SCN Event                 SCNEvent      0x0007       *
 State Change Notification SCN           0x0008       *
 DD Register               DDReg         0x0009       *       *
 DD Deregister             DDDereg       0x000A       *       *
 DDS Register              DDSReg        0x000B       *       *
 DDS Deregister            DDSDereg      0x000C       *       *
 Entity Status Inquiry     ESI           0x000D       *
 Name Service Heartbeat    Heartbeat     0x000E
 RESERVED                                0x000F-0x00FF
 Vendor Specific                         0x0100-0x01FF
 RESERVED                                0x0200-0x7FFF
 The following are iSNSP response messages used in support of iSCSI:
                                                    REQUIRED for:
 Response Message Desc     Abbreviation  Func_ID    Server  Client
 ---------------------     ------------  -------    ------  ------
 RESERVED                                0x8000
 Device Attr Register Rsp  DevAttrRegRsp 0x8001       *       *
 Device Attr Query Rsp     DevAttrQryRsp 0x8002       *       *
 Device Get Next Rsp       DevGetNextRsp 0x8003       *
 Device Dereg Rsp          DevDeregRsp   0x8004       *       *
 SCN Register Rsp          SCNRegRsp     0x8005       *

Tseng, et al. Standards Track [Page 30] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 SCN Deregister Rsp        SCNDeregRsp   0x8006       *
 SCN Event Rsp             SCNEventRsp   0x8007       *
 SCN Response              SCNRsp        0x8008       *
 DD Register Rsp           DDRegRsp      0x8009       *       *
 DD Deregister Rsp         DDDeregRsp    0x800A       *       *
 DDS Register Rsp          DDSRegRsp     0x800B       *       *
 DDS Deregister Rsp        DDSDeregRsp   0x800C       *       *
 Entity Stat Inquiry Rsp   ESIRsp        0x800D       *
 RESERVED                                0x800E-0x80FF
 Vendor Specific                         0x8100-0x81FF
 RESERVED                                0x8200-0xFFFF

4.2. iFCP Requirements

 In iFCP, use of iSNS is REQUIRED.  No alternatives exist for support
 of iFCP Naming & Discovery functions.

4.2.1. Required Attributes for Support of iFCP

 The following table displays attributes that are used by iSNS to
 support iFCP.  Attributes indicated in the REQUIRED for Server column
 MUST be implemented by the iSNS server that supports iFCP.
 Attributes indicated in the REQUIRED for Client column MUST be
 supported by iFCP gateways.  Attributes indicated in the K (Key)
 column uniquely identify the object type in the iSNS Server.  A more
 detailed description of each attribute is found in Section 6.
                                                     REQUIRED for:
 Object             Attribute                   K    Server  Client
 ------             ---------                   -    ------  ------
 NETWORK ENTITY     Entity Identifier           *       *       *
                    Entity Protocol                     *       *
                    Management IP Address               *
                    Timestamp                           *
                    Protocol Version Range              *
                    Registration period
                    Entity Index
                    Entity IKE Phase-1 Proposal
                    Entity Certificate
 PORTAL             IP Address                  *       *       *
                    TCP/UDP Port                *       *       *
                    Symbolic Name                       *
                    ESI Interval                        *
                    ESI Port                            *
                    SCN Port                            *
                    Portal IKE Phase-1 Proposal
                    Portal IKE Phase-2 Proposal

Tseng, et al. Standards Track [Page 31] RFC 4171 Internet Storage Name Service (iSNS) September 2005

                    Portal Certificate
                    Security Bitmap                     *
 STORAGE NODE       FC Port Name (WWPN)         *       *       *
 (FC Port)          Port_ID                             *       *
                    FC Port Type                        *       *
                    Port Symbolic Name                  *
                    Fabric Port Name (FWWN)             *
                    Hard Address                        *
                    Port IP Address                     *
                    Class of Service                    *
                    FC FC-4 Types                       *
                    FC FC-4 Descriptors                 *
                    FC FC-4 Features                    *
                    SCN Bitmap                          *
                    iFCP Port Role                      *
                    Permanent Port Name                 *
 FC DEVICE          FC Node Name (WWNN)         *       *       *
 (FC Node)          Node Symbolic Name                  *
                    Node IP Address                     *
                    Node IPA                            *
                    Proxy iSCSI Name
 DISCOVERY DOMAIN   DD ID                       *       *       *
                    DD Symbolic Name                    *
                    DD Member FC Port Name              *
                    DD Member Portal Index              *
                    DD Member Portal IP Addr            *
                    DD Member Portal TCP/UDP            *
 DISCOVERY DOMAIN   DDS ID                      *       *
 SET                DDS Symbolic Name                   *
                    DDS Status                          *
 OTHER              Switch Name
                    Preferred_ID
                    Assigned_ID
                    Virtual_Fabric_ID
 All iFCP user-specified and vendor-specified attributes are OPTIONAL
 to implement and use.

4.2.2. Example: iFCP Object Model Diagram

 The iFCP protocol allows native Fibre Channel devices or Fibre
 Channel fabrics connected to an iFCP gateway to be directly
 internetworked using IP.

Tseng, et al. Standards Track [Page 32] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 When supporting iFCP, the iSNS server stores Fibre Channel device
 attributes, iFCP gateway attributes, and Fibre Channel fabric switch
 attributes that might also be stored in an FC name server.
 The following diagram shows a representation of a gateway supporting
 multiple Fibre Channel devices behind it.  The two Portal objects
 represent IP interfaces on the iFCP gateway that can be used to
 access any of the three Storage Node objects behind it.  Note that
 the FC Device object is not contained in the Network Entity object.
 However, each FC Device has a relationship to one or more Storage
 Node objects.
 +--------------------------------------------------------+
 |                         IP Network                     |
 +--------+-----------------+-----------------------------+
          |                 |
 +-+------+------+---+------+------+----------------------+
 | | PORTAL      |   | PORTAL      | NETWORK ENTITY       |
 | | -IP Addr 1  |   | -IP Addr 2  | -Entity ID (FQDN):   |
 | | -TCP Port 1 |   | -TCP Port 2 |  "gtwy1.example.com" |
 | +-----+ +-----+   +-----+ +-----+ -Protocol: iFCP      |
 |       | |               | |                            |
 | +-----+ +---------------+ +----------------------+     |
 | +-----+ +---------------+ +-------------+ +------+     |
 |       | |               | |             | |            |
 | +-----+ +-----+    +----+ +------+ +----+ +------+     |
 | |STORAGE NODE |    |STORAGE NODE | |STORAGE NODE |     |
 | | -WWPN 1     |    | -WWPN 2     | | -WWPN 3     |     |
 | | -Port ID 1  |    | -Port ID 2  | | -Port ID 3  |     |
 | | -FWWN 1     |    | -FWWN 2     | | -FWWN 3     |     |
 | | -FC COS     |    | -FC COS     | | -FC COS     |     |
 | +------+------+    +-------+-----+ +----+--------+     |
 +--------|-------------------|------------|--------------+
          |                   |            |
   +------+------+        +---+------------+---+
   | FC DEVICE   |        |    FC DEVICE       |
   | -WWNN 1     |        |   -WWNN 2          |
   |             |        |                    |
   +-------------+        +--------------------+

Tseng, et al. Standards Track [Page 33] RFC 4171 Internet Storage Name Service (iSNS) September 2005

4.2.3. Required Commands and Response Messages for Support of iFCP

 The iSNSP messages and responses displayed in the following tables
 are available to support iFCP gateways.  Messages indicated in the
 REQUIRED TO IMPLEMENT column MUST be supported by the iSNS server
 used by iFCP gateways.  Messages indicated in the REQUIRED TO USE
 column MUST be supported by the iFCP gateways themselves.
                                                   REQUIRED for:
 Message Description       Abbreviation  Func ID   Server   Client
 -------------------       ------------  -------   ------   ------
 RESERVED                                0x0000
 Device Attr Reg Request   DevAttrReg    0x0001       *       *
 Device Attr Query Request DevAttrQry    0x0002       *       *
 Device Get Next Request   DevGetNext    0x0003       *
 Device Dereg Request      DevDereg      0x0004       *       *
 SCN Register Request      SCNReg        0x0005       *
 SCN Deregister Request    SCNDereg      0x0006       *
 SCN Event                 SCNEvent      0x0007       *
 State Change Notification SCN           0x0008       *
 DD Register               DDReg         0x0009       *       *
 DD Deregister             DDDereg       0x000A       *       *
 DDS Register              DDSReg        0x000B       *       *
 DDS Deregister            DDSDereg      0x000C       *       *
 Entity Status Inquiry     ESI           0x000D       *
 Name Service Heartbeat    Heartbeat     0x000E       *
 Reserved                  Reserved      0x000F-0x0010
 Request FC_DOMAIN_ID      RqstDomId     0x0011
 Release FC_DOMAIN_ID      RlseDomId     0x0012
 Get FC_DOMAIN_IDs         GetDomId      0x0013
 RESERVED                                0x0014-0x00FF
 Vendor Specific                         0x0100-0x01FF
 RESERVED                                0x0200-0x7FFF
 The following are iSNSP response messages in support of iFCP:
                                                   REQUIRED for:
 Response Message Desc     Abbreviation  Func_ID   Server   Client
 ---------------------     ------------  -------   ------   ------
 RESERVED                                0x8000
 Device Attr Reg Rsp       DevAttrRegRsp 0x8001       *       *
 Device Attr Query Rsp     DevAttrQryRsp 0x8002       *       *
 Device Get Next Rsp       DevGetNextRsp 0x8003       *
 Device Deregister Rsp     DevDeregRsp   0x8004       *       *
 SCN Register Rsp          SCNRegRsp     0x8005       *
 SCN Deregister Rsp        SCNDeregRsp   0x8006       *
 SCN Event Rsp             SCNEventRsp   0x8007       *
 SCN Rsp                   SCNRsp        0x8008       *

Tseng, et al. Standards Track [Page 34] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 DD Register Rsp           DDRegRsp      0x8009       *       *
 DD Deregister Rsp         DDDeregRsp    0x800A       *       *
 DDS Register Rsp          DDSRegRsp     0x800B       *       *
 DDS Deregister Rsp        DDSDeregRsp   0x800C       *       *
 Entity Status Inquiry Rsp ESIRsp        0x800D       *
 NOT USED                                0x800E
 RESERVED                                0x800F-0x8010
 Request FC_DOMAIN_ID Rsp  RqstDomIdRsp  0x8011
 Release FC_DOMAIN_ID Rsp  RlseDomIdRsp  0x8012
 Get FC_DOMAIN_IDs         GetDomIdRsp   0x0013
 RESERVED                                0x8014-0x80FF
 Vendor Specific                         0x8100-0x81FF
 RESERVED                                0x8200-0xFFFF

5. iSNSP Message Format

 The iSNSP message format is similar to the format of other common
 protocols such as DHCP, DNS and BOOTP.  An iSNSP message may be sent
 in one or more iSNS Protocol Data Units (PDU).  Each PDU is 4-byte
 aligned.  The following describes the format of the iSNSP PDU:
 Byte   MSb                                        LSb
 Offset 0                   15 16                   31
        +---------------------+----------------------+
      0 |   iSNSP VERSION     |    FUNCTION ID       | 4 Bytes
        +---------------------+----------------------+
      4 |     PDU LENGTH      |       FLAGS          | 4 Bytes
        +---------------------+----------------------+
      8 |   TRANSACTION ID    |    SEQUENCE ID       | 4 Bytes
        +---------------------+----------------------+
     12 |                                            |
        |                PDU PAYLOAD                 | N Bytes
        |                    ...                     |
        +--------------------------------------------+
   12+N | AUTHENTICATION BLOCK (Multicast/Broadcast) | L Bytes
        +--------------------------------------------+
                 Total Length = 12 + N + L

5.1. iSNSP PDU Header

 The iSNSP PDU header contains the iSNSP VERSION, FUNCTION ID, PDU
 LENGTH, FLAGS, TRANSACTION ID, and SEQUENCE ID fields as defined
 below.

Tseng, et al. Standards Track [Page 35] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.1.1. iSNSP Version

 The iSNSP version described in this document is 0x0001.  All other
 values are RESERVED.  The iSNS server MAY reject messages for iSNSP
 version numbers that it does not support.

5.1.2. iSNSP Function ID

 The FUNCTION ID defines the type of iSNS message and the operation to
 be executed.  FUNCTION_ID values with the leading bit cleared
 indicate query, registration, and notification messages, whereas
 FUNCTION_ID values with the leading bit set indicate response
 messages.
 See Section 4 under the appropriate protocol (i.e., iSCSI or iFCP)
 for a mapping of the FUNCTION_ID value to the iSNSP Command or
 Response message.  All PDUs comprising an iSNSP message must have the
 same FUNCTION_ID value.

5.1.3. iSNSP PDU Length

 The iSNS PDU Length specifies the length of the PDU PAYLOAD field in
 bytes.  The PDU Payload contains TLV attributes for the operation.
 Additionally, response messages contain a success/failure code.  The
 PDU Length MUST be 4-byte aligned.

5.1.4. iSNSP Flags

 The FLAGS field indicates additional information about the message
 and the type of Network Entity that generated the message.  The
 following table displays the valid flags:
        Bit Position      Enabled (1) means:
        ------------      -----------------
         16               Sender is the iSNS client
         17               Sender is the iSNS server
         18               Authentication block is present
         19               Replace flag (for DevAttrReg)
         20               Last PDU of the iSNS message
         21               First PDU of the iSNS message
         22-31            RESERVED

5.1.5. iSNSP Transaction ID

 The TRANSACTION ID MUST be set to a unique value for each
 concurrently outstanding request message.  Replies MUST use the same
 TRANSACTION ID value as the associated iSNS request message.  If a

Tseng, et al. Standards Track [Page 36] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 message is retransmitted, the original TRANSACTION ID value MUST be
 used.  All PDUs comprising an iSNSP message must have the same
 TRANSACTION ID value.

5.1.6. iSNSP Sequence ID

 The SEQUENCE ID has a unique value for each PDU within a single
 transaction.  The SEQUENCE_ID value of the first PDU transmitted in a
 given iSNS message MUST be zero (0), and each SEQUENCE_ID value in
 each PDU MUST be numbered sequentially in the order in which the PDUs
 are transmitted.  Note that the two-byte SEQUENCE ID allows for up to
 65536 PDUs per iSNS message.

5.2. iSNSP Message Segmentation and Reassembly

 iSNS messages may be carried in one or more iSNS PDUs.  If only one
 iSNS PDU is used to carry the iSNS message, then bit 21 (First PDU)
 and bit 20 in the FLAGS field (Last PDU) SHALL both be set.  If
 multiple PDUs are used to carry the iSNS message, then bit 21 SHALL
 be set in the first PDU of the message, and bit 20 SHALL be set in
 the last PDU.
 All PDUs comprising the same iSNSP message SHALL have the same
 FUNCTION_ID and TRANSACTION_ID values.  Each PDU comprising an iSNSP
 message SHALL have a unique SEQUENCE_ID value.

5.3. iSNSP PDU Payload

 The iSNSP PDU PAYLOAD is of variable length and contains attributes
 used for registration and query operations.  The attribute data items
 use a format similar to that of other protocols, such as DHCP
 [RFC2131] options.  Each iSNS attribute is specified in the PDU
 Payload using Tag-Length-Value (TLV) data format, as shown below:
 Byte   MSb                                        LSb
 Offset 0                                           31
        +--------------------------------------------+
      0 |               Attribute Tag                | 4 Bytes
        +--------------------------------------------+
      4 |            Attribute Length (N)            | 4 Bytes
        +--------------------------------------------+
      8 |                                            |
        |              Attribute Value               | N Bytes
        |                                            |
        +--------------------------------------------+
                 Total Length = 8 + N

Tseng, et al. Standards Track [Page 37] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Attribute Tag:    a 4-byte field that identifies the attribute as
                   defined in Section 6.1.  This field contains the
                   tag value from the indicated table.
 Attribute Length: a 4-byte field that indicates the length, in bytes,
                   of the value field to follow in the TLV.  For
                   variable-length attributes, the value field MUST
                   contain padding bytes, if necessary, in order to
                   achieve 4-byte alignment.  A "zero-length TLV"
                   contains only the attribute tag and length fields.
 Attribute Value:  a variable-length field containing the attribute
                   value and padding bytes (if necessary).
 The above format is used to identify each attribute in the PDU
 Payload.  Note that TLV boundaries need not be aligned with PDU
 boundaries; PDUs may carry one or more TLVs, or any fraction thereof.
 The Response Status Code, contained in response message PDU Payloads
 and described below, is not in TLV format.  PDU Payloads for messages
 that do not contain iSNS attributes, such as the Name Service
 Heartbeat, do not use the TLV format.

5.3.1. Attribute Value 4-Byte Alignment

 All attribute values are aligned to 4-byte boundaries.  For variable
 length attributes, if necessary, the TLV length MUST be increased to
 the next 4-byte boundary through padding with bytes containing zero
 (0).  If an attribute value is padded, a combination of the tag and
 attribute value itself is used to determine the actual value length
 and number of pad bytes.  There is no explicit count of the number of
 pad bytes provided in the TLV.

Tseng, et al. Standards Track [Page 38] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.4. iSNSP Response Status Codes

 All iSNSP response messages contain a 4-byte Status Code field as the
 first field in the iSNSP PDU PAYLOAD.  If the original iSNSP request
 message was processed normally by the iSNS server, or by the iSNS
 client for ESI and SCN messages, then this field SHALL contain a
 status code of 0 (Successful).  A non-zero status code indicates
 rejection of the entire iSNS client request message.
        Status Code      Status Description
        -----------      -----------------
          0              Successful
          1              Unknown Error
          2              Message Format Error
          3              Invalid Registration
          4              RESERVED
          5              Invalid Query
          6              Source Unknown
          7              Source Absent
          8              Source Unauthorized
          9              No Such Entry
         10              Version Not Supported
         11              Internal Error
         12              Busy
         13              Option Not Understood
         14              Invalid Update
         15              Message (FUNCTION_ID) Not Supported
         16              SCN Event Rejected
         17              SCN Registration Rejected
         18              Attribute Not Implemented
         19              FC_DOMAIN_ID Not Available
         20              FC_DOMAIN_ID Not Allocated
         21              ESI Not Available
         22              Invalid Deregistration
         23              Registration Feature Not Supported
         24 and above    RESERVED

5.5. Authentication for iSNS Multicast and Broadcast Messages

 For iSNS multicast and broadcast messages (see Section 2.9.3), the
 iSNSP provides authentication capability.  The following section
 details the iSNS Authentication Block, which is identical in format
 to the SLP authentication block [RFC2608]. iSNS unicast messages
 SHOULD NOT include the authentication block, but rather should rely
 upon IPSec security mechanisms.

Tseng, et al. Standards Track [Page 39] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 If a message contains an authentication block, then the
 "Authentication block present" bit in the iSNSP PDU header FLAGS
 field SHALL be enabled.
 If a PKI is available with an [X.509] Certificate Authority (CA),
 then public key authentication of the iSNS server is possible.  The
 authentication block leverages the DSA with SHA-1 algorithm, which
 can easily integrate into a public key infrastructure.
 The authentication block contains a digital signature for the
 multicast message.  The digital signature is calculated on a per-PDU
 basis.  The authentication block contains the following information:
 1.  A time stamp, to prevent replay attacks.
 2.  A structured authenticator containing a signature calculated over
     the time stamp and the message being secured.
 3.  An indicator of the cryptographic algorithm that was used to
     calculate the signature.
 4.  An indicator of the keying material and algorithm parameters,
     used to calculate the signature.
 The authentication block is described in the following figure:
    Byte   MSb                              LSb
    Offset 0                                 31
           +----------------------------------+
       0   |    BLOCK STRUCTURE DESCRIPTOR    |     4 Bytes
           +----------------------------------+
       4   |   AUTHENTICATION BLOCK LENGTH    |     4 Bytes
           +----------------------------------+
       8   |           TIMESTAMP              |     8 Bytes
           +----------------------------------+
      16   |       SPI STRING LENGTH          |     4 Bytes
           +----------------------------------+
      20   |           SPI STRING             |     N Bytes
           +----------------------------------+
  20 + N   |     STRUCTURED AUTHENTICATOR     |     M Bytes
           +----------------------------------+
              Total Length = 20 + N + M
 BLOCK STRUCTURE DESCRIPTOR (BSD): Defines the structure and algorithm
            to use for the STRUCTURED AUTHENTICATOR.  BSD values from
            0x00000000 to 0x00007FFF are assigned by IANA, while
            values 0x00008000 to 0x00008FFF are for private use.

Tseng, et al. Standards Track [Page 40] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 AUTHENTICATION BLOCK LENGTH: Defines the length of the authentication
            block, beginning with the BSD field and running through
            the last byte of the STRUCTURED AUTHENTICATOR.
 TIMESTAMP: This is an 8-byte unsigned, fixed-point integer giving the
            number of seconds since 00:00:00 GMT on January 1, 1970.
 SPI STRING LENGTH: The length of the SPI STRING field.
 SPI STRING (Security Parameters Index): Index to the key and
            algorithm used by the message recipient to decode the
            STRUCTURED AUTHENTICATOR field.
 STRUCTURED AUTHENTICATOR: Contains the digital signature.  For the
            default BSD value of 0x0002, this field SHALL contain the
            binary ASN.1 encoding of output values from the DSA with
            SHA-1 signature calculation as specified in Section 2.2.2
            of [RFC3279].

5.6. Registration and Query Messages

 The iSNSP registration and query message PDU Payloads contain a list
 of attributes, and have the following format:
           +----------------------------------------+
           |     Source Attribute (Requests Only)   |
           +----------------------------------------+
           |  Message Key Attribute[1] (if present) |
           +----------------------------------------+
           |  Message Key Attribute[2] (if present) |
           +----------------------------------------+
           |               . . .                    |
           +----------------------------------------+
           |       - Delimiter Attribute -          |
           +----------------------------------------+
           |   Operating Attribute[1] (if present)  |
           +----------------------------------------+
           |   Operating Attribute[2] (if present)  |
           +----------------------------------------+
           |   Operating Attribute[3] (if present)  |
           +----------------------------------------+
           |                 . . .                  |
           +----------------------------------------+
 Each Source, Message Key, Delimiter, and Operating attribute is
 specified in the PDU Payload using the Tag-Length-Value (TLV) data
 format. iSNS Registration and Query messages are sent by iSNS Clients

Tseng, et al. Standards Track [Page 41] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 to the iSNS server IP Address and well-known TCP/UDP Port.  The iSNS
 Responses will be sent to the iSNS Client IP address and TCP/UDP port
 number from the original request message.

5.6.1. Source Attribute

 The Source Attribute is used to identify the Storage Node to the iSNS
 server for queries and other messages that require source
 identification.  The Source Attribute uniquely identifies the source
 of the message.  Valid Source Attribute types are shown below.
        Valid Source Attributes
        -----------------------
         iSCSI Name
         FC Port Name WWPN
 For a query operation, the Source Attribute is used to limit the
 scope of the specified operation to the Discovery Domains of which
 the source is a member.  Special Control Nodes, identified by the
 Source Attribute, may be administratively configured to perform the
 specified operation on all objects in the iSNS database without
 scoping to Discovery Domains.
 For messages that change the contents of the iSNS database, the iSNS
 server MUST verify that the Source Attribute identifies either a
 Control Node or a Storage Node that is a part of the Network Entity
 containing the added, deleted, or modified objects.

5.6.2. Message Key Attributes

 Message Key attributes are used to identify matching objects in the
 iSNS database for iSNS query and registration messages.  If present,
 the Message Key MUST be a Registration or Query Key for an object as
 described in Sections 5.6.5 and 6.1.  A Message Key is not required
 when a query spans the entire set of objects available to the Source
 or a registration is for a new Entity.
 iSCSI Names used in the Message Key MUST be normalized according to
 the stringprep template [STRINGPREP].  Entity Identifiers (EIDs) used
 in the Message Key MUST be normalized according to the nameprep
 template [NAMEPREP].

5.6.3. Delimiter Attribute

 The Delimiter Attribute separates the Message Key attributes from the
 Operating Attributes in a PDU Payload.  The Delimiter Attribute has a
 tag value of 0 and a length value of 0.  The Delimiter Attribute is
 always 8 bytes long (a 4-byte tag field and a 4-byte length field,

Tseng, et al. Standards Track [Page 42] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 all containing zeros).  If a Message Key is not required for a
 message, then the Delimiter Attribute immediately follows the Source
 Attribute.

5.6.4. Operating Attributes

 The Operating Attributes are a list of one or more key and non-key
 attributes related to the actual iSNS registration or query operation
 being performed.
 Operating Attributes include object key attributes and non-key
 attributes.  Object key attributes uniquely identify iSNS objects.
 Key attributes MUST precede the non-key attributes of each object in
 the Operating Attributes.  The tag value distinguishes the attribute
 as an object key attribute (i.e., tag=1, 16&17, 32, 64, and 96) or a
 non-key attribute. iSCSI Names used in the Operating Attributes MUST
 be normalized according to the stringprep template [STRINGPREP].
 Entity Identifiers (EIDs) used in the Operating Attributes MUST be
 normalized according to the nameprep template [NAMEPREP].
 The ordering of Operating Attributes in the message is important for
 determining the relationships among objects and their ownership of
 non-key attributes.  iSNS protocol messages that violate these
 ordering rules SHALL be rejected with the Status Code of 2 (Message
 Format Error).  See the message descriptions for proper operating
 attribute ordering requirements.
 Some objects are keyed by more than one object key attribute value.
 For example, the Portal object is keyed by attribute tags 16 and 17.
 When describing an object keyed by more than one key attribute, every
 object key attribute of that object MUST be listed sequentially by
 tag value in the message before non-key attributes of that object and
 key attributes of the next object.  A group of key attributes of this
 kind is treated as a single logical key attribute when identifying an
 object.
 Non-key attributes that immediately follow key attributes MUST be
 attributes of the object referenced by the key attributes.  All non-
 key attributes of an object MUST be listed before the object key
 attributes introducing the next object.
 Objects MUST be listed in inheritance order, according to their
 containment order.  Storage Node and Portal objects and their
 respective attributes MUST follow the Network Entity object to which
 they have a relationship.  Similarly, FC Device objects MUST follow
 the Storage Node object to which they have a relationship.

Tseng, et al. Standards Track [Page 43] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Vendor-specific objects defined by tag values in the range 1537-2048
 have the same requirements described above.

5.6.4.1. Operating Attributes for Query and Get Next Requests

 In Query and Get Next request messages, TLV attributes with length
 value of 0 are used to indicate which Operating Attributes are to be
 returned in the corresponding response.  Operating Attribute values
 that match the TLV attributes in the original message are returned in
 the response message.

5.6.5. Registration and Query Request Message Types

 The following describes each query and message type.

5.6.5.1. Device Attribute Registration Request (DevAttrReg)

 The DevAttrReg message type is 0x0001.  The DevAttrReg message
 provides the means for iSNS clients to update existing objects or
 register new objects.  The value of the replace bit in the FLAGs
 field determines whether the DevAttrReg message updates or replaces
 an existing registration.
 The Source Attribute identifies the Node initiating the registration
 request.
 The Message Key identifies the object the DevAttrReg message acts
 upon.  It MUST contain the key attribute(s) identifying an object.
 This object MUST contain all attributes and related subordinate
 object attributes that will be included in the Operating Attributes
 of the DevAttrReg PDU Payload.  The key attribute(s) identifying this
 object MUST also be included among the Operating Attributes.
 If the Message Key contains an EID and no pre-existing objects match
 the Message Key, then the DevAttrReg message SHALL create a new
 Entity with the specified EID and any new object(s) specified by the
 Operating Attributes.  The replace bit SHALL be ignored.
 If the Message Key does not contain an EID, and no pre-existing
 objects match the Message Key, then the DevAttrReg message SHALL be
 rejected with a status code of 3 (Invalid Registration).
 If the Message Key is not present, then the DevAttrReg message
 implicitly registers a new Network Entity.  In this case, the replace
 bit SHALL be ignored; a new Network Entity SHALL be created.
 Existing entities, their objects, and their relationships remain
 unchanged.

Tseng, et al. Standards Track [Page 44] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 The replace bit determines the kind of operation conducted on the
 object identified in the DevAttrReg Message Key.  The replace bit
 only applies to the DevAttrReg message; it is ignored for all other
 message types.
 If the replace bit is set, then the objects, attributes, and
 relationships specified in the Operating Attributes SHALL replace the
 object identified by the Message Key.  The object and all of its
 subordinate objects SHALL be deregistered, and the appropriate SCNs
 SHALL be sent by the iSNS server for the deregistered objects.  The
 objects listed in the Operating Attributes are then used to replace
 the just-deregistered objects.  Note that additional SCNs SHALL be
 sent for the newly-registered objects, if appropriate.  Existing
 objects and relationships that are not identified or that are
 subordinate to the object identified by the Message Key MUST NOT be
 affected or changed.
 If the replace bit is not set, then the message updates the
 attributes of the object identified by the Message Key and its
 subordinate objects.  Existing object containment relationships MUST
 NOT be changed.  For existing objects, key attributes MUST NOT be
 modified, but new subordinate objects MAY be added.
 The Operating Attributes represent objects, attributes, and
 relationships that are to be registered.  Multiple related objects
 and attributes MAY be registered in a single DevAttrReg message.  The
 ordering of the objects in this message indicates the structure of,
 and associations among, the objects to be registered.  At least one
 object MUST be listed in the Operating Attributes.  Additional
 objects (if any) MUST be subordinate to the first object listed.  Key
 attributes MUST precede non-key attributes of each object.  A given
 object may only appear a maximum of once in the Operating Attributes
 of a message.  If the Node identified by the Source Attribute is not
 a Control Node, then the objects in the operating attributes MUST be
 members of the same Network Entity as the Source Node.
 For example, to establish relationships between a Network Entity
 object and its Portal and Storage Node objects, the Operating
 Attributes list the key and non-key attributes of the Network Entity
 object, followed by the key and non-key attributes of each Portal and
 Storage Node object to be linked to that Network Entity.  Similarly,
 an FC Device object that follows a Storage Node object is considered
 subordinate to that Storage Node.
 New PG objects are registered when an associated Portal or iSCSI Node
 object is registered.  An explicit PG object registration MAY follow
 a Portal or iSCSI Node object registration in a DevAttrReg message.

Tseng, et al. Standards Track [Page 45] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 When a Portal is registered, the Portal attributes MAY immediately be
 followed by a PGT attribute.  The PGT attribute SHALL be followed by
 the set of PG iSCSI Names representing nodes that will be associated
 to the Portal using the indicated PGT value.  Additional sets of PGTs
 and PG iSCSI Names to be associated to the registered Portal MAY
 follow.  Indicated PGT values are assigned to the PG object
 associated with the newly registered Portal and to the iSCSI Storage
 Node(s) referenced immediately following the PGT attribute in the
 operating attributes.
 When an iSCSI Storage Node is registered, the Storage Node attributes
 MAY immediately be followed by a PGT attribute.  The PGT attribute
 SHALL be followed by the set of PG Portal IP-Address, PG TCP/UDP Port
 pairs representing Portal objects that will be associated with the
 Storage Node using the indicated PGT value.  Additional sets of PGTs
 and PG Portal IP-Address PG TCP/UDP Port pairs to be associated with
 the registered Storage Node MAY follow.  Indicated PGT values are
 assigned to the PG object associated with the newly registered iSCSI
 Storage Node and Portal object(s) referenced immediately following
 the PGT attribute in the operating attributes.
 If the PGT value is not included in the Storage Node or Portal object
 registration, and if a PGT value was not previously registered for
 the relationship, then the PGT for the corresponding PG object SHALL
 be registered with a value of 0x00000001.  If the PGT attribute is
 included in the registration message as a 0-length TLV, then the PGT
 value for the corresponding PG object SHALL be registered as NULL.  A
 0-length TLV for the PGT in an update registration message overwrites
 the previous PGT value with NULL, indicating that there is no
 relationship between the Storage Node and Portal.
 A maximum of one Network Entity object can be created or updated with
 a single DevAttrReg message.  Consequently, the Operating Attributes
 MUST NOT contain more than one Network Entity object.  There is no
 limit to the number of Portal, Storage Node, and FC Device objects
 that can listed in the Operating Attributes, provided they are all
 subordinate to the listed Network Entity object.
 If the Message Key and Operating Attributes do not contain an EID
 attribute, or if the EID attribute has a length of 0, then a new
 Network Entity object SHALL be created and the iSNS server SHALL
 supply a unique EID value for it.  The assigned EID value SHALL be
 included in the DevAttrReg Response message.  If the Message Key and
 Operating Attributes contain an EID that does not match the EID of an
 existing Network Entity in the iSNS database, then a new Network
 Entity SHALL be created and assigned the value contained in that EID
 attribute.  Finally, if the Message Key and Operating Attributes
 contain an EID that matches the EID of an existing object in the iSNS

Tseng, et al. Standards Track [Page 46] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 database, then the objects, attributes, and relationships specified
 in the Operating Attributes SHALL be appended to the existing Network
 Entity identified by the EID.
 A registration message that creates a new Network Entity object MUST
 contain at least one Portal or one Storage Node.  If the message does
 not, then it SHALL be considered invalid and result in a response
 with Status Code of 3 (Invalid Registration).
 If an iSNS Server does not support a registration feature, such as
 explicit PG object registration, then the server SHALL return a
 Status Code of 23 (Registration Feature Not Supported).
 Note that the iSNS server may modify or reject the registration of
 certain attributes, such as ESI Interval.  In addition, the iSNS
 server may assign values for additional Operating Attributes that are
 not explicitly registered in the original DevAttrReg message, such as
 the EID and WWNN Token.

5.6.5.2. Device Attribute Query Request (DevAttrQry)

 The DevAttrQry message type is 0x0002.  The DevAttrQry message
 provides an iSNS client with the means to query the iSNS server for
 object attributes.
 The Source Attribute identifies the Node initiating the request.  For
 non-Control Nodes initiating the DevAttrQry message, the query is
 scoped to the Discovery Domains of which the initiating Node is a
 member.  The DevAttrQry message SHALL only return information on
 Storage Nodes and their related parent and subordinate objects, where
 the Storage Node has a common Discovery Domain with the Node
 identified in the Source Attribute.
 The Message Key may contain key or non-key attributes or no
 attributes at all.  If multiple attributes are used as the Message
 Key, then they MUST all be from the same object type (e.g., IP
 address and TCP/UDP Port are attributes of the Portal object type).
 A Message Key with non-key attributes may match multiple instances of
 the specific object type.  A Message Key with zero-length TLV(s) is
 scoped to every object of the type indicated by the zero-length
 TLV(s).  An empty Message Key field indicates the query is scoped to
 the entire database accessible by the source Node.
 The DevAttrQry response message returns attributes of objects listed
 in the Operating Attributes that are related to the Message Key of
 the original DevAttrQry message.  The Operating Attributes of the
 DevAttrQry message contain zero-length TLVs that specify the
 attributes that are to be returned in the DevAttrQryRsp message.  A

Tseng, et al. Standards Track [Page 47] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Message Key containing zero-length TLVs indicates that the set of
 attributes specified in the Operating Attributes are to be returned
 for each object matching the type indicated by the Message Key.
 If the Message Key contains non-zero length TLVs, then Operating
 Attributes for the object matching the Message Key SHALL be returned
 in the DevAttrQryRsp message.  Each attribute type (i.e., zero-length
 TLV) in the Operating Attributes indicates an attribute from the
 object matching the Message Key, or from other objects in the same
 Entity having a relationship to the object matching the Message Key,
 is to be returned in the response.  The ordering of the object keys
 and associated attributes returned in the DevAttrQry response message
 SHALL be the same as in the original query message.  If no objects
 match the Message Key, then the DevAttrQryRsp message SHALL NOT
 return any operating attributes.  Such a message and its
 corresponding response SHALL NOT be considered an error.
 The Portal Group object determines whether a relationship exists
 between a given Storage Node and Portal object.  If the PGT of the
 Portal Group is not NULL, then a relationship exists between the
 indicated Storage Node and Portal; if the PGT is NULL, then no
 relationship exists.  Therefore, the value (NULL or not NULL) of the
 PGT attribute of each Portal Group object determines the structure
 and ordering of the DevAttrQry response to a query for Storage Nodes
 and Portals.
 For example, an iSNS database contains a Network Entity having two
 Portals and two Nodes.  Each Storage Node has two Portal Groups, one
 with a NULL PGT value for one Portal and another with a non-NULL PGT
 value for the other Portal.  The DevAttrQry message contains a
 Message Key entry matching one of the Nodes, and Operating Attributes
 with zero-length TLVs listing first the Node attributes, Portal
 attributes, and then the PG attributes.  The response message SHALL
 therefore return first the matching Node object, then the requested
 attributes of the one Portal object that can be used to access the
 Storage Node (as indicated by the PGT), and finally the requested
 attributes of the PG object used to access that Storage Node.  The
 order in which each object's attributes are listed is the same as the
 ordering of the object's attributes in the Operating Attributes of
 the original request message.
 If the Message Key Attribute contains zero-length TLV(s), then the
 query returns requested attributes for all objects matching the
 Message Key type (DD restrictions SHALL apply for non-Control Nodes).
 If multiple objects match the Message Key type, then the attributes
 for each object matching the Message Key MUST be listed before the
 attributes for the next matching object are listed in the query

Tseng, et al. Standards Track [Page 48] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 response.  In other words, the process described above must be
 iterated in the message response for each object that matches the
 Message Key type specified by the zero-length TLV(s).
 For example, an iSNS database contains only one Network Entity having
 two Portals and three Nodes.  All PG objects in the Entity have a PGT
 value of 0x00000001.  In the DevAttrQry message, the Message Key
 contains a zero-length TLV specifying a Node type, and Operating
 Attributes listing first the Node attributes, and then the Portal
 attributes.  The response message will return, in the following
 order, the attributes for the first, next, and last Node objects,
 each followed by attributes for both Portals.  If that same
 DevAttrQry message had instead contained a zero-length TLV specifying
 the Network Entity type, then the response message would have
 returned attributes for all three Node objects, followed by
 attributes for the two Portals.
 If there is no Message Key Attribute, then the query returns all
 attributes in the iSNS database (once again, DD restrictions SHALL
 apply for non-Control Nodes).  All attributes matching the type
 specified by each zero-length TLV in the Operating Attributes SHALL
 be listed.  All attributes of each type SHALL be listed before the
 attributes matching the next zero-length TLV are listed.
 For example, an iSNS database contains two Entities, each having two
 Nodes and two Portals.  The DevAttrQry message contains no Message
 Key attribute, and Operating Attributes list first the Portal
 attributes, and then the Node attributes.  The Operating Attributes
 of the response message will return attributes from each of the four
 Portals, followed by attributes from each of the four nodes.
 If a DevAttrQry message requests an attribute for which the iSNS
 server has no value, then the server SHALL NOT return the requested
 attribute in the query response.  Such query and response messages
 SHALL NOT be considered errors.
 Registration and query messages for iSNS server-specific attributes
 (i.e., tags in the range 132 to 384) SHALL be formatted using the
 identifying key attribute of the Storage Node originating the query
 (i.e., iSCSI Name or FC Port Name WWPN) for both the Source Attribute
 and Message Key attribute.  Operating Attributes SHALL include the
 TLV of the server-specific attribute being requested.
 DD membership can be discovered through the DevAttrQry message by
 including either DD member attributes (i.e., DD Member iSCSI Index,
 DD Member iSCSI Node, DD Member iFCP Node, DD Member Portal Index, DD
 Member Portal IP Addr, and DD Member Portal TCP/UDP) or the object
 key of the Storage Node or Portal (i.e., iSCSI Name, iSCSI Index,

Tseng, et al. Standards Track [Page 49] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Portal IP Addr, Portal TCP/UDP Port, and Portal Index) in the
 Operating Attributes.  Using DD member attributes SHALL return both
 registered and unregistered member Storage Nodes and/or Portals of a
 DD.  DevAttrQry messages using the Storage Node and/or Portal object
 key SHALL return only member Storage Nodes or Portals that are
 currently registered in the iSNS database.
 The DevAttrQry message SHALL support the following minimum set of
 Message Key Attributes:
        Valid Message Key Attributes for Queries
        ----------------------------------------
         Entity Identifier
         Entity Protocol
         Portal IP-Address & Portal TCP/UDP Port
         Portal Index
         iSCSI Node Type
         iSCSI Name
         iSCSI Index
         PG Index
         FC Port Name WWPN
         FC Port Type
         FC-4 Type
         Discovery Domain ID
         Discovery Domain Set ID
         Source Attribute (for server-specific attributes)
         Switch Name (FC Device WWNN--for Virtual_Fabric_ID queries)

5.6.5.3. Device Get Next Request (DevGetNext)

 The DevGetNext message type is 0x0003.  This message provides the
 iSNS client with the means to retrieve each and every instance of an
 object type exactly once.
 The Source Attribute identifies the Node initiating the DevGetNext
 request, and is used to scope the retrieval process to the Discovery
 Domains of which the initiating Node is a member.
 The Message Key Attribute may be an Entity Identifier (EID), iSCSI
 Name, iSCSI Index, Portal IP Address and TCP/UDP Port, Portal Index,
 PG Index, FC Node Name WWNN, or FC Port Name WWPN.  If the TLV length
 of the Message Key Attribute(s) is zero, then the first object entry
 in the iSNS database matching the Message Key type SHALL be returned
 in the Message Key of the corresponding DevGetNextRsp message.  If
 non-zero-length TLV attributes are contained in the Message Key, then
 the DevGetNext response message SHALL return the next object stored
 after the object identified by the Message Key in the original
 DevGetNext request message.

Tseng, et al. Standards Track [Page 50] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 If the Message Key provided matches the last object instance in the
 iSNS database, then the Status Code of 9 (No Such Entry) SHALL be
 returned in the response.
 The Operating Attributes can be used to specify the scope of the
 DevGetNext request, and to specify the attributes of the next object,
 which are to be returned in the DevGetNext response message.  All
 Operating Attributes MUST be attributes of the object type identified
 by the Message Key.  For example, if the Message Key is an Entity_ID
 attribute, then the Operating Attributes MUST NOT contain attributes
 of Portals.
 Non-zero-length TLV attributes in the Operating Attributes are used
 to scope the DevGetNext message.  Only the next object with attribute
 values that match the non-zero-length TLV attributes SHALL be
 returned in the DevGetNext response message.
 Zero-length TLV attributes MUST be listed after non-zero-length
 attributes in the Operating Attributes of the DevGetNext request
 message.  Zero-length TLV attributes specify the attributes of the
 next object which are to be returned in the DevGetNext response
 message.
 Note that there are no specific requirements concerning the order in
 which object entries are retrieved from the iSNS database; the
 retrieval order of object entries using the DevGetNext message is
 implementation specific.
 The iSNS client is responsible for ensuring that information acquired
 through use of the DevGetNext message is accurate and up-to-date.
 There is no assurance that the iSNS database will not change between
 successive DevGetNext request messages.  If the Message Key provided
 does not match an existing database entry, then attributes for the
 next object key following the provided Message Key SHALL be returned.
 For example, an object entry may have been deleted between successive
 DevGetNext messages.  This may result in a DevGetNext request in
 which the Message Key does not match an existing object entry.  In
 this case, attributes for the next object stored in the iSNS database
 are returned.

5.6.5.4. Device Deregister Request (DevDereg)

 The DevDereg message type is 0x0004.  This message is used to remove
 object entries from the iSNS database.  One or more objects may be
 removed through a single DevDereg message.  Note that deregistered
 Storage Node objects will retain membership in their Discovery
 Domain(s) until explicit deregistration of the membership(s) or
 Discovery Domain(s).

Tseng, et al. Standards Track [Page 51] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Upon receiving the DevDereg, the iSNS server removes all objects
 identified by the Operating Attribute(s), and all subordinate objects
 that are solely dependent on those identified objects.  For example,
 removal of a Network Entity also results in removal of all associated
 Portal, Portal Group, Storage Node, and FC Device objects associated
 with that Network Entity.  FC Device objects SHALL not be
 deregistered in this manner unless all Storage Nodes associated with
 them have been deregistered.
 The DevDereg request PDU Payload contains a Source Attribute and
 Operating Attribute(s); there are no Message Key Attributes.  If the
 Node identified by the Source Attribute is not a Control Node, then
 it MUST be from the same Network Entity as the object(s) identified
 for removal by the Operating Attribute(s).  Valid Operating
 Attributes are shown below:
        Valid Operating Attributes for DevDereg
        ---------------------------------------
         Entity Identifier
         Portal IP-Address & Portal TCP/UDP Port
         Portal Index
         iSCSI Name
         iSCSI Index
         FC Port Name WWPN
         FC Node Name WWNN
 The removal of the object may result in SCN messages to the
 appropriate iSNS clients.
 Attempted deregistration of non-existing entries SHALL not be
 considered an error.
 If all Nodes and Portals associated with a Network Entity are
 deregistered, then the Network Entity SHALL also be removed.
 If both the Portal and iSCSI Storage Node objects associated with a
 Portal Group object are removed, then that Portal Group object SHALL
 also be removed.  The Portal Group object SHALL remain registered as
 long as either of its associated Portal or iSCSI Storage Node objects
 remain registered.  If a deleted Storage Node or Portal object is
 subsequently re-registered, then a relationship between the re-
 registered object and an existing Portal or Storage Node object
 registration, indicated by the PG object, SHALL be restored.

Tseng, et al. Standards Track [Page 52] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.6.5.5. SCN Register Request (SCNReg)

 The SCNReg message type is 0x0005.  The State Change Notification
 Registration Request (SCNReg) message allows an iSNS client to
 register a Storage Node to receive State Change Notification (SCN)
 messages.
 The SCN notifies the Storage Node of changes to any Storage Nodes
 within any DD of which it is a member.  If the Storage Node is a
 Control Node, it SHALL receive SCN notifications for changes in the
 entire network.  Note that whereas SCNReg sets the SCN Bitmap field,
 the DevAttrReg message registers the UDP or TCP Port used by each
 Portal to receive SCN messages.  If no SCN Port fields of any Portals
 of the Storage Node are registered to receive SCN messages, then the
 SCNReg message SHALL be rejected with Status Code 17 (SCN
 Registration Rejected).
 The SCNReg request PDU Payload contains a Source Attribute, a Message
 Key Attribute, and an Operating Attribute.  Valid Message Key
 Attributes for a SCNReg are shown below:
        Valid Message Key Attributes for SCNReg
        ---------------------------------------
         iSCSI Name
         FC Port Name WWPN
 The node with the iSCSI Name or FC Port Name WWPN attribute that
 matches the Message Key in the SCNReg message is registered to
 receive SCNs using the specified SCN bitmap.  A maximum of one Node
 SHALL be registered for each SCNReg message.
 The SCN Bitmap is the only operating attribute of this message, and
 it always overwrites the previous contents of this field in the iSNS
 database.  The bitmap indicates the SCN event types for which the
 Node is registering.
 Note that the settings of this bitmap determine whether the SCN
 registration is for regular SCNs or management SCNs.  Control Nodes
 MAY conduct registrations for management SCNs; iSNS clients that are
 not supporting Control Nodes MUST NOT conduct registrations for
 management SCNs.  Control Nodes that register for management SCNs
 receive a copy of every SCN message generated by the iSNS server.  It
 is recommended that management registrations be used only when needed
 in order to conserve iSNS server resources.  In addition, a Control
 Node that conducts such registrations should be prepared to receive
 the anticipated volume of SCN message traffic.

Tseng, et al. Standards Track [Page 53] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.6.5.6. SCN Deregister Request (SCNDereg)

 The SCNDereg message type is 0x0006.  The SCNDereg message allows an
 iSNS client to stop receiving State Change Notification (SCN)
 messages.
 The SCNDereg request message PDU Payload contains a Source Attribute
 and Message Key Attribute(s).  Valid Message Key Attributes for a
 SCNDereg are shown below:
        Valid Message Key Attributes for SCNDereg
        -----------------------------------------
         iSCSI Name
         FC Port Name WWPN
 The node with an iSCSI Name or FC Port Name WWPN attribute that
 matches the Message Key Attributes in the SCNDereg message is
 deregistered for SCNs.  The SCN bitmap field of such Nodes are
 cleared.  A maximum of one Node SHALL be deregistered for each
 SCNDereg message.
 There are no Operating Attributes in the SCNDereg message.

5.6.5.7. SCN Event (SCNEvent)

 The SCNEvent message type is 0x0007.  The SCNEvent is a message sent
 by an iSNS client to request generation of a State Change
 Notification (SCN) message by the iSNS server.  The SCN, sent by the
 iSNS server, then notifies iFCP, iSCSI, and Control Nodes within the
 affected DD of the change indicated in the SCNEvent.
 Most SCNs are automatically generated by the iSNS server when Nodes
 are registered or deregistered from the directory database.  SCNs are
 also generated when a network management application or Control Node
 makes changes to the DD membership in the iSNS server.  However, an
 iSNS client can trigger an SCN by using SCNEvent.
 The SCNEvent message PDU Payload contains a Source Attribute, a
 Message Key Attribute, and an Operating Attribute.  Valid Key
 Attributes for a SCNEvent are shown below:
        Valid Message Key Attributes for SCNEvent
        -----------------------------------------
         iSCSI Name
         FC Port Name WWPN

Tseng, et al. Standards Track [Page 54] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 The Operating Attributes section SHALL contain the SCN Event Bitmap
 attribute.  The bitmap indicates the event that caused the SCNEvent
 to be generated.

5.6.5.8. State Change Notification (SCN)

 The SCN message type is 0x0008.  The SCN is a message generated by
 the iSNS server, notifying a registered Storage Node of changes.
 There are two types of SCN registrations: regular registrations and
 management registrations.  Regular SCNs notify iSNS clients of events
 within the discovery domain.  Management SCNs notify Control Nodes
 that register for management SCNs of events occurring anywhere in the
 network.
 If no active TCP connection to the SCN recipient exists, then the SCN
 message SHALL be sent to one Portal of the registered Storage Node
 that has a registered TCP or UDP Port value in the SCN Port field.
 If more than one Portal of the Storage Node has a registered SCN Port
 value, then the SCN SHALL be delivered to any one of the indicated
 Portals, provided that the selected Portal is not the subject of the
 SCN.
 The types of events that can trigger an SCN message, and the amount
 of information contained in the SCN message, depend on the registered
 SCN Event Bitmap for the Storage Node.  The iSCSI Node SCN Bitmap is
 described in Section 6.4.4.  The iFCP SCN Bitmap is described in
 Section 6.6.12.

Tseng, et al. Standards Track [Page 55] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 The format of the SCN PDU Payload is shown below:
        +----------------------------------------+
        |         Destination Attribute          |
        +----------------------------------------+
        |               Timestamp                |
        +----------------------------------------+
        |          Source SCN Bitmap 1           |
        +----------------------------------------+
        |          Source Attribute [1]          |
        +----------------------------------------+
        |    Source Attribute [2](if present)    |
        +----------------------------------------+
        |    Source Attribute [3](if present)    |
        +----------------------------------------+
        |    Source Attribute [n](if present)    |
        +----------------------------------------+
        |    Source SCN Bitmap 2 (if present)    |
        +----------------------------------------+
        |                 . . .                  |
        +----------------------------------------+
 All PDU Payload attributes are in TLV format.
 The Destination Attribute is the Node identifier that is receiving
 the SCN.  The Destination Attribute can be an iSCSI Name or FC Port
 Name.
 The Timestamp field, using the Timestamp TLV format, described in
 Section 6.2.4, indicates the time the SCN was generated.
 The Source SCN Bitmap field indicates the type of SCN notification
 (i.e., regular or management SCN), and the type of event that caused
 the SCN to be generated; it does not necessarily correlate with the
 original SCN bitmap registered in the iSNS server.
 Following the timestamp, the SCN message SHALL list the SCN bitmap,
 followed by the key attribute (i.e., iSCSI Name or FC Port Name) of
 the Storage Node affected by the SCN event.  If the SCN is a
 Management SCN, then the SCN message SHALL also list the DD_ID and/or
 DDS_ID of the Discovery Domains and Discovery Domain Sets (if any)
 that caused the change in state for that Storage Node.  These
 additional attributes (i.e., DD_ID and/or DDS_ID) shall immediately
 follow the iSCSI Name or FC Port Name and precede the next SCN bitmap
 for the next notification message (if any).  The SCN bitmap is used
 as a delineator for SCN messages providing multiple state change
 notifications.

Tseng, et al. Standards Track [Page 56] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 For example, a regular SCN for notifying an iSNS client of a new
 Portal available for a particular iSCSI target would contain the SCN
 bitmap followed by the iSCSI Name of the target device as the source
 attribute.  If the SCN were a management SCN, then the iSCSI Name
 would be followed by the DD_ID(s) of the shared Discovery Domains
 that allow the destination Storage Node to have visibility to the
 affected Storage Node.  If a Discovery Domain Set (DDS) was enabled
 in order to provide this visibility, then the appropriate DDS_ID
 would be included as well.
 A management SCN is also generated to notify a Control Node of the
 creation, deletion, or modification of a Discovery Domain or
 Discovery Domain Set.  In this case, the DD_ID and/or DDS_ID of the
 affected Discovery Domain and/or Discovery Domain Set would follow
 the SCN bitmap.
 For example, a management SCN to notify a Control Node of a new DD
 within a Discovery Domain Set would contain both the DD_ID and the
 DDS_ID of the affected Discovery Domain and Discovery Domain Set
 among the Source Attributes.
 See Sections 6.4.4 and 6.6.12 for additional information on the SCN
 Bitmap.

5.6.5.9. DD Register (DDReg)

 The DDReg message type is 0x0009.  This message is used to create a
 new Discovery Domain (DD), to update an existing DD Symbolic Name
 and/or DD Features attribute, and to add DD members.
 DDs are uniquely defined using DD_IDs.  DD registration attributes
 are described in Section 6.11.
 The DDReg message PDU Payload contains the Source Attribute and
 optional Message Key and Operating Attributes.
 The Message Key, if used, contains the DD_ID of the Discovery Domain
 to be registered.  If the Message Key contains a DD_ID of an existing
 DD entry in the iSNS database, then the DDReg message SHALL attempt
 to update the existing entry.  If the DD_ID in the Message Key (if
 used) does not match an existing DD entry, then the iSNS server SHALL
 reject the DDReg message with a status code of 3 (Invalid
 Registration).  If the DD_ID is included in both the Message Key and
 Operating Attributes, then the DD_ID value in the Message Key MUST be
 the same as the DD_ID value in the Operating Attributes.

Tseng, et al. Standards Track [Page 57] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 A DDReg message with no Message Key SHALL result in the attempted
 creation of a new Discovery Domain (DD).  If the DD_ID attribute
 (with non-zero length) is included among the Operating Attributes in
 the DDReg message, then the new Discovery Domain SHALL be assigned
 the value contained in that DD_ID attribute.  Otherwise, if the DD_ID
 attribute is not contained among the Operating Attributes of the
 DDReg message, or if the DD_ID is an operating attribute with a TLV
 length of 0, then the iSNS server SHALL assign a DD_ID value.  The
 assigned DD_ID value is then returned in the DDReg Response message.
 The Operating Attributes can also contain the DD Member iSCSI Node
 Index, DD Member iSCSI Name, DD Member FC Port Name, DD Member Portal
 IP Address, DD Member Portal TCP/UDP Port Number, or DD Member Portal
 Index of members to be added to the DD.  It may also contain the
 DD_Symbolic_Name and/or DD_Features of the DD.
 This message SHALL add any DD members listed as Operating Attributes
 to the Discovery Domain specified by the DD_ID.  If the DD_Features
 attribute is an Operating Attribute, then it SHALL be stored in the
 iSNS server as the feature list for the specified DD.  If the
 DD_Symbolic_Name is an operating attribute and its value is unique
 (i.e., it does not match the registered DD_Symbolic_Name for another
 DD), then the value SHALL be stored in the iSNS database as the
 DD_Symbolic_Name for the specified Discovery Domain.  If the value
 for the DD_Symbolic_Name is not unique, then the iSNS server SHALL
 reject the attempted DD registration with a status code of 3 (Invalid
 Registration).
 When creating a new DD, if the DD_Symbolic_Name is not included in
 the Operating Attributes, or if it is included with a zero-length
 TLV, then the iSNS server SHALL provide a unique DD_Symbolic_Name
 value for the created DD.  The assigned DD_Symbolic_Name value SHALL
 be returned in the DDRegRsp message.
 When creating a new DD, if the DD_Features attribute is not included
 in the Operating Attributes, then the iSNS server SHALL assign the
 default value.  The default value for DD_Features is 0.
 DD Member iSCSI Name, DD Member iFCP Node, DD Member Portal IP
 Address, and DD Member TCP/UDP Port Number attributes included in the
 Operating Attributes need not match currently existing iSNS database
 entries.  This allows, for example, a Storage Node to be added to a
 DD even if the Storage Node is not currently registered in the iSNS
 database.  A Storage Node or Portal can thereby be added to a DD at
 the time of the DDs creation, even if the Storage Node or Portal is
 not currently active in the storage network.

Tseng, et al. Standards Track [Page 58] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 If the Operating Attributes contain a DD Member iSCSI Name value for
 a Storage Node that is currently not registered in the iSNS database,
 then the iSNS server MUST allocate an unused iSCSI Node Index for
 that Storage Node.  The assigned iSCSI Node Index SHALL be returned
 in the DDRegRsp message as the DD Member iSCSI Node Index.  The
 allocated iSCSI Node Index value SHALL be assigned to the Storage
 Node if and when it registers in the iSNS database.
 If the Operating Attributes contain a DD Member Portal IP Addr and DD
 Member Portal TCP/UDP value for a Portal that is not currently
 registered in the iSNS database, then the iSNS server MUST allocate
 an unused Portal Index value for that Portal.  The assigned Portal
 Index value SHALL be returned in the DDRegRsp message as the DD
 Member Portal Index.  The allocated Portal Index value SHALL be
 assigned to the Portal if and when it registers in the iSNS database.
 DD Member iSCSI Node Index and DD Member Portal Index attributes that
 are provided in the Operating Attributes MUST match a corresponding
 iSCSI Node Index or Portal Index of an existing Storage Node or
 Portal entry in the iSNS database.  Furthermore, the DD Member iSCSI
 Node Index and DD Member Portal Index SHALL NOT be used to add
 Storage Nodes or Portals to a DD unless those Storage Nodes or
 Portals are actively registered in the iSNS database.

5.6.5.10. DD Deregister (DDDereg)

 The DDDereg message type is 0x000A.  This message allows an iSNS
 client to deregister an existing Discovery Domain (DD) and to remove
 members from an existing DD.
 DDs are uniquely identified using DD_IDs.  DD registration attributes
 are described in Section 6.11.
 The DDDereg message PDU Payload contains a Source Attribute, Message
 Key Attribute, and optional Operating Attributes.
 The Message Key Attribute for a DDDereg message is the DD ID for the
 Discovery Domain being removed or having members removed.  If the DD
 ID matches an existing DD and there are no Operating Attributes, then
 the DD SHALL be removed and a success Status Code returned.  Any
 existing members of that DD SHALL remain in the iSNS database without
 membership in the just-removed DD.
 If the DD ID matches an existing DD and there are Operating
 Attributes matching DD members, then the DD members identified by the
 Operating Attributes SHALL be removed from the DD and a successful
 Status Code returned.

Tseng, et al. Standards Track [Page 59] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 If a DD Member iSCSI Name identified in the Operating Attributes
 contains an iSCSI Name for a Storage Node that is not currently
 registered in the iSNS database or contained in another DD, then the
 association between that Storage Node and its pre-assigned iSCSI Node
 Index SHALL be removed.  The pre-assigned iSCSI Node Index value no
 longer has an association to a specific iSCSI Name and can now be
 re-assigned.
 If a DD Member Portal IP Address and DD Member TCP/UDP Port
 identified in the Operating Attributes reference a Portal that is not
 currently registered in the iSNS database or contained in another DD,
 then the association between that Portal and its pre-assigned Portal
 Index SHALL be removed.  The pre-assigned Portal Index value can now
 be reassigned.
 The attempted deregistration of non-existent DD entries SHALL not be
 considered an error.

5.6.5.11. DDS Register (DDSReg)

 The DDSReg message type is 0x000B.  This message allows an iSNS
 client to create a new Discovery Domain Set (DDS), to update an
 existing DDS Symbolic Name and/or DDS Status, or to add DDS members.
 DDSs are uniquely defined using DDS_IDs.  DDS registration attributes
 are described in Section 6.11.1.
 The DDSReg message PDU Payload contains the Source Attribute and,
 optionally, Message Key and Operating Attributes.
 The Message Key, if used, contains the DDS_ID of the Discover Domain
 Set to be registered or modified.  If the Message Key contains a
 DDS_ID of an existing DDS entry in the iSNS database, then the DDSReg
 message SHALL attempt to update the existing entry.  If the DDS_ID in
 the Message Key (if used) does not match an existing DDS entry, then
 the iSNS server SHALL reject the DDSReg message with a status code of
 3 (Invalid Registration).  If the DDS_ID is included in both the
 Message Key and Operating Attributes, then the DDS_ID value in the
 Message Key MUST be the same as the DDS_ID value in the Operating
 Attributes.
 A DDSReg message with no Message Key SHALL result in the attempted
 creation of a new Discovery Domain Set (DDS).  If the DDS_ID
 attribute (with non-zero length) is included among the Operating
 Attributes in the DDSReg message, then the new Discovery Domain Set
 SHALL be assigned the value contained in that DDS_ID attribute.
 Otherwise, if the DDS_ID attribute is not contained among the
 Operating Attributes of the DDSReg message, or if the DDS_ID is an

Tseng, et al. Standards Track [Page 60] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 operating attribute with a TLV length of 0, then the iSNS server
 SHALL assign a DDS_ID value.  The assigned DDS_ID value is then
 returned in the DDSReg Response message.  The Operating Attributes
 can also contain the DDS_Symbolic_Name, the DDS Status, and the
 DD_IDs of Discovery Domains to be added to the DDS.
 When creating a new DDS, if the DDS Symbolic Name is included in the
 Operating Attributes and its value is unique (i.e., it does not match
 the registered DDS Symbolic Name for another DDS), then the value
 SHALL be stored in the iSNS database as the DDS Symbolic Name for
 that DDS.  If the value for the DDS Symbolic Name is not unique, then
 the iSNS server SHALL reject the attempted DDS registration with a
 status code of 3 (Invalid Registration).
 When creating a new DDS, if the DDS Symbolic Name is not included in
 the Operating Attributes, or if it is included with a zero-length
 TLV, then the iSNS server SHALL provide a unique DDS Symbolic Name
 value for the created DDS.  The assigned DDS Symbolic Name value
 SHALL be returned in the DDSRegRsp message.
 This message SHALL add any DD_IDs listed as Operating Attributes to
 the Discovery Domain Set specified by the DDS_ID Message Key
 Attribute.  In addition, if the DDS_Symbolic_Name is an operating
 attribute and the value is unique, then it SHALL be stored in the
 iSNS database as the DDS_Symbolic_Name for the specified Discovery
 Domain Set.
 If a DD_ID listed in the Operating Attributes does not match an
 existing DD, then a new DD using the DD_ID SHALL be created.  In this
 case for the new DD, the iSNS server SHALL assign a unique value for
 the DD Symbolic Name and SHALL set the DD Features attribute to the
 default value of 0.  These assigned values SHALL be returned in the
 DDSRegRsp message.

5.6.5.12. DDS Deregister (DDSDereg)

 The DDSDereg message type is 0x000C.  This message allows an iSNS
 client to deregister an existing Discovery Domain Set (DDS) or to
 remove some DDs from an existing DDS.
 The DDSDereg message PDU Payload contains a Source Attribute, a
 Message Key Attribute, and optional Operating Attributes.
 The Message Key Attribute for a DDSDereg message is the DDS ID for
 the DDS being removed or having members removed.  If the DDS ID
 matches an existing DDS and there are no Operating Attributes, then

Tseng, et al. Standards Track [Page 61] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 the DDS SHALL be removed and a success Status Code returned.  Any
 existing members of that DDS SHALL remain in the iSNS database
 without membership in the just-removed DDS.
 If the DDS ID matches an existing DDS, and there are Operating
 Attributes matching DDS members, then the DDS members SHALL be
 removed from the DDS and a success Status Code returned.
 The attempted deregistration of non-existent DDS entries SHALL not be
 considered an error.

5.6.5.13. Entity Status Inquiry (ESI)

 The ESI message type is 0x000D.  This message is sent by the iSNS
 server, and is used to verify that an iSNS client Portal is reachable
 and available.  The ESI message is sent to the ESI UDP port provided
 during registration, or to the TCP connection used for ESI
 registration, depending on which communication type that is being
 used.
 The ESI message PDU Payload contains the following attributes in TLV
 format and in the order listed: the current iSNS timestamp, the EID,
 the Portal IP Address, and the Portal TCP/UDP Port.  The format of
 this message is shown below:
        +----------------------------------------+
        |               Timestamp                |
        +----------------------------------------+
        |               Entity_ID                |
        +----------------------------------------+
        |           Portal IP Address            |
        +----------------------------------------+
        |          Portal TCP/UDP Port           |
        +----------------------------------------+
 The ESI response message PDU Payload contains a status code, followed
 by the Attributes from the original ESI message.
 If the Portal fails to respond to an administratively-determined
 number of consecutive ESI messages, then the iSNS server SHALL remove
 that Portal from the iSNS database.  If there are no other remaining
 ESI-monitored Portals for the associated Network Entity, then the
 Network Entity SHALL also be removed.  The appropriate State Change
 Notifications, if any, SHALL be triggered.

Tseng, et al. Standards Track [Page 62] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.6.5.14. Name Service Heartbeat (Heartbeat)

 This message, if used, is only sent by the active iSNS server.  It
 allows iSNS clients and backup servers listening to a broadcast or
 multicast address to discover the IP address of the primary and
 backup iSNS servers.  It also allows concerned parties to monitor the
 health and status of the primary iSNS server.
 This message is NOT in TLV format.  There is no response message to
 the Name Service Heartbeat.
        MSb                                            LSb
        0                                               31
        +------------------------------------------------+
        |            Active Server IP-Address            | 16 Bytes
        +------------------------------------------------+
        |     iSNS TCP Port     |      iSNS UDP Port     | 4 Bytes
        +------------------------------------------------+
        |                   Interval                     | 4 Bytes
        +------------------------------------------------+
        |                    Counter                     | 4 Bytes
        +------------------------------------------------+
        |      RESERVED         |    Backup Servers      | 4 Bytes
        +------------------------------------------------+
        |    Primary Backup Server IP Address(if any)    | 16 Bytes
        +------------------------------------------------+
        |Backup TCP Port(if any)|Backup UDP Port(if any) | 4 Bytes
        +------------------------------------------------+
        |      2nd Backup Server IP Address(if any)      | 16 Bytes
        +------------------------------------------------+
        |Backup TCP Port(if any)|Backup UDP Port(if any) | 4 Bytes
        +------------------------------------------------+
        |                     . . .                      |
        +------------------------------------------------+
        |                VENDOR SPECIFIC                 |
        +------------------------------------------------+
 The heartbeat PDU Payload contains the following:
 Active Server IP Address: the IP Address of the active iSNS server in
                  IPv6 format.  When this field contains an IPv4
                  value, it is stored as an IPv4-mapped IPv6 address.
                  That is, the most significant 10 bytes are set to
                  0x00, with the next two bytes set to 0xFFFF
                  [RFC2373].  When this field contains an IPv6 value,
                  the entire 16-byte field is used.
 Active TCP Port: the TCP Port of the server currently in use.

Tseng, et al. Standards Track [Page 63] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Active UDP Port: the UDP Port of the server currently in use,
                  otherwise 0.
 Interval:        the interval, in seconds, of the heartbeat.
 Counter:         a count that begins at 0 when this server becomes
                  active.  The count increments by one for each
                  heartbeat sent since this server became active.
 Backup Servers:  the number of iSNS backup servers.  The IP address,
                  TCP Port, and UDP Port of each iSNS backup server
                  follow this field.  Note that if backup servers are
                  used, then the active iSNS server SHOULD be among
                  the list of backup servers.
 The content of the remainder of this message after the list of backup
 servers is vendor-specific.  Vendors may use additional fields to
 coordinate between multiple iSNS servers, and/or to identify vendor-
 specific features.

5.6.5.15. Request FC_DOMAIN_ID (RqstDomId)

 The RqstDomId message type is 0x0011.  This message is used for iFCP
 Transparent Mode to allocate non-overlapping FC_DOMAIN_ID values
 between 1 and 239.  The iSNS server becomes the address assignment
 authority for the entire iFCP fabric.  To obtain multiple
 FC_DOMAIN_ID values, this request must be repeated to the iSNS server
 multiple times.  iSNS clients that acquire FC_DOMAIN_ID values from
 an iSNS server MUST register for ESI monitoring from that iSNS
 server.
 The RqstDomId PDU Payload contains three TLV attributes in the
 following order: the requesting Switch Name (WWN) as the Source
 Attribute, the Virtual_Fabric_ID as the Message Key Attribute, and
 Preferred ID as the operating attribute.  The Virtual_Fabric_ID is a
 string identifying the domain space for which the iSNS server SHALL
 allocate non-overlapping integer FC_DOMAIN_ID values between 1 and
 239.  The Preferred_ID is the nominal FC_DOMAIN_ID value requested by
 the iSNS client.  If the Preferred_ID value is available and has not
 already been allocated for the Virtual_Fabric_ID specified in the
 message, the iSNS server SHALL return the requested Preferred_ID
 value as the Assigned_ID to the requesting client.
 The RqstDomId response contains a Status Code, and the TLV attribute
 Assigned ID, which contains the integer value in the space requested.
 If no further unallocated values are available from this space, the
 iSNS server SHALL respond with the Status Code 18 "FC_DOMAIN_ID Not
 Available".

Tseng, et al. Standards Track [Page 64] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Once a FC_DOMAIN_ID value has been allocated to an iSNS client by the
 iSNS server for a given Virtual_Fabric_ID, that FC_DOMAIN_ID value
 SHALL NOT be reused until it has been deallocated, or until ESI
 monitoring detects that the iSNS client no longer exists on the
 network and objects for that client are removed from the iSNS
 database.
 The iSNS server and client SHALL use TCP to transmit and receive
 RqstDomId, RqstDomIdRsp, RlseDomId, and RlseDomIdRsp messages.

5.6.5.16. Release FC_DOMAIN_ID (RlseDomId)

 The RlseDomId message type is 0x0012.  This message may be used by
 iFCP Transparent Mode to release integer identifier values used to
 assign 3-byte Fibre Channel PORT_ID values.
 The RlseDomId message contains three TLV attributes in the following
 order: the requesting EID as the Source Attribute, the
 Virtual_Fabric_ID as the Message Key Attribute, and Assigned_ID as
 the operating attribute.  Upon receiving the RlseDomId message, the
 iSNS server SHALL deallocate the FC_DOMAIN_ID value contained in the
 Assigned_ID attribute for the Virtual_Fabric_ID attribute specified.
 Upon deallocation, that FC_DOMAIN_ID value can then be requested by
 and assigned to a different iSNS client.
 The iSNS server and client SHALL use TCP to transmit and receive
 RqstDomId, RqstDomIdRsp, RlseDomId, and RlseDomIdRsp messages.

5.6.5.17. Get FC_DOMAIN_IDs (GetDomId)

 The GetDomId message type is 0x0013.  This message is used to learn
 the currently-allocated FC_DOMAIN_ID values for a given
 Virtual_Fabric_ID.
 The GetDomId message PDU Payload contains a Source Attribute and
 Message Key Attribute.
 The Message Key Attribute for the GetDomId message is the
 Virtual_Fabric_ID.  The response to this message returns all the
 FC_DOMAIN_ID values that have been allocated for the
 Virtual_Fabric_ID specified.

Tseng, et al. Standards Track [Page 65] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.7. Messages

 The iSNSP response message PDU Payloads contain a Status Code,
 followed by a list of attributes, and have the following format:
        MSb                                    LSb
        0                                       31
        +----------------------------------------+
        |          4-byte STATUS CODE            |
        +----------------------------------------+
        |  Message Key Attribute[1] (if present) |
        +----------------------------------------+
        |  Message Key Attribute[2] (if present) |
        +----------------------------------------+
        |                 . . .                  |
        +----------------------------------------+
        |  - Delimiter Attribute - (if present)  |
        +----------------------------------------+
        |   Operating Attribute[1] (if present)  |
        +----------------------------------------+
        |   Operating Attribute[2] (if present)  |
        +----------------------------------------+
        |   Operating Attribute[3] (if present)  |
        +----------------------------------------+
        |                 . . .                  |
        +----------------------------------------+
 The iSNSP Response messages SHALL be sent to the iSNS Client IP
 Address and the originating TCP/UDP Port that was used for the
 associated registration and query message.

5.7.1. Status Code

 The first field in an iSNSP response message PDU Payload is the
 Status Code for the operation that was performed.  The Status Code
 encoding is defined in Section 5.4.

5.7.2. Message Key Attributes in Response

 Depending on the specific iSNSP request, the response message MAY
 contain Message Key Attributes.  Message Key Attributes generally
 contain the interesting key attributes that are affected by the
 operation specified in the original iSNS registration or query
 message.

Tseng, et al. Standards Track [Page 66] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.7.3. Delimiter Attribute in Response

 The Delimiter Attribute separates the key and Operating Attributes in
 a response message, if they exist.  The Delimiter Attribute has a tag
 value of 0 and a length value of 0.  The Delimiter Attribute is
 effectively 8 bytes long: a 4-byte tag containing 0x00000000, and a 4
 Byte length field containing 0x00000000.

5.7.4. Operating Attributes in Response

 The Operating Attributes in a response are the results related to the
 iSNS registration or query operation being performed.  Some response
 messages will not have Operating Attributes.

5.7.5. Registration and Query Response Message Types

 The following sections describe each query and message type.

5.7.5.1. Device Attribute Registration Response (DevAttrRegRsp)

 The DevAttrRegRsp message type is 0x8001.  The DevAttrRegRsp message
 contains the results for the DevAttrReg message with the same
 TRANSACTION ID.
 The Message Key in the DevAttrRegRsp message SHALL return the Message
 Key in the original registration message.  If the iSNS server
 assigned the Entity Identifier for a Network Entity, then the Message
 Key Attribute field SHALL contain the assigned Entity Identifier.
 The Operating Attributes of the DevAttrRegRsp message SHALL contain
 the affected object's key and non-key attributes that have been
 explicitly modified or created by the original DevAttrReg message.
 Among the Operating Attributes, each modified or added non-key
 attribute SHALL be listed after its key attribute(s) in the
 DevAttrRegRsp message.  Implicitly registered attributes MUST NOT be
 returned in the DevAttrRegRsp message.  Implicitly registered
 attributes are those that are assigned a fixed default value or
 secondary index value by the iSNS server.
 Implicitly registered PG objects (i.e., PG objects that are not
 explicitly included in the registration or replace message) MUST NOT
 have their key or non-key attributes returned in the DevAttrRegRsp
 message.  However, explicitly registered PG objects (i.e., those with
 PGT values that are explicitly included in the registration or
 replace message) SHALL have their PGT values returned in the
 DevAttrRegRsp message.

Tseng, et al. Standards Track [Page 67] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 For example, three Portals are registered in the original DevAttrReg
 request message.  Due to lack of resources, the iSNS server needs to
 modify the registered ESI Interval value of one of those Portals.  To
 accomplish this, the iSNS server returns the key attributes
 identifying the Portal, followed by the non-key modified ESI Interval
 attribute value, as Operating Attributes of the corresponding
 DevAttrRegRsp message.
 If the iSNS server rejects a registration due to invalid attribute
 values or types, then the indicated status code SHALL be 3 (Invalid
 Registration).  If this occurs, then the iSNS server MAY include the
 list of invalid attributes in the Operating Attributes of the
 DevAttrRsp message.
 Some attributes values (e.g., ESI Interval, Registration Period) in
 the original registration message MAY be modified by the iSNS server.
 This can occur only for a limited set of attribute types, as
 indicated in the table in Section 6.1.  When this occurs, the
 registration SHALL be considered a success (with status code 0), and
 the changed value(s) indicated in the Operating Attributes of the
 DevAttrRsp message.

5.7.5.2. Device Attribute Query Response (DevAttrQryRsp)

 The DevAttrQryRsp message type is 0x8002.  The DevAttrQryRsp message
 contains the results for the DevAttrQry message with the same
 TRANSACTION ID.
 The Message Key in the DevAttrQryRsp message SHALL return the Message
 Key in the original query message.
 If no Operating Attributes are included in the original query, then
 all Operating Attributes SHALL be returned in the response.
 For a successful query result, the DevAttrQryRsp Operating Attributes
 SHALL contain the results of the original DevAttrQry message.

5.7.5.3. Device Get Next Response (DevGetNextRsp)

 The DevGetNextRsp message type is 0x8003.  The DevGetNextRsp message
 contains the results for the DevGetNext message with the same
 TRANSACTION ID.
 The Message Key Attribute field returns the object keys for the next
 object after the Message Key Attribute in the original DevGetNext
 message.

Tseng, et al. Standards Track [Page 68] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 The Operating Attribute field returns the Operating Attributes of the
 next object as requested in the original DevGetNext message.  The
 values of the Operating Attributes are those associated with the
 object identified by the Message Key Attribute field of the
 DevGetNextRsp message.

5.7.5.4. Deregister Device Response (DevDeregRsp)

 The DevDeregRsp message type is 0x8004.  This message is the response
 to the DevDereg request message.
 This message response does not contain a Message Key, but MAY contain
 Operating Attributes.
 In the event of an error, this response message contains the
 appropriate status code as well as a list of objects from the
 original DevDereg message that were not successfully deregistered
 from the iSNS database.  This list of objects is contained in the
 Operating Attributes of the DevDeregRsp message.  Note that an
 attempted deregistration of a non-existent object does not constitute
 an error, and non-existent entries SHALL not be returned in the
 DevDeregRsp message.

5.7.5.5. SCN Register Response (SCNRegRsp)

 The SCNRegRsp message type is 0x8005.  This message is the response
 to the SCNReg request message.
 The SCNRegRsp message does not contain any Message Key or Operating
 Attributes.

5.7.5.6. SCN Deregister Response (SCNDeregRsp)

 The SCNDeregRsp message type is 0x8006.  This message is the response
 to the SCNDereg request message.
 The SCNDeregRsp message does not contain any Message Key or Operating
 Attributes.

5.7.5.7. SCN Event Response (SCNEventRsp)

 The SCNEventRsp message type is 0x8007.  This message is the response
 to the SCNEvent request message.
 The SCNEventRsp message does not contain any Message Key or Operating
 Attributes.

Tseng, et al. Standards Track [Page 69] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.7.5.8. SCN Response (SCNRsp)

 The SCNRsp message type is 0x8008.  This message is sent by an iSNS
 client, and provides confirmation that the SCN message was received
 and processed.
 The SCNRsp response contains the SCN Destination Attribute
 representing the Node identifier that received the SCN.

5.7.5.9. DD Register Response (DDRegRsp)

 The DDRegRsp message type is 0x8009.  This message is the response to
 the DDReg request message.
 The Message Key in the DDRegRsp message SHALL return the Message Key
 in the original query message.  If the original DDReg message did not
 have a Message Key, then the DDRegRsp message SHALL not have a
 Message Key.
 If the DDReg operation is successful, the DD ID of the DD created or
 updated SHALL be returned as an operating attribute of the message.
 If the DD Symbolic Name attribute or DD Features attribute was
 assigned or updated during the DDReg operation, then any new values
 SHALL be returned as an operating attribute of the DDRegRsp message.
 If the iSNS server rejects a DDReg due to invalid attribute values or
 types, then the indicated status code SHALL be 3 (Invalid
 Registration).  If this occurs, then the iSNS server MAY include the
 list of invalid attributes in the Operating Attributes of the
 DDRegRsp message.

5.7.5.10. DD Deregister Response (DDDeregRsp)

 The DDDeregRsp message type is 0x800A.  This message is the response
 to the DDDereg request message.
 The DDDeregRsp message does not contain any Message Key or Operating
 Attributes.

Tseng, et al. Standards Track [Page 70] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.7.5.11. DDS Register Response (DDSRegRsp)

 The DDSRegRsp message type is 0x800B.  This message is the response
 to the DDSReg request message.
 The Message Key in the DDSRegRsp message SHALL contain the Message
 Key of the original DDSReg message.  If the original DDSReg message
 did not have a Message Key, then the DDSRegRsp message SHALL NOT have
 a Message Key.
 If the DDSReg operation is successful, the DDS ID of the DDS created
 or updated SHALL be returned as an operating attribute of the
 message.
 If the DDS Symbolic Name attribute or DDS Status attribute was
 assigned or updated during the DDSRegRsp operation, then any new
 values SHALL be returned as an operating attribute of the DDSRegRsp
 message.
 If the iSNS server rejects a DDSReg due to invalid attribute values
 or types, then the indicated status code SHALL be 3 (Invalid
 Registration).  If this occurs, then the iSNS server MAY include the
 list of invalid attributes in the Operating Attributes of the
 DDSRegRsp message.

5.7.5.12. DDS Deregister Response (DDSDeregRsp)

 The DDSDeregRsp message type is 0x800C.  This message is the response
 to the DDSDereg request message.
 The DDSDeregRsp message does not contain any Message Key or Operating
 Attributes.

5.7.5.13. Entity Status Inquiry Response (ESIRsp)

 The ESIRsp message type is 0x800D.  This message is sent by an iSNS
 client and provides confirmation that the ESI message was received
 and processed.
 The ESIRsp response message PDU Payload contains the attributes from
 the original ESI message.  These attributes represent the Portal that
 is responding to the ESI.  The ESIRsp Attributes are in the order
 they were provided in the original ESI message.
 Upon receiving the ESIRsp from the iSNS client, the iSNS server SHALL
 update the timestamp attribute for that Network Entity and Portal.

Tseng, et al. Standards Track [Page 71] RFC 4171 Internet Storage Name Service (iSNS) September 2005

5.7.5.14. Request FC_DOMAIN_ID Response (RqstDomIdRsp)

 The RqstDomIdRsp message type is 0x8011.  This message provides the
 response for RqstDomId.
 The RqstDomId response contains a Status Code and the TLV attribute
 Assigned ID, which contains the integer value in the space requested.
 If no further unallocated values are available from this space, the
 iSNS server SHALL respond with the Status Code 19 "FC_DOMAIN_ID Not
 Available".
 Once a FC_DOMAIN_ID value is allocated by the iSNS server, it SHALL
 NOT be reused until it has been deallocated by the iSNS client to
 which the value was assigned, or until the ESI message detects that
 the iSNS client no longer exists on the network.
 The iSNS server and client SHALL use TCP to transmit and receive
 RqstDomId, RqstDomIdRsp, RlseDomId, and RlseDomIdRsp messages.

5.7.5.15. Release FC_DOMAIN_ID Response (RlseDomIdRsp)

 The RlseDomIdRsp message type is 0x8012.  This message provides the
 response for RlseDomId.  The response contains an Error indicating
 whether the request was successful.  If the Assigned_ID value in the
 original RlseDomId message is not allocated, then the iSNS server
 SHALL respond with this message using the Status Code 20
 "FC_DOMAIN_ID Not Allocated".
 The iSNS server and client SHALL use TCP to transmit and receive
 RqstDomId, RqstDomIdRsp, RlseDomId, and RlseDomIdRsp messages.

5.7.5.16. Get FC_DOMAIN_IDs Response (GetDomIdRsp)

 The GetDomIdRsp message type is 0x8013.  This message is used to
 determine which FC_DOMAIN_ID values have been allocated for the
 Virtual_Fabric_ID specified in the original GetDomId request message.
 The GetDomId response message PDU Payload contains a Status Code
 indicating whether the request was successful, and a list of the
 Assigned IDs from the space requested.  The Assigned_ID attributes
 are listed in TLV format.

5.8. Vendor-Specific Messages

 Vendor-specific iSNSP messages have a functional ID of between 0x0100
 and 0x01FF, whereas vendor-specific responses have a functional ID of
 between 0x8100 and 0x81FF.  The first Message Key Attribute in a

Tseng, et al. Standards Track [Page 72] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 vendor-specific message SHALL be the company OUI (tag=256)
 identifying the original creator of the proprietary iSNSP message.
 The contents of the remainder of the message are vendor-specific.

6. iSNS Attributes

 Attributes can be stored in the iSNS server using iSNSP registration
 messages, and they can be retrieved using iSNSP query messages.
 Unless otherwise indicated, these attributes are supplied by iSNS
 clients using iSNSP registration messages.

6.1. iSNS Attribute Summary

 The complete registry of iSNS attributes is maintained by IANA, and
 the following table summarizes the initial set of iSNS attributes
 available at the time of publication of this document.
 Attributes               Length   Tag   Reg Key   Query Key
 ----------               ------   ---   -------   ---------
 Delimiter                 0        0      N/A        N/A
 Entity Identifier (EID) 4-256      1       1     1|2|16&17|32|64
 Entity Protocol           4        2       1     1|2|16&17|32|64
 Management IP Address     16       3       1     1|2|16&17|32|64
 Timestamp                 8        4      --     1|2|16&17|32|64
 Protocol Version Range    4        5       1     1|2|16&17|32|64
 Registration Period       4        6       1     1|2|16&17|32|64
 Entity Index              4        7       1     1|2|16&17|32|64
 Entity Next Index         4        8      --     1|2|16&17|32|64
 Entity ISAKMP Phase-1    var       11      1     1|2|16&17|32|64
 Entity Certificate       var       12      1     1|2|16&17|32|64
 Portal IP Address         16       16      1     1|16&17|32|64
 Portal TCP/UDP Port       4        17      1     1|16&17|32|64
 Portal Symbolic Name    4-256      18    16&17   1|16&17|32|64
 ESI Interval              4        19    16&17   1|16&17|32|64
 ESI Port                  4        20    16&17   1|16&17|32|64
 Portal Index              4        22    16&17   1|16&17|32|64
 SCN Port                  4        23    16&17   1|16&17|32|64
 Portal Next Index         4        24     --     1|16&17|32|64
 Portal Security Bitmap    4        27    16&17   1|16&17|32|64
 Portal ISAKMP Phase-1    var       28    16&17   1|16&17|32|64
 Portal ISAKMP Phase-2    var       29    16&17   1|16&17|32|64
 Portal Certificate       var       31    16&17   1|16&17|32|64
 iSCSI Name              4-224      32      1     1|16&17|32|33
 iSCSI Node Type           4        33     32     1|16&17|32
 iSCSI Alias             4-256      34     32     1|16&17|32
 iSCSI SCN Bitmap          4        35     32     1|16&17|32
 iSCSI Node Index          4        36     32     1|16&17|32
 WWNN Token                8        37     32     1|16&17|32

Tseng, et al. Standards Track [Page 73] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 iSCSI Node Next Index     4        38     --     1|16&17|32
 iSCSI AuthMethod         var       42     32     1|16&17|32
 PG iSCSI Name           4-224      48   32|16&17 1|16&17|32|52
 PG Portal IP Addr        16        49   32|16&17 1|16&17|32|52
 PG Portal TCP/UDP Port    4        50   32|16&17 1|16&17|32|52
 PG Tag (PGT)              4        51   32|16&17 1|16&17|32|52
 PG Index                  4        52   32|16&17 1|16&17|32|52
 PG Next Index             4        53     --     1|16&17|32|52
 FC Port Name WWPN         8        64     1     1|16&17|64|66|96|128
 Port ID                   4        65     64     1|16&17|64
 FC Port Type              4        66     64     1|16&17|64
 Symbolic Port Name      4-256      67     64     1|16&17|64
 Fabric Port Name          8        68     64     1|16&17|64
 Hard Address              4        69     64     1|16&17|64
 Port IP-Address          16        70     64     1|16&17|64
 Class of Service          4        71     64     1|16&17|64
 FC-4 Types               32        72     64     1|16&17|64
 FC-4 Descriptor         4-256      73     64     1|16&17|64
 FC-4 Features            128       74     64     1|16&17|64
 iFCP SCN bitmap           4        75     64     1|16&17|64
 Port Role                 4        76     64     1|16&17|64
 Permanent Port Name       8        77     --     1|16&17|64
 FC-4 Type Code            4        95     --     1|16&17|64
 FC Node Name WWNN         8        96     64     1|16&17|64|96
 Symbolic Node Name      4-256      97     96     64|96
 Node IP-Address           16       98     96     64|96
 Node IPA                  8        99     96     64|96
 Proxy iSCSI Name        4-256     101     96     64|96
 Switch Name               8       128     128    128
 Preferred ID              4       129     128    128
 Assigned ID               4       130     128    128
 Virtual_Fabric_ID       4-256     131     128    128
 iSNS Server Vendor OUI    4       256     --     SOURCE Attribute
 Vendor-Spec iSNS Srvr          257-384    --     SOURCE Attribute
 Vendor-Spec Entity             385-512     1     1|2|16&17|32|64
 Vendor-Spec Portal             513-640   16&17   1|16&17|32|64
 Vendor-Spec iSCSI Node         641-768    32     16&17|32
 Vendor-Spec FC Port Name       769-896    64     1|16&17|64
 Vendor-Spec FC Node Name       897-1024   96     64|96
 Vendor-Specific DDS           1025-1280   2049   2049
 Vendor-Specific DD            1281-1536   2065   2065
 Other Vendor-Specific         1537-2048
 DD_Set ID                 4      2049     2049   1|32|64|2049|2065
 DD_Set Sym Name         4-256    2050     2049   2049
 DD_Set Status             4      2051     2049   2049
 DD_Set_Next_ID            4      2052     --     2049
 DD_ID                     4      2065     2049   1|32|64|2049|2065
 DD_Symbolic Name        4-256    2066     2065   2065

Tseng, et al. Standards Track [Page 74] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 DD_Member iSCSI Index     4      2067     2065   2065
 DD_Member iSCSI Name    4-224    2068     2065   2065
 DD_Member FC Port Name    8      2069     2065   2065
 DD_Member Portal Index    4      2070     2065   2065
 DD_Member Portal IP Addr 16      2071     2065   2065
 DD_Member Portal TCP/UDP  4      2072     2065   2065
 DD_Features               4      2078     2065   2065
 DD_ID Next ID             4      2079     --     2065
 The following are descriptions of the columns used in the above
 table:
 Length:    indicates the attribute length in bytes used for the TLV
            format.  Variable-length identifiers are NULL-terminated
            and 4-byte aligned (NULLs are included in the length).
 Tag:       the IANA-assigned integer tag value used to identify the
            attribute.  All undefined tag values are reserved.
 Reg Key:   indicates the tag values for the object key in DevAttrReg
            messages for registering a new attribute value in the
            database.  These tags represent attributes defined as
            object keys in Section 4.
 Query Key: indicates the possible tag values for the Message Key and
            object key that are used in the DevAttrQry messages for
            retrieving a stored value from the iSNS database.
 The following is a summary of iSNS attribute tag values available for
 future allocation by IANA at the time of publication:
 Tag Values           Reg Key          Query Key
 ----------           -------          ---------
 9-10, 13-15          1                1|2|16&17|32|64
 21, 25-26, 30        16&17            1|16&17|32|64
 39-41, 44-47         32               1|16&17|32
 54-63                32|16&17         1|16&17|32|52
 78-82, 85-94         64               1|16&17|64
 102-127              96               64|96
 132-255              --               SOURCE Attribute
 2053-2064            2049             2049
 2073-2077            2065             2065
 2080-65535           To be assigned   To be assigned
 Registration and query keys for attributes with tags in the range
 2080 to 65535 are to be documented in the RFC introducing the new
 iSNS attributes.  IANA will maintain registration of these values as
 required by the new RFC.

Tseng, et al. Standards Track [Page 75] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 New iSNS attributes with any of the above tag values MAY also be
 designated as "read-only" attributes.  The new RFC introducing these
 attributes as "read-only" SHALL document them as such, and IANA will
 record their corresponding Registration Keys (Reg Keys) as "--".

6.2. Entity Identifier-Keyed Attributes

 The following attributes are stored in the iSNS server using the
 Entity Identifier attribute as the key.

6.2.1. Entity Identifier (EID)

 The Entity Identifier (EID) is variable-length UTF-8 encoded NULL-
 terminated text-based description for a Network Entity.  This key
 attribute uniquely identifies each Network Entity registered in the
 iSNS server.  The attribute length varies from 4 to 256 bytes
 (including the NULL termination), and is a unique value within the
 iSNS server.
 If the iSNS client does not provide an EID during registration, the
 iSNS server SHALL generate one that is unique within the iSNS
 database.  If an EID is to be generated, then the EID attribute value
 in the registration message SHALL be empty (0 length).  The generated
 EID SHALL be returned in the registration response.
 In environments where the iSNS server is integrated with a DNS
 infrastructure, the Entity Identifier may be used to store the Fully
 Qualified Domain Name (FQDN) of the iSCSI or iFCP device.  FQDNs of
 greater than 255 bytes MUST NOT be used.
 If FQDNs are not used, the iSNS server can be used to generate EIDs.
 EIDs generated by the iSNS server MUST begin with the string "isns:".
 iSNS clients MUST NOT generate and register EIDs beginning with the
 string "isns:".
 This field MUST be normalized according to the nameprep template
 [NAMEPREP] before it is stored in the iSNS database.

6.2.2. Entity Protocol

 The Entity Protocol is a required 4-byte integer attribute that
 indicates the block storage protocol used by the registered NETWORK
 ENTITY.  Values used for this attribute are assigned and maintained
 by IANA.  The initial set of protocols supported by iSNS is as
 follows:

Tseng, et al. Standards Track [Page 76] RFC 4171 Internet Storage Name Service (iSNS) September 2005

        Value          Entity Protocol Type
        -----          --------------------
         1             No Protocol
         2             iSCSI
         3             iFCP
         All others    To be assigned by IANA
 'No Protocol' is used to indicate that the Network Entity does not
 support an IP block storage protocol.  A Control Node or monitoring
 Node would likely (but not necessarily) use this value.
 This attribute is required during initial registration of the Network
 Entity.

6.2.3. Management IP Address

 This field contains the IP Address that may be used to manage the
 Network Entity and all Storage Nodes contained therein via the iSNS
 MIB [iSNSMIB].  Some implementations may also use this IP address to
 support vendor-specific proprietary management protocols.  The
 Management IP Address is a 16-byte field that may contain an IPv4 or
 IPv6 address.  When this field contains an IPv4 value, it is stored
 as an IPv4-mapped IPv6 address.  That is, the most significant 10
 bytes are set to 0x00, with the next two bytes set to 0xFFFF
 [RFC2373].  When this field contains an IPv6 value, the entire 16-
 byte field is used.  If this field is not set, then in-band
 management through the IP address of one of the Portals of the
 Network Entity is assumed.

6.2.4. Entity Registration Timestamp

 This field indicates the most recent time when the Network Entity
 registration occurred or when an associated object attribute was
 updated or queried by the iSNS client registering the Network Entity.
 The time format is, in seconds, the update period since the standard
 base time of 00:00:00 GMT on January 1, 1970.  This field cannot be
 explicitly registered.  This timestamp TLV format is also used in the
 SCN and ESI messages.

6.2.5. Protocol Version Range

 This field contains the minimum and maximum version of the block
 storage protocol supported by the Network Entity.  The most
 significant two bytes contain the maximum version supported, and the
 least significant two bytes contain the minimum version supported.
 If a range is not registered, then the Network Entity is assumed to

Tseng, et al. Standards Track [Page 77] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 support all versions of the protocol.  The value 0xffff is a wildcard
 that indicates no minimum or maximum.  If the Network Entity does not
 support a protocol, then this field SHALL be set to 0.

6.2.6. Registration Period

 This 4-byte unsigned integer field indicates the maximum period, in
 seconds, that the registration SHALL be maintained by the server
 without receipt of an iSNS message from the iSNS client that
 registered the Network Entity.  Entities that are not registered for
 ESI monitoring MUST have a non-zero Registration Period.  If a
 Registration Period is not requested by the iSNS client and Entity
 Status Inquiry (ESI) messages are not enabled for that client, then
 the Registration Period SHALL be set to a non-zero value by the iSNS
 server.  This implementation-specific value for the Registration
 Period SHALL be returned in the registration response to the iSNS
 client.  The Registration Period may be set to zero, indicating its
 non-use, only if ESI messages are enabled for that Network Entity.
 The registration SHALL be removed from the iSNS database if an iSNS
 Protocol message is not received from the iSNS client before the
 registration period has expired.  Receipt of any iSNS Protocol
 message from the iSNS client automatically refreshes the Entity
 Registration Period and Entity Registration Timestamp.  To prevent a
 registration from expiring, the iSNS client should send an iSNS
 Protocol message to the iSNS server at intervals shorter than the
 registration period.  Such a message can be as simple as a query for
 one of its own attributes, using its associated iSCSI Name or FC Port
 Name WWPN as the Source attribute.
 For an iSNS client that is supporting a Network Entity with multiple
 Storage Node objects, receipt of an iSNS message from any Storage
 Node of that Network Entity is sufficient to refresh the registration
 for all Storage Node objects of the Network Entity.
 If ESI support is requested as part of a Portal registration, the ESI
 Response message received from the iSNS client by the iSNS server
 SHALL refresh the registration.

6.2.7. Entity Index

 The Entity Index is an unsigned non-zero integer value that uniquely
 identifies each Network Entity registered in the iSNS server.  Upon
 initial registration of a Network Entity, the iSNS server assigns an
 unused value for the Entity Index.  Each Network Entity in the iSNS
 database MUST be assigned a value for the Entity Index that is not

Tseng, et al. Standards Track [Page 78] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 assigned to any other Network Entity.  Furthermore, Entity Index
 values for recently deregistered Network Entities SHOULD NOT be
 reused in the short term.
 The Entity Index MAY be used to represent the Network Entity in
 situations when the Entity Identifier is too long or otherwise
 inappropriate.  An example of this is when SNMP is used for
 management, as described in Section 2.10.

6.2.8. Entity Next Index

 This is a virtual attribute containing a 4-byte integer value that
 indicates the next available (i.e., unused) Entity Index value.  This
 attribute may only be queried; the iSNS server SHALL return an error
 code of 3 (Invalid Registration) to any client that attempts to
 register a value for this attribute.  A Message Key is not required
 when exclusively querying for this attribute.
 The Entity Next Index MAY be used by an SNMP client to create an
 entry in the iSNS server.  SNMP requirements are described in Section
 2.10.

6.2.9. Entity ISAKMP Phase-1 Proposals

 This field contains the IKE Phase-1 proposal, listing in decreasing
 order of preference the protection suites acceptable to protect all
 IKE Phase-2 messages sent and received by the Network Entity.  This
 includes Phase-2 SAs from the iSNS client to the iSNS server as well
 as to peer iFCP and/or iSCSI devices.  This attribute contains the SA
 payload, proposal payload(s), and transform payload(s) in the ISAKMP
 format defined in [RFC2408].
 This field should be used if the implementer wishes to define a
 single phase-1 SA security configuration used to protect all phase-2
 IKE traffic.  If the implementer desires to have a different phase-1
 SA security configuration to protect each Portal interface, then the
 Portal Phase-1 Proposal (Section 6.3.10) should be used.

6.2.10. Entity Certificate

 This attribute contains one or more X.509 certificates that are bound
 to the Network Entity.  This certificate is uploaded and registered
 to the iSNS server by clients wishing to allow other clients to
 authenticate themselves and to access the services offered by that
 Network Entity.  The format of the X.509 certificate is found in
 [RFC3280].  This certificate MUST contain a Subject Name with an
 empty sequence and MUST contain a SubjectAltName extension encoded

Tseng, et al. Standards Track [Page 79] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 with the dNSName type.  The Entity Identifier (Section 6.2.1) of the
 identified Entity MUST be stored in the SubjectAltName field of the
 certificate.

6.3. Portal-Keyed Attributes

 The following Portal attributes are registered in the iSNS database
 using the combined Portal IP-Address and Portal TCP/UDP Port as the
 key.  Each Portal is associated with one Entity Identifier object
 key.

6.3.1. Portal IP Address

 This attribute is the IP address of the Portal through which a
 Storage Node can transmit and receive storage data.  The Portal IP
 Address is a 16-byte field that may contain an IPv4 or IPv6 address.
 When this field contains an IPv4 address, it is stored as an IPv4-
 mapped IPv6 address.  That is, the most significant 10 bytes are set
 to 0x00, with the next 2 bytes set to 0xFFFF [RFC2373].  When this
 field contains an IPv6 address, the entire 16-byte field is used.
 The Portal IP Address and the Portal TCP/UDP Port number (see 6.3.2
 below) are used as a key to identify a Portal uniquely.  It is a
 required attribute for registration of a Portal.

6.3.2. Portal TCP/UDP Port

 The TCP/UDP port of the Portal through which a Storage Node can
 transmit and receive storage data.  Bits 16 to 31 represents the
 TCP/UDP port number.  Bit 15 represents the port type.  If bit 15 is
 set, then the port type is UDP.  Otherwise it is TCP.  Bits 0 to 14
 are reserved.
 If the field value is 0, then the port number is the implied
 canonical port number and type of the protocol indicated by the
 associated Entity Type.
 The Portal IP Address and the Portal TCP/UDP Port number are used as
 a key to identify a Portal uniquely.  It is a required attribute for
 registration of a Portal.

6.3.3. Portal Symbolic Name

 A variable-length UTF-8 encoded NULL-terminated text-based
 description of up to 256 bytes.  The Portal Symbolic Name is a user-
 readable description of the Portal entry in the iSNS server.

Tseng, et al. Standards Track [Page 80] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.3.4. Entity Status Inquiry Interval

 This field indicates the requested time, in seconds, between Entity
 Status Inquiry (ESI) messages sent from the iSNS server to this
 Network Entity.  ESI messages can be used to verify that a Portal
 registration continues to be valid.  To request monitoring by the
 iSNS server, an iSNS client registers a non-zero value for this
 Portal attribute using a DevAttrReg message.  The client MUST
 register an ESI Port on at least one of its Portals to receive the
 ESI monitoring.
 If the iSNS server does not receive an expected response to an ESI
 message, it SHALL attempt an administratively configured number of
 re-transmissions of the ESI message.  The ESI Interval period begins
 with the iSNS server's receipt of the last ESI Response.  All re-
 transmissions MUST be sent before twice the ESI Interval period has
 passed.  If no response is received from any of the ESI messages,
 then the Portal SHALL be deregistered.  Note that only Portals that
 have registered a value in their ESI Port field can be deregistered
 in this way.
 If all Portals associated with a Network Entity that have registered
 for ESI messages are deregistered due to non-response, and if no
 registrations have been received from the client for at least two ESI
 Interval periods, then the Network Entity and all associated objects
 (including Storage Nodes) SHALL be deregistered.
 If the iSNS server is unable to support ESI messages or the ESI
 Interval requested, it SHALL either reject the ESI request by
 returning an "ESI Not Available" Status Code or modify the ESI
 Interval attribute by selecting its own suitable value and returning
 that value in the Operating Attributes of the registration response
 message.
 If at any time an iSNS client that is registered for ESI messages has
 not received an ESI message to any of its Portals as expected, then
 the client MAY attempt to query the iSNS server using a DevAttrQry
 message using its Entity_ID as the key.  If the query result is the
 error "no such entry", then the client SHALL close all remaining TCP
 connections to the iSNS server and assume that it is no longer
 registered in the iSNS database.  Such a client MAY attempt re-
 registration.

Tseng, et al. Standards Track [Page 81] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.3.5. ESI Port

 This field contains the TCP or UDP port used for ESI monitoring by
 the iSNS server at the Portal IP Address.  Bits 16 to 31 represent
 the port number.  If bit 15 is set, then the port type is UDP.
 Otherwise, the port is TCP.  Bits 0 to 14 are reserved.
 If the iSNS client registers a valid TCP or UDP port number in this
 field, then the client SHALL allow ESI messages to be received at the
 indicated TCP or UDP port.  If a TCP port is registered and a pre-
 existing TCP connection from that TCP port to the iSNS server does
 not already exist, then the iSNS client SHALL accept new TCP
 connections from the iSNS server at the indicated TCP port.
 The iSNS server SHALL return an error if a Network Entity is
 registered for ESI monitoring and none of the Portals of that Network
 Entity has an entry for the ESI Port field.  If multiple Portals have
 a registered ESI port, then the ESI message may be delivered to any
 one of the indicated Portals.

6.3.6. Portal Index

 The Portal Index is a 4-byte non-zero integer value that uniquely
 identifies each Portal registered in the iSNS database.  Upon initial
 registration of a Portal, the iSNS server assigns an unused value for
 the Portal Index of that Portal.  Each Portal in the iSNS database
 MUST be assigned a value for the Portal Index that is not assigned to
 any other Portal.  Furthermore, Portal Index values for recently
 deregistered Portals SHOULD NOT be reused in the short term.
 The Portal Index MAY be used to represent a registered Portal in
 situations where the Portal IP-Address and Portal TCP/UDP Port is
 unwieldy to use.  An example of this is when SNMP is used for
 management, as described in Section 2.10.

6.3.7. SCN Port

 This field contains the TCP or UDP port used by the iSNS client to
 receive SCN messages from the iSNS server.  When a value is
 registered for this attribute, an SCN message may be received on the
 indicated port for any of the Storage Nodes supported by the Portal.
 Bits 16 to 31 contain the port number.  If bit 15 is set, then the
 port type is UDP.  Otherwise, the port type is TCP.  Bits 0 to 14 are
 reserved.
 If the iSNS client registers a valid TCP or UDP port number in this
 field, then the client SHALL allow SCN messages to be received at the
 indicated TCP or UDP port.  If a TCP port is registered and a pre-

Tseng, et al. Standards Track [Page 82] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 existing TCP connection from that TCP port to the iSNS server does
 not already exist, then the iSNS client SHALL accept new TCP
 connections from the iSNS server at the indicated TCP port.
 The iSNS server SHALL return an error if an SCN registration message
 is received and none of the Portals of the Network Entity has an
 entry for the SCN Port.  If multiple Portals have a registered SCN
 Port, then the SCN SHALL be delivered to any one of the indicated
 Portals of that Network Entity.

6.3.8. Portal Next Index

 This is a virtual attribute containing a 4-byte integer value that
 indicates the next available (i.e., unused) Portal Index value.  This
 attribute may only be queried; the iSNS server SHALL return an error
 code of 3 (Invalid Registration) to any client that attempts to
 register a value for this attribute.  A Message Key is not required
 when exclusively querying for this attribute.
 The Portal Next Index MAY be used by an SNMP client to create an
 entry in the iSNS server.  SNMP requirements are described in Section
 2.10.

6.3.9. Portal Security Bitmap

 This 4-byte field contains flags that indicate security attribute
 settings for the Portal.  Bit 31 (Lsb) of this field must be 1
 (enabled) for this field to contain significant information.  If Bit
 31 is enabled, this signifies that the iSNS server can be used to
 store and distribute security policies and settings for iSNS clients
 (i.e., iSCSI devices).  Bit 30 must be 1 for bits 25-29 to contain
 significant information.  All other bits are reserved for non-
 IKE/IPSec security mechanisms to be specified in the future.
 Bit Position        Flag Description
 ------------        ----------------
    25               1 = Tunnel Mode Preferred; 0 = No Preference
    26               1 = Transport Mode Preferred; 0 = No Preference
    27               1 = Perfect Forward Secrecy (PFS) Enabled;
                     0 = PFS Disabled
    28               1 = Aggressive Mode Enabled; 0 = Disabled
    29               1 = Main Mode Enabled; 0 = MM Disabled
    30               1 = IKE/IPSec Enabled; 0 = IKE/IPSec Disabled
    31 (Lsb)         1 = Bitmap VALID; 0 = INVALID
    All others       RESERVED

Tseng, et al. Standards Track [Page 83] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.3.10. Portal ISAKMP Phase-1 Proposals

 This field contains the IKE Phase-1 proposal listing in decreasing
 order of preference of the protection suites acceptable to protect
 all IKE Phase-2 messages sent and received by the Portal.  This
 includes Phase-2 SAs from the iSNS client to the iSNS server as well
 as to peer iFCP and/or iSCSI devices.  This attribute contains the SA
 payload, proposal payload(s), and transform payload(s) in the ISAKMP
 format defined in [RFC2408].
 This field should be used if the implementer wishes to define phase-1
 SA security configuration on a per-Portal basis, as opposed to on a
 per-Network Entity basis.  If the implementer desires to have a
 single phase-1 SA security configuration to protect all phase-2
 traffic regardless of the interface used, then the Entity Phase-1
 Proposal (Section 6.2.9) should be used.

6.3.11. Portal ISAKMP Phase-2 Proposals

 This field contains the IKE Phase-2 proposal, in ISAKMP format
 [RFC2408], listing in decreasing order of preference the security
 proposals acceptable to protect traffic sent and received by the
 Portal.  This field is used only if bits 31, 30, and 29 of the
 Security Bitmap (see 6.3.9) are enabled.  This attribute contains the
 SA payload, proposal payload(s), and associated transform payload(s)
 in the ISAKMP format defined in [RFC2408].

6.3.12. Portal Certificate

 This attribute contains one or more X.509 certificates that are a
 credential of the Portal.  This certificate is used to identify and
 authenticate communications to the IP address and TCP/UDP Port
 supported by the Portal.  The format of the X.509 certificate is
 specified in [RFC3280].  This certificate MUST contain a Subject Name
 with an empty sequence and MUST contain a SubjectAltName extension
 encoded with the iPAddress type.  The Portal IP Address (Section
 6.3.1) of the identified Portal SHALL be stored in the SubjectAltName
 field of the certificate.

6.4. iSCSI Node-Keyed Attributes

 The following attributes are stored in the iSNS database using the
 iSCSI Name attribute as the key.  Each set of Node-Keyed attributes
 is associated with one Entity Identifier object key.
 Although the iSCSI Name key is associated with one Entity Identifier,
 it is unique across the entire iSNS database.

Tseng, et al. Standards Track [Page 84] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.4.1. iSCSI Name

 This is a variable-length UTF-8 encoded NULL-terminated text-based
 description of up to 224 bytes.  This key attribute is required for
 iSCSI Storage Nodes and is provided by the iSNS client.  The
 registered iSCSI Name MUST conform to the format described in [iSCSI]
 for iSCSI Names.  The maximum size for an iSCSI Name is 223 bytes.
 Including the NULL character and 4-byte alignment (see Section
 5.3.1), the maximum iSCSI Name field size is 224 bytes.
 If an iSCSI Name is registered without an EID key, then a Network
 Entity SHALL be created and an EID assigned.  The assigned EID SHALL
 be returned in the registration response as an operating attribute.
 This field MUST be normalized according to the stringprep template
 [STRINGPREP] before it is stored in the iSNS database.

6.4.2. iSCSI Node Type

 This required 32-bit field is a bitmap indicating the type of iSCSI
 Storage Node.  The bit positions are defined below.  A set bit (1)
 indicates that the Node has the corresponding characteristics.
        Bit Position    Node Type
        ------------    ---------
         29             Control
         30             Initiator
         31 (Lsb)       Target
         All others     RESERVED
 If the Target bit is set to 1, then the Node represents an iSCSI
 target.  The Target bit MAY be set by iSNS clients using the iSNSP.
 If the Initiator bit is set to 1, then the Node represents an iSCSI
 initiator.  The Initiator bit MAY be set by iSNS clients using the
 iSNSP.
 If the control bit is set to 1, then the Node represents a gateway, a
 management station, a backup iSNS server, or another device that is
 not an initiator or target, but that requires the ability to send and
 receive iSNSP messages, including state change notifications.
 Setting the control bit is an administrative task that MUST be
 performed on the iSNS server; iSNS clients SHALL NOT be allowed to
 change this bit using the iSNSP.

Tseng, et al. Standards Track [Page 85] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 This field MAY be used by the iSNS server to distinguish among
 permissions by different iSCSI Node types for accessing various iSNS
 functions.  More than one Node Type bit may be simultaneously
 enabled.

6.4.3. iSCSI Node Alias

 This is a variable-length UTF-8 encoded NULL-terminated text-based
 description of up to 256 bytes.  The Alias is a user-readable
 description of the Node entry in the iSNS database.

6.4.4. iSCSI Node SCN Bitmap

 The iSCSI Node SCN Bitmap indicates events for which the registering
 iSNS client wishes to receive a notification message.  The following
 table displays events that result in notifications, and the bit field
 in the SCN Bitmap that, when enabled, results in the corresponding
 notification.
 Note that this field is of dual use: it is used in the SCN
 registration process to define interested events that will trigger an
 SCN message, and it is also contained in each SCN message itself, to
 indicate the type of event that triggered the SCN message.  A set bit
 (1) indicates the corresponding type of SCN.
        Bit Position       Flag Description
        ------------       ----------------
         24                INITIATOR AND SELF INFORMATION ONLY
         25                TARGET AND SELF INFORMATION ONLY
         26                MANAGEMENT REGISTRATION/SCN
         27                OBJECT REMOVED
         28                OBJECT ADDED
         29                OBJECT UPDATED
         30                DD/DDS MEMBER REMOVED (Mgmt Reg/SCN only)
         31 (Lsb)          DD/DDS MEMBER ADDED (Mgmt Reg/SCN only)
         All others        RESERVED
 DD/DDS MEMBER REMOVED indicates that an existing member of a
 Discovery Domain and/or Discovery Domain Set has been removed.
 DD/DDS MEMBER ADDED indicates that a new member was added to an
 existing DD and/or DDS.
 OBJECT REMOVED, OBJECT ADDED, and OBJECT UPDATED indicate a Network
 Entity, Portal, Storage Node, FC Device, DD, and/or DDS object was
 removed from, added to, or updated in the Discovery Domain or in the
 iSNS database (Control Nodes only).

Tseng, et al. Standards Track [Page 86] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Regular SCNs provide information about objects that are updated in,
 added to or removed from Discovery Domains of which the Storage Node
 is a member.  An SCN or SCN registration is considered a regular SCN
 or regular SCN registration if the MANAGEMENT REGISTRATION/SCN flag
 is cleared.  All iSNS clients may register for regular SCNs.
 Management SCNs provide information about all changes to the network,
 regardless of discovery domain membership.  Registration for
 management SCNs is indicated by setting bit 26 to 1.  Only Control
 Nodes may register for management SCNs.  Bits 30 and 31 may only be
 enabled if bit 26 is set to 1.
 TARGET AND SELF INFORMATION ONLY SCNs (bit 25) provides information
 only about changes to target devices, or if the iSCSI Storage Node
 itself has undergone a change.  Similarly, INITIATOR AND SELF
 INFORMATION ONLY SCNs (bit 24) provides information only about
 changes to initiator Nodes, or to the target itself.

6.4.5. iSCSI Node Index

 The iSCSI Node Index is a 4-byte non-zero integer value used as a key
 that uniquely identifies each iSCSI Storage Node registered in the
 iSNS database.  Upon initial registration of the iSCSI Storage Node,
 the iSNS server assigns an unused value for the iSCSI Node Index.
 Each iSCSI Node MUST be assigned a value for the iSCSI Node Index
 that is not assigned to any other iSCSI Storage Node.  Furthermore,
 iSCSI Node Index values for recently deregistered iSCSI Storage Nodes
 SHOULD NOT be reused in the short term.
 The iSCSI Node Index may be used as a key to represent a registered
 Node in situations where the iSCSI Name is too long to be used as a
 key.  An example of this is when SNMP is used for management, as
 described in Section 2.10.
 The value assigned for the iSCSI Node Index SHALL persist as long as
 the iSCSI Storage Node is registered in the iSNS database or a member
 of a Discovery Domain.  An iSCSI Node Index value that is assigned
 for a Storage Node SHALL NOT be used for any other Storage Node as
 long as the original node is registered in the iSNS database or a
 member of a Discovery Domain.

6.4.6. WWNN Token

 This field contains a globally unique 64-bit integer value that can
 be used to represent the World Wide Node Name of the iSCSI device in
 a Fibre Channel fabric.  This identifier is used during the device
 registration process and MUST conform to the requirements in [FC-FS].

Tseng, et al. Standards Track [Page 87] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 The FC-iSCSI gateway uses the value found in this field to register
 the iSCSI device in the Fibre Channel name server.  It is stored in
 the iSNS server to prevent conflict when "proxy" WWNN values are
 assigned to iSCSI initiators establishing storage sessions to devices
 in the FC fabric.
 If the iSNS client does not assign a value for WWNN Token, then the
 iSNS server SHALL provide a value for this field upon initial
 registration of the iSCSI Storage Node.  The process by which the
 WWNN Token is assigned by the iSNS server MUST conform to the
 following requirements:
 1.  The assigned WWNN Token value MUST be unique among all WWN
     entries in the existing iSNS database, and among all devices that
     can potentially be registered in the iSNS database.
 2.  Once the value is assigned, the iSNS server MUST persistently
     save the mapping between the WWNN Token value and registered
     iSCSI Name.  That is, successive re-registrations of the iSCSI
     Storage Node keyed by the same iSCSI Name maintain the original
     mapping to the associated WWNN Token value in the iSNS server.
     Similarly, the mapping SHALL be persistent across iSNS server
     reboots.  Once assigned, the mapping can only be changed if a
     DevAttrReg message from an authorized iSNS client explicitly
     provides a different WWNN Token value.
 3.  Once a WWNN Token value has been assigned and mapped to an iSCSI
     name, that WWNN Token value SHALL NOT be reused or mapped to any
     other iSCSI name.
 4.  The assigned WWNN Token value MUST conform to the formatting
     requirements of [FC-FS] for World Wide Names (WWNs).
 An iSNS client, such as an FC-iSCSI gateway or the iSCSI initiator,
 MAY register its own WWNN Token value or overwrite the iSNS Server-
 supplied WWNN Token value, if it wishes to supply its own iSCSI-FC
 name mapping.  This is accomplished using the DevAttrReg message with
 the WWNN Token (tag=37) as an operating attribute.  Once overwritten,
 the new WWNN Token value MUST be stored and saved by the iSNS server,
 and all requirements specified above continue to apply.  If an iSNS
 client attempts to register a value for this field that is not unique
 in the iSNS database or that is otherwise invalid, then the
 registration SHALL be rejected with an Status Code of 3 (Invalid
 Registration).

Tseng, et al. Standards Track [Page 88] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 There MAY be matching records in the iSNS database for the Fibre
 Channel device specified by the WWNN Token.  These records may
 contain device attributes for that FC device registered in the Fibre
 Channel fabric name server.

6.4.7. iSCSI Node Next Index

 This is a virtual attribute containing a 4-byte integer value that
 indicates the next available (i.e., unused) iSCSI Node Index value.
 This attribute may only be queried; the iSNS server SHALL return an
 error code of 3 (Invalid Registration) to any client that attempts to
 register a value for this attribute.  A Message Key is not required
 when exclusively querying for this attribute.
 The iSCSI Node Next Index MAY be used by an SNMP client to create an
 entry in the iSNS server.  SNMP requirements are described in Section
 2.10.

6.4.8. iSCSI AuthMethod

 This attribute contains a NULL-terminated string of UTF-8 text
 listing the iSCSI authentication methods enabled for this iSCSI
 Storage Node, in order of preference.  The text values used to
 identify iSCSI authentication methods are embedded in this string
 attribute and delineated by a comma.  The text values are identical
 to those found in the main iSCSI document [iSCSI]; additional
 vendor-specific text values are also possible.
        Text Value       Description                   Reference
        ----------       -----------                   ---------
         KB5             Kerberos V5                   [RFC1510]
         SPKM1           Simple Public Key GSS-API     [RFC2025]
         SPKM2           Simple Public Key GSS-API     [RFC2025]
         SRP             Secure Remote Password        [RFC2945]
         CHAP            Challenge Handshake Protocol  [RFC1994]
         none            No iSCSI Authentication

6.5. Portal Group (PG) Object-Keyed Attributes

 The following attributes are used to associate Portal and iSCSI
 Storage Node objects.  PG objects are stored in the iSNS database
 using the PG iSCSI Name, the PG Portal IP Address, and the PG Portal
 TCP/UDP Port as keys.  New PG objects are implicitly or explicitly
 created at the time that the corresponding Portal and/or iSCSI
 Storage Node objects are registered.  Section 3.4 has a general
 discussion of PG usage.  For further details on use of Portal Groups,
 see [iSCSI].

Tseng, et al. Standards Track [Page 89] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.5.1. Portal Group iSCSI Name

 This is the iSCSI Name for the iSCSI Storage Node that is associated
 with the PG object.  This name MAY represent an iSCSI Storage Node
 not currently registered in the server.

6.5.2. PG Portal IP Addr

 This is the Portal IP Address attribute for the Portal that is
 associated with the PG object.  This Portal IP Address MAY be that of
 a Portal that is not currently registered in the server.

6.5.3. PG Portal TCP/UDP Port

 This is the Portal TCP/UDP Port attribute for the Portal that is
 associated with the PG object.  This Portal TCP/UDP Port MAY be that
 of a Portal that is not currently registered in the server.

6.5.4. Portal Group Tag (PGT)

 This field is used to group Portals in order to coordinate
 connections in a session across Portals to a specified iSCSI Node.
 The PGT is a value in the range of 0-65535, or NULL.  A NULL PGT
 value is registered by using 0 for the length in the TLV during
 registration.  The two least significant bytes of the value contain
 the PGT for the object.  The two most significant bytes are reserved.
 If a PGT value is not explicitly registered for an iSCSI Storage Node
 and Portal pair, then the PGT value SHALL be implicitly registered as
 0x00000001.

6.5.5. Portal Group Index

 The PG Index is a 4-byte non-zero integer value used as a key that
 uniquely identifies each PG object registered in the iSNS database.
 Upon initial registration of a PG object, the iSNS server MUST assign
 an unused value for the PG Index.  Furthermore, PG Index values for
 recently deregistered PG objects SHOULD NOT be reused in the short
 term.
 The PG Index MAY be used as the key to reference a registered PG in
 situations where a unique index for each PG object is required.  It
 MAY also be used as the message key in an iSNS message to query or
 update a pre-existing PG object.  An example of this is when SNMP is
 used for management, as described in Section 2.10.  The value
 assigned for the PG Index SHALL persist as long as the server is
 active.

Tseng, et al. Standards Track [Page 90] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.5.6. Portal Group Next Index

 The PG Next Index is a virtual attribute containing a 4-byte integer
 value that indicates the next available (i.e., unused) PG Index
 value.  This attribute may only be queried; the iSNS server SHALL
 return an error code of 3 (Invalid Registration) to any client that
 attempts to register a value for this attribute.  A Message Key is
 not required when exclusively querying for this attribute.
 The Portal Group Next Index MAY be used by an SNMP client to create
 an entry in the iSNS server.  SNMP requirements are described in
 Section 2.10.

6.6. FC Port Name-Keyed Attributes

 The following attributes are registered in the iSNS database using
 the FC Port World Wide Name (WWPN) attribute as the key.  Each set of
 FC Port-Keyed attributes is associated with one Entity Identifier
 object key.
 Although the FC Port World Wide Name is associated with one Entity
 Identifier, it is also globally unique.

6.6.1. FC Port Name (WWPN)

 This 64-bit identifier uniquely defines the FC Port, and it is the
 World Wide Port Name (WWPN) of the corresponding Fibre Channel
 device.  This attribute is the key for the iFCP Storage Node.  This
 globally unique identifier is used during the device registration
 process, and it uses a value conforming to IEEE EUI-64 [EUI-64].

6.6.2. Port ID (FC_ID)

 The Port Identifier is a Fibre Channel address identifier assigned to
 an N_Port or NL_Port during fabric login.  The format of the Port
 Identifier is defined in [FC-FS].  The least significant 3 bytes
 contain this address identifier.  The most significant byte is
 RESERVED.

Tseng, et al. Standards Track [Page 91] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.6.3. FC Port Type

 Indicates the type of FC port.  Encoded values for this field are
 listed in the following table:
        Type              Description
        ----              -----------
         0x0000           Unidentified/Null Entry
         0x0001           Fibre Channel N_Port
         0x0002           Fibre Channel NL_Port
         0x0003           Fibre Channel F/NL_Port
         0x0004-0080      RESERVED
         0x0081           Fibre Channel F_Port
         0x0082           Fibre Channel FL_Port
         0x0083           RESERVED
         0x0084           Fibre Channel E_Port
         0x0085-00FF      RESERVED
         0xFF11           RESERVED
         0xFF12           iFCP Port
         0xFF13-FFFF      RESERVED

6.6.4. Symbolic Port Name

 This is a variable-length UTF-8 encoded NULL-terminated text-based
 description of up to 256 bytes that is associated with the iSNS-
 registered FC Port Name in the network.

6.6.5. Fabric Port Name (FWWN)

 This 64-bit identifier uniquely defines the fabric port.  If the port
 of the FC Device is attached to a Fibre Channel fabric port with a
 registered Port Name, then that fabric Port Name SHALL be indicated
 in this field.

6.6.6. Hard Address

 This field is the requested hard address 24-bit NL Port Identifier,
 included in the iSNSP for compatibility with Fibre Channel Arbitrated
 Loop devices and topologies.  The least significant 3 bytes of this
 field contain the address.  The most significant byte is RESERVED.

6.6.7. Port IP Address

 The Fibre Channel IP address associated with the FC Port.  When this
 field contains an IPv4 value, it is stored as an IPv4-mapped IPv6
 address.  That is, the most significant 10 bytes are set to 0x00,
 with the next two bytes set to 0xFFFF [RFC2373].  When an IPv6 value
 is contained in this field, then the entire 16-byte field is used.

Tseng, et al. Standards Track [Page 92] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.6.8. Class of Service (COS)

 This 32-bit bit-map field indicates the Fibre Channel Class of
 Service types that are supported by the registered port.  In the
 following table, a set bit (1) indicates a Class of Service
 supported.
        Bit Position       Description
        ------------       -----------
         29                Fibre Channel Class 2 Supported
         28                Fibre Channel Class 3 Supported

6.6.9. FC-4 Types

 This 32-byte field indicates the FC-4 protocol types supported by the
 associated port.  This field can be used to support Fibre Channel
 devices and is consistent with FC-GS-4.

6.6.10. FC-4 Descriptor

 This is a variable-length UTF-8 encoded NULL-terminated text-based
 description of up to 256 bytes that is associated with the iSNS-
 registered device port in the network.  This field can be used to
 support Fibre Channel devices and is consistent with FC-GS-4.

6.6.11. FC-4 Features

 This is a 128-byte array, 4 bits per type, for the FC-4 protocol
 types supported by the associated port.  This field can be used to
 support Fibre Channel devices and is consistent with FC-GS-4.

6.6.12. iFCP SCN Bitmap

 This field indicates the events the iSNS client is interested in.
 These events can cause SCNs to be generated.  SCNs provide
 information about objects that are updated in, added to or removed
 from Discovery Domains of which the source and destination are a
 member.  Management SCNs provide information about all changes to the
 network.  A set bit (1) indicates the type of SCN for the bitmap as
 follows:

Tseng, et al. Standards Track [Page 93] RFC 4171 Internet Storage Name Service (iSNS) September 2005

        Bit Position       Flag Description
        ------------       ----------------
         24                INITIATOR AND SELF INFORMATION ONLY
         25                TARGET AND SELF INFORMATION ONLY
         26                MANAGEMENT REGISTRATION/SCN
         27                OBJECT REMOVED
         28                OBJECT ADDED
         29                OBJECT UPDATED
         30                DD/DDS MEMBER REMOVED (Mgmt Reg/SCN only)
         31 (Lsb)          DD/DDS MEMBER ADDED (Mgmt Reg/SCN only)
         All others        RESERVED
 Further information on the use of the bit positions specified above
 can be found in Section 6.4.4.

6.6.13. Port Role

 This required 32-bit field is a bitmap indicating the type of iFCP
 Storage Node.  The bit fields are defined below.  A set bit indicates
 the Node has the corresponding characteristics.
        Bit Position       Node Type
        ------------       ---------
         29                Control
         30                FCP Initiator
         31 (Lsb)          FCP Target
         All Others        RESERVED
 If the 'Target' bit is set to 1, then the port represents an FC
 target.  Setting of the 'Target' bit MAY be performed by iSNS clients
 using the iSNSP.
 If the 'Initiator' bit is set to 1, then the port represents an FC
 initiator.  Setting of the 'Initiator' bit MAY be performed by iSNS
 clients using the iSNSP.
 If the 'Control' bit is set to 1, then the port represents a gateway,
 a management station, an iSNS backup server, or another device.
 This is usually a special device that is neither an initiator nor a
 target, which requires the ability to send and receive iSNSP
 messages, including state-change notifications.  Setting the control
 bit is an administrative task that MUST be administratively
 configured on the iSNS server; iSNS clients SHALL NOT be allowed to
 change this bit using the iSNSP.

Tseng, et al. Standards Track [Page 94] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 This field MAY be used by the iSNS server to distinguish among
 permissions by different iSNS clients.  For example, an iSNS server
 implementation may be administratively configured to allow only
 targets to receive ESIs, or to permit only Control Nodes to add,
 modify, or delete discovery domains.

6.6.14. Permanent Port Name (PPN)

 The Permanent Port Name can be used to support Fibre Channel devices
 and is consistent with the PPN description in FC-GS-4 [FC-GS-4].  The
 format of the PPN is identical to the FC Port Name WWPN attribute
 format.

6.7. Node-Keyed Attributes

 The following attributes are registered in the iSNS database using
 the FC Node Name (WWNN) attribute as the key.  Each set of FC Node-
 Keyed attributes represents a single device and can be associated
 with many FC Ports.
 The FC Node Name is unique across the entire iSNS database.

6.7.1. FC Node Name (WWNN)

 The FC Node Name is a 64-bit identifier that is the World Wide Node
 Name (WWNN) of the corresponding Fibre Channel device.  This
 attribute is the key for the FC Device.  This globally unique
 identifier is used during the device registration process, and it
 uses a value conforming to IEEE EUI-64 [EUI-64].

6.7.2. Symbolic Node Name

 This is a variable-length UTF-8 encoded NULL-terminated text-based
 description of up to 256 bytes that is associated with the iSNS-
 registered FC Device in the network.

6.7.3. Node IP Address

 This IP address is associated with the device Node in the network.
 This field is included for compatibility with Fibre Channel.  When
 this field contains an IPv4 value, it is stored as an IPv4-mapped
 IPv6 address.  That is, the most significant 10 bytes are set to
 0x00, with the next two bytes set to 0xFFFF [RFC2373].  When an IPv6
 value is contained in this field, the entire 16-byte field is used.

Tseng, et al. Standards Track [Page 95] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.7.4. Node IPA

 This field is the 8-byte Fibre Channel Initial Process Associator
 (IPA) associated with the device Node in the network.  The initial
 process associator is used for communication between Fibre Channel
 devices.

6.7.5. Proxy iSCSI Name

 This is a variable-length UTF-8 encoded NULL-terminated text-based
 field that contains the iSCSI Name used to represent the FC Node in
 the IP network.  It is used as a pointer to the matching iSCSI Name
 entry in the iSNS server.  Its value is usually registered by an FC-
 iSCSI gateway connecting the IP network to the fabric containing the
 FC device.
 Note that if this field is used, there SHOULD be a matching entry in
 the iSNS database for the iSCSI device specified by the iSCSI name.
 The database entry should include the full range of iSCSI attributes
 needed for discovery and management of the "iSCSI proxy image" of the
 FC device.

6.8. Other Attributes

 The following are not attributes of the previously-defined objects.

6.8.1. FC-4 Type Code

 This is a 4-byte field used to provide a FC-4 type during a FC-4 Type
 query.  The FC-4 types are consistent with the FC-4 Types as defined
 in FC-FS.  Byte 0 contains the FC-4 type.  All other bytes are
 reserved.

6.8.2. iFCP Switch Name

 The iFCP Switch Name is a 64-bit World Wide Name (WWN) identifier
 that uniquely identifies a distinct iFCP gateway in the network.
 This globally unique identifier is used during the switch
 registration/FC_DOMAIN_ID assignment process.  The iFCP Switch Name
 value used MUST conform to the requirements stated in [FC-FS] for
 World Wide Names.  The iSNS server SHALL track the state of all
 FC_DOMAIN_ID values that have been allocated to each iFCP Switch
 Name.  If a given iFCP Switch Name is deregistered from the iSNS
 database, then all FC_DOMAIN_ID values allocated to that iFCP Switch
 Name SHALL be returned to the unused pool of values.

Tseng, et al. Standards Track [Page 96] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.8.3. iFCP Transparent Mode Commands

6.8.3.1. Preferred ID

 This is a 4-byte unsigned integer field, and it is the requested
 value that the iSNS client wishes to use for the FC_DOMAIN_ID.  The
 iSNS server SHALL grant the iSNS client the use of the requested
 value as the FC_DOMAIN_ID, if the requested value has not already
 been allocated.  If the requested value is not available, the iSNS
 server SHALL return a different value that has not been allocated.

6.8.3.2. Assigned ID

 This is a 4-byte unsigned integer field that is used by an iFCP
 gateway to reserve its own unique FC_DOMAIN_ID value from the range 1
 to 239.  When a FC_DOMAIN_ID is no longer required, it SHALL be
 released by the iFCP gateway using the RlseDomId message.  The iSNS
 server MUST use the Entity Status Inquiry message to determine
 whether an iFCP gateway is still present on the network.

6.8.3.3. Virtual_Fabric_ID

 This is a variable-length UTF-8 encoded NULL-terminated text-based
 field of up to 256 bytes.  The Virtual_Fabric_ID string is used as a
 key attribute to identify a range of non-overlapping FC_DOMAIN_ID
 values to be allocated using RqstDomId.  Each Virtual_Fabric_ID
 string submitted by an iSNS client SHALL have its own range of non-
 overlapping FC_DOMAIN_ID values to be allocated to iSNS clients.

6.9. iSNS Server-Specific Attributes

 Access to the following attributes may be administratively
 controlled.  These attributes are specific to the iSNS server
 instance; the same value is returned for all iSNS clients accessing
 the iSNS server.  Only query messages may be performed on these
 attributes.  Attempted registrations of values for these attributes
 SHALL return a status code of 3 (Invalid Registration).
 A query for an iSNS Server-Specific attribute MUST contain the
 identifying key attribute (i.e., iSCSI Name or FC Port Name WWPN) of
 the Node originating the registration or query message as the Source
 and Message Key attributes.  The Operating Attributes are the
 server-specific attributes being registered or queried.

Tseng, et al. Standards Track [Page 97] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.9.1. iSNS Server Vendor OUI

 This attribute is the OUI (Organizationally Unique Identifier)
 [802-1990] identifying the specific vendor implementing the iSNS
 server. This attribute can only be queried; iSNS clients SHALL NOT be
 allowed to register a value for the iSNS Server Vendor OUI.

6.10. Vendor-Specific Attributes

 iSNS server implementations MAY define vendor-specific attributes for
 private use.  These attributes MAY be used to store optional data
 that is registered and/or queried by iSNS clients in order to gain
 optional capabilities.  Note that any implementation of vendor-
 specific attributes in the iSNS server SHALL NOT impose any form of
 mandatory behavior on the part of the iSNS client.
 The tag values used for vendor-specific and user-specific use are
 defined in Section 6.1.  To avoid misinterpreting proprietary
 attributes, the vendor's own OUI (Organizationally Unique Identifier)
 MUST be placed in the upper three bytes of the attribute value field
 itself.
 The OUI is defined in IEEE Std 802-1990 and is the same constant used
 to generate 48 bit Universal LAN MAC addresses.  A vendor's own iSNS
 implementation will then be able to recognize the OUI in the
 attribute field and be able to execute vendor-specific handling of
 the attribute.

6.10.1. Vendor-Specific Server Attributes

 Attributes with tags in the range 257 to 384 are vendor-specific or
 site-specific attributes of the iSNS server.  Values for these
 attributes are administratively set by the specific vendor providing
 the iSNS server implementation.  Query access to these attributes may
 be administratively controlled.  These attributes are unique for each
 logical iSNS server instance.  Query messages for these attributes
 SHALL use the key identifier (i.e., iSCSI Name or FC Port Name WWPN)
 for both the Source attribute and Message Key attribute.  These
 attributes can only be queried; iSNS clients SHALL NOT be allowed to
 register a value for server attributes.

6.10.2. Vendor-Specific Entity Attributes

 Attributes in the range 385 to 512 are vendor-specific or site-
 specific attributes used to describe the Network Entity object.
 These attributes are keyed by the Entity Identifier attribute
 (tag=1).

Tseng, et al. Standards Track [Page 98] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.10.3. Vendor-Specific Portal Attributes

 Attributes in the range 513 to 640 are vendor-specific or site-
 specific attributes used to describe the Portal object.  These
 attributes are keyed by the Portal IP-Address (tag=16) and Portal
 TCP/UDP Port (tag=17).

6.10.4. Vendor-Specific iSCSI Node Attributes

 Attributes in the range 641 to 768 are vendor-specific or site-
 specific attributes used to describe the iSCSI Node object.  These
 attributes are keyed by the iSCSI Name (tag=32).

6.10.5. Vendor-Specific FC Port Name Attributes

 Attributes in the range 769 to 896 are vendor-specific or site-
 specific attributes used to describe the N_Port Port Name object.
 These attributes are keyed by the FC Port Name WWPN (tag=64).

6.10.6. Vendor-Specific FC Node Name Attributes

 Attributes in the range 897 to 1024 are vendor-specific or site-
 specific attributes used to describe the FC Node Name object.  These
 attributes are keyed by the FC Node Name WWNN (tag=96).

6.10.7. Vendor-Specific Discovery Domain Attributes

 Attributes in the range 1025 to 1280 are vendor-specific or site-
 specific attributes used to describe the Discovery Domain object.
 These attributes are keyed by the DD_ID (tag=104).

6.10.8. Vendor-Specific Discovery Domain Set Attributes

 Attributes in the range 1281 to 1536 are vendor-specific or site-
 specific attributes used to describe the Discovery Domain Set object.
 These attributes are keyed by the DD Set ID (tag=101)

6.10.9. Other Vendor-Specific Attributes

 Attributes in the range 1537 to 2048 can be used for key and non-key
 attributes that describe new vendor-specific objects specific to the
 vendor's iSNS server implementation.

Tseng, et al. Standards Track [Page 99] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.11. Discovery Domain Registration Attributes

6.11.1. DD Set ID Keyed Attributes

6.11.1.1. Discovery Domain Set ID (DDS ID)

 The DDS ID is an unsigned non-zero integer identifier used in the
 iSNS directory database as a key to indicate a Discovery Domain Set
 uniquely.  A DDS is a collection of Discovery Domains that can be
 enabled or disabled by a management station.  This value is used as a
 key for DDS attribute queries.  When a Discovery Domain is
 registered, it is initially not in any DDS.
 If the iSNS client does not provide a DDS_ID in a DDS registration
 request message, the iSNS server SHALL generate a DDS_ID value that
 is unique within the iSNS database for that new DDS.  The created DDS
 ID SHALL be returned in the response message.  The DDS ID value of 0
 is reserved, and the DDS ID value of 1 is used for the default DDS
 (see Section 2.2.2).

6.11.1.2. Discovery Domain Set Symbolic Name

 A variable-length UTF-8 encoded NULL-terminated text-based field of
 up to 256 bytes.  This is a user-readable field used to assist a
 network administrator in tracking the DDS function.  When a client
 registers a DDS symbolic name, the iSNS server SHALL verify it is
 unique.  If the name is not unique, then the DDS registration SHALL
 be rejected with an "Invalid Registration" Status Code.  The invalid
 attribute(s), in this case the DDS symbolic name, SHALL be included
 in the response.

6.11.1.3. Discovery Domain Set Status

 The DDS_Status field is a 32-bit bitmap indicating the status of the
 DDS.  Bit 0 of the bitmap indicates whether the DDS is Enabled (1) or
 Disabled (0).  The default value for the DDS Enabled flag is Disabled
 (0).
        Bit Position    DDS Status
        ------------    ---------
         31  (Lsb)      DDS Enabled (1) / DDS Disabled (0)
         All others     RESERVED

6.11.1.4. Discovery Domain Set Next ID

 This is a virtual attribute containing a 4-byte integer value that
 indicates the next available (i.e., unused) Discovery Domain Set
 Index value.  This attribute may only be queried; the iSNS server

Tseng, et al. Standards Track [Page 100] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 SHALL return an error code of 3 (Invalid Registration) to any client
 that attempts to register a value for this attribute.  A Message Key
 is not required when exclusively querying for this attribute.
 The Discovery Domain Set Next Index MAY be used by an SNMP client to
 create an entry in the iSNS server.  SNMP requirements are described
 in Section 2.10.

6.11.2. DD ID Keyed Attributes

6.11.2.1. Discovery Domain ID (DD ID)

 The DD ID is an unsigned non-zero integer identifier used in the iSNS
 directory database as a key to identify a Discovery Domain uniquely.
 This value is used as the key for any DD attribute query.  If the
 iSNS client does not provide a DD_ID in a DD registration request
 message, the iSNS server SHALL generate a DD_ID value that is unique
 within the iSNS database for that new DD (i.e., the iSNS client will
 be registered in a new DD).  The created DD ID SHALL be returned in
 the response message.  The DD ID value of 0 is reserved, and the DD
 ID value of 1 is used for the default DD (see Section 2.2.2).

6.11.2.2. Discovery Domain Symbolic Name

 A variable-length UTF-8 encoded NULL-terminated text-based field of
 up to 256 bytes.  When a client registers a DD symbolic name, the
 iSNS server SHALL verify it is unique.  If the name is not unique,
 then the DD registration SHALL be rejected with an "Invalid
 Registration" Status Code.  The invalid attribute(s), in this case
 the DD symbolic name, SHALL be included in the response.

6.11.2.3. Discovery Domain Member: iSCSI Node Index

 This is the iSCSI Node Index of a Storage Node that is a member of
 the DD.  The DD may have a list of 0 to n members.  The iSCSI Node
 Index is one alternative representation of membership in a Discovery
 Domain, the other alternative being the iSCSI Name.  The Discovery
 Domain iSCSI Node Index is a 4-byte non-zero integer value.
 The iSCSI Node Index can be used to represent a DD member in
 situations where the iSCSI Name is too long to be used.  An example
 of this is when SNMP is used for management, as described in Section
 2.10.
 The iSCSI Node Index and the iSCSI Name stored as a member in a DD
 SHALL be consistent with the iSCSI Node Index and iSCSI Name
 attributes registered for the Storage Node object in the iSNS server.

Tseng, et al. Standards Track [Page 101] RFC 4171 Internet Storage Name Service (iSNS) September 2005

6.11.2.4. Discovery Domain Member: iSCSI Name

 A variable-length UTF-8 encoded NULL-terminated text-based field of
 up to 224 bytes.  It indicates membership for the specified iSCSI
 Storage Node in the Discovery Domain.  Note that the referenced
 Storage Node does not need to be actively registered in the iSNS
 database before the iSNS client uses this attribute.  There is no
 limit to the number of members that may be in a DD.  Membership is
 represented by the iSCSI Name of the iSCSI Storage Node.

6.11.2.5. Discovery Domain Member: FC Port Name

 This 64-bit identifier attribute indicates membership for an iFCP
 Storage Node (FC Port) in the Discovery Domain.  Note that the
 referenced Storage Node does not need to be actively registered in
 the iSNS database before the iSNS client uses this attribute.  There
 is no limit to the number of members that may be in a DD.  Membership
 is represented by the FC Port Name (WWPN) of the iFCP Storage Node.

6.11.2.6. Discovery Domain Member: Portal Index

 This attribute indicates membership in the Discovery Domain for a
 Portal.  It is an alternative representation for Portal membership to
 the Portal IP Address and Portal TCP/UDP Port.  The referenced Portal
 MUST be actively registered in the iSNS database before the iSNS
 client uses this attribute.

6.11.2.7. Discovery Domain Member: Portal IP Address

 This attribute and the Portal TCP/UDP Port attribute indicate
 membership in the Discovery Domain for the specified Portal.  Note
 that the referenced Portal does not need to be actively registered in
 the iSNS database before the iSNS client uses this attribute.

6.11.2.8. Discovery Domain Member: Portal TCP/UDP Port

 This attribute and the Portal IP Address attribute indicate
 membership in the Discovery Domain for the specified Portal.  Note
 that the referenced Portal does not need to be actively registered in
 the iSNS database before the iSNS client uses this attribute.

6.11.2.9. Discovery Domain Features

 The Discovery Domain Features is a bitmap indicating the features of
 this DD.  The bit positions are defined below.  A bit set to 1
 indicates the DD has the corresponding characteristics.

Tseng, et al. Standards Track [Page 102] RFC 4171 Internet Storage Name Service (iSNS) September 2005

        Bit Position     DD Feature
        ------------     ----------
         31 (Lsb)        Boot List Enabled (1)/Boot List Disabled (0)
         All others      RESERVED
 Boot List: this feature indicates that the target(s) in this DD
 provides boot capabilities for the member initiators, as described in
 [iSCSI-boot].

6.11.2.10. Discovery Domain Next ID

 This is a virtual attribute containing a 4-byte integer value that
 indicates the next available (i.e., unused) Discovery Domain Index
 value.  This attribute may only be queried; the iSNS server SHALL
 return an error code of 3 (Invalid Registration) to any client that
 attempts to register a value for this attribute.  A Message Key is
 not required when exclusively querying for this attribute.

7. Security Considerations

7.1. iSNS Security Threat Analysis

 When the iSNS protocol is deployed, the interaction between iSNS
 server and iSNS clients is subject to the following security threats:
 a)  An attacker could alter iSNS protocol messages, such as to direct
     iSCSI and iFCP devices to establish connections with rogue peer
     devices, or to weaken/eliminate IPSec protection for iSCSI or
     iFCP traffic.
 b)  An attacker could masquerade as the real iSNS server using false
     iSNS heartbeat messages.  This could cause iSCSI and iFCP devices
     to use rogue iSNS servers.
 c)  An attacker could gain knowledge about iSCSI and iFCP devices by
     snooping iSNS protocol messages.  Such information could aid an
     attacker in mounting a direct attack on iSCSI and iFCP devices,
     such as a denial-of-service attack or outright physical theft.
 To address these threats, the following capabilities are needed:
 a)  Unicast iSNS protocol messages may need to be authenticated.  In
     addition, to protect against threat c), confidentiality support
     is desirable and is REQUIRED when certain functions of iSNS
     server are utilized.

Tseng, et al. Standards Track [Page 103] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 b)  Multicast iSNS protocol messages such as the iSNS heartbeat
     message may need to be authenticated.  These messages need not be
     confidential since they do not leak critical information.

7.2. iSNS Security Implementation and Usage Requirements

 If the iSNS server is used to distribute authorizations for
 communications between iFCP and iSCSI peer devices, IPsec ESP with
 null transform MUST be implemented, and non-null transform MAY be
 implemented.  If a non-null transform is implemented, then the DES
 encryption algorithm SHOULD NOT be used.
 If the iSNS server is used to distribute security policy for iFCP and
 iSCSI devices, then authentication, data integrity, and
 confidentiality MUST be supported and used.  Where confidentiality is
 desired or required, IPSec ESP with non-null transform SHOULD be
 used, and the DES encryption algorithm SHOULD NOT be used.
 If the iSNS server is used to provide the boot list for clients, as
 described in Section 6.11.2.9, then the iSCSI boot client SHOULD
 implement a secure iSNS connection.
 In order to protect against an attacker masquerading as an iSNS
 server, client devices MUST support the ability to authenticate
 broadcast or multicast messages such as the iSNS heartbeat.  The iSNS
 authentication block (which is identical in format to the SLP
 authentication block) SHALL be used for this purpose.  iSNS clients
 MUST implement the iSNS authentication block and MUST support BSD
 value 0x002.  If the iSNS server supports broadcast or multicast iSNS
 messages (i.e., the heartbeat), then the server MUST implement the
 iSNS authentication block and MUST support BSD value 0x002.  Note
 that the authentication block is used only for iSNS broadcast or
 multicast messages and MUST NOT be used in unicast iSNS messages.
 There is no requirement that the communicating identities in iSNS
 protocol messages be kept confidential.  Specifically, the identity
 and location of the iSNS server is not considered confidential.
 For protecting unicast iSNS protocol messages, iSNS servers
 supporting security MUST implement ESP in tunnel mode and MAY
 implement transport mode.
 All iSNS implementations supporting security MUST support the replay
 protection mechanisms of IPsec.
 iSNS security implementations MUST support both IKE Main Mode and
 Aggressive Mode for authentication, negotiation of security
 associations, and key management, using the IPSec DOI [RFC2407].

Tseng, et al. Standards Track [Page 104] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 Manual keying SHOULD NOT be used since it does not provide the
 necessary rekeying support.  Conforming iSNS security implementations
 MUST support authentication using a pre-shared key, and MAY support
 certificate-based peer authentication using digital signatures.  Peer
 authentication using the public key encryption methods outlined in
 IKEs Sections 5.2 and 5.3 [RFC2409] SHOULD NOT be supported.
 Conforming iSNS implementations MUST support both IKE Main Mode and
 Aggressive Mode.  IKE Main Mode with pre-shared key authentication
 SHOULD NOT be used when either of the peers use dynamically assigned
 IP addresses.  Although Main Mode with pre-shared key authentication
 offers good security in many cases, situations where dynamically
 assigned addresses are used force the use of a group pre-shared key,
 which is vulnerable to man-in-the-middle attack.  IKE Identity
 Payload ID_KEY_ID MUST NOT be used.
 When digital signatures are used for authentication, either IKE Main
 Mode or IKE Aggressive Mode MAY be used.  In all cases, access to
 locally stored secret information (pre-shared key or private key for
 digital signing) MUST be suitably restricted, since compromise of the
 secret information nullifies the security properties of the IKE/IPsec
 protocols.
 When digital signatures are used to achieve authentication, an IKE
 negotiator SHOULD use IKE Certificate Request Payload(s) to specify
 the certificate authority (or authorities) that are trusted in
 accordance with its local policy.  IKE negotiators SHOULD check the
 pertinent Certificate Revocation List (CRL) before accepting a PKI
 certificate for use in IKE's authentication procedures.
 When the iSNS server is used without security, IP block storage
 protocol implementations MUST support a negative cache for
 authentication failures.  This allows implementations to avoid
 continually contacting discovered endpoints that fail authentication
 within IPsec or at the application layer (in the case of iSCSI
 Login).  The negative cache need not be maintained within the IPsec
 implementation, but rather within the IP block storage protocol
 implementation.

7.3. Discovering Security Requirements of Peer Devices

 Once communication between iSNS clients and the iSNS server has been
 secured through use of IPSec, the iSNS client devices have the
 capability to discover the security settings that they need to use
 for their peer-to-peer communications using the iSCSI and/or iFCP
 protocols.  This provides a potential scaling advantage over device-
 by-device configuration of individual security policies for each
 iSCSI and iFCP device.

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 The iSNS server stores security settings for each iSCSI and iFCP
 device interface.  These security settings, which can be retrieved by
 authorized hosts, include use or non-use of IPSec, IKE, Main Mode,
 and Aggressive Mode.  For example, IKE may not be enabled for a
 particular interface of a peer device.  If a peer device can learn of
 this in advance by consulting the iSNS server, it will not need to
 waste time and resources attempting to initiate an IKE phase 1
 session with that peer device interface.
 If iSNS is used for this purpose, then the minimum information that
 should be learned from the iSNS server is the use or non-use of IKE
 and IPSec by each iFCP or iSCSI peer device interface.  This
 information is encoded in the Security Bitmap field of each Portal of
 the peer device, and is applicable on a per-interface basis for the
 peer device.  iSNS queries for acquiring security configuration data
 about peer devices MUST be protected by IPSec/ESP authentication.

7.4. Configuring Security Policies of iFCP/iSCSI Devices

 Use of iSNS for distribution of security policies offers the
 potential to reduce the burden of manual device configuration, and to
 decrease the probability of communications failures due to
 incompatible security policies.  If iSNS is used to distribute
 security policies, then IPSec authentication, data integrity, and
 confidentiality MUST be used to protect all iSNS protocol messages.
 The complete IKE/IPSec configuration of each iFCP and/or iSCSI device
 can be stored in the iSNS server, including policies that are used
 for IKE Phase 1 and Phase 2 negotiations between client devices.  The
 IKE payload format includes a series of one or more proposals that
 the iSCSI or iFCP device will use when negotiating the appropriate
 IPsec policy to use to protect iSCSI or iFCP traffic.
 In addition, the iSCSI Authentication Methods used by each iSCSI
 device can also be stored in the iSNS server.  The iSCSI AuthMethod
 field (tag=42) contains a null-terminated string embedded with the
 text values indicating iSCSI authentication methods to be used by
 that iSCSI device.
 Note that iSNS distribution of security policy is not necessary if
 the security settings can be determined by other means, such as
 manual configuration or IPsec security policy distribution.  If a
 network entity has already obtained its security configuration via
 other mechanisms, then it MUST NOT request security policy via iSNS.

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7.5. Resource Issues

 The iSNS protocol is lightweight and will not generate a significant
 amount of traffic.  iSNS traffic is characterized by occasional
 registration, notification, and update messages that do not consume
 significant amounts of bandwidth.  Even software-based IPSec
 implementations should not have a problem handling the traffic loads
 generated by the iSNS protocol.
 To fulfill iSNS security requirements, the only additional resources
 needed beyond what is already required for iSCSI and iFCP involve the
 iSNS server.  Because iSCSI and iFCP end nodes are already required
 to implement IKE and IPSec, these existing requirements can also be
 used to fulfill IKE and IPSec requirements for iSNS clients.

7.6. iSNS Interaction with IKE and IPSec

 When IPSec security is enabled, each iSNS client with at least one
 Storage Node that is registered in the iSNS database SHALL maintain
 at least one phase-1 security association with the iSNS server.  All
 iSNS protocol messages between iSNS clients and the iSNS server SHALL
 be protected by a phase-2 security association.
 When a Network Entity is removed from the iSNS database, the iSNS
 server SHALL send a phase-1 delete message to the associated iSNS
 client IKE peer, and tear down all phase-1 and phase-2 SAs associated
 with that iSNS client.

8. IANA Considerations

 The well-known TCP and UDP port number for iSNS is 3205.
 The standards action of this RFC creates two registries to be
 maintained by IANA in support of iSNSP and assigns initial values for
 both registries.  The first registry is of Block Storage Protocols
 supported by iSNS.  The second registry is a detailed registry of
 standard iSNS attributes that can be registered to and queried from
 the iSNS server.  Note that this RFC uses the registry created for
 Block Structure Descriptor (BSD) in Section 15 of Service Location
 Protocol, Version 2 [RFC2608].

8.1. Registry of Block Storage Protocols

 In order to maintain a registry of block storage protocols supported
 by iSNSP, IANA will assign a 32-bit unsigned integer number for each
 block storage protocol supported by iSNS.  This number is stored in
 the iSNS database as the Entity Protocol.  The initial set of values
 to be maintained by IANA for Entity Protocol is indicated in the

Tseng, et al. Standards Track [Page 107] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 table in Section 6.2.2.  Additional values for new block storage
 protocols to be supported by iSNS SHALL be assigned by the IPS WG
 Chairperson, or by a Designated Expert [RFC2434] appointed by the
 IETF Transport Area Director.

8.2. Registry of Standard iSNS Attributes

 IANA is responsible for creating and maintaining the Registry of
 Standard iSNS Attributes.  The initial list of iSNS attributes is
 described in Section 6.  For each iSNS attribute this information
 MUST include, its tag value, the attribute length, and the tag values
 for the set of permissible registration and query keys that can be
 used for that attribute.  The initial list of iSNS attributes to be
 maintained by IANA is indicated in Section 6.1.
 Additions of new standard attributes to the Registry of Standard iSNS
 Attributes SHALL require IETF Consensus [RFC2434].  The RFC required
 for this process SHALL specify use of tag values reserved for IANA
 allocation in Section 6.1.  The RFC SHALL specify as a minimum, the
 new attribute tag value, attribute length, and the set of permissible
 registration and query keys that can be used for the new attribute.
 The RFC SHALL also include a discussion of the reasons for the new
 attribute(s) and how the new attribute(s) are to be used.
 As part of the process of obtaining IETF Consensus, the proposed RFC
 and its supporting documentation SHALL be made available to the IPS
 WG mailing list or, if the IPS WG is disbanded at the time, to a
 mailing list designated by the IETF Transport Area Director.  The
 review and comment period SHALL last at least three months before the
 IPS WG Chair or a person designated by the IETF Transport Area
 Director decides either to reject the proposal or to forward the
 draft to the IESG for publication as an RFC.  When the specification
 is published as an RFC, then IANA will register the new iSNS
 attribute(s) and make the registration available to the community.

8.3. Block Structure Descriptor (BSD) Registry

 Note that IANA is already responsible for assigning and maintaining
 values used for the Block Structure Descriptor for the iSNS
 Authentication Block (see Section 5.5).  Section 15 of [RFC2608]
 describes the process for allocation of new BSD values.

Tseng, et al. Standards Track [Page 108] RFC 4171 Internet Storage Name Service (iSNS) September 2005

9. Normative References

 [iSCSI]      Satran, J., Meth, K., Sapuntzakis, C., Chadalapaka, M.,
              and E. Zeidner, "Internet Small Computer Systems
              Interface (iSCSI)", RFC 3720, April 2004.
 [iFCP]       Monia, C., Mullendore, R., Travostino, F., Jeong, W.,
              and M. Edwards, "iFCP - A Protocol for Internet Fibre
              Channel Storage Networking", RFC 4172, September 2005.
 [iSNSOption] Monia, C., Tseng, J., and K. Gibbons, The IPv4 Dynamic
              Host Configuration Protocol (DHCP) Option for the
              Internet Storage Name Service, RFC 4174, September 2005.
 [RFC2608]    Guttman, E., Perkins, C., Veizades, J., and M. Day,
              "Service Location Protocol, Version 2 ", RFC 2608, June
              1999.
 [iSCSI-SLP]  Bakke, M., Hufferd, J., Voruganti, K., Krueger, M., and
              T. Sperry, "Finding Internet Small Computer Systems
              Interface (iSCSI) Targets and Name Servers by Using
              Service Location Protocol version 2 (SLP), RFC 4018,
              April 2005.
 [iSCSI-boot] Sarkar, P., Missimer, D., and C. Sapuntzakis,
              "Bootstrapping Clients using the Internet Samll Computer
              System Interface (iSCSI) Protocol", RFC 4173, September
              2005.
 [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.
 [STRINGPREP] Bakke, M., "String Profile for Internet Small Computer
              Systems Interface (iSCSI) Names", RFC 3722, April 2004.
 [NAMEPREP]   Hoffman, P. Nameprep: A Stringprep Profile for
              Internationalized Domain Names, July 2002.
 [RFC2407]    Piper, D., "The Internet IP Security Domain of
              Interpretation for ISAKMP", RFC 2407, November 1998.
 [RFC2408]    Maughan, D., Schertler, M., Schneider, M., and J.
              Turner, "Internet Security Association and Key
              Management Protocol (ISAKMP)", RFC 2408, November 1998.
 [RFC2409]    Harkins, D. and D. Carrel, "The Internet Key Exchange
              (IKE)", RFC 2409, November 1998.

Tseng, et al. Standards Track [Page 109] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 [EUI-64]     Guidelines for 64-bit Global Identifier (EUI-64)
              Registration Authority, May 2001, IEEE
 [RFC3279]    Bassham, L., Polk, W., and R. Housley, "Algorithms and
              Identifiers for the Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation
              List (CRL) Profile", RFC 3279, April 2002.
 [RFC3280]    Housley, R., Polk, W., Ford, W., and D. Solo, "Internet
              X.509 Public Key Infrastructure Certificate and
              Certificate Revocation List (CRL) Profile", RFC 3280,
              April 2002.
 [802-1990]   IEEE Standards for Local and Metropolitan Area Networks:
              Overview and Architecture, Technical Committee on
              Computer Communications of the IEEE Computer Society,
              May 31, 1990
 [FC-FS]      Fibre Channel Framing and Signaling Interface, NCITS
              Working Draft Project 1331-D

10. Informative References

 [iSNSMIB]    Gibbons, K., et al., "Definitions of Managed Objects for
              iSNS (Internet Storage name Service)", Work in Progress,
              July 2003.
 [X.509]      ITU-T Recommendation X.509 (1997 E): Information
              Technology - Open Systems Interconnection - The
              Directory: Authentication Framework, June 1997
 [FC-GS-4]    Fibre Channel Generic Services-4 (work in progress),
              NCITS Working Draft Project 1505-D
 [RFC1510]    Kohl, J. and C. Neuman, "The Kerberos Network
              Authentication Service (V5)", RFC 1510, September 1993.
 [RFC2025]    Adams, C., "The Simple Public-Key GSS-API Mechanism
              (SPKM)", RFC 2025, October 1996.
 [RFC2434]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.
 [RFC2945]    Wu, T., "The SRP Authentication and Key Exchange
              System", RFC 2945, September 2000.

Tseng, et al. Standards Track [Page 110] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 [RFC1994]    Simpson, W., "PPP Challenge Handshake Authentication
              Protocol (CHAP)", RFC 1994, August 1996.
 [RFC2131]    Droms, R., "Dynamic Host Configuration Protocol", RFC
              2131, March 1997.
 [RFC3410]    Case, J., Mundy, R., Partain, D., and B. Stewart,
              "Introduction and Applicability Statements for
              Internet-Standard Management Framework", RFC 3410,
              December 2002.
 [RFC3411]    Harrington, D., Presuhn, R., and B. Wijnen, "An
              Architecture for Describing Simple Network Management
              Protocol (SNMP) Management Frameworks", STD 62, RFC
              3411, December 2002.

Tseng, et al. Standards Track [Page 111] RFC 4171 Internet Storage Name Service (iSNS) September 2005

Appendix A: iSNS Examples

A.1. iSCSI Initialization Example

 This example assumes an SLP Service Agent (SA) has been implemented
 on the iSNS host, and an SLP User Agent (UA) has been implemented on
 the iSNS initiator.  See [RFC2608] for further details on SAs and
 UAs.  This example also assumes that the target is configured to use
 the iSNS server, and have its access control policy subordinated to
 the iSNS server.

A.1.1. Simple iSCSI Target Registration

 In this example, a simple target with a single iSCSI name registers
 with the iSNS server.  The target is represented in the iSNS by an
 Entity containing one Storage Node, one Portal, and an implicitly
 registered Portal Group that provides a relationship between the
 Storage Node and Portal.  The target has not been assigned a Fully
 Qualified Domain Name (FQDN) by the administrator.  In this example,
 because a PG object is not explicitly registered, a Portal Group with
 a PGT of 1 is implicitly registered.  In this example SLP is used to
 discover the location of the iSNS Server.  An alternative is to use
 the iSNS DHCP option [iSNSOption] to discover the iSNS server.
 +--------------------------+------------------+-------------------+
 |    iSCSI Target Device   |    iSNS Server   |Management Station |
 +--------------------------+------------------+-------------------+
 |Discover iSNS--SLP------->|                  |/*mgmt station is  |
 |                          |<--SLP--iSNS Here:| administratively  |
 |                          |      192.0.2.100 | authorized to view|
 |                          |                  | all DDs.  Device  |
 |      DevAttrReg--------->|                  | NAMEabcd was      |
 |Src:(tag=32) "NAMEabcd"   |                  | previously placed |
 |Key: <none present>       |                  | into DDabcd along |
 |Oper Attrs:               |                  | with devpdq and   |
 |tag=1: NULL               |                  | devrst.           |
 |tag=2: "iSCSI"            |                  |                   |
 |tag=16: 192.0.2.5         |                  |                   |
 |tag=17: 5001              |                  |                   |
 |tag=32: "NAMEabcd"        |                  |                   |
 |tag=33: target            |                  |                   |
 |tag=34: "disk 1"          |                  |                   |
 |                          |<---DevAttrRegRsp |                   |
 |                          |SUCCESS           |                   |
 |                          |Key:(tag=1) "isns:0001"               |
 |                          |Oper Attrs:       |                   |
 |                          |tag=1: "isns:0001"|                   |
 |                          |tag=2: "iSCSI"    |                   |

Tseng, et al. Standards Track [Page 112] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 |                          |tag=16: 192.0.2.5 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=32: "NAMEabcd"|/* previously      |
 |                          |tag=33: target    | placed in a DD */ |
 |                          |tag=34: "disk 1"  |                   |
 |                          |                  |                   |
 |                          |      SCN-------->|                   |
 |                          |(or SNMP notification)                |
 |                          |dest:(tag=32):"MGMTname1"             |
 |                          |time:(tag=4): <current time>          |
 |                          |tag=35: "MGT-SCN, OBJ-ADD"            |
 |                          |tag=32: "NAMEabcd"|                   |
 |                          |                  |<-------SCNRsp     |
 |      DevAttrQry--------->|                  |                   |
 |Src:(tag=32) "NAMEabcd"   |                  |                   |
 |Key:(tag=33) "initiator"  |                  |                   |
 |Oper Attrs:               |                  |                   |
 |tag=16:  NULL             |                  |                   |
 |tag=17:  NULL             |                  |                   |
 |tag=32:  NULL             |                  |                   |
 |/*Query asks for all initr|                  |                   |
 |devices' IP address, port |<---DevAttrQryRsp |                   |
 |number, and Name*/        |SUCCESS           |                   |
 |                          |tag=16:192.0.2.1  |                   |
 |                          |tag=17:50000      |                   |
 |                          |tag=32:"devpdq"   |                   |
 |                          |tag=16:192.0.2.2  |                   |
 |                          |tag=17:50000      |                   |
 |                          |tag=32:"devrst"   |                   |
 |/*************************|                  |<-----DevAttrQry   |
 |Our target "NAMEabcd"     |                  |src: "MGMTname1"   |
 |discovers two initiators  |                  key:(tag=32)"NAMEabcd"
 |in shared DDs.  It will   |                  |Op Attrs:          |
 |accept iSCSI logins from  |                  |tag=16:  NULL      |
 |these two identified      |                  |tag=17:  NULL      |
 |initiators presented by   |                  |tag=32:  NULL      |
 |iSNS                      |                  |                   |
 |*************************/| DevAttrQryRsp--->|                   |
 |                          |SUCCESS           |                   |
 |                          |tag=16: 192.0.2.5 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=32: "NAMEabcd"|                   |
 +--------------------------+------------------+-------------------+

Tseng, et al. Standards Track [Page 113] RFC 4171 Internet Storage Name Service (iSNS) September 2005

A.1.2. Target Registration and DD Configuration

 In this example, a more complex target, with two Storage Nodes and
 two Portals using ESI monitoring, registers with the iSNS.  This
 target has been configured with a Fully Qualified Domain Name (FQDN)
 in the DNS servers, and the user wishes to use this identifier for
 the device.  The target explicitly registers Portal Groups to
 describe how each Portal provides access to each Storage Node.  One
 target Storage Node allows coordinated access through both Portals.
 The other Storage Node allows access, but not coordinated access,
 through both Portals.
 +--------------------------+------------------+-------------------+
 |    iSCSI Target Device   |    iSNS Server   |Management Station |
 +--------------------------+------------------+-------------------+
 |Discover iSNS--SLP-->     |                  |/*mgmt station is  |
 |                          |<--SLP--iSNS Here:| administratively  |
 |                          |      192.0.2.100 | authorized to view|
 | DevAttrReg-->            |                  | all DDs */        |
 |Src:                      |                  |                   |
 |tag=32: "NAMEabcd"        |                  |                   |
 |Msg Key:                  |                  |                   |
 |tag=1: "jbod1.example.com"|                  |                   |
 |Oper Attrs:               |                  |                   |
 |tag=1: "jbod1.example.com"|                  |                   |
 |tag=2: "iSCSI"            |                  |                   |
 |tag=16: 192.0.2.4         |                  |                   |
 |tag=17: 5001              |                  |                   |
 |tag=19: 5                 |                  |                   |
 |tag=20: 5002              |                  |                   |
 |tag=16: 192.0.2.5         |                  |                   |
 |tag=17: 5001              |                  |                   |
 |tag=19: 5                 |                  |                   |
 |tag=20: 5002              |                  |                   |
 |tag=32: "NAMEabcd"        |                  |                   |
 |tag=33: "Target"          |                  |                   |
 |tag=34: "Storage Array 1" |                  |                   |
 |tag=51: 10                |                  |                   |
 |tag=49: 192.0.2.4         |                  |                   |
 |tag=50: 5001              |                  |                   |
 |tag=49: 192.0.2.5         |                  |                   |
 |tag=50: 5001              |                  |                   |
 |tag=32: "NAMEefgh"        |                  |                   |
 |tag=33: "Target"          |                  |                   |
 |tag=34: "Storage Array 2" |/*****************|                   |
 |tag=51: 20                |jbod1.example.com is                  |
 |tag=49: 192.0.2.4         |now registered in |                   |
 |tag=50: 5001              |iSNS, but is not  |                   |

Tseng, et al. Standards Track [Page 114] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 |tag=51: 30                |in any DD. Therefore,                 |
 |tag=49: 192.0.2.5         |no other devices  |                   |
 |tag=50: 5001              |can "see" it.     |                   |
 |                          |*****************/|                   |
 |                          |<--DevAttrRegRsp  |                   |
 |                          |SUCCESS           |                   |
 |                          |Msg Key:          |                   |
 |                          |tag=1: "jbod1.example.com"            |
 |                          |Oper Attrs:       |                   |
 |                          |tag=1: "jbod1.example.com"            |
 |                          |tag=2: "iSCSI"    |                   |
 |                          |tag=16: 192.0.2.4 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=19: 5         |                   |
 |                          |tag=20: 5002      |                   |
 |                          |tag=16: 192.0.2.5 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=19: 5         |                   |
 |                          |tag=20: 5002      |                   |
 |                          |tag=32: "NAMEabcd"|                   |
 |                          |tag=33: "Target"  |                   |
 |                          |tag=34: "Storage Array 1"             |
 |                          |tag=48: "NAMEabcd"|                   |
 |                          |tag=49: 192.0.2.4 |                   |
 |                          |tag=50: 5001      |                   |
 |                          |tag=51: 10        |                   |
 |                          |tag=48: "NAMEabcd"|                   |
 |                          |tag=49: 192.0.2.5 |                   |
 |                          |tag=50: 5001      |                   |
 |                          |tag=51: 10        |                   |
 |                          |tag=32: "NAMEefgh"|                   |
 |                          |tag=33: "Target"  |                   |
 |                          |tag=34: "Storage Array 2"             |
 |                          |tag=43: X.509 cert|                   |
 |                          |tag=48: "NAMEefgh"|                   |
 |                          |tag=49: 192.0.2.4 |                   |
 |                          |tag=50: 5001      |                   |
 |                          |tag=51: 20        |                   |
 |                          |tag=48: "NAMEefgh"|                   |
 |                          |tag=49: 192.0.2.5 |                   |
 |                          |tag=50: 5001      |                   |
 |                          |tag=51: 30        |                   |
 |                          |                  |                   |
 |                          | SCN------>       |                   |
 |                          | (or SNMP notification)               |
 |                          |dest:(tag=32)"mgmt.example.com"       |
 |                          |time:(tag=4): <current time>          |
 |                          |tag=35: "MGT-SCN, OBJ-ADD"            |

Tseng, et al. Standards Track [Page 115] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 |                          |tag=32: "NAMEabcd"|                   |
 |                          |tag=35: "MGT-SCN, OBJ-ADD"            |
 |                          |tag=32: "NAMEefgh"|                   |
 |                          |                  |<--SCNRsp          |
 |                          |                  |SUCCESS            |
 |                          |             tag=32:"mgmt.example.com"|
 |                          |                  |                   |
 |                          |                  |<--DevAttrQry      |
 |                          |                  |Src:               |
 |                          |               tag=32:"mgmt.example.com"
 |                          |                  |Msg Key:           |
 |                          |                  |tag=32: "NAMEabcd" |
 |                          |                  |Oper Attrs:        |
 |                          |                  |tag=16: <0-length> |
 |                          |                  |tag=17: <0-length> |
 |                          |                  |tag=32: <0-length> |
 |                          |                  |                   |
 |                          | DevAttrQryRsp--> |                   |
 |                          |SUCCESS           |                   |
 |                          |Msg Key:          |                   |
 |                          |tag=32: "NAMEabcd"|                   |
 |                          |Oper Attrs:       |                   |
 |                          |tag=16: 192.0.2.4 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=32:"NAMEabcd" |                   |
 |                          |tag=16: 192.0.2.5 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=32:"NAMEabcd" |                   |
 |                          |                  |Src:               |
 |                          |               tag=32:"mgmt.example.com"
 |                          |                  |Msg Key:           |
 |                          |                  |tag=32: "NAMEefgh" |
 |                          |                  |Oper Attrs:        |
 |                          |                  |tag=16: <0-length> |
 |                          |                  |tag=17: <0-length> |
 |                          |                  |tag=32: <0-length> |
 |                          |                  |                   |
 |                          | DevAttrQryRsp--> |                   |
 |                          |SUCCESS           |                   |
 |                          |Msg Key:          |                   |
 |                          |tag=32: "NAMEefgh"|                   |
 |                          |Oper Attrs:       |                   |
 |                          |tag=16: 192.0.2.4 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=32:"NAMEefgh" |                   |
 |                          |tag=16: 192.0.2.5 |/**Mgmt Station ***|
 |                          |tag=17: 5001      |displays device,   |
 |                          |tag=32:"NAMEefgh" |the operator decides

Tseng, et al. Standards Track [Page 116] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 |                          |                  |to place "NAMEabcd"|
 |                          |                  |into Domain "DDxyz"|
 |/*************************|                  |******************/|
 |Target is now registered  |                  |                   |
 |in iSNS. It is then placed|                  |<--DDReg           |
 |in a pre-existing DD with |                  |Src:               |
 |DD_ID 123 by a management |               tag=32:"mgmt.example.com"
 |station.                  |                  |Msg Key:           |
 |*************************/|                  |tag=2065: 123      |
 |                          |                  |Oper Attrs:        |
 |                          |                  |tag=2068: "NAMEabcd"
 |                          | DDRegRsp----->   |                   |
 |                          |SUCCESS           |                   |
 |                          |Msg Key:          |                   |
 |                          |tag=2065: 123     |                   |
 |                          |Oper Attrs:       |                   |
 |                          |tag=2065: 123     |                   |
 +--------------------------+------------------+-------------------+

A.1.3. Initiator Registration and Target Discovery

 The following example illustrates a new initiator registering with
 the iSNS, and discovering the target NAMEabcd from the example in
 A.1.2.
 +--------------------------+------------------+-------------------+
 |    iSCSI Initiator       |    iSNS          |Management Station |
 +--------------------------+------------------+-------------------+
 |Discover iSNS--SLP-->     |                  |/*mgmt station is  |
 |                          |<--SLP--iSNS Here:| administratively  |
 |                          |      192.36.53.1 | authorized to view|
 |DevAttrReg-->             |                  | all DDs ********/ |
 |Src:                      |                  |                   |
 |tag=32: "NAMEijkl"        |                  |                   |
 |Msg Key:                  |                  |                   |
 |tag=1: "svr1.example.com" |                  |                   |
 |Oper Attrs:               |                  |                   |
 |tag=1: "svr1.example.com" |                  |                   |
 |tag=2: "iSCSI"            |                  |                   |
 |tag=16: 192.20.3.1        |/*****************|                   |
 |tag=17: 5001              |Device not in any |                   |
 |tag=19: 5                 |DD, so it is      |                   |
 |tag=20: 5002              |inaccessible by   |                   |
 |tag=32: "NAMEijkl"        |other devices     |                   |
 |tag=33: "Initiator"       |*****************/|                   |
 |tag=34: "Server1"         |                  |                   |
 |tag=51: 11                |                  |                   |
 |tag=49: 192.20.3.1        |                  |                   |

Tseng, et al. Standards Track [Page 117] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 |tag=50: 5001              |                  |                   |
 |                          |<--DevAttrRegRsp  |                   |
 |                          |SUCCESS           |                   |
 |                          |Msg Key:          |                   |
 |                          |tag=1: "svr1.example.com"             |
 |                          |Oper Attrs:       |                   |
 |                          |tag=1: "svr1.example.com"             |
 |                          |tag=2: "iSCSI"    |                   |
 |                          |tag=16: 192.20.3.1|                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=19: 5         |                   |
 |                          |tag=20: 5002      |                   |
 |                          |tag=32: "NAMEijkl"|                   |
 |                          |tag=33: "Initiator"                   |
 |                          |tag=34: "Server1" |                   |
 |                          |tag=48: "NAMEijkl"|                   |
 |                          |tag=49: 192.20.3.1|                   |
 |                          |tag=50: 5001      |                   |
 |                          |tag=51: 11        |                   |
 |                          |                  |                   |
 |                          |       SCN------> |                   |
 |                          |  (or SNMP notification)              |
 |                          |dest:(tag=32)"mgmt.example.com"       |
 |                          |time:(tag=4): <current time>          |
 |                          |tag=35: "MGT-SCN, OBJ-ADD"            |
 |                          |tag=32: "NAMEijkl"|                   |
 |                          |                  |                   |
 |                          |                  |<------SCNRsp      |
 |                          |                  |SUCCESS            |
 |                          |               tag=32:"mgmt.example.com"
 |                          |                  |                   |
 |SCNReg-->                 |                  |                   |
 |Src:                      |                  |                   |
 |tag=32: "NAMEijkl"        |                  |                   |
 |Msg Key:                  |                  |                   |
 |tag=32: "NAMEijkl"        |                  |                   |
 |Oper Attrs:               |                  |                   |
 |tag=35: <TARG&SELF, OBJ-RMV/ADD/UPD>         |                   |
 |                          |<--SCNRegRsp      |                   |
 |                          |SUCCESS           |                   |
 |                          |                  |                   |
 |                          |                  |<----DevAttrQry    |
 |                          |                  |Src:               |
 |                          |               tag=32:"mgmt.example.com"
 |                          |                  |Msg Key:           |
 |                          |                  |tag=32: "NAMEijkl" |
 |                          |                  |Oper Attrs:        |
 |                          |                  |tag=16: <0-length> |

Tseng, et al. Standards Track [Page 118] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 |                          |                  |tag=17: <0-length> |
 |                          |                  |tag=32: <0-length> |
 |                          | DevAttrQryRsp--->|                   |
 |                          |SUCCESS           |                   |
 |                          |Msg Key:          |                   |
 |                          |tag=32: "NAMEijkl"|                   |
 |                          |Oper Attrs:       |                   |
 |                          |tag=16:192.20.3.1 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=32:"NAMEijkl" |                   |
 |                          |                  |/**Mgmt Station ***|
 |                          |                  |displays device, the
 |                          |                  |operator decides to|
 |                          |                  |place "NAMEijkl" into
 |                          |                  |pre-existing Disc  |
 |                          |                  |Domain "DDxyz" with|
 |                          |                  |device NAMEabcd    |
 |                          |                  |******************/|
 |                          |                  |<--DDReg           |
 |                          |                  |Src:               |
 |                          |               tag=32:"mgmt.example.com"
 |                          |                  |Msg Key:           |
 |                          |                  |tag=2065: 123      |
 |                          |                  |Oper Attrs:        |
 |                          |                  |tag=2068: "NAMEijkl"
 |                          |                  |                   |
 |                          |     DDRegRsp---->|                   |
 |                          |SUCCESS           |                   |
 |                          |Msg Key:          |                   |
 |                          |tag=2065: 123     |                   |
 |                          |Oper Attrs:       |                   |
 |                          |tag=2065: 123     |/******************|
 |                          |                  |"NAMEijkl" has been|
 |                          |                  |moved to "DDxyz"   |
 |                          |                  |******************/|
 |                          |        SCN------>|                   |
 |                          |dest:(tag=32)"mgmt.example.com"       |
 |                          |time:(tag=4): <current time>          |
 |                          |tag=35: <MGT-SCN, DD/DDS-MBR-ADD>     |
 |                          |tag=2065: 123     |                   |
 |                          |tag=2068: "NAMEijkl"                  |
 |                          |                  |                   |
 |                          |                  |<------SCNRsp      |
 |                          |                  |SUCCESS            |
 |                          |               tag=32:"mgmt.example.com"
 |                          |<-----SCN         |                   |
 |                          |dest:(tag=32)"NAMEijkl"               |
 |                          |time:(tag=4): <current time>          |

Tseng, et al. Standards Track [Page 119] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 |                          |tag=35: <TARG&SELF, OBJ-ADD>          |
 |                          |tag=32: "NAMEijkl"|                   |
 |    SCNRsp------>         |                  |                   |
 |SUCCESS                   |                  |                   |
 |tag=32:"NAMEijkl"         |                  |                   |
 |                          |                  |                   |
 |                          |/*****************|                   |
 |                          |Note that NAMEabcd|                   |
 |                          |also receives an  |                   |
 |                          |SCN that NAMEijkl |                   |
 |                          |is in the same DD |                   |
 |                          |*****************/|                   |
 |           (to "NAMEabcd")|<-----SCN         |                   |
 |                          |dest:(tag=32)"NAMEabcd"               |
 |                          |time:(tag=4): <current time>          |
 |                          |tag=35: <INIT&SELF, OBJ-ADD>          |
 |                          |tag=32: "NAMEijkl"|                   |
 |    SCNRsp------>         |                  |                   |
 |SUCCESS                   |                  |                   |
 |tag=32:"NAMEabcd"         |                  |                   |
 |                          |                  |                   |
 |    DevAttrQry----------->|                  |                   |
 |Src:                      |                  |                   |
 |tag=32: "NAMEijkl"        |                  |                   |
 |Msg Key:                  |                  |                   |
 |tag=33: "Target"          |                  |                   |
 |Oper Attrs:               |                  |                   |
 |tag=16: <0-length>        |                  |                   |
 |tag=17: <0-length>        |                  |                   |
 |tag=32: <0-length>        |                  |                   |
 |tag=34: <0-length>        |                  |                   |
 |tag=43: <0-length>        |                  |                   |
 |tag=48: <0-length>        |                  |                   |
 |tag=49: <0-length>        |                  |                   |
 |tag=50: <0-length>        |                  |                   |
 |tag=51: <0-length>        |                  |                   |
 |                          |<--DevAttrQryRsp  |                   |
 |                          |SUCCESS           |                   |
 |                          |Msg Key:          |                   |
 |                          |tag=33:"Target"   |                   |
 |                          |Oper Attrs:       |                   |
 |                          |tag=16: 192.0.2.4 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=32: "NAMEabcd"|                   |
 |                          |tag=34: "Storage Array 1"             |
 |                          |tag=16: 192.0.2.5 |                   |
 |                          |tag=17: 5001      |                   |
 |                          |tag=32: "NAMEabcd"|                   |

Tseng, et al. Standards Track [Page 120] RFC 4171 Internet Storage Name Service (iSNS) September 2005

 |                          |tag=34: "Storage Array 1"             |
 |                          |tag=43: X.509 cert|                   |
 |                          |tag=48: "NAMEabcd"|                   |
 |                          |tag=49: 192.0.2.4 |                   |
 |                          |tag=50: 5001      |                   |
 |                          |tag=51: 10        |                   |
 |                          |tag=48: "NAMEabcd"|                   |
 |                          |tag=49: 192.0.2.5 |                   |
 |                          |tag=50: 5001      |                   |
 |                          |tag=51: 10        |                   |
 |                          |                  |                   |
 |/***The initiator has discovered             |                   |
 |the target, and has everything               |                   |
 |needed to complete iSCSI login               |                   |
 |The same process occurs on the               |                   |
 |target side; the SCN prompts the             |                   |
 |target to download the list of               |                   |
 |authorized initiators from the               |                   |
 |iSNS (i.e., those initiators in the          |                   |
 |same DD as the target.************/          |                   |
 +--------------------------+------------------+-------------------+

Acknowledgements

 Numerous individuals contributed to the creation of this document
 through their careful review and submissions of comments and
 recommendations.  We acknowledge the following persons for their
 technical contributions to this document: Mark Bakke (Cisco), John
 Hufferd (IBM), Julian Satran (IBM), Kaladhar Voruganti(IBM), Joe Czap
 (IBM), John Dowdy (IBM), Tom McSweeney (IBM), Jim Hafner (IBM), Chad
 Gregory (Intel), Yaron Klein (Sanrad), Larry Lamers (Adaptec), Jack
 Harwood (EMC), David Black (EMC), David Robinson (Sun), Alan Warwick
 (Microsoft), Bob Snead (Microsoft), Fa Yoeu (Intransa), Joe White
 (McDATA), Charles Monia (McDATA), Larry Hofer (McDATA), Ken Hirata
 (Vixel), Howard Hall (Pirus), Malikarjun Chadalapaka (HP), Marjorie
 Krueger (HP), Siva Vaddepuri (McDATA), and Vinai Singh (American
 Megatrends).

Tseng, et al. Standards Track [Page 121] RFC 4171 Internet Storage Name Service (iSNS) September 2005

Authors' Addresses

 Josh Tseng
 Riverbed Technology
 501 2nd Street, Suite 410
 San Francisco, CA 94107
 Phone:  (650)274-2109
 EMail:  joshtseng@yahoo.com
 Kevin Gibbons
 McDATA Corporation
 4555 Great America Parkway
 Santa Clara, CA 95054-1208
 Phone: (408) 567-5765
 EMail: kevin.gibbons@mcdata.com
 Franco Travostino
 Nortel
 600 Technology Park Drive
 Billerica, MA 01821 USA
 Phone: (978) 288-7708
 EMail: travos@nortel.com
 Curt du Laney
 Rincon Research Corporation
 101 North Wilmot Road, Suite 101
 Tucson AZ 85711
 Phone: (520) 519-4409
 EMail: cdl@rincon.com
 Joe Souza
 Microsoft Corporation
 One Microsoft Way
 Redmond, WA  98052-6399
 Phone: (425) 706-3135
 EMail: joes@exmsft.com

Tseng, et al. Standards Track [Page 122] RFC 4171 Internet Storage Name Service (iSNS) September 2005

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Tseng, et al. Standards Track [Page 123]

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