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rfc:rfc4172

Network Working Group C. Monia Request for Comments: 4172 Consultant Category: Standards Track R. Mullendore

                                                                McDATA
                                                         F. Travostino
                                                                Nortel
                                                              W. Jeong
                                                       Troika Networks
                                                            M. Edwards
                                                     Adaptec (UK) Ltd.
                                                        September 2005
  iFCP - A Protocol for Internet Fibre Channel Storage Networking

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 an architecture and a gateway-to-gateway
 protocol for the implementation of fibre channel fabric functionality
 over an IP network.  This functionality is provided through TCP
 protocols for fibre channel frame transport and the distributed
 fabric services specified by the fibre channel standards.  The
 architecture enables internetworking of fibre channel devices through
 gateway-accessed regions with the fault isolation properties of
 autonomous systems and the scalability of the IP network.

Table of Contents

 1.  Introduction..................................................  4
     1.1.  Conventions used in This Document.......................  4
           1.1.1.  Data Structures Internal to an Implementation...  4
     1.2.  Purpose of This Document................................  4
 2.  iFCP Introduction.............................................  4
     2.1.  Definitions.............................................  5
 3.  Fibre Channel Communication Concepts..........................  7
     3.1.  The Fibre Channel Network...............................  8

Monia, et al. Standards Track [Page 1] RFC 4172 Internet Fibre Channel Networking September 2005

     3.2.  Fibre Channel Network Topologies........................  9
           3.2.1.  Switched Fibre Channel Fabrics.................. 11
           3.2.2.  Mixed Fibre Channel Fabric...................... 12
     3.3.  Fibre Channel Layers and Link Services.................. 12
           3.3.1.  Fabric-Supplied Link Services................... 13
     3.4.  Fibre Channel Nodes..................................... 14
     3.5.  Fibre Channel Device Discovery.......................... 14
     3.6.  Fibre Channel Information Elements...................... 15
     3.7.  Fibre Channel Frame Format.............................. 15
           3.7.1.  N_PORT Address Model............................ 16
     3.8.  Fibre Channel Transport Services........................ 17
     3.9.  Login Processes......................................... 18
 4.  The iFCP Network Model........................................ 18
     4.1.  iFCP Transport Services................................. 21
           4.1.1.  Fibre Channel Transport Services Supported by
                   iFCP............................................ 21
     4.2.  iFCP Device Discovery and Configuration Management...... 21
     4.3.  iFCP Fabric Properties.................................. 22
           4.3.1.  Address Transparency............................ 22
           4.3.2.  Configuration Scalability....................... 23
           4.3.3.  Fault Tolerance................................. 23
     4.4.  The iFCP N_PORT Address Model........................... 24
     4.5.  Operation in Address Transparent Mode................... 25
           4.5.1.  Transparent Mode Domain ID Management........... 26
           4.5.2.  Incompatibility with Address Translation Mode... 26
     4.6.  Operation in Address Translation Mode................... 27
           4.6.1.  Inbound Frame Address Translation............... 28
           4.6.2.  Incompatibility with Address Transparent Mode... 29
 5.  iFCP Protocol................................................. 29
     5.1.  Overview ............................................... 29
           5.1.1.  iFCP Transport Services......................... 29
           5.1.2.  iFCP Support for Link Services.................. 30
     5.2.  TCP Stream Transport of iFCP Frames..................... 30
           5.2.1.  iFCP Session Model.............................. 30
           5.2.2.  iFCP Session Management......................... 31
           5.2.3.  Terminating iFCP Sessions....................... 39
     5.3.  Fibre Channel Frame Encapsulation....................... 40
           5.3.1.  Encapsulation Header Format..................... 41
           5.3.2.  SOF and EOF Delimiter Fields.................... 44
           5.3.3.  Frame Encapsulation............................. 45
           5.3.4.  Frame De-encapsulation.......................... 46
 6.  TCP Session Control Messages.................................. 47
     6.1.  Connection Bind (CBIND)................................. 50
     6.2.  Unbind Connection (UNBIND).............................. 52
     6.3.  LTEST -- Test Connection Liveness....................... 54
 7.  Fibre Channel Link Services................................... 55
     7.1.  Special Link Service Messages........................... 56
     7.2.  Link Services Requiring Payload Address Translation..... 58

Monia, et al. Standards Track [Page 2] RFC 4172 Internet Fibre Channel Networking September 2005

     7.3.  Fibre Channel Link Services Processed by iFCP........... 61
           7.3.1.  Special Extended Link Services.................. 63
           7.3.2.  Special FC-4 Link Services...................... 83
     7.4.  FLOGI Service Parameters Supported by an iFCP Gateway... 84
 8.  iFCP Error Detection.......................................... 86
     8.1.  Overview................................................ 86
     8.2.  Stale Frame Prevention.................................. 86
           8.2.1.  Enforcing R_A_TOV Limits........................ 86
 9.  Fabric Services Supported by an iFCP Implementation........... 88
     9.1.  F_PORT Server........................................... 88
     9.2.  Fabric Controller....................................... 89
     9.3.  Directory/Name Server................................... 89
     9.4.  Broadcast Server........................................ 89
           9.4.1.  Establishing the Broadcast Configuration........ 90
           9.4.2.  Broadcast Session Management.................... 91
           9.4.3.  Standby Global Broadcast Server................. 91
 10. iFCP Security................................................. 91
     10.1. Overview................................................ 91
     10.2. iFCP Security Threats and Scope......................... 92
           10.2.1. Context......................................... 92
           10.2.2. Security Threats................................ 92
           10.2.3. Interoperability with Security Gateways......... 93
           10.2.4. Authentication.................................. 93
           10.2.5. Confidentiality................................. 93
           10.2.6. Rekeying........................................ 93
           10.2.7. Authorization................................... 94
           10.2.8. Policy Control.................................. 94
           10.2.9. iSNS Role....................................... 94
     10.3. iFCP Security Design.................................... 94
           10.3.1. Enabling Technologies........................... 94
           10.3.2. Use of IKE and IPsec............................ 96
           10.3.3. Signatures and Certificate-Based Authentication. 98
     10.4. iSNS and iFCP Security.................................. 99
     10.5. Use of iSNS to Distribute Security Policy............... 99
     10.6. Minimal Security Policy for an iFCP Gateway............. 99
 11. Quality of Service Considerations.............................100
     11.1. Minimal Requirements....................................100
     11.2. High Assurance..........................................100
 12. IANA Considerations...........................................101
 13. Normative References..........................................101
 14. Informative References........................................103
 Appendix A.  iFCP Support for Fibre Channel Link Services.........105
     A.1.  Basic Link Services.....................................105
     A.2.  Pass-Through Link Services..............................105
     A.3.  Special Link Services...................................107
 Appendix B.  Supporting the Fibre Channel Loop Topology...........108
     B.1.  Remote Control of a Public Loop.........................108
 Acknowledgements..................................................109

Monia, et al. Standards Track [Page 3] RFC 4172 Internet Fibre Channel Networking September 2005

1. Introduction

1.1. Conventions Used in 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 BCP 14, RFC 2119
 [RFC2119].
 Unless specified otherwise, numeric quantities are given as decimal
 values.
 All diagrams that portray bit and byte ordering, including the
 depiction of structures defined by fibre channel standards, adhere to
 the IETF conventions whereby bit 0 is the most significant bit and
 the first addressable byte is in the upper left corner.  This IETF
 convention differs from that used for INCITS T11 fibre channel
 standards, in which bit 0 is the least significant bit.

1.1.1. Data Structures Internal to an Implementation

 To facilitate the specification of required behavior, this document
 may define and refer to internal data structures within an iFCP
 implementation.  Such structures are intended for explanatory
 purposes only and need not be instantiated within an implementation
 as described in this specification.

1.2. Purpose of This Document

 This is a standards-track document that specifies a protocol for the
 implementation of fibre channel transport services on a TCP/IP
 network.  Some portions of this document contain material from
 standards controlled by INCITS T10 and T11.  This material is
 included here for informational purposes only.  The authoritative
 information is given in the appropriate NCITS standards document.
 The authoritative portions of this document specify the mapping of
 standards-compliant fibre channel protocol implementations to TCP/IP.
 This mapping includes sections of this document that describe the
 "iFCP Protocol" (see Section 5).

2. iFCP Introduction

 iFCP is a gateway-to-gateway protocol that provides fibre channel
 fabric services to fibre channel devices over a TCP/IP network.  iFCP
 uses TCP to provide congestion control, error detection, and
 recovery.  iFCP's primary objective is to allow interconnection and

Monia, et al. Standards Track [Page 4] RFC 4172 Internet Fibre Channel Networking September 2005

 networking of existing fibre channel devices at wire speeds over an
 IP network.
 The protocol and method of frame address translation described in
 this document permit the attachment of fibre channel storage devices
 to an IP-based fabric by means of transparent gateways.
 The protocol achieves this transparency by allowing normal fibre
 channel frame traffic to pass through the gateway directly, with
 provisions, where necessary, for intercepting and emulating the
 fabric services required by a fibre channel device.

2.1. Definitions

 Terms needed to describe the concepts presented in this document are
 presented here.
 Address-translation mode -- A mode of gateway operation in which the
    scope of N_PORT fabric addresses, for locally attached devices,
    are local to the iFCP gateway region in which the devices reside.
 Address-transparent mode -- A mode of gateway operation in which the
    scope of N_PORT fabric addresses, for all fibre channel devices,
    are unique to the bounded iFCP fabric to which the gateway
    belongs.
 Bounded iFCP Fabric -- The union of two or more gateway regions
    configured to interoperate in address-transparent mode.
 DOMAIN_ID -- The value contained in the high-order byte of a 24-bit
    N_PORT fibre channel address.
 F_PORT -- The interface used by an N_PORT to access fibre channel
    switched-fabric functionality.
 Fabric -- From [FC-FS]: "The entity that interconnects N_PORTs
    attached to it and is capable of routing frames by using only the
    address information in the fibre channel frame."
 Fabric Port -- The interface through which an N_PORT accesses a fibre
    channel fabric.  The type of fabric port depends on the fibre
    channel fabric topology.  In this specification, all fabric port
    interfaces are considered functionally equivalent.
 FC-2 -- The fibre channel transport services layer, described in
    [FC-FS].

Monia, et al. Standards Track [Page 5] RFC 4172 Internet Fibre Channel Networking September 2005

 FC-4 -- The fibre channel mapping of an upper-layer protocol, such as
    [FCP-2], the fibre channel to SCSI mapping.
 Fibre Channel Device -- An entity implementing the functionality
    accessed through an FC-4 application protocol.
 Fibre Channel Network -- A native fibre channel fabric and all
    attached fibre channel nodes.
 Fibre Channel Node -- A collection of one or more N_PORTs controlled
    by a level above the FC-2 layer.  A node is attached to a fibre
    channel fabric by means of the N_PORT interface, described in
    [FC-FS].
 Gateway Region -- The portion of an iFCP fabric accessed through an
    iFCP gateway by a remotely attached N_PORT.  Fibre channel devices
    in the region consist of all those locally attached to the
    gateway.
 iFCP -- The protocol discussed in this document.
 iFCP Frame -- A fibre channel frame encapsulated in accordance with
    the FC Frame Encapsulation Specification [ENCAP] and this
    specification.
 iFCP Portal -- An entity representing the point at which a logical or
    physical iFCP device is attached to the IP network.  The network
    address of the iFCP portal consists of the IP address and TCP port
    number to which a request is sent when the TCP connection is
    created for an iFCP session (see Section 5.2.1).
 iFCP Session -- An association comprised of a pair of N_PORTs and a
    TCP connection that carries traffic between them.  An iFCP session
    may be created as the result of a PLOGI fibre channel login
    operation.
 iSNS -- The server functionality and IP protocol that provide storage
    name services in an iFCP network.  Fibre channel name services are
    implemented by an iSNS name server, as described in [ISNS].
 Locally Attached Device -- With respect to a gateway, a fibre channel
    device accessed through the fibre channel fabric to which the
    gateway is attached.
 Logical iFCP Device -- The abstraction representing a single fibre
    channel device as it appears on an iFCP network.

Monia, et al. Standards Track [Page 6] RFC 4172 Internet Fibre Channel Networking September 2005

 N_PORT -- An iFCP or fibre channel entity representing the interface
    to fibre channel device functionality.  This interface implements
    the fibre channel N_PORT semantics, specified in [FC-FS].  Fibre
    channel defines several variants of this interface that depend on
    the fibre channel fabric topology.  As used in this document, the
    term applies equally to all variants.
 N_PORT Alias --  The N_PORT address assigned by a gateway to
    represent a remote N_PORT accessed via the iFCP protocol.
 N_PORT fabric address -- The address of an N_PORT within the fibre
    channel fabric.
 N_PORT ID -- The address of a locally attached N_PORT within a
    gateway region.  N_PORT IDs are assigned in accordance with the
    fibre channel rules for address assignment, specified in [FC-FS].
 N_PORT Network Address -- The address of an N_PORT in the iFCP
    fabric.  This address consists of the IP address and TCP port
    number of the iFCP Portal and the N_PORT ID of the locally
    attached fibre channel device.
 Port Login (PLOGI) -- The fibre channel Extended Link Service (ELS)
    that establishes an iFCP session through the exchange of
    identification and operation parameters between an originating
    N_PORT and a responding N_PORT.
 Remotely Attached Device -- With respect to a gateway, a fibre
    channel device accessed from the gateway by means of the iFCP
    protocol.
 Unbounded iFCP Fabric -- The union of two or more gateway regions
    configured to interoperate in address-translation mode.

3. Fibre Channel Communication Concepts

 Fibre channel is a frame-based, serial technology designed for peer-
 to-peer communication between devices at gigabit speeds and with low
 overhead and latency.
 This section contains a discussion of the fibre channel concepts that
 form the basis for the iFCP network architecture and protocol
 described in this document.  Readers familiar with this material may
 skip to Section 4.

Monia, et al. Standards Track [Page 7] RFC 4172 Internet Fibre Channel Networking September 2005

 Material presented in this section is drawn from the following T11
 specifications:
  1. - The Fibre Channel Framing and Signaling Interface, [FC-FS]
  1. - Fibre Channel Switch Fabric -2, [FC-SW2]
  1. - Fibre Channel Generic Services, [FC-GS3]
  1. - Fibre Channel Fabric Loop Attachment, [FC-FLA]
 The reader will find an in-depth treatment of the technology in
 [KEMCMP] and [KEMALP].

3.1. The Fibre Channel Network

 The fundamental entity in fibre channel is the fibre channel network.
 Unlike a layered network architecture, a fibre channel network is
 largely specified by functional elements and the interfaces between
 them.  As shown in Figure 1, these consist, in part, of the
 following:
 a) N_PORTs -- The end points for fibre channel traffic.  In the FC
    standards, N_PORT interfaces have several variants, depending on
    the topology of the fabric to which they are attached.  As used in
    this specification, the term applies to any one of the variants.
 b) FC Devices -- The fibre channel devices to which the N_PORTs
    provide access.
 c) Fabric Ports -- The interfaces within a fibre channel network that
    provide attachment for an N_PORT.  The types of fabric port depend
    on the fabric topology and are discussed in Section 3.2.
 d) The network infrastructure for carrying frame traffic between
    N_PORTs.
 e) Within a switched or mixed fabric (see Section 3.2), a set of
    auxiliary servers, including a name server for device discovery
    and network address resolution.  The types of service depend on
    the network topology.

Monia, et al. Standards Track [Page 8] RFC 4172 Internet Fibre Channel Networking September 2005

       +--------+   +--------+          +--------+  +--------+
       |  FC    |   |  FC    |          |  FC    |  |  FC    |
       | Device |   | Device |<-------->| Device |  | Device |
       |........|   |........|          |........|  |........|
       | N_PORT |   | N_PORT |          | N_PORT |  | N_PORT |
       +---+----+   +----+---+          +----+---+  +----+---+
           |             |                   |           |
       +---+----+   +----+---+          +----+---+  +----+---+
       | Fabric |   | Fabric |          | Fabric |  | Fabric |
       | Port   |   | Port   |          | Port   |  | Port   |
       +========+===+========+==========+========+==+========+
       |                        Fabric                       |
       |                          &                          |
       |                     Fabric Services                 |
       +-----------------------------------------------------+
                 Figure 1. A Fibre Channel Network
 The following sections describe fibre channel network topologies and
 give an overview of the fibre channel communications model.

3.2. Fibre Channel Network Topologies

 The principal fibre channel network topologies consist of the
 following:
 a) Arbitrated Loop -- A series of N_PORTs connected together in
    daisy-chain fashion.  In [FC-FS], loop-connected N_PORTs are
    referred to as NL_PORTs.  Data transmission between NL_PORTs
    requires arbitration for control of the loop in a manner similar
    to that of a token ring network.
 b) Switched Fabric --  A network consisting of switching elements, as
    described in Section 3.2.1.
 c) Mixed Fabric -- A network consisting of switches and "fabric-
    attached" loops.  A description can be found in [FC-FLA].  A
    loop-attached N_PORT (NL_PORT) is connected to the loop through an
    L_PORT and accesses the fabric by way of an FL_PORT.

Monia, et al. Standards Track [Page 9] RFC 4172 Internet Fibre Channel Networking September 2005

 Depending on the topology, the N_PORT and its means of network
 attachment may be one of the following:
       FC Network
       Topology         Network Interface   N_PORT Variant
       ---------------  -----------------   --------------
       Loop             L_PORT              NL_PORT
       Switched         F_PORT              N_PORT
       Mixed            FL_PORT via L_PORT  NL_PORT
                        F_PORT              N_PORT
 The differences in each N_PORT variant and its corresponding fabric
 port are confined to the interactions between them.  To an external
 N_PORT, all fabric ports are transparent, and all remote N_PORTs are
 functionally identical.

Monia, et al. Standards Track [Page 10] RFC 4172 Internet Fibre Channel Networking September 2005

3.2.1. Switched Fibre Channel Fabrics

 An example of a multi-switch fibre channel fabric is shown in Figure
 2.
              +----------+          +----------+
              |    FC    |          |  FC      |
              |   Device |          | Device   |
              |..........|          |..........|
              |   N_PORT |<........>| N_PORT   |
              +----+-----+          +-----+----+
                   |                      |
              +----+-----+          +-----+----+
              | F_PORT   |          | F_PORT   |
    ==========+==========+==========+==========+==============
              |  FC      |          | FC       |
              |  Switch  |          | Switch   |
              +----------+          +----------+ Fibre Channel
              |Inter-    |          |Inter-    |   Fabric
              |Switch    |          |Switch    |
              |Interface |          |Interface |
              +-----+----+          +-----+----+
                    |                     |
                    |                     |
              +-----+----+----------+-----+----+
              |Inter-    |          |Inter-    |
              |Switch    |          |Switch    |
              |Interface |          |Interface |
              +----------+          +----------+
              |            FC Switch           |
              |                                |
              +--------------------------------+
          Figure 2. Multi-Switch Fibre Channel Fabric
 The interface between switch elements is either a proprietary
 interface or the standards-compliant E_PORT interface, which is
 described by the FC-SW2 specification, [FC-SW2].

Monia, et al. Standards Track [Page 11] RFC 4172 Internet Fibre Channel Networking September 2005

3.2.2. Mixed Fibre Channel Fabric

 A mixed fabric contains one or more arbitrated loops connected to a
 switched fabric as shown in Figure 3.
              +----------+          +----------+   +---------+
              |    FC    |          |  FC      |   |  FC     |
              |   Device |          | Device   |   | Device  |
              |..........| FC       |..........|   |.........|
              |   N_PORT |<........>| NL_PORT  +---+ NL_PORT |
              +----+-----+ Traffic  +-----+----+   +----+----+
                   |                      |   FC Loop   |
              +----+-----+          +-----+----+        |
              | F_PORT   |          | FL_PORT  +--------+
              |          |          |          |
    ==========+==========+==========+==========+==============
              |  FC      |          | FC       |
              |  Switch  |          | Switch   |
              +----------+          +----------+
              |Inter-    |          |Inter-    |
              |Switch    |          |Switch    |
              |Interface |          |Interface |
              +-----+----+          +-----+----+
                    |                     |
                    |                     |
              +-----+----+----------+-----+----+
              |Inter-    |          |Inter-    |
              |Switch    |          |Switch    |
              |Interface |          |Interface |
              +----------+          +----------+
              |            FC Switch           |
              |                                |
              +--------------------------------+
             Figure 3. Mixed Fibre Channel Fabric
 As noted previously, the protocol for communications between peer
 N_PORTs is independent of the fabric topology, N_PORT variant, and
 type of fabric port to which an N_PORT is attached.

3.3. Fibre Channel Layers and Link Services

 A fibre channel consists of the following layers:
    FC-0 -- The interface to the physical media.
    FC-1 -- The encoding and decoding of data and out-of-band physical
    link control information for transmission over the physical media.

Monia, et al. Standards Track [Page 12] RFC 4172 Internet Fibre Channel Networking September 2005

    FC-2 -- The transfer of frames, sequences, and Exchanges
    comprising protocol information units.
    FC-3 -- Common Services.
    FC-4 -- Application protocols such as the fibre channel protocol
    for SCSI (FCP).
 In addition to the layers defined above, a fibre channel defines a
 set of auxiliary operations, some of which are implemented within the
 transport layer fabric, called link services.  These are required in
 order to manage the fibre channel environment, establish
 communications with other devices, retrieve error information,
 perform error recovery, and provide other similar services.  Some
 link services are executed by the N_PORT.  Others are implemented
 internally within the fabric.  These internal services are described
 in the next section.

3.3.1. Fabric-Supplied Link Services

 Servers that are internal to a switched fabric handle certain classes
 of Link Service requests and service-specific commands.  The servers
 appear as N_PORTs located at the 'well-known' N_PORT fabric addresses
 specified in [FC-FS].  Service requests use the standard fibre
 channel mechanisms for N_PORT-to-N_PORT communications.
 All switched fabrics must provide the following services:
    Fabric F_PORT server -- Services N_PORT requests to access the
    fabric for communications.
    Fabric Controller -- Provides state change information to inform
    other FC devices when an N_PORT exits or enters the fabric (see
    Section 3.5).
    Directory/Name Server - Allows N_PORTs to register information in
    a database, retrieve information about other N_PORTs, and to
    discover other devices as described in Section 3.5.
 A switched fabric may also implement the following optional services:
    Broadcast Address/Server -- Transmits single-frame, class 3
    sequences to all N_PORTs.
    Time Server -- Intended for the management of fabric-wide
    expiration timers or elapsed time values; not intended for precise
    time synchronization.

Monia, et al. Standards Track [Page 13] RFC 4172 Internet Fibre Channel Networking September 2005

    Management Server - Collects and reports management information,
    such as link usage, error statistics, link quality, and similar
    items.
    Quality of Service Facilitator - Performs fabric-wide bandwidth
    and latency management.

3.4. Fibre Channel Nodes

 A fibre channel node has one or more fabric-attached N_PORTs.  The
 node and its N_PORTs have the following associated identifiers:
 a) A worldwide-unique identifier for the node.
 b) A worldwide-unique identifier for each N_PORT associated with the
    node.
 c) For each N_PORT attached to a fabric, a 24-bit fabric-unique
    address with the properties defined in Section 3.7.1.  The fabric
    address is the address to which frames are sent.
 Each worldwide-unique identifier is a 64-bit binary quantity with the
 format defined in [FC-FS].

3.5. Fibre Channel Device Discovery

 In a switched or mixed fabric, fibre channel devices and changes in
 the device configuration may be discovered by means of services
 provided by the fibre channel Name Server and Fabric Controller.
 The Name Server provides registration and query services that allow a
 fibre channel device to register its presence on the fabric and to
 discover the existence of other devices.  For example, one type of
 query obtains the fabric address of an N_PORT from its 64-bit
 worldwide-unique name.  The full set of supported fibre channel name
 server queries is specified in [FC-GS3].
 The Fabric Controller complements the static discovery capabilities
 provided by the Name Server through a service that dynamically alerts
 a fibre channel device whenever an N_PORT is added or removed from
 the configuration.  A fibre channel device receives these
 notifications by subscribing to the service as specified in [FC-FS].

Monia, et al. Standards Track [Page 14] RFC 4172 Internet Fibre Channel Networking September 2005

3.6. Fibre Channel Information Elements

 The fundamental element of information in fibre channel is the frame.
 A frame consists of a fixed header and up to 2112 bytes of payload
 with the structure described in Section 3.7.  The maximum frame size
 that may be transmitted between a pair of fibre channel devices is
 negotiable up to the payload limit, based on the size of the frame
 buffers in each fibre channel device and the path maximum
 transmission unit (MTU) supported by the fabric.
 Operations involving the transfer of information between N_PORT pairs
 are performed through 'Exchanges'.  In an Exchange, information is
 transferred in one or more ordered series of frames, referred to as
 Sequences.
 Within this framework, an upper layer protocol is defined in terms of
 transactions carried by Exchanges.  In turn, each transaction
 consists of protocol information units, each of which is carried by
 an individual Sequence within an Exchange.

3.7. Fibre Channel Frame Format

 A fibre channel frame consists of a header, payload and 32-bit CRC
 bracketed by SOF and EOF delimiters.  The header contains the control
 information necessary to route frames between N_PORTs and manage
 Exchanges and Sequences.  The following diagram gives a schematic
 view of the frame.

Monia, et al. Standards Track [Page 15] RFC 4172 Internet Fibre Channel Networking September 2005

             Bit  0                          31
                 +-----------------------------+
          Word 0 |   Start-of-frame Delimiter  |
                 +-----+-----------------------+<----+
                 |     | Destination N_PORT    |     |
               1 |     | Fabric Address (D_ID) |     |
                 |     |  (24 bits)            |     |
                 +-----+-----------------------+   24-byte
                 |     | Source N_PORT         |   Frame
               2 |     | Fabric Address (S_ID) |   Header
                 |     | (24 bits)             |     |
                 +-----+-----------------------+     |
               3 |    Control information for  |     |
               . |    frame type, Exchange     |     |
               . |    management, IU           |     |
               . |    segmentation and         |     |
               6 |    re-assembly              |     |
                 +-----------------------------+<----+
               7 |                             |
               . |        Frame payload        |
               . |       (0 - 2112 bytes)      |
               . |                             |
               . |                             |
               . |                             |
                 +-----------------------------+
               . |            CRC              |
                 +-----------------------------+
               n |    End-of-Frame Delimiter   |
                 +-----------------------------+
              Figure 4. Fibre Channel Frame Format
 The source and destination N_PORT fabric addresses embedded in the
 S_ID and D_ID fields represent the physical addresses of originating
 and receiving N_PORTs, respectively.

3.7.1. N_PORT Address Model

 N_PORT fabric addresses are 24-bit values with the following format,
 defined by the fibre channel specification [FC-FS]:
          Bit   0         7 8         15 16       23
               +-----------+------------+----------+
               | Domain ID | Area ID    |  Port ID |
               +-----------+------------+----------+
               Figure 5. Fibre Channel Address Format

Monia, et al. Standards Track [Page 16] RFC 4172 Internet Fibre Channel Networking September 2005

 A fibre channel device acquires an address when it logs into the
 fabric.  Such addresses are volatile and subject to change based on
 modifications in the fabric configuration.
 In a fibre channel fabric, each switch element has a unique Domain ID
 assigned by the principal switch.  The value of the Domain ID ranges
 from 1 to 239 (0xEF).  Each switch element, in turn, administers a
 block of addresses divided into area and port IDs.  An N_PORT
 connected to an F_PORT receives a unique fabric address, consisting
 of the switch's Domain ID concatenated with switch-assigned area and
 port IDs.
 A loop-attached NL_PORT (see Figure 3) obtains the Port ID component
 of its address during the loop initialization process described in
 [FC-AL2].  The area and domain IDs are supplied by the fabric when
 the fabric login (FLOGI) is executed.

3.8. Fibre Channel Transport Services

 N_PORTs communicate by means of the following classes of service,
 which are specified in the fibre channel standard ([FC-FS]):
    Class 1 - A dedicated physical circuit connecting two N_PORTs.
    Class 2 - A frame-multiplexed connection with end-to-end flow
    control and delivery confirmation.
    Class 3 - A frame-multiplexed connection with no provisions for
    end-to-end flow control or delivery confirmation.
    Class 4 -- A connection-oriented service, based on a virtual
    circuit model, providing confirmed delivery with bandwidth and
    latency guarantees.
    Class 6 -- A reliable multicast service derived from class 1.
 Classes 2 and 3 are the predominant services supported by deployed
 fibre channel storage and clustering systems.
 Class 3 service is similar to UDP or IP datagram service.  Fibre
 channel storage devices using this class of service rely on the ULP
 implementation to detect and recover from transient device and
 transport errors.
 For class 2 and class 3 service, the fibre channel fabric is not
 required to provide in-order delivery of frames unless it is
 explicitly requested by the frame originator (and supported by the
 fabric).  If ordered delivery is not in effect, it is the

Monia, et al. Standards Track [Page 17] RFC 4172 Internet Fibre Channel Networking September 2005

 responsibility of the frame recipient to reconstruct the order in
 which frames were sent, based on information in the frame header.

3.9. Login Processes

 The Login processes are FC-2 operations that allow an N_PORT to
 establish the operating environment necessary to communicate with the
 fabric, other N_PORTs, and ULP implementations accessed via the
 N_PORT.  Three login operations are supported:
 a) Fabric Login (FLOGI) -- An operation whereby the N_PORT registers
    its presence on the fabric, obtains fabric parameters, such as
    classes of service supported, and receives its N_PORT address,
 b) Port Login (PLOGI) -- An operation by which an N_PORT establishes
    communication with another N_PORT.
 c) Process Login (PRLOGI) -- An operation that establishes the
    process-to-process communications associated with a specific FC-4
    ULP, such as FCP-2, the fibre channel SCSI mapping.
 Since N_PORT addresses are volatile, an N_PORT originating a login
 (PLOGI) operation executes a Name Server query to discover the fibre
 channel address of the remote device.  A common query type involves
 use of the worldwide-unique name of an N_PORT to obtain the 24-bit
 N_PORT fibre channel address to which the PLOGI request is sent.

4. The iFCP Network Model

 The iFCP protocol enables the implementation of fibre channel fabric
 functionality on an IP network in which IP components and technology
 replace the fibre channel switching and routing infrastructure
 described in Section 3.2.
 The example of Figure 6 shows a fibre channel network with attached
 devices.  Each device accesses the network through an N_PORT
 connected to an interface whose behavior is specified in [FC-FS] or
 [FC-AL2].  In this case, the N_PORT represents any of the variants
 described in Section 3.2.  The interface to the fabric may be an
 L_PORT, F_PORT, or FL_PORT.
 Within the fibre channel device domain, addressable entities consist
 of other N_PORTs and fibre channel devices internal to the network
 that perform the fabric services defined in [FC-GS3].

Monia, et al. Standards Track [Page 18] RFC 4172 Internet Fibre Channel Networking September 2005

                    Fibre Channel Network
                +--------+        +--------+
                |  FC    |        |  FC    |
                | Device |        | Device |
                |........| FC     |........| Fibre Channel
                | N_PORT |<......>| N_PORT | Device Domain
                +---+----+ Traffic+----+---+       ^
                    |                  |           |
                +---+----+        +----+---+       |
                | Fabric |        | Fabric |       |
                | Port   |        | Port   |       |
      ==========+========+========+========+==============
                |       FC Network &       |       |
                |     Fabric Services      |       v
                |                          | Fibre Channel
                +--------------------------+ Network Domain
                  Figure 6. A Fibre Channel Network
          Gateway Region                   Gateway Region
     +--------+  +--------+           +--------+  +--------+
     |   FC   |  |  FC    |           |   FC   |  |   FC   |
     | Device |  | Device |           | Device |  | Device |  Fibre
     |........|  |........| FC        |........|  |........|  Channel
     | N_PORT |  | N_PORT |<.........>| N_PORT |  | N_PORT |  Device
     +---+----+  +---+----+ Traffic   +----+---+  +----+---+  Domain
         |           |                     |           |         ^
     +---+----+  +---+----+           +----+---+  +----+---+     |
     | F_PORT |  | F_PORT |           | F_PORT |  | F_PORT |     |
    =+========+==+========+===========+========+==+========+==========
     |    iFCP Layer      |<--------->|     iFCP Layer     |     |
     |....................|     ^     |....................|     |
     |     iFCP Portal    |     |     |     iFCP Portal    |     v
     +--------+-----------+     |     +----------+---------+    IP
          iFCP|Gateway      Control          iFCP|Gateway      Network
              |              Data                |
              |                                  |
              |                                  |
              |<------Encapsulated Frames------->|
              |      +------------------+        |
              |      |                  |        |
              +------+    IP Network    +--------+
                     |                  |
                     +------------------+
                   Figure 7. An iFCP Fabric Example

Monia, et al. Standards Track [Page 19] RFC 4172 Internet Fibre Channel Networking September 2005

 One example of an equivalent iFCP fabric is shown in Figure 7.  The
 fabric consists of two gateway regions, each accessed by a single
 iFCP gateway.
 Each gateway contains two standards-compliant F_PORTs and an iFCP
 Portal for attachment to the IP network.  Fibre channel devices in
 the region are those locally connected to the iFCP fabric through the
 gateway fabric ports.
 Looking into the fabric port, the gateway appears as a fibre channel
 switch element.  At this interface, remote N_PORTs are presented as
 fabric-attached devices.  Conversely, on the IP network side, the
 gateway presents each locally connected N_PORT as a logical fibre
 channel device.
 Extrapolating to the general case, each gateway region behaves like
 an autonomous system whose configuration is invisible to the IP
 network and other gateway regions.  Consequently, in addition to the
 F_PORT shown in the example, a gateway implementation may
 transparently support the following fibre channel interfaces:
    Inter-Switch Link -- A fibre channel switch-to-switch interface
    used to access a region containing fibre channel switch elements.
    An implementation may support the E_PORT defined by [FC-SW2] or
    one of the proprietary interfaces provided by various fibre
    channel switch vendors.  In this case, the gateway acts as a
    border switch connecting the gateway region to the IP network.
    FL_PORT -- An interface that provides fabric access for loop-
    attached fibre channel devices, as specified in [FC-FLA].
    L_PORT -- An interface through which a gateway may emulate the
    fibre channel loop environment specified in [FC-AL2].  As
    discussed in appendix B, the gateway presents remotely accessed
    N_PORTS as loop-attached devices.
 The manner in which these interfaces are provided by a gateway is
 implementation specific and therefore beyond the scope of this
 document.
 Although each region is connected to the IP network through one
 gateway, a region may incorporate multiple gateways for added
 performance and fault tolerance if the following conditions are met:
 a) The gateways MUST coordinate the assignment of N_PORT IDs and
    aliases so that each N_PORT has one and only one address.

Monia, et al. Standards Track [Page 20] RFC 4172 Internet Fibre Channel Networking September 2005

 b) All iFCP traffic between a given remote and local N_PORT pair MUST
    flow through the same iFCP session (see Section 5.2.1).  However,
    iFCP sessions to a given remotely attached N_PORT need not
    traverse the same gateway.
 Coordinating address assignments and managing the flow of traffic is
 implementation specific and outside the scope of this specification.

4.1. iFCP Transport Services

 N_PORT to N_PORT communications that traverse a TCP/IP network
 require the intervention of the iFCP layer within the gateway.  This
 consists of the following operations:
 a) Execution of the frame-addressing and -mapping functions described
    in Section 4.4.
 b) Encapsulation of fibre channel frames for injection into the
    TCP/IP network and de-encapsulation of fibre channel frames
    received from the TCP/IP network.
 c) Establishment of an iFCP session in response to a PLOGI directed
    to a remote device.
 Section 4.4 discusses the iFCP frame-addressing mechanism and the way
 that it is used to achieve communications transparency between
 N_PORTs.

4.1.1. Fibre Channel Transport Services Supported by iFCP

 An iFCP fabric supports Class 2 and Class 3 fibre channel transport
 services, as specified in [FC-FS].  An iFCP fabric does not support
 Class 4, Class 6, or Class 1 (dedicated connection) service.  An
 N_PORT discovers the classes of transport services supported by the
 fabric during fabric login.

4.2. iFCP Device Discovery and Configuration Management

 An iFCP implementation performs device discovery and iFCP fabric
 management through the Internet Storage Name Service defined in
 [ISNS].  Access to an iSNS server is required to perform the
 following functions:
 a) Emulate the services provided by the fibre channel name server
    described in Section 3.3.1, including a mechanism for
    asynchronously notifying an N_PORT of changes in the iFCP fabric
    configuration.

Monia, et al. Standards Track [Page 21] RFC 4172 Internet Fibre Channel Networking September 2005

 b) Aggregate gateways into iFCP fabrics for interoperation.
 c) Segment an iFCP fabric into fibre channel zones through the
    definition and management of device discovery scopes, referred to
    as 'discovery domains'.
 d) Store and distribute security policies, as described in Section
    10.2.9.
 e) Implementation of the fibre channel broadcast mechanism.

4.3. iFCP Fabric Properties

 A collection of iFCP gateways may be configured for interoperation as
 either a bounded or an unbounded iFCP fabric.
 Gateways in a bounded iFCP fabric operate in address transparent
 mode, as described in Section 4.5.  In this mode, the scope of a
 fibre channel N_PORT address is fabric-wide and is derived from
 domain IDs issued by the iSNS server from a common pool.  As
 discussed in Section 4.3.2, the maximum number of domain IDs allowed
 by the fibre channel limits the configuration of a bounded iFCP
 fabric.
 Gateways in an unbounded iFCP fabric operate in address translation
 mode as described in Section 4.6.  In this mode, the scope of an
 N_PORT address is local to a gateway region.  For fibre channel
 traffic between regions, the translation of frame-embedded N_PORT
 addresses is performed by the gateway.  As discussed below, the
 number of switch elements and gateways in an unbounded iFCP fabric
 may exceed the limits of a conventional fibre channel fabric.
 All iFCP gateways MUST support unbounded iFCP fabrics.  Support for
 bounded iFCP fabrics is OPTIONAL.
 The decision to support bounded iFCP fabrics in a gateway
 implementation depends on the address transparency, configuration
 scalability, and fault tolerance considerations given in the
 following sections.

4.3.1. Address Transparency

 Although iFCP gateways in an unbounded fabric will convert N_PORT
 addresses in the frame header and payload of standard link service
 messages, a gateway cannot convert such addresses in the payload of
 vendor- or user-specific fibre channel frame traffic.

Monia, et al. Standards Track [Page 22] RFC 4172 Internet Fibre Channel Networking September 2005

 Consequently, although both bounded and unbounded iFCP fabrics
 support standards-compliant FC-4 protocol implementations and link
 services used by mainstream fibre channel applications, a bounded
 iFCP fabric may also support vendor- or user-specific protocol and
 link service implementations that carry N_PORT IDs in the frame
 payload.

4.3.2. Configuration Scalability

 The scalability limits of a bounded fabric configuration are a
 consequence of the fibre channel address allocation policy discussed
 in Section 3.7.1.  As noted, a bounded iFCP fabric using this address
 allocation scheme is limited to a combined total of 239 gateways and
 fibre channel switch elements.  As the system expands, the network
 may grow to include many switch elements and gateways, each of which
 controls a small number of devices.  In this case, the limitation in
 switch and gateway count may become a barrier to extending and fully
 integrating the storage network.
 Since N_PORT fibre channel addresses in an unbounded iFCP fabric are
 not fabric-wide, the limits imposed by fibre channel address
 allocation only apply within the gateway region.  Across regions, the
 number of iFCP gateways, fibre channel devices, and switch elements
 that may be internetworked are not constrained by these limits.  In
 exchange for improved scalability, however, implementations must
 consider the incremental overhead of address conversion, as well as
 the address transparency issues discussed in Section 4.3.1.

4.3.3. Fault Tolerance

 In a bounded iFCP fabric, address reassignment caused by a fault or
 reconfiguration, such as the addition of a new gateway region, may
 cascade to other regions, causing fabric-wide disruption as new
 N_PORT addresses are assigned.  Furthermore, before a new gateway can
 be merged into the fabric, its iSNS server must be slaved to the iSNS
 server in the bounded fabric to centralize the issuance of domain
 IDs.  In an unbounded iFCP fabric, coordinating the iSNS databases
 requires only that the iSNS servers exchange client attributes with
 one another.
 A bounded iFCP fabric also has an increased dependency on the
 availability of the iSNS server, which must act as the central
 address assignment authority.  If connectivity with the server is
 lost, new DOMAIN_ID values cannot be automatically allocated as
 gateways and fibre channel switch elements are added.

Monia, et al. Standards Track [Page 23] RFC 4172 Internet Fibre Channel Networking September 2005

4.4. The iFCP N_PORT Address Model

 This section discusses iFCP extensions to the fibre channel
 addressing model of Section 3.7.1, which are required for the
 transparent routing of frames between locally and remotely attached
 N_PORTs.
 In the iFCP protocol, an N_PORT is represented by the following
 addresses:
 a) A 24-bit N_PORT ID.  The fibre channel N_PORT address of a locally
    attached device.  Depending on the gateway addressing mode, the
    scope is local either to a region or to a bounded iFCP fabric.  In
    either mode, communications between N_PORTs in the same gateway
    region use the N_PORT ID.
 b) A 24-bit N_PORT alias.  The fibre channel N_PORT address assigned
    by each gateway operating in address translation mode to identify
    a remotely attached N_PORT.  Frame traffic is intercepted by an
    iFCP gateway and directed to a remotely attached N_PORT by means
    of the N_PORT alias.  The address assigned by each gateway is
    unique within the scope of the gateway region.
 c) An N_PORT network address.  A tuple consisting of the gateway IP
    address, TCP port number, and N_PORT ID.  The N_PORT network
    address identifies the source and destination N_PORTs for fibre
    channel traffic on the IP network.
 To provide transparent communications between a remote and local
 N_PORT, a gateway MUST maintain an iFCP session descriptor (see
 Section 5.2.2.2) reflecting the association between the fibre channel
 address representing the remote N_PORT and the remote device's N_PORT
 network address.  To establish this association, the iFCP gateway
 assigns and manages fibre channel N_PORT fabric addresses as
 described in the following paragraphs.
 In an iFCP fabric, the iFCP gateway performs the address assignment
 and frame routing functions of an FC switch element.  Unlike an FC
 switch, however, an iFCP gateway must also direct frames to external
 devices attached to remote gateways on the IP network.
 In order to be transparent to FC devices, the gateway must deliver
 such frames using only the 24-bit destination address in the frame
 header.  By exploiting its control of address allocation and access
 to frame traffic entering or leaving the gateway region, the gateway
 is able to achieve the necessary transparency.

Monia, et al. Standards Track [Page 24] RFC 4172 Internet Fibre Channel Networking September 2005

 N_PORT addresses within a gateway region may be allocated in one of
 two ways:
 a) Address Translation Mode - A mode of N_PORT address assignment in
    which the scope of an N_PORT fibre channel address is unique to
    the gateway region.  The address of a remote device is represented
    in that gateway region by its gateway-assigned N_PORT alias.
 b) Address Transparent Mode - A mode of N_PORT address assignment in
    which the scope of an N_PORT fibre channel address is unique
    across the set of gateway regions comprising a bounded iFCP
    fabric.
 In address transparent mode, gateways within a bounded fabric
 cooperate in the assignment of addresses to locally attached N_PORTs.
 Each gateway in control of a region is responsible for obtaining and
 distributing unique domain IDs from the address assignment authority,
 as described in Section 4.5.1.  Consequently, within the scope of a
 bounded fabric, the address of each N_PORT is unique.  For that
 reason, gateway-assigned aliases are not required for representing
 remote N_PORTs.
 All iFCP implementations MUST support operations in address
 translation mode.  Implementation of address transparent mode is
 OPTIONAL but, of course, must be provided if bounded iFCP fabric
 configurations are to be supported.
 The mode of gateway operation is settable in an implementation-
 specific manner.  The implementation MUST NOT:
 a) allow the mode to be changed after the gateway begins processing
    fibre channel frame traffic,
 b) permit operation in more than one mode at a time, or
 c) establish an iFCP session with a gateway that is not in the same
    mode.

4.5. Operation in Address Transparent Mode

 The following considerations and requirements apply to this mode of
 operation:
 a) iFCP gateways in address transparent mode will not interoperate
    with iFCP gateways that are not in address transparent mode.

Monia, et al. Standards Track [Page 25] RFC 4172 Internet Fibre Channel Networking September 2005

 b) When interoperating with locally attached fibre channel switch
    elements, each iFCP gateway MUST assume control of DOMAIN_ID
    assignments in accordance with the appropriate fibre channel
    standard or vendor-specific protocol specification.  As described
    in Section 4.5.1, DOMAIN_ID values that are assigned to FC
    switches internal to the gateway region must be issued by the iSNS
    server.
 c) When operating in address transparent Mode, fibre channel address
    translation SHALL NOT take place.
 When operating in address transparent mode, however, the gateway MUST
 establish and maintain the context of each iFCP session in accordance
 with Section 5.2.2.

4.5.1. Transparent Mode Domain ID Management

 As described in Section 4.5, each gateway and fibre channel switch in
 a bounded iFCP fabric has a unique domain ID.  In a gateway region
 containing fibre channel switch elements, each element obtains a
 domain ID by querying the principal switch as described in [FC-SW2]
 -- in this case, the iFCP gateway itself.  The gateway, in turn,
 obtains domain IDs on demand from the iSNS name server acting as the
 central address allocation authority.  In effect, the iSNS server
 assumes the role of principal switch for the bounded fabric.  In that
 case, the iSNS database contains:
 a) The definition for one or more bounded iFCP fabrics, and
 b) For each bounded fabric, a worldwide-unique name identifying each
    gateway in the fabric.  A gateway in address transparent mode MUST
    reside in one, and only one, bounded fabric.
 As the Principal Switch within the gateway region, an iFCP gateway in
 address transparent mode SHALL obtain domain IDs for use in the
 gateway region by issuing the appropriate iSNS query, using its
 worldwide name.

4.5.2. Incompatibility with Address Translation Mode

 Except for the session control frames specified in Section 6, iFCP
 gateways in address transparent mode SHALL NOT originate or accept
 frames that do not have the TRP bit set to one in the iFCP flags
 field of the encapsulation header (see Section 5.3.1).  The iFCP
 gateway SHALL immediately terminate all iFCP sessions with the iFCP
 gateway from which it receives such frames.

Monia, et al. Standards Track [Page 26] RFC 4172 Internet Fibre Channel Networking September 2005

4.6. Operation in Address Translation Mode

 This section describes the process for managing the assignment of
 addresses within a gateway region that is part of an unbounded iFCP
 fabric, including the modification of FC frame addresses embedded in
 the frame header for frames sent and received from remotely attached
 N_PORTs.
 As described in Section 4.4, the scope of N_PORT addresses in this
 mode is local to the gateway region.  A principal switch within the
 gateway region, possibly the iFCP gateway itself, oversees the
 assignment of such addresses, in accordance with the rules specified
 in [FC-FS] and [FC-FLA].
 The assignment of N_PORT addresses to locally attached devices is
 controlled by the switch element to which the device is connected.
 The assignment of N_PORT addresses for remotely attached devices is
 controlled by the gateway by which the remote device is accessed.  In
 this case, the gateway MUST assign a locally significant N_PORT alias
 to be used in place of the N_PORT ID assigned by the remote gateway.
 The N_PORT alias is assigned during device discovery, as described in
 Section 5.2.2.1.
 To perform address conversion and to enable the appropriate routing,
 the gateway MUST establish an iFCP session and generate the
 information required to map each N_PORT alias to the appropriate
 TCP/IP connection context and N_PORT ID of the remotely accessed
 N_PORT.  These mappings are created and updated by means specified in
 Section 5.2.2.2.  As described in that section, the required mapping
 information is represented by the iFCP session descriptor reproduced
 in Figure 8.
                    +-----------------------+
                    |TCP Connection Context |
                    +-----------------------+
                    |  Local N_PORT ID      |
                    +-----------------------+
                    |  Remote N_PORT ID     |
                    +-----------------------+
                    |  Remote N_PORT Alias  |
                    +-----------------------+
    Figure 8. iFCP Session Descriptor (from Section 5.2.2.2)

Monia, et al. Standards Track [Page 27] RFC 4172 Internet Fibre Channel Networking September 2005

 Except for frames comprising special link service messages (see
 Section 7.2), outbound frames are encapsulated and sent without
 modification.  Address translation is deferred until receipt from the
 IP network, as specified in Section 4.6.1.

4.6.1. Inbound Frame Address Translation

 For inbound frames received from the IP network, the receiving
 gateway SHALL reference the session descriptor to fill in the D_ID
 field with the destination N_PORT ID and the S_ID field with the
 N_PORT alias it assigned.  The translation process for inbound frames
 is shown in Figure 9.
      Network Format of Inbound Frame
 +--------------------------------------------+            iFCP
 |          FC Encapsulation Header           |           Session
 +--------------------------------------------+           Descriptor
 |            SOF Delimiter Word              |              |
 +========+===================================+              V
 |        |         D_ID Field                |     +--------+-----+
 +--------+-----------------------------------+     | Lookup source|
 |        |         S_ID Field                |     | N_PORT Alias |
 +--------+-----------------------------------+     | and          |
 |        Control Information, Payload,       |     | destination  |
 |        and FC CRC                          |     | N_PORT ID    |
 |                                            |     +--------+-----+
 |                                            |              |
 |                                            |              |
 +============================================+              |
 |         EOF Delimiter Word                 |              |
 +--------------------------------------------+              |
                                                             |
                                                             |
 Frame after Address Translation and De-encapsulation        |
 +--------+-----------------------------------+              |
 |        |  Destination N_PORT ID            |<-------------+
 +--------+-----------------------------------+              |
 |        |  Source N_PORT Alias              |<-------------+
 +--------+-----------------------------------+
 |                                            |
 |        Control information, Payload,       |
 |        and FC CRC                          |
 +--------------------------------------------+
          Figure 9. Inbound Frame Address Translation

Monia, et al. Standards Track [Page 28] RFC 4172 Internet Fibre Channel Networking September 2005

 The receiving gateway SHALL consider the contents of the S_ID and
 D_ID fields to be undefined when received.  After replacing these
 fields, the gateway MUST recalculate the FC CRC.

4.6.2. Incompatibility with Address Transparent Mode

 iFCP gateways in address translation mode SHALL NOT originate or
 accept frames that have the TRP bit set to one in the iFCP flags
 field of the encapsulation header.  The iFCP gateway SHALL
 immediately abort all iFCP sessions with the iFCP gateway from which
 it receives frames such as those described in Section 5.2.3.

5. iFCP Protocol

5.1. Overview

5.1.1. iFCP Transport Services

 The main function of the iFCP protocol layer is to transport fibre
 channel frame images between locally and remotely attached N_PORTs.
 When transporting frames to a remote N_PORT, the iFCP layer
 encapsulates and routes the fibre channel frames comprising each
 fibre channel Information Unit via a predetermined TCP connection for
 transport across the IP network.
 When receiving fibre channel frame images from the IP network, the
 iFCP layer de-encapsulates and delivers each frame to the appropriate
 N_PORT.
 The iFCP layer processes the following types of traffic:
 a) FC-4 frame images associated with a fibre channel application
    protocol.
 b) FC-2 frames comprising fibre channel link service requests and
    responses.
 c) Fibre channel broadcast frames.
 d) iFCP control messages required to set up, manage, or terminate an
    iFCP session.
 For FC-4 N_PORT traffic and most FC-2 messages, the iFCP layer never
 interprets the contents of the frame payload.
 iFCP does interpret and process iFCP control messages and certain
 link service messages, as described in Section 5.1.2.

Monia, et al. Standards Track [Page 29] RFC 4172 Internet Fibre Channel Networking September 2005

5.1.2. iFCP Support for Link Services

 iFCP must intervene in the processing of those fibre channel link
 service messages that contain N_PORT addresses in the message payload
 or that require other special handling, such as an N_PORT login
 request (PLOGI).
 In the former case, an iFCP gateway operating in address translation
 mode MUST supplement the payload with additional information that
 enables the receiving gateway to convert such embedded N_PORT
 addresses to its frame of reference.
 For out bound fibre channel frames comprising such a link service,
 the iFCP layer creates the supplemental information based on frame
 content, modifies the frame payload, and then transmits the resulting
 fibre channel frame with supplemental data through the appropriate
 TCP connection.
 For incoming iFCP frames containing supplemented fibre channel link
 service frames, iFCP must interpret the frame, including any
 supplemental information, modify the frame content, and forward the
 resulting frame to the destination N_PORT for further processing.
 Section 7.1 describes the processing of these link service messages
 in detail.

5.2. TCP Stream Transport of iFCP Frames

5.2.1. iFCP Session Model

 An iFCP session consists of the pair of N_PORTs comprising the
 session endpoints joined by a single TCP/IP connection.  No more than
 one iFCP session SHALL exist between a given pair of N_PORTs.
 An N_PORT is identified by its network address, consisting of:
 a) the N_PORT ID assigned by the gateway to which the N_PORT is
    locally attached, and
 b) the iFCP Portal address, consisting of its IP address and TCP port
    number.
 Because only one iFCP session may exist between a pair of N_PORTs,
 the iFCP session is uniquely identified by the network addresses of
 the session end points.
 TCP connections that may be used for iFCP sessions between pairs of
 iFCP portals are either "bound" or "unbound".  An unbound connection

Monia, et al. Standards Track [Page 30] RFC 4172 Internet Fibre Channel Networking September 2005

 is a TCP connection that is not actively supporting an iFCP session.
 A gateway implementation MAY establish a pool of unbound connections
 to reduce the session setup time.  Such pre-existing TCP connections
 between iFCP Portals remain unbound and uncommitted until allocated
 to an iFCP session through a CBIND message (see Section 6.1).
 When the iFCP layer creates an iFCP session, it may select an
 existing unbound TCP connection or establish a new TCP connection and
 send the CBIND message down that TCP connection.  This allocates the
 TCP connection to that iFCP session.

5.2.2. iFCP Session Management

 This section describes the protocols and data structures required to
 establish and terminate an iFCP session.

5.2.2.1. The Remote N_PORT Descriptor

 In order to establish an iFCP session, an iFCP gateway MUST maintain
 information allowing it to locate a remotely attached N_PORT.  For
 explanatory purposes, such information is assumed to reside in a
 descriptor with the format shown in Figure 10.
                  +--------------------------------+
                  |  N_PORT Worldwide Unique Name  |
                  +--------------------------------+
                  |  iFCP Portal Address           |
                  +--------------------------------+
                  |  N_PORT ID of Remote N_PORT    |
                  +--------------------------------+
                  |  N_PORT Alias                  |
                  +--------------------------------+
                  Figure 10. Remote N_PORT Descriptor
 Each descriptor aggregates the following information about a remotely
 attached N_PORT:
    N_PORT Worldwide Unique Name -- 64-bit N_PORT worldwide name as
    specified in [FC-FS].  A Remote N_PORT descriptor is uniquely
    identified by this parameter.
    iFCP Portal Address -- The IP address and TCP port number
    referenced when creation of the TCP connection associated with an
    iFCP session is requested.
    N_PORT ID --  N_PORT fibre channel address assigned to the remote
    device by the remote iFCP gateway.

Monia, et al. Standards Track [Page 31] RFC 4172 Internet Fibre Channel Networking September 2005

    N_PORT Alias -- N_PORT fibre channel address assigned to the
    remote device by the 'local' iFCP gateway when it operates in
    address translation mode.
 An iFCP gateway SHALL have one and only one descriptor for each
 remote N_PORT it accesses.  If a descriptor does not exist, one SHALL
 be created using the information returned by an iSNS name server
 query.  Such queries may result from:
 a) a fibre channel Name Server request originated by a locally
    attached N_PORT (see Sections 3.5 and 9.3), or
 b) a CBIND request received from a remote fibre channel device (see
    Section 5.2.2.2).
 When creating a descriptor in response to an incoming CBIND request,
 the iFCP gateway SHALL perform an iSNS name server query using the
 worldwide port name of the remote N_PORT in the SOURCE N_PORT NAME
 field within the CBIND payload.  The descriptor SHALL be filled in
 using the query results.
 After creating the descriptor, a gateway operating in address
 translation mode SHALL create and add the 24-bit N_PORT alias.

5.2.2.1.1. Updating a Remote N_PORT Descriptor

 A Remote N_PORT descriptor SHALL only be updated as the result of an
 iSNS query to obtain information for the specified worldwide port
 name or from information returned by an iSNS state change
 notification.  Following such an update, a new N_PORT alias SHALL NOT
 be assigned.
 Before such an update, the contents of a descriptor may have become
 stale because of an event that invalidated or triggered a change in
 the N_PORT network address of the remote device, such as a fabric
 reconfiguration or the device's removal or replacement.
 A collateral effect of such an event is that a fibre channel device
 that has been added or whose N_PORT ID has changed will have no
 active N_PORT logins.  Consequently, FC-4 traffic directed to such an
 N_PORT, because of a stale descriptor, will be rejected or discarded.
 Once the originating N_PORT learns of the reconfiguration, usually
 through the name server state change notification mechanism,
 information returned in the notification or the subsequent name
 server lookup needed to reestablish the iFCP session will
 automatically purge such stale data from the gateway.

Monia, et al. Standards Track [Page 32] RFC 4172 Internet Fibre Channel Networking September 2005

5.2.2.1.2. Deleting a Remote N_PORT Descriptor

 Deleting a remote N_PORT descriptor is equivalent to freeing up the
 corresponding N_PORT alias for reuse.  Consequently, the descriptor
 MUST NOT be deleted while there are any iFCP sessions that reference
 the remote N_PORT.
 Descriptors eligible for deletion should be removed based on a last
 in, first out policy.

5.2.2.2. Creating an iFCP Session

 An iFCP session may be in one of the following states:
    OPEN  --  The session state in which fibre channel frame images
    may be sent and received.
    OPEN PENDING -- The session state after a gateway has issued a
    CBIND request but no response has yet been received.  No fibre
    channel frames may be sent.
 The session may be initiated in response to a PLOGI ELS (see Section
 7.3.1.7) or for any other implementation-specific reason.
 The gateway SHALL create the iFCP session as follows:
 a) Locate the remote N_PORT descriptor corresponding to the session
    end point.  If the session is created in order to forward a fibre
    channel frame, then the session endpoint may be obtained by
    referencing the remote N_PORT alias contained in the frame header
    D_ID field.  If no descriptor exists, an iFCP session SHALL NOT be
    created.
 b) Allocate a TCP connection to the gateway to which the remote
    N_PORT is locally attached.  An implementation may use an existing
    connection in the Unbound state, or a new connection may be
    created and placed in the Unbound state.
    When a connection is created, the IP address and TCP Port number
    SHALL be obtained by referencing the remote N_PORT descriptor as
    specified in Section 5.2.2.1.
 c) If the TCP connection cannot be allocated or cannot be created due
    to limited resources, the gateway SHALL terminate session
    creation.

Monia, et al. Standards Track [Page 33] RFC 4172 Internet Fibre Channel Networking September 2005

 d) If the TCP connection is aborted for any reason before the iFCP
    session enters the OPEN state, the gateway SHALL respond in
    accordance with Section 5.2.3 and MAY terminate the attempt to
    create a session or MAY try to establish the TCP connection again.
 e) The gateway SHALL then issue a CBIND session control message (see
    Section 6.1) and place the session in the OPEN PENDING state.
 f) If a CBIND response is returned with a status other than "Success"
    or "iFCP session already exists", the session SHALL be terminated,
    and the TCP connection returned to the Unbound state.
 g) A CBIND STATUS of "iFCP session already exists" indicates that the
    remote gateway has concurrently initiated a CBIND request to
    create an iFCP session between the same pair of N_PORTs.  A
    gateway receiving such a response SHALL terminate this attempt and
    process the incoming CBIND request in accordance with Section
    5.2.2.3.
 h) In response to a CBIND STATUS of "Success", the gateway SHALL
    place the session in the OPEN state.
 Once the session is placed in the OPEN state, an iFCP session
 descriptor SHALL be created, containing the information shown in
 Figure 11:
                      +-----------------------+
                      |TCP Connection Context |
                      +-----------------------+
                      |  Local N_PORT ID      |
                      +-----------------------+
                      |  Remote N_PORT ID     |
                      +-----------------------+
                      |  Remote N_PORT Alias  |
                      +-----------------------+
                   Figure 11. iFCP Session Descriptor
    TCP Connection Context -- Information required to identify the TCP
    connection associated with the iFCP session.
    Local N_PORT ID --  N_PORT ID of the locally attached fibre
    channel device.
    Remote N_PORT ID -- N_PORT ID assigned to the remote device by the
    remote gateway.

Monia, et al. Standards Track [Page 34] RFC 4172 Internet Fibre Channel Networking September 2005

    Remote N_PORT Alias -- Alias assigned to the remote N_PORT by the
    local gateway when it operates in address translation mode.  If in
    this mode, the gateway SHALL copy this parameter from the Remote
    N_PORT descriptor.  Otherwise, it is not filled in.

5.2.2.3. Responding to a CBIND Request

 The gateway receiving a CBIND request SHALL respond as follows:
 a) If the receiver has a duplicate iFCP session in the OPEN PENDING
    state, then the receiving gateway SHALL compare the Source N_PORT
    Name in the incoming CBIND payload with the Destination N_PORT
    Name.
 b) If the Source N_PORT Name is greater, the receiver SHALL issue a
    CBIND response of "Success" and SHALL place the session in the
    OPEN state.
 c) If the Source N_PORT Name is less, the receiver shall issue a
    CBIND RESPONSE of Failed - N_PORT session already exists.  The
    state of the receiver-initiated iFCP session SHALL BE unchanged.
 d) If there is no duplicate iFCP session in the OPEN PENDING state,
    the receiving gateway SHALL issue a CBIND response.  If a status
    of Success is returned, the receiving gateway SHALL create the
    iFCP session and place it in the OPEN state.  An iFCP session
    descriptor SHALL be created as described in Section 5.2.2.2.
 e) If a remote N_PORT descriptor does not exist, one SHALL be created
    and filled in as described in Section 5.2.2.1.

5.2.2.4. Monitoring iFCP Connectivity

 During extended periods of inactivity, an iFCP session may be
 terminated due to a hardware failure within the gateway or through
 loss of TCP/IP connectivity.  The latter may occur when the session
 traverses a stateful intermediate device, such as a NA(P)T box or
 firewall, that detects and purges connections it believes are unused.
 To test session liveness, expedite the detection of connectivity
 failures, and avoid spontaneous connection termination, an iFCP
 gateway may maintain a low level of session activity and monitor the
 session by requesting that the remote gateway periodically transmit
 the LTEST message described in Section 6.3.  All iFCP gateways SHALL
 support liveness testing as described in this specification.

Monia, et al. Standards Track [Page 35] RFC 4172 Internet Fibre Channel Networking September 2005

 A gateway requests the LTEST heartbeat by specifying a non-zero value
 for the LIVENESS TEST INTERVAL in the CBIND request or response
 message as described in Section 6.1.  If both gateways seek to
 monitor liveness, each must set the LIVENESS TEST INTERVAL in the
 CBIND request or response.
 Upon receiving such a request, the gateway providing the heartbeat
 SHALL transmit LTEST messages at the specified interval.  The first
 message SHALL be sent as soon as the iFCP session enters the OPEN
 state.  LTEST messages SHALL NOT be sent when the iFCP session is not
 in the OPEN state.
 An iFCP session SHALL be terminated as described in Section 5.2.3 if:
 a) the contents of the LTEST message are incorrect, or
 b) an LTEST message is not received within twice the specified
    interval or the iFCP session has been quiescent for longer than
    twice the specified interval.
 The gateway to receive the LTEST message SHALL measure the interval
 for the first expected LTEST message from when the session is placed
 in the OPEN state.  Thereafter, the interval SHALL be measured
 relative to the last LTEST message received.
 To maximize liveness test coverage, LTEST messages SHOULD flow
 through all the gateway components used to enter and retrieve fibre
 channel frames from the IP network, including the mechanisms for
 encapsulating and de-encapsulating fibre channel frames.
 In addition to monitoring a session, information in the LTEST message
 encapsulation header may also be used to compute an estimate of
 network propagation delay, as described in Section 8.2.1.  However,
 the propagation delay limit SHALL NOT be enforced for LTEST traffic.

5.2.2.5. Use of TCP Features and Settings

 This section describes ground rules for the use of TCP features in an
 iFCP session.  The core TCP protocol is defined in [RFC793].  TCP
 implementation requirements and guidelines are specified in
 [RFC1122].

Monia, et al. Standards Track [Page 36] RFC 4172 Internet Fibre Channel Networking September 2005

 +-----------+------------+--------------+------------+------------+
 | Feature   | Applicable |  RFC         |  Peer-Wise | Requirement|
 |           | RFCs       |  Status      |  Agreement | Level      |
 |           |            |              |  Required? |            |
 +===========+============+==============+============+============+
 | Keep Alive| [RFC1122]  |  None        |  No        | Should not |
 |           |(discussion)|              |            | use        |
 +-----------+------------+--------------+------------+------------+
 | Tiny      | [RFC896]   |  Standard    |  No        | Should not |
 | Segment   |            |              |            | use        |
 | Avoidance |            |              |            |            |
 | (Nagle)   |            |              |            |            |
 +-----------+------------+--------------+------------+------------+
 | Window    | [RFC1323]  |  Proposed    |  No        | Should use |
 | Scale     |            |  Standard    |            |            |
 +-----------+------------+--------------+------------+------------+
 | Wrapped   | [RFC1323]  |  Proposed    |  No        | SHOULD use |
 | Sequence  |            |  Standard    |            |            |
 | Protection|            |              |            |            |
 | (PAWS)    |            |              |            |            |
 +-----------+------------+--------------+------------+------------+
               Table 1. Usage of Optional TCP Features
 The following sections describe these options in greater detail.

5.2.2.5.1. Keep Alive

 Keep Alive speeds the detection and cleanup of dysfunctional TCP
 connections by sending traffic when a connection would otherwise be
 idle.  The issues are discussed in [RFC1122].
 In order to test the device more comprehensively, fibre channel
 applications, such as storage, may implement an equivalent keep alive
 function at the FC-4 level.  Alternatively, periodic liveness test
 messages may be issued as described in Section 5.2.2.4.  Because of
 these more comprehensive end-to-end mechanisms and the considerations
 described in [RFC1122], keep alive at the transport layer should not
 be implemented.

5.2.2.5.2. 'Tiny' Segment Avoidance (Nagle)

 The Nagle algorithm described in [RFC896] is designed to avoid the
 overhead of small segments by delaying transmission in order to
 agglomerate transfer requests into a large segment.  In iFCP, such
 small transfers often contain I/O requests.  The transmission delay
 of the Nagle algorithm may decrease I/O throughput.  Therefore, the
 Nagle algorithm should not be used.

Monia, et al. Standards Track [Page 37] RFC 4172 Internet Fibre Channel Networking September 2005

5.2.2.5.3. Window Scale

 Window scaling, as specified in [RFC1323], allows full use of links
 with large bandwidth - delay products and should be supported by an
 iFCP implementation.

5.2.2.5.4. Wrapped Sequence Protection (PAWS)

 TCP segments are identified with 32-bit sequence numbers.  In
 networks with large bandwidth - delay products, it is possible for
 more than one TCP segment with the same sequence number to be in
 flight.  In iFCP, receipt of such a sequence out of order may cause
 out-of-order frame delivery or data corruption.  Consequently, this
 feature SHOULD be supported as described in [RFC1323].

Monia, et al. Standards Track [Page 38] RFC 4172 Internet Fibre Channel Networking September 2005

5.2.3. Terminating iFCP Sessions

 iFCP sessions SHALL be terminated in response to one of the events in
 Table 2:
 +-------------------------------------------+---------------------+
 |                Event                      |     iFCP Sessions   |
 |                                           |     to Terminate    |
 +===========================================+=====================+
 | PLOGI terminated with LS_RJT response     | Peer N_PORT         |
 +-------------------------------------------+---------------------+
 | State change notification indicating      | All iFCP Sessions   |
 | N_PORT removal or reconfiguration.        | from the            |
 |                                           | reconfigured N_PORT |
 +-------------------------------------------+---------------------+
 | LOGO ACC response from peer N_PORT        | Peer N_PORT         |
 +-------------------------------------------+---------------------+
 | ACC response to LOGO ELS sent to F_PORT   | All iFCP sessions   |
 | server (D_ID = 0xFF-FF-FE) (fabric        | from the originating|
 | logout)                                   | N_PORT              |
 +-------------------------------------------+---------------------+
 | Implicit N_PORT LOGO as defined in        | All iFCP sessions   |
 | [FC-FS]                                   | from the N_PORT     |
 |                                           | logged out          |
 +-------------------------------------------+---------------------+
 | LTEST Message Error (see Section 5.2.2.4) | Peer N_PORT         |
 +-------------------------------------------+---------------------+
 | Non fatal encapsulation error as          | Peer N_PORT         |
 | specified in Section 5.3.3                |                     |
 +-------------------------------------------+---------------------+
 | Failure of the TCP connection associated  | Peer N_PORT         |
 | with the iFCP session                     |                     |
 +-------------------------------------------+---------------------+
 | Receipt of an UNBIND session control      | Peer N_PORT         |
 | message                                   |                     |
 +-------------------------------------------+---------------------+
 | Gateway enters the Unsynchronized state   | All iFCP sessions   |
 | (see Section 8.2.1)                       |                     |
 +-------------------------------------------+---------------------+
 | Gateway detects incorrect address mode    | All iFCP sessions   |
 | to peer gateway(see Section 4.6.2)        | with peer gateway   |
 +-------------------------------------------+---------------------+
                 Table 2. Session Termination Events

Monia, et al. Standards Track [Page 39] RFC 4172 Internet Fibre Channel Networking September 2005

 If a session is being terminated due to an incorrect address mode
 with the peer gateway, the TCP connection SHALL be aborted by means
 of a connection reset (RST) without performing an UNBIND.  Otherwise,
 if the TCP connection is still open following the event, the gateway
 SHALL shut down the connection as follows:
 a) Stop sending fibre channel frames over the TCP connection.
 b) Discard all incoming traffic, except for an UNBIND session control
    message.
 c) If an UNBIND message is received at any time, return a response in
    accordance with Section 6.2.
 d) If session termination was not triggered by an UNBIND message,
    issue the UNBIND session control message, as described in Section
    6.2.
 e) If the UNBIND message completes with a status of Success, the TCP
    connection MAY remain open at the discretion of either gateway and
    may be kept in a pool of unbound connections in order to speed up
    the creation of a new iFCP session.
    If the UNBIND fails for any reason, the TCP connection MUST be
    terminated.  In this case, the connection SHOULD be aborted with a
    connection reset (RST).
 For each terminated session, the session descriptor SHALL be deleted.
 If a session was terminated by an event other than an implicit LOGO
 or a LOGO ACC response, the gateway shall issue a LOGO to the locally
 attached N_PORT on behalf of the remote N_PORT.
 To recover resources, either gateway may spontaneously close an
 unbound TCP connection at any time.  If a gateway terminates a
 connection with a TCP close operation, the peer gateway MUST respond
 by executing a TCP close.

5.3. Fibre Channel Frame Encapsulation

 This section describes the iFCP encapsulation of fibre channel
 frames.  The encapsulation complies with the common encapsulation
 format defined in [ENCAP], portions of which are included here for
 convenience.

Monia, et al. Standards Track [Page 40] RFC 4172 Internet Fibre Channel Networking September 2005

 The format of an encapsulated frame is shown below:
                   +--------------------+
                   |       Header       |
                   +--------------------+-----+
                   |        SOF         |   f |
                   +--------------------+ F r |
                   |  FC frame content  | C a |
                   +--------------------+   m |
                   |        EOF         |   e |
                   +--------------------+-----+
                 Figure 12. Encapsulation Format
 The encapsulation consists of a 7-word header, an SOF delimiter word,
 the FC frame (including the fibre channel CRC), and an EOF delimiter
 word.  The header and delimiter formats are described in the
 following sections.

5.3.1. Encapsulation Header Format

 W|------------------------------Bit------------------------------|
 o|                                                               |
 r|                    1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3|
 d|0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1|
  +---------------+---------------+---------------+---------------+
 0|   Protocol#   |    Version    |  -Protocol#   |   -Version    |
  +---------------+---------------+---------------+---------------+
 1|                  Reserved (must be zero)                      |
  +---------------+---------------+---------------+---------------+
 2| LS_COMMAND_ACC|  iFCP Flags   |     SOF       |      EOF      |
  +-----------+---+---------------+-----------+---+---------------+
 3|   Flags   |   Frame Length    |   -Flags  |   -Frame Length   |
  +-----------+-------------------+-----------+-------------------+
 4|                      Time Stamp [integer]                     |
  +---------------------------------------------------------------+
 5|                      Time Stamp [fraction]                    |
  +---------------------------------------------------------------+
 6|                              CRC                              |
  +---------------------------------------------------------------+
               Figure 13. Encapsulation Header Format
 Common Encapsulation Fields:
 Protocol#            IANA-assigned protocol number identifying the
                      protocol using the encapsulation.  For iFCP, the
                      value assigned by [ENCAP] is 2.

Monia, et al. Standards Track [Page 41] RFC 4172 Internet Fibre Channel Networking September 2005

 Version              Encapsulation version, as specified in [ENCAP].
  1. Protocol# Ones complement of the Protocol#.
  1. Version Ones complement of the version.
 Flags                Encapsulation flags (see 5.3.1.1).
 Frame Length         Contains the length of the entire FC
                      Encapsulated frame, including the FC
                      Encapsulation Header and the FC frame (including
                      SOF and EOF words) in units of 32-bit words.
  1. Flags Ones complement of the Flags field.
  1. Frame Length Ones complement of the Frame Length field.
 Time Stamp [integer] Integer component of the frame time stamp, as
                      specified in [ENCAP].
 Time Stamp           Fractional component of the time stamp,
 [fraction]           as specified in [ENCAP].
 CRC                  Header CRC.  MUST be valid for iFCP.
 The time stamp fields are used to enforce the limit on the lifetime
 of a fibre channel frame as described in Section 8.2.1.
 iFCP-Specific Fields:
 LS_COMMAND_ACC       For a special link service ACC response to be
                      processed by iFCP, the LS_COMMAND_ACC field
                      SHALL contain a copy of bits 0 through 7 of the
                      LS_COMMAND to which the ACC applies.  Otherwise,
                      the LS_COMMAND_ACC field SHALL be set to zero.
 iFCP Flags           iFCP-specific flags (see below).
 SOF                  Copy of the SOF delimiter encoding (see Section
                      5.3.2).
 EOF                  Copy of the EOF delimiter encoding (see Section
                      5.3.2).

Monia, et al. Standards Track [Page 42] RFC 4172 Internet Fibre Channel Networking September 2005

 The iFCP flags word has the following format:
      |------------------------Bit----------------------------|
      |                                                       |
      |   8      9     10     11     12     13     14    15   |
      +------+------+------+------+------+------+------+------+
      |             Reserved             | SES  | TRP  |  SPC |
      +------+------+------+------+------+------+------+------+
                     Figure 14. iFCP Flags Word
 iFCP Flags:
 SES         1 = Session control frame (TRP and SPC MUST be 0)
 TRP         1 = Address transparent mode enabled
             0 = Address translation mode enabled
 SPC         1 = Frame is part of a link service message requiring
                 special processing by iFCP prior to forwarding to the
                 destination N_PORT.

5.3.1.1. Common Encapsulation Flags

 The iFCP usage of the common encapsulation flags defined in [ENCAP]
 is shown in Figure 15:
       |------------------------Bit--------------------------|
       |                                                     |
       |    0        1        2        3        4        5   |
       +--------------------------------------------+--------+
       |                  Reserved                  |  CRCV  |
       +--------------------------------------------+--------+
             Figure 15. iFCP Common Encapsulation Flags
 For iFCP, the CRC field MUST be valid, and CRCV MUST be set to one.

Monia, et al. Standards Track [Page 43] RFC 4172 Internet Fibre Channel Networking September 2005

5.3.2. SOF and EOF Delimiter Fields

 The format of the delimiter fields is shown below.
 W|------------------------------Bit------------------------------|
 o|                                                               |
 r|                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 3 3|
 d|0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1|
  +---------------+---------------+---------------+---------------+
 0|      SOF      |      SOF      |     -SOF      |     -SOF      |
  +---------------+---------------+---------------+---------------+
 1|                                                               |
  +-----                   FC frame content                  -----+
  |                                                               |
  +---------------+---------------+---------------+---------------+
 n|      EOF      |      EOF      |     -EOF      |     -EOF      |
  +---------------+---------------+---------------+---------------+
              Figure 16. FC Frame Encapsulation Format
 SOF (bits 0-7 and bits 8-15 in word 0):  iFCP uses the following
 subset of the SOF fields specified in [ENCAP].  For convenience,
 these are reproduced in Table 3.  The authoritative encodings should
 be obtained from [ENCAP].
                         +-------+----------+
                         |  FC   |          |
                         |  SOF  | SOF Code |
                         +-------+----------+
                         | SOFi2 |   0x2D   |
                         | SOFn2 |   0x35   |
                         | SOFi3 |   0x2E   |
                         | SOFn3 |   0x36   |
                         +-------+----------+
     Table 3. Translation of FC SOF Values to SOF Field Contents
  1. SOF (bits 16-23 and 24-31 in word 0): The -SOF fields contain the

ones complement the value in the SOF fields.

 EOF (bits 0-7 and 8-15 in word n):  iFCP uses the following subset of
 EOF fields specified in [ENCAP].  For convenience, these are
 reproduced in Table 4.  The authoritative encodings should be
 obtained from [ENCAP].

Monia, et al. Standards Track [Page 44] RFC 4172 Internet Fibre Channel Networking September 2005

                         +-------+----------+
                         |  FC   |          |
                         |  EOF  | EOF Code |
                         +-------+----------+
                         | EOFn  |   0x41   |
                         | EOFt  |   0x42   |
                         +-------+----------+
     Table 4. Translation of FC EOF Values to EOF Field Contents
  1. EOF (bits 16-23 and 24-31 in word n): The -EOF fields contain the

ones complement the value in the EOF fields.

 iFCP implementations SHALL place a copy of the SOF and EOF delimiter
 codes in the appropriate header fields.

5.3.3. Frame Encapsulation

 A fibre channel Frame to be encapsulated MUST first be validated as
 described in [FC-FS].  Any frames received from a locally attached
 fibre channel device that do not pass the validity tests in [FC-FS]
 SHALL be discarded by the gateway.
 If the frame is a PLOGI ELS, the creation of an iFCP session, as
 described in Section 7.3.1.7, may precede encapsulation.  Once the
 session has been created, frame encapsulation SHALL proceed as
 follows.
 The S_ID and D_ID fields in the frame header SHALL be referenced to
 look up the iFCP session descriptor (see Section 5.2.2.2).  If no
 iFCP session descriptor exists, the frame SHALL be discarded.
 Frame types submitted for encapsulation and forwarding on the IP
 network SHALL have one of the SOF delimiters in Table 3 and an EOF
 delimiter from Table 4.  Other valid frame types MUST be processed
 internally by the gateway as specified in the appropriate fibre
 channel specification.
 If operating in address translation mode and processing a special
 link service message requiring the inclusion of supplemental data,
 the gateway SHALL format the frame payload and add the supplemental
 information specified in Section 7.1.  The gateway SHALL then
 calculate a new FC CRC on the reformatted frame.
 Otherwise, the frame contents SHALL NOT be modified and the gateway
 MAY encapsulate and transmit the frame image without recalculating
 the FC CRC.

Monia, et al. Standards Track [Page 45] RFC 4172 Internet Fibre Channel Networking September 2005

 The frame originator MUST then create and fill in the header and the
 SOF and EOF delimiter words, as specified in Sections 5.3.1 and
 5.3.2.

5.3.4. Frame De-encapsulation

 The receiving gateway SHALL perform de-encapsulation as follows:
 Upon receiving the encapsulated frame, the gateway SHALL check the
 header CRC.  If the header CRC is valid, the receiving gateway SHALL
 check the iFCP flags field.  If one of the error conditions in Table
 5 is detected, the gateway SHALL handle the error as specified in
 Section 5.2.3.
    +------------------------------+-------------------------+
    |      Condition               |      Error Type         |
    +==============================+=========================+
    | Header CRC Invalid           | Encapsulation error     |
    +------------------------------+-------------------------+
    | SES = 1, TRP or SPC not 0    | Encapsulation error     |
    +------------------------------+-------------------------+
    | SES = 0, TRP set incorrectly | Incorrect address mode  |
    +------------------------------+-------------------------+
               Table 5. Encapsulation Header Errors
 The receiving gateway SHALL then verify the frame propagation delay
 as described in Section 8.2.1.  If the propagation delay is too long,
 the frame SHALL be discarded.  Otherwise, the gateway SHALL check the
 SOF and EOF in the encapsulation header.  A frame SHALL be discarded
 if it has an SOF code that is not in Table 3 or an EOF code that is
 not in Table 4.
 The gateway SHALL then de-encapsulate the frame as follows:
 a) Check the FC CRC and discard the frame if the CRC is invalid.
 b) If operating in address translation mode, replace the S_ID field
    with the N_PORT alias of the frame originator, and the D_ID with
    the N_PORT ID, of the frame recipient.  Both parameters SHALL be
    obtained from the iFCP session descriptor.
 c) If processing a special link service message, replace the frame
    with a copy whose payload has been modified as specified in
    Section 7.1.

Monia, et al. Standards Track [Page 46] RFC 4172 Internet Fibre Channel Networking September 2005

 The de-encapsulated frame SHALL then be forwarded to the N_PORT
 specified in the D_ID field.  If the frame contents have been
 modified by the receiving gateway, a new FC CRC SHALL be calculated.

6. TCP Session Control Messages

 TCP session control messages are used to create and manage an iFCP
 session as described in Section 5.2.2.  They are passed between peer
 iFCP Portals and are only processed within the iFCP layer.
 The message format is based on the fibre channel extended link
 service message template shown below.
  Word
    0<--Bits-->7 8<---------------Bits------------------------>31
   +------------+------------------------------------------------+
  0| R_CTL      |            D_ID [0x00 00 00]                   |
   |[Req = 0x22]| [Destination of extended link Service request] |
   |[Rep = 0x23]|                                                |
   +------------+------------------------------------------------+
  1| CS_CTL     |            S_ID [0x00 00 00]                   |
   | [0x0]      | [Source of extended link service request]      |
   +------------+------------------------------------------------+
  2|TYPE [0x1]  |               F_CTL [0]                        |
   +------------+------------------+-----------------------------+
  3|SEQ_ID      | DF_CTL [0x00]    |          SEQ_CNT [0x00]     |
   |[0x0]       |                  |                             |
   +------------+------------------+-----------------------------+
  4|         OX_ID [0x0000]        |          RX_ID_[0x0000]     |
   +-------------------------------+-----------------------------+
  5|                           Parameter                         |
   |                         [ 00 00 00 00 ]                     |
   +-------------------------------------------------------------+
  6|                        LS_COMMAND                           |
   |                [Session Control Command Code]               |
   +-------------------------------------------------------------+
  7|                                                             |
  .|             Additional Session Control Parameters           |
  .|                      ( if any )                             |
  n|                                                             |
   +=============================================================+
  n|                    Fibre Channel CRC                        |
  +|                                                             |
  1+=============================================================+
           Figure 17. Format of Session Control Message

Monia, et al. Standards Track [Page 47] RFC 4172 Internet Fibre Channel Networking September 2005

 The LS_COMMAND value for the response remains the same as that used
 for the request.
 The session control frame is terminated with a fibre channel CRC.
 The frame SHALL be encapsulated and de-encapsulated according to the
 rules specified in Section 5.3.
 The encapsulation header for the link Service frame carrying a
 session control message SHALL be set as follows:
 Encapsulation Header Fields:
    LS_COMMAND_ACC       0
    iFCP Flags           SES = 1
                         TRP = 0
                         INT = 0
    SOF code             SOFi3 encoding (0x2E)
    EOF code             EOFt encoding (0x42)
 The encapsulation time stamp words SHALL be set as described for each
 message type.
 The SOF and EOF delimiter words SHALL be set based on the SOF and EOF
 codes specified above.

Monia, et al. Standards Track [Page 48] RFC 4172 Internet Fibre Channel Networking September 2005

 Table 6 lists the values assigned to byte 0 of the LS_COMMAND field
 for iFCP session control messages.
 +--------------+-------------------------+----------+-------------+
 | LS_COMMAND   |       Function          | Mnemonic | iFCP        |
 | field, byte 0|                         |          | Support     |
 +--------------+-------------------------+----------+-------------+
 |    0xE0      |    Connection Bind      |  CBIND   |  REQUIRED   |
 +--------------+-------------------------+----------+-------------+
 |    0xE4      |    Unbind Connection    |  UNBIND  |  REQUIRED   |
 +--------------+-------------------------+----------+-------------+
 |    0xE5      | Test Connection Liveness|  LTEST   |  REQUIRED   |
 +--------------+-------------------------+----------+-------------+
 | 0x01-0x7F    |    Vendor-Specific      |          |             |
 +--------------+-------------------------+----------+-------------+
 |    0x00      | Reserved -- Unassignable|          |             |
 +--------------+-------------------------+----------+-------------+
 | All other    |    Reserved             |          |             |
 | values       |                         |          |             |
 +--------------+-------------------------+----------+-------------+
      Table 6. Session Control LS_COMMAND Field, Byte 0 Values

Monia, et al. Standards Track [Page 49] RFC 4172 Internet Fibre Channel Networking September 2005

6.1. Connection Bind (CBIND)

 As described in Section 5.2.2.2, the CBIND message and response are
 used to bind an N_PORT login to a specific TCP connection and
 establish an iFCP session.  In the CBIND request message, the source
 and destination N_PORTs are identified by their worldwide port names.
 The time stamp words in the encapsulation header SHALL be set to zero
 in the request and response message frames.
 The following shows the format of the CBIND request.
    +------+------------+------------+-----------+----------+
    | Word |   Byte 0   |   Byte 1   |   Byte 2  |  Byte 3  |
    +------+------------+------------+-----------+----------+
    | 0    | Cmd = 0xE0 |   0x00     |   0x00    |  0x00    |
    +------+------------+------------+-----------+----------+
    | 1    |  LIVENESS TEST INTERVAL | Addr Mode | iFCP Ver |
    |      |        (Seconds)        |           |          |
    +------+-------------------------+-----------+----------+
    | 2    |                  USER INFO                     |
    +------+------------+------------+-----------+----------+
    | 3    |                                                |
    +------+              SOURCE N_PORT NAME                |
    | 4    |                                                |
    +------+------------------------------------------------+
    | 5    |                                                |
    +------+              DESTINATION N_PORT NAME           |
    | 6    |                                                |
    +------+------------------------------------------------+
 Addr Mode:             The addressing mode of the originating
                        gateway.  0 = Address Translation mode;
                        1 = Address Transparent mode.
 iFCP Ver:              iFCP version number.  SHALL be set to 1.
 LIVENESS TEST          If non-zero, requests that the receiving
 INTERVAL:              gateway transmit an LTEST message at the
                        specified interval in seconds.  If set to
                        zero, LTEST messages SHALL NOT be sent.
 USER INFO:             Contains any data desired by the requestor.
                        This information MUST be echoed by the
                        recipient in the CBIND response message.
 SOURCE N_PORT NAME:    The Worldwide Port Name (WWPN) of the N_PORT
                        locally attached to the gateway originating
                        the CBIND request.

Monia, et al. Standards Track [Page 50] RFC 4172 Internet Fibre Channel Networking September 2005

 DESTINATION N_PORT     The Worldwide Port Name (WWPN) of the
 NAME:                  N_PORT locally attached to the gateway
                        receiving the CBIND request.
 The following shows the format of the CBIND response.
       +------+------------+------------+-----------+----------+
       | Word |   Byte 0   |   Byte 1   |   Byte 2  |  Byte 3  |
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0xE0 |   0x00     |   0x00    |  0x00    |
       +------+------------+------------+-----------+----------+
       | 1    |  LIVENESS TEST INTERVAL | Addr Mode | iFCP Ver |
       |      |      (Seconds)          |           |          |
       +------+-------------------------+-----------+----------+
       | 2    |                  USER INFO                     |
       +------+------------+------------+-----------+----------+
       | 3    |                                                |
       +------+               SOURCE N_PORT NAME               |
       | 4    |                                                |
       +------+------------------------------------------------+
       | 5    |                                                |
       +------+              DESTINATION N_PORT NAME           |
       | 6    |                                                |
       +------+-------------------------+----------------------+
       | 7    |        Reserved         |     CBIND Status     |
       +------+-------------------------+----------------------+
       | 8    |        Reserved         |  CONNECTION HANDLE   |
       +------+-------------------------+----------------------+
                         Total Length = 36
 Addr Mode:             The address translation mode of the
                        responding gateway.  0 = Address
                        Translation mode, 1 = Address Transparent
                        mode.
 iFCP Ver:              iFCP version number.  Shall be set to 1.
 LIVENESS TEST          If non-zero, requests that the gateway
 INTERVAL:              receiving the CBIND RESPONSE transmit an
                        LTEST message at the specified interval in
                        seconds.  If zero, LTEST messages SHALL NOT
                        be sent.
 USER INFO:             Echoes the value received in the USER INFO
                        field of the CBIND request message.

Monia, et al. Standards Track [Page 51] RFC 4172 Internet Fibre Channel Networking September 2005

 SOURCE N_PORT NAME:    Contains the Worldwide Port Name (WWPN) of
                        the N_PORT locally attached to the gateway
                        issuing the CBIND request.
 DESTINATION N_PORT     Contains the Worldwide Port Name (WWPN) of
 NAME:                  the N_PORT locally attached to the gateway
                        issuing the CBIND response.
 CBIND STATUS:          Indicates success or failure of the CBIND
                        request.  CBIND values are shown below.
 CONNECTION HANDLE:     Contains a value assigned by the gateway to
                        identify the connection.  The connection
                        handle is required when the UNBIND
                        request is issued.
 CBIND Status       Description
 ------------       -----------
     0              Success
   1 - 15           Reserved
     16             Failed - Unspecified Reason
     17             Failed - No such device
     18             Failed - iFCP session already exists
     19             Failed - Lack of resources
     20             Failed - Incompatible address translation mode
     21             Failed - Incorrect protocol version number
     22             Failed - Gateway not Synchronized (see Section
                    8.2)
     Others         Reserved

6.2. Unbind Connection (UNBIND)

 UNBIND is used to terminate an iFCP session and disassociate the TCP
 connection as described in Section 5.2.3.
 The UNBIND message is transmitted over the connection that is to be
 unbound.  The time stamp words in the encapsulation header shall be
 set to zero in the request and response message frames.

Monia, et al. Standards Track [Page 52] RFC 4172 Internet Fibre Channel Networking September 2005

 The following is the format of the UNBIND request message.
       +------+------------+------------+-----------+----------+
       | Word |   Byte 0   |   Byte 1   |   Byte 2  |  Byte 3  |
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0xE4 |   0x00     |   0x00    |  0x00    |
       +------+------------+------------+-----------+----------+
       | 1    |                  USER INFO                     |
       +------+------------+------------+-----------+----------+
       | 2    |       Reserved          |  CONNECTION HANDLE   |
       +------+------------+------------+----------------------+
       | 3    |                  Reserved                      |
       +------+------------+------------+-----------+----------+
       | 4    |                  Reserved                      |
       +------+------------+------------+-----------+----------+
 USER INFO              Contains any data desired by the requestor.
                        This information MUST be echoed by the
                        recipient in the UNBIND response message.
 CONNECTION HANDLE:     Contains the gateway-assigned value from
                        the CBIND request.
 The following shows the format of the UNBIND response message.
       +------+------------+------------+-----------+----------+
       | Word |   Byte 0   |   Byte 1   |   Byte 2  |  Byte 3  |
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0xE4 |   0x00     |   0x00    |  0x00    |
       +------+------------+------------+-----------+----------+
       | 1    |                  USER INFO                     |
       +------+------------+------------+-----------+----------+
       | 2    |       Reserved          |  CONNECTION HANDLE   |
       +------+------------+------------+-----------+----------+
       | 3    |                  Reserved                      |
       +------+------------+------------+-----------+----------+
       | 4    |                  Reserved                      |
       +------+------------+------------+-----------+----------+
       | 5    |         Reserved        |     UNBIND STATUS    |
       +------+------------+------------+-----------+----------+
 USER INFO              Echoes the value received in the USER INFO
                        field of the UNBIND request message.
 CONNECTION HANDLE:     Echoes the CONNECTION HANDLE specified in
                        the UNBIND request message.

Monia, et al. Standards Track [Page 53] RFC 4172 Internet Fibre Channel Networking September 2005

 UNBIND STATUS:         Indicates the success or failure of the
                        UNBIND request as follows:
       Unbind Status      Description
       -------------      -----------
                0         Successful - No other status
             1 - 15       Reserved
               16         Failed - Unspecified Reason
               18         Failed - Connection ID Invalid
             Others       Reserved

6.3. LTEST – Test Connection Liveness

 The LTEST message is sent at the interval specified in the CBIND
 request or response payload.  The LTEST encapsulation time stamp
 SHALL be set as described in Section 8.2.1 and may be used by the
 receiver to compute an estimate of propagation delay.  However, the
 propagation delay limit SHALL NOT be enforced.
       +------+------------+------------+-----------+----------+
       | Word |   Byte 0   |   Byte 1   |   Byte 2  |  Byte 3  |
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0xE5 |   0x00     |   0x00    |  0x00    |
       +------+------------+------------+-----------+----------+
       | 1    |  LIVENESS TEST INTERVAL |        Reserved      |
       |      |        (Seconds)        |                      |
       +------+-------------------------+----------------------+
       | 2    |                   COUNT                        |
       +------+------------+------------+-----------+----------+
       | 3    |                                                |
       +------+              SOURCE N_PORT NAME                |
       | 4    |                                                |
       +------+------------------------------------------------+
       | 5    |                                                |
       +------+              DESTINATION N_PORT NAME           |
       | 6    |                                                |
       +------+------------------------------------------------+
 LIVENESS TEST          Copy of the LIVENESS TEST INTERVAL
 INTERVAL:              specified in the CBIND request or reply
                        message.
 COUNT:                 Monotonically increasing value, initialized
                        to 0 and incremented by one for each
                        successive LTEST message.

Monia, et al. Standards Track [Page 54] RFC 4172 Internet Fibre Channel Networking September 2005

 SOURCE N_PORT NAME:    Contains a copy of the SOURCE N_PORT NAME
                        specified in the CBIND request.
 DESTINATION N_PORT     Contains a copy of the DESTINATION N_PORT
 NAME:                  NAME specified in the CBIND request.

7. Fibre Channel Link Services

 Link services provide a set of fibre channel functions that allow a
 port to send control information or request another port to perform a
 specific control function.
 There are three types of link services:
 a) Basic
 b) Extended
 c) ULP-specific (FC-4)
 Each link service message (request and reply) is carried by a fibre
 channel sequence and can be segmented into multiple frames.
 The iFCP layer is responsible for transporting link service messages
 across the IP network.  This includes mapping link service messages
 appropriately from the domain of the fibre channel transport to that
 of the IP network.  This process may require special processing and
 the inclusion of supplemental data by the iFCP layer.
 Each link service MUST be processed according to one of the following
 rules:
 a) Pass-through - The link service message and reply MUST be
    delivered to the receiving N_PORT by the iFCP protocol layer
    without altering the message payload.  The link service message
    and reply are not processed by the iFCP protocol layer.
 b) Special -  Applies to a link service reply or request requiring
    the intervention of the iFCP layer before forwarding to the
    destination N_PORT.  Such messages may contain fibre channel
    addresses in the payload or may require other special processing.
 c) Rejected - When issued by a locally attached N_PORT, the specified
    link service request MUST be rejected by the iFCP gateway.  The
    gateway SHALL return an LS_RJT response with a Reason Code of 0x0B
    (Command Not Supported), and a Reason Code Explanation of 0x0 (No
    Additional Explanation).

Monia, et al. Standards Track [Page 55] RFC 4172 Internet Fibre Channel Networking September 2005

 This section describes the processing for special link services,
 including the manner in which supplemental data is added to the
 message payload.
 Appendix A enumerates all link services and the iFCP processing
 policy that applies to each.

7.1. Special Link Service Messages

 Special link service messages require the intervention of the iFCP
 layer before forwarding to the destination N_PORT.  Such intervention
 is required in order to:
 a) service any link service message that requires special handling,
    such as a PLOGI, and
 b) service any link service message that has an N_PORT address in the
    payload in address translation mode only .
 Unless the link service description specifies otherwise, support for
 each special link service is MANDATORY.
 Such messages SHALL be transmitted in a fibre channel frame with the
 format shown in Figure 18 for extended link services or Figure 19 for
 FC-4 link services.

Monia, et al. Standards Track [Page 56] RFC 4172 Internet Fibre Channel Networking September 2005

  Word
    0<---Bit-->7 8<-------------------------------------------->31
   +------------+------------------------------------------------+
  0| R_CTL      |                     D_ID                       |
   |[Req = 0x22]|[Destination of extended link Service request]  |
   |[Rep = 0x23]|                                               |
   +------------+------------------------------------------------+
  1| CS_CTL     |                     S_ID                       |
   |            | [Source of extended link service request]      |
   +------------+------------------------------------------------+
  2| TYPE       |                     F_CTL                      |
   | [0x01]     |                                                |
   +------------+------------------+-----------------------------+
  3| SEQ_ID     |        DF_CTL    |          SEQ_CNT            |
   +------------+------------------+-----------------------------+
  4|          OX_ID                |             RX_ID           |
   +-------------------------------+-----------------------------+
  5|                         Parameter                           |
   |                      [ 00 00 00 00 ]                        |
   +-------------------------------------------------------------+
  6|                         LS_COMMAND                          |
   |               [Extended Link Service Command Code]          |
   +-------------==----------------------------------------------+
  7|                                                             |
  .|             Additional Service Request Parameters           |
  .|                      ( if any )                             |
  n|                                                             |
   +-------------------------------------------------------------+
        Figure 18. Format of an Extended Link Service Frame

Monia, et al. Standards Track [Page 57] RFC 4172 Internet Fibre Channel Networking September 2005

  Word
    0<---Bit-->7 8<-------------------------------------------->31
   +------------+------------------------------------------------+
  0| R_CTL      |                     D_ID                       |
   |[Req = 0x32]|   [Destination of FC-4 link Service request]   |
   |[Rep = 0x33]|                                                |
   +------------+------------------------------------------------+
  1| CS_CTL     |                     S_ID                       |
   |            |    [Source of FC-4 link service request]       |
   +------------+------------------------------------------------+
  2| TYPE       |                     F_CTL                      |
   | (FC-4      |                                                |
   |  specific) |                                                |
   +------------+------------------+-----------------------------+
  3| SEQ_ID     |        DF_CTL    |          SEQ_CNT            |
   +------------+------------------+-----------------------------+
  4|         OX_ID                 |             RX_ID           |
   +-------------------------------+-----------------------------+
  5|                        Parameter                            |
   |                     [ 00 00 00 00 ]                         |
   +-------------------------------------------------------------+
  6|                        LS_COMMAND                           |
   |               [FC-4 Link Service Command Code]              |
   +-------------------------------------------------------------+
  7|                                                             |
  .|             Additional Service Request Parameters           |
  .|                      ( if any )                             |
  n|                                                             |
   +-------------------------------------------------------------+
          Figure 19. Format of an FC-4 Link Service Frame

7.2. Link Services Requiring Payload Address Translation

 This section describes the handling for link service frames
 containing N_PORT addresses in the frame payload.  Such addresses
 SHALL only be translated when the gateway is operating in address
 translation mode.  When operating in address transparent mode, these
 addresses SHALL NOT be translated, and such link service messages
 SHALL NOT be sent as special frames unless other processing by the
 iFCP layer is required.
 Supplemental data includes information required by the receiving
 gateway to convert an N_PORT address in the payload to an N_PORT
 address in the receiving gateway's address space.  The following
 rules define the manner in which such supplemental data shall be
 packaged and referenced.

Monia, et al. Standards Track [Page 58] RFC 4172 Internet Fibre Channel Networking September 2005

 For an N_PORT address field, the gateway originating the frame MUST
 set the value in the payload to identify the address translation type
 as follows:
    0x00 00 01 - The gateway receiving the frame from the IP network
    MUST replace the contents of the field with the N_PORT alias of
    the frame originator.  This translation type MUST be used when the
    address to be converted is that of the source N_PORT.
    0x00 00 02 - The gateway receiving the frame from the IP network
    MUST replace the contents of the field with the N_PORT ID of the
    destination N_PORT.  This translation type MUST be used when the
    address to be converted is that of the destination N_PORT
    0x00 00 03 - The gateway receiving the frame from the IP network
    MUST reference the specified supplemental data to set the field
    contents.  The supplemental information is the 64-bit worldwide
    identifier of the N_PORT, as set forth in the fibre channel
    specification [FC-FS].  If not otherwise part of the link service
    payload, this information MUST be appended in accordance with the
    applicable link service description.  Unless specified otherwise,
    this translation type SHALL NOT be used if the address to be
    converted corresponds to that of the frame originator or
    recipient.
 Since fibre channel addressing rules prohibit the assignment of
 fabric addresses with a domain ID of 0, the above codes will never
 correspond to valid N_PORT fabric IDs.
 If the sending gateway cannot obtain the worldwide identifier of an
 N_PORT, the gateway SHALL terminate the request with an LS_RJT
 message as described in [FC-FS].  The Reason Code SHALL be set to
 0x07 (protocol error), and the Reason Explanation SHALL be set to
 0x1F (Invalid N_PORT identifier).
 Supplemental data is sent with the link service request or ACC frames
 in one of the following ways:
 a) By appending the necessary data to the end of the link service
    frame.
 b) By extending the sequence with additional frames.
 In the first case, a new frame SHALL be created whose length includes
 the supplemental data.  The procedure for extending the link service
 sequence with additional frames is dependent on the link service
 type.

Monia, et al. Standards Track [Page 59] RFC 4172 Internet Fibre Channel Networking September 2005

 For each field requiring address translation, the receiving gateway
 SHALL reference the translation type encoded in the field and replace
 it with the N_PORT address as shown in Table 7.
       +------------------+------------------------------------+
       |    Translation   |          N_PORT Translation        |
       |    Type Code     |                                    |
       +------------------+------------------------------------+
       | 0x00 00 01       | Replace field contents with N_PORT |
       |                  | alias of frame originator.         |
       +------------------+------------------------------------+
       | 0x00 00 02       | Replace field contents with N_PORT |
       |                  | ID of frame recipient.             |
       +------------------+------------------------------------+
       |                  | Lookup N_PORT via iSNS query.      |
       |                  | If locally attached, replace with  |
       | 0x00 00 03       | N_PORT ID.                         |
       |                  | If remotely attached, replace with |
       |                  | N_PORT alias from remote N_PORT.   |
       |                  | descriptor (see Section 5.2.2.1).  |
       +------------------+------------------------------------+
               Table 7. Link Service Address Translation
 For translation type 3, the receiving gateway SHALL obtain the
 information needed to fill in the field in the link service frame
 payload by converting the specified N_PORT worldwide identifier to a
 gateway IP address and N_PORT ID.  This information MUST be obtained
 through an iSNS name server query.  If the query is unsuccessful, the
 gateway SHALL terminate the request with an LS_RJT response message
 as described in [FC-FS].  The Reason Code SHALL be set to 0x07
 (protocol error), and the Reason Explanation SHALL be set to 0x1F
 (Invalid N_PORT identifier).
 After applying the supplemental data, the receiving gateway SHALL
 forward the resulting link service frames to the destination N_PORT
 with the supplemental information removed.

Monia, et al. Standards Track [Page 60] RFC 4172 Internet Fibre Channel Networking September 2005

7.3. Fibre Channel Link Services Processed by iFCP

 The following Extended and FC-4 Link Service Messages must receive
 special processing.
       Extended Link Service            LS_COMMAND   Mnemonic
       Messages                         ----------   --------
       ----------------------
       Abort Exchange                  0x06 00 00 00 ABTX
       Discover Address                0x52 00 00 00 ADISC
       Discover Address Accept         0x02 00 00 00 ADISC ACC
       FC Address Resolution           0x55 00 00 00 FARP-REPLY
       Protocol Reply
       FC Address Resolution           0x54 00 00 00 FARP-REQ
       Protocol Request
       Logout                          0x05 00 00 00 LOGO
       Port Login                      0x30 00 00 00 PLOGI
       Read Exchange Concise           0x13 00 00 00 REC
       Read Exchange Concise           0x02 00 00 00 REC ACC
       Accept
       Read Exchange Status Block      0x08 00 00 00 RES
       Read Exchange Status Block      0x02 00 00 00 RES ACC
       Accept
       Read Link Error Status          0x0F 00 00 00 RLS
       Block
       Read Sequence Status Block      0x09 00 00 00 RSS
       Reinstate Recovery              0x12 00 00 00 RRQ
       Qualifier
       Request Sequence                0x0A 00 00 00 RSI
       Initiative
       Scan Remote Loop                0x7B 00 00 00 SRL
       Third Party Process Logout      0x24 00 00 00 TPRLO
       Third Party Process Logout      0x02 00 00 00 TPRLO ACC
       Accept
       FC-4 Link Service Messages       LS_COMMAND   Mnemonic
       --------------------------       ----------   --------
       FCP Read Exchange Concise       0x13 00 00 00 FCP REC
       FCP Read Exchange Concise       0x02 00 00 00 FCP REC
       Accept                                        ACC
 Each encapsulated fibre channel frame that is part of a special link
 service MUST have the SPC bit set to one in the iFCP FLAGS field of
 the encapsulation header, as specified in Section 5.3.1.  If an ACC
 link service response requires special processing, the responding
 gateway SHALL place a copy of LS_COMMAND bits 0 through 7, from the

Monia, et al. Standards Track [Page 61] RFC 4172 Internet Fibre Channel Networking September 2005

 link service request frame, in the LS_COMMAND_ACC field of the ACC
 encapsulation header.  Supplemental data (if any) MUST be appended as
 described in the following section.
 The format of each special link service message, including
 supplemental data, where applicable, is shown in the following
 sections.  Each description shows the basic format, as specified in
 the applicable FC standard, followed by supplemental data as shown in
 the example below.
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    |                  LS_COMMAND                    |
       +------+------------+------------+-----------+----------+
       | 1    |                                                |
       | .    |                                                |
       | .    |          Link Service Frame Payload            |
       |      |                                                |
       | n    |                                                |
       +======+============+============+===========+==========+
       | n+1  |                                                |
       |  .   |            Supplemental Data                   |
       |  .   |               (if any)                         |
       | n+k  |                                                |
       +======+================================================+
             Figure 20. Special Link Service Frame Payload

Monia, et al. Standards Track [Page 62] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1. Special Extended Link Services

 The following sections define extended link services for which
 special processing is required.

7.3.1.1. Abort Exchange (ABTX)

    ELS Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x6  |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | RRQ Status |     Exchange Originator S_ID      |
       +------+------------+------------+-----------+----------+
       | 2    |   OX_ID of Tgt exchange | RX_ID of tgt exchange|
       +------+------------+------------+-----------+----------+
       | 3-10 |  Optional association header (32 bytes         |
       +======+============+============+===========+==========+
       Fields Requiring       Translation   Supplemental Data
       Address Translation     Type (see      (type 3 only)
       -------------------    Section 7.2)     ------------
                              -----------
       Exchange Originator        1, 2              N/A
       S_ID
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 63] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.2. Discover Address (ADISC)

    Format of ADISC ELS:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x52 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Reserved   |  Hard address of ELS Originator   |
       +------+------------+------------+-----------+----------+
       | 2-3  |     Port Name of Originator                    |
       +------+------------+------------+-----------+----------+
       | 4-5  |     Node Name of originator                    |
       +------+------------+------------+-----------+----------+
       | 6    |  Rsvd      |  N_PORT ID  of ELS Originator     |
       +======+============+============+===========+==========+
       Fields Requiring       Translation    Supplemental Data
       Address Translation     Type (see       (type 3 only)
       -------------------    Section 7.2)     -------------
                              ------------
       N_PORT ID of ELS            1                N/A
       Originator
       Other Special Processing:
          The Hard Address of the ELS originator SHALL be set to 0.

Monia, et al. Standards Track [Page 64] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.3. Discover Address Accept (ADISC ACC)

    Format of ADISC ACC ELS:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x20 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Reserved   |  Hard address of ELS Originator   |
       +------+------------+------------+-----------+----------+
       | 2-3  |     Port Name of Originator                    |
       +------+------------+------------+-----------+----------+
       | 4-5  |     Node Name of originator                    |
       +------+------------+------------+-----------+----------+
       | 6    |  Rsvd      |  N_PORT ID of ELS Originator      |
       +======+============+============+===========+==========+
       Fields Requiring       Translation    Supplemental Data
       Address Translation     Type (see       (type 3 only)
       -------------------    Section 7.2)     -------------
                              ------------
       N_PORT ID of ELS            1                N/A
       Originator
       Other Special Processing:
          The Hard Address of the ELS originator SHALL be set to 0.

Monia, et al. Standards Track [Page 65] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.4. FC Address Resolution Protocol Reply (FARP-REPLY)

 The FARP-REPLY ELS is used in conjunction with the FARP-REQ ELS (see
 Section 7.3.1.5) to perform the address resolution services required
 by the FC-VI protocol [FC-VI] and the fibre channel mapping of IP and
 ARP specified in RFC 2625 [RFC2625].
    Format of FARP-REPLY ELS:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x55 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Match Addr |  Requesting N_PORT Identifier     |
       |      | Code Points|                                   |
       +------+------------+------------+-----------+----------+
       | 2    | Responder  |  Responding N_PORT Identifier     |
       |      | Action     |                                   |
       +------+------------+------------+-----------+----------+
       | 3-4  |     Requesting N_PORT Port_Name                |
       +------+------------+------------+-----------+----------+
       | 5-6  |     Requesting N_PORT Node_Name                |
       +------+------------+------------+-----------+----------+
       | 7-8  |     Responding N_PORT Port_Name                |
       +------+------------+------------+-----------+----------+
       | 9-10 |     Responding N_PORT Node_Name                |
       +------+------------+------------+-----------+----------+
       | 11-14|     Requesting N_PORT IP Address               |
       +------+------------+------------+-----------+----------+
       | 15-18|     Responding N_PORT IP Address               |
       +======+============+============+===========+==========+
       Fields Requiring       Translation    Supplemental Data
       Address Translation     Type (see       (type 3 only)
       -------------------    Section 7.2)   -----------------
                              ------------
       Requesting N_PORT           2                N/A
       Identifier
       Responding N_PORT           1                N/A
       Identifier
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 66] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.5. FC Address Resolution Protocol Request (FARP-REQ)

 The FARP-REQ ELS is used in conjunction with the FC-VI protocol
 [FC-VI] and IP-to-FC mapping of RFC 2625 [RFC2625] to perform IP and
 FC address resolution in an FC fabric.  The FARP-REQ ELS is usually
 directed to the fabric broadcast server at well-known address
 0xFF-FF-FF for retransmission to all attached N_PORTs.
 Section 9.4 describes the iFCP implementation of FC broadcast server
 functionality in an iFCP fabric.
    Format of FARP_REQ ELS:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x54 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Match Addr |  Requesting N_PORT Identifier     |
       |      | Code Points|                                   |
       +------+------------+------------+-----------+----------+
       | 2    | Responder  |  Responding N_PORT Identifier     |
       |      | Action     |                                   |
       +------+------------+------------+-----------+----------+
       | 3-4  |     Requesting N_PORT Port_Name                |
       +------+------------+------------+-----------+----------+
       | 5-6  |     Requesting N_PORT Node_Name                |
       +------+------------+------------+-----------+----------+
       | 7-8  |     Responding N_PORT Port_Name                |
       +------+------------+------------+-----------+----------+
       | 9-10 |     Responding N_PORT Node_Name                |
       +------+------------+------------+-----------+----------+
       | 11-14|     Requesting N_PORT IP Address               |
       +------+------------+------------+-----------+----------+
       | 15-18|     Responding N_PORT IP Address               |
       +======+============+============+===========+==========+
       Fields Requiring       Translation   Supplemental Data
       Address Translation     Type (see      (type 3 only)
       -------------------    Section 7.2)  -----------------
                              -----------
       Requesting N_PORT           3        Requesting N_PORT
       Identifier                           Port Name
       Responding N_PORT           3        Responding N_PORT
       Identifier                           Port Name

Monia, et al. Standards Track [Page 67] RFC 4172 Internet Fibre Channel Networking September 2005

       Other Special Processing:
          None.

7.3.1.6. Logout (LOGO) and LOGO ACC

    ELS Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x5  |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Rsvd       |     N_PORT ID being logged out    |
       +------+------------+------------+-----------+----------+
       | 2-3  |  Port name of the LOGO originator (8 bytes)    |
       +======+============+============+===========+==========+
 This ELS SHALL always be sent as a special ELS regardless of the
 translation mode in effect.
       Fields Requiring       Translation   Supplemental Data
       Address Translation     Type (see      (type 3 only)
       -------------------    Section 7.2)   ---------------
                              -----------
       N_PORT ID Being             1               N/A
       Logged Out
       Other Special Processing:
          See Section 5.2.3.

7.3.1.7. Port Login (PLOGI) and PLOGI ACC

 A PLOGI ELS establishes fibre channel communications between two
 N_PORTs and triggers the creation of an iFCP session if one does not
 exist.
 The PLOGI request and ACC response carry information identifying the
 originating N_PORT, including a specification of its capabilities.
 If the destination N_PORT accepts the login request, it sends an
 Accept response (an ACC frame with PLOGI payload) specifying its
 capabilities.  This exchange establishes the operating environment
 for the two N_PORTs.

Monia, et al. Standards Track [Page 68] RFC 4172 Internet Fibre Channel Networking September 2005

 The following figure is duplicated from [FC-FS], and shows the PLOGI
 message format for both the request and Accept (ACC) response.  An
 N_PORT will reject a PLOGI request by transmitting an LS_RJT message
 containing no payload.
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x3  |   0x00     |    0x00   |   0x00   |
       |      | Acc = 0x2  |            |           |          |
       +------+------------+------------+-----------+----------+
       | 1-4  |            Common Service Parameters           |
       +------+------------+------------+-----------+----------+
       | 5-6  |            N_PORT Name                         |
       +------+------------+------------+-----------+----------+
       | 7-8  |            Node Name                           |
       +------+------------+------------+-----------+----------+
       | 9-12 |            Class 1 Service Parameters          |
       +------+------------+------------+-----------+----------+
       |13-17 |            Class 2 Service Parameters          |
       +------+------------+------------+-----------+----------+
       |18-21 |            Class 3 Service Parameters          |
       +------+------------+------------+-----------+----------+
       |22-25 |            Class 4 Service Parameters          |
       +------+------------+------------+-----------+----------+
       |26-29 |            Vendor Version Level                |
       +======+============+============+===========+==========+
          Figure 21. Format of PLOGI Request and ACC Payloads
 Details of the above fields, including common and class-based service
 parameters, can be found in [FC-FS].
 Special Processing
    As specified in Section 5.2.2.2, a PLOGI request addressed to a
    remotely attached N_PORT MUST cause the creation of an iFCP
    session if one does not exist.  Otherwise, the PLOGI and PLOGI ACC
    payloads MUST be passed through without modification to the
    destination N_PORT using the existing iFCP session.  In either
    case, the SPC bit must be set in the frame encapsulation header as
    specified in 5.3.3.
    If the CBIND to create the iFCP session fails, the issuing gateway
    SHALL terminate the PLOGI with an LS_RJT response.  The Reason
    Code and Reason Code Explanation SHALL be selected from Table 8
    based on the CBIND failure status.

Monia, et al. Standards Track [Page 69] RFC 4172 Internet Fibre Channel Networking September 2005

    +---------------+-------------------+---------------------+
    | CBIND Failure | LS_RJT Reason     | LS_RJT Reason Code  |
    | Status        | Code              | Explanation         |
    +===============+===================+=====================+
    | Unspecified   | Unable to Perform | No Additional       |
    | Reason (16)   | Command Request   | Explanation (0x00)  |
    |               | (0x09)            |                     |
    +---------------+-------------------+---------------------+
    | No Such       | Unable to Perform | Invalid N_PORT      |
    | Device (17)   | Command Request   | Name (0x0D)         |
    |               | (0x09)            |                     |
    +---------------+-------------------+---------------------+
    | Lack of       | Unable to Perform | Insufficient        |
    | Resources (19)| Command Request   | Resources to Support|
    |               | (0x09)            | Login (0x29)        |
    +---------------+-------------------+---------------------+
    | Incompatible  | Unable to Perform | No Additional       |
    | Address       | Command Request   | Explanation (0x00)  |
    | Translation   | (0x09)            |                     |
    | Mode (20)     |                   |                     |
    +---------------+-------------------+---------------------+
    | Incorrect iFCP| Unable to Perform | No Additional       |
    | Protocol      | Command Request   | Explanation (0x00)  |
    | version Number| (0x09)            |                     |
    | (21)          |                   |                     |
    +---------------+-------------------+---------------------+
    | Gateway Not   | Unable to Perform | No Additional       |
    | Synchronized  | Command Request   | Explanation (0x00)  |
    | (22)          | (0x09)            |                     |
    +---------------+-------------------+---------------------+
         Table 8. PLOGI LS_RJT Status for CBIND Failures

Monia, et al. Standards Track [Page 70] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.8. Read Exchange Concise (REC)

    Link Service Request Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  |Bits 16-24 |Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x13 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Rsvd       |     Exchange Originator S_ID      |
       +------+------------+------------+-----------+----------+
       | 2    |          OX_ID          |         RX_ID        |
       +======+============+============+===========+==========+
       | 3-4  |Port Name of the Exchange Originator (8 bytes)  |
       |      |   (present only for translation type 3)        |
       +======+============+============+===========+==========+
       Fields Requiring       Translation   Supplemental Data
       Address Translation     Type (see      (type 3 only)
       -------------------    Section 7.2)  -----------------
                              -----------
       Exchange Originator    1, 2, or 3    Port Name of the
       S_ID                                 Exchange Originator
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 71] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.9. Read Exchange Concise Accept (REC ACC)

    Format of REC ACC Response:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  |Bits 16-24 |Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Acc = 0x02 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    |          OX_ID          |         RX_ID        |
       +------+------------+------------+-----------+----------+
       | 2    | Rsvd       | Originator Address Identifier     |
       +------+------------+------------+-----------+----------+
       | 3    | Rsvd       | Responder Address Identifier      |
       +------+------------+------------+-----------+----------+
       | 4    |       FC4VALUE  (FC-4-Dependent Value)         |
       +------+------------+------------+-----------+----------+
       | 5    |       E_STAT (Exchange Status)                 |
       +======+============+============+===========+==========+
       | 6-7  |Port Name of the Exchange Originator (8 bytes)  |
       +======+============+============+===========+==========+
       | 8-9  |Port Name of the Exchange Responder (8 bytes)   |
       +======+============+============+===========+==========+
       Fields Requiring       Translation     Supplemental Data
       Address Translation     Type (see       (type 3 only)
       -------------------    Section 7.2)    ------------------
                              -----------
       Originator Address     1, 2, or 3      Port Name of the
       Identifier                             Exchange Originator
       Responder Address      1, 2, or 3      Port Name of the
       Identifier                             Exchange Responder
 When supplemental data is required, the frame SHALL always be
 extended by 4 words as shown above.  If the translation type for the
 Originator Address Identifier or the Responder Address Identifier is
 1 or 2, the corresponding 8-byte port name SHALL be set to all zeros.
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 72] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.10. Read Exchange Status Block (RES)

    ELS Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x13 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Rsvd       |     Exchange Originator S_ID      |
       +------+------------+------------+-----------+----------+
       | 2    |          OX_ID          |         RX_ID        |
       +------+------------+------------+-----------+----------+
       | 3-10 |  Association Header (may be optionally req**d)  |
       +======+============+============+===========+==========+
       | 11-12| Port Name of the Exchange Originator (8 bytes) |
       +======+============+============+===========+==========+
       Fields Requiring       Translation     Supplemental Data
       Address Translation     Type (see       (type 3 only)
       -------------------    Section 7.2)    ------------------
                              -----------
       Exchange Originator    1, 2, or 3      Port Name of the
       S_ID                                   Exchange Originator
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 73] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.11. Read Exchange Status Block Accept (RES ACC)

    Format of ELS Accept Response:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Acc = 0x02 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    |          OX_ID          |         RX_ID        |
       +------+------------+------------+-----------+----------+
       | 2    | Rsvd       | Exchange Originator N_PORT ID     |
       +------+------------+------------+-----------+----------+
       | 3    | Rsvd       | Exchange Responder N_PORT ID      |
       +------+------------+------------+-----------+----------+
       | 4    |          Exchange Status Bits                  |
       +------+------------+------------+-----------+----------+
       | 5    |               Reserved                         |
       +------+------------+------------+-----------+----------+
       | 6-n  |    Service Parameters and Sequence Statuses    |
       |      |    as described in [FC-FS]                     |
       +======+============+============+===========+==========+
       |n+1-  | Port Name of the Exchange Originator (8 bytes) |
       |n+2   |                                                |
       +======+============+============+===========+==========+
       |n+3-  | Port Name of the Exchange Responder (8 bytes)  |
       |n+4   |                                                |
       +======+============+============+===========+==========+
       Fields Requiring       Translation     Supplemental Data
       Address Translation     Type (see        (type 3 only)
       -------------------    Section 7.2)    ------------------
                              -----------
       Exchange Originator    1, 2, or 3      Port Name of the
       N_PORT ID                              Exchange Originator
       Exchange Responder     1, 2, or 3      Port Name of the
       N_PORT ID                              Exchange Responder
 When supplemental data is required, the ELS SHALL be extended by 4
 words as shown above.  If the translation type for the Exchange
 Originator N_PORT ID or the Exchange Responder N_PORT ID is 1 or 2,
 the corresponding 8-byte port name SHALL be set to all zeros.
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 74] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.12. Read Link Error Status (RLS)

    ELS Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x0F |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Rsvd       |     N_PORT Identifier             |
       +======+============+============+===========+==========+
       | 2-3  |           Port Name of the N_PORT (8 bytes)    |
       +======+============+============+===========+==========+
       Fields Requiring       Translation     Supplemental Data
       Address Translation     Type (see       (type 3 only)
       -------------------    Section 7.2)    -----------------
                              -----------
       N_PORT Identifier      1, 2, or 3      Port Name of the
                                              N_PORT
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 75] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.13. Read Sequence Status Block (RSS)

    ELS Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x09 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | SEQ_ID     |     Exchange Originator S_ID      |
       +------+------------+------------+-----------+----------+
       | 2    |          OX_ID          |         RX_ID        |
       +======+============+============+===========+==========+
       | 3-4  |Port Name of the Exchange Originator (8 bytes)  |
       +======+============+============+===========+==========+
       Fields Requiring       Translation    Supplemental Data
       Address Translation     Type (see        (type 3 only)
       -------------------    Section 7.2)   ------------------
                              -----------
       Exchange Originator    1, 2, or 3     Port Name of the
       S_ID                                  Exchange Originator
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 76] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.14. Reinstate Recovery Qualifier (RRQ)

    ELS Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x12 |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Rsvd       |     Exchange Originator S_ID      |
       +------+------------+------------+-----------+----------+
       | 2    |          OX_ID          |         RX_ID        |
       +------+------------+------------+-----------+----------+
       | 3-10 |  Association Header (may be optionally req**d)  |
       +======+============+============+===========+==========+
       Fields Requiring       Translation   Supplemental Data
       Address Translation     Type (see      (type 3 only)
       -------------------    Section 7.2)  ------------------
                              -----------
       Exchange Originator      1 or 2             N/A
       S_ID
       Other Special Processing:
           None.

Monia, et al. Standards Track [Page 77] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.15. Request Sequence Initiative (RSI)

    ELS Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x0A |   0x00     |    0x00   |   0x00   |
       +------+------------+------------+-----------+----------+
       | 1    | Rsvd       |     Exchange Originator S_ID      |
       +------+------------+------------+-----------+----------+
       | 2    |          OX_ID          |         RX_ID        |
       +------+------------+------------+-----------+----------+
       | 3-10 |  Association Header (may be optionally req**d)  |
       +======+============+============+===========+==========+
       Fields Requiring       Translation   Supplemental Data
       Address Translation     Type (see      (type 3 only)
       -------------------    Section 7.2)   ------------------
                              -----------
       Exchange Originator      1 or 2             N/A
       S_ID
       Other Special Processing:
          None.

Monia, et al. Standards Track [Page 78] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.16. Scan Remote Loop (SRL)

 SRL allows a remote loop to be scanned to detect changes in the
 device configuration.  Any changes will trigger a fibre channel state
 change notification and subsequent update of the iSNS database.
    ELS Format:
       +------+------------+------------+-----------+----------+
       | Word | Bits 0-7   | Bits 8-15  | Bits 16-24|Bits 25-31|
       +------+------------+------------+-----------+----------+
       | 0    | Cmd = 0x7B |           Reserved                |
       +------+------------+------------+-----------+----------+
       | 1    | Flag       | Address Identifier of the FL_PORT |
       |      |            | (see B.1)                         |
       +======+============+============+===========+==========+
       | 2-3  | Worldwide Name of the Remote FL_PORT           |
       +======+============+============+===========+==========+
       Fields Requiring       Translation   Supplemental Data
       Address Translation     Type (see      (type 3 only)
       -------------------    Section 7.2)  ------------------
                              -----------
       Address Identifier         3         Worldwide Name of
       of the FL_PORT                       the Remote FL_PORT
 Other Special Processing:
    The D_ID field is the address of the Domain Controller associated
    with the remote loop.  The format of the Domain Controller address
    is the hex 'FF FC' || Domain_ID, where Domain_ID is the gateway-
    assigned alias representing the remote gateway or switch element
    being queried.  After translation by the remote gateway, the D_ID
    identifies the gateway or switch element to be scanned within the
    remote gateway region.
    The FLAG field defines the scope of the SRL.  If set to 0, all
    loop port interfaces on the given switch element or gateway are
    scanned.  If set to one, the loop port interface on the gateway or
    switch element to be scanned MUST be specified in bits 8 through
    31.
    If the Flag field is zero, the SRL request SHALL NOT be sent as a
    special ELS.

Monia, et al. Standards Track [Page 79] RFC 4172 Internet Fibre Channel Networking September 2005

    If the Domain_ID represents a remote switch or gateway and an iFCP
    session to the remote Domain Controller does not exist, the
    requesting gateway SHALL create the iFCP session.

7.3.1.17. Third Party Process Logout (TPRLO)

 TPRLO provides a mechanism for an N_PORT (third party) to remove one
 or more process login sessions that exist between the destination
 N_PORT and other N_PORTs specified in the command.  This command
 includes one or more TPRLO LOGOUT PARAMETER PAGEs, each of which,
 when combined with the destination N_PORT, identifies a process login
 to be terminated by the command.
 +--------+------------+--------------------+----------------------+
 | Word   | Bits 0-7   |     Bits 8-15      |     Bits 16 - 31     |
 +--------+------------+--------------------+----------------------+
 | 0      | Cmd = 0x24 | Page Length (0x10) |    Payload Length    |
 +--------+------------+--------------------+----------------------+
 | 1      |          TPRLO Logout Parameter Page 0                 |
 +--------+--------------------------------------------------------+
 | 5      |          TPRLO Logout Parameter Page 1                 |
 +--------+--------------------------------------------------------+
                          ....
 +--------+--------------------------------------------------------+
 |(4*n)+1 |          TPRLO Logout Parameter Page n                 |
 +--------+--------------------------------------------------------+
                   Figure 22. Format of TPRLO ELS
 Each TPRLO parameter page contains parameters identifying one or more
 image pairs and may be associated with a single FC-4 protocol type
 that is common to all FC-4 protocol types between the specified image
 pair or global to all specified image pairs.  The format of a TPRLO
 page requiring address translation is shown in Figure 23.  Additional
 information on TPRLO can be found in [FC-FS].

Monia, et al. Standards Track [Page 80] RFC 4172 Internet Fibre Channel Networking September 2005

    +------+------------+------------+-----------+----------+
    | Word | Bits 0-7   | Bits 8-15  |       Bits 16-31     |
    +------+------------+------------+-----------+----------+
    | 0    | TYPE Code  | TYPE CODE  |                      |
    |      | or         | EXTENSION  |      TPRLO Flags     |
    |      | Common SVC |            |                      |
    |      | Parameters |            |                      |
    +------+------------+------------+-----------+----------+
    | 1    |         Third Party Process Associator         |
    +------+------------+------------+-----------+----------+
    | 2    |         Responder Process Associator           |
    +------+------------+------------+-----------+----------+
    | 3    | Reserved   | Third Party Originator N_PORT ID  |
    +======+============+============+===========+==========+
    | 4-5  | Worldwide Name of Third Party Originator       |
    |      | N_PORT                                         |
    +------+------------------------------------------------+
      Figure 23. Format of an Augmented TPRLO Parameter Page
 The TPRLO flags that affect supplemented ELS processing are as
 follows:
 Bit 18:   Third party Originator N_PORT Validity.  When set to one,
           this bit indicates that word 3, bits 8-31 (Third Party
           Originator N_PORT ID), are meaningful.
 Bit 19:   Global Process logout.  When set to one, this bit indicates
           that all image pairs for all N_PORTs of the specified FC-4
           protocol shall be invalidated.  When the value of this bit
           is one, only one logout parameter page is permitted in the
           TPRLO payload.
 If bit 18 has a value of zero and bit 19 has a value of one in the
 TPRLO flags field, then the ELS SHALL NOT be sent as a special ELS.
 Otherwise, the originating gateway SHALL process the ELS as follows:
 a) The first word of the TPRLO payload SHALL NOT be modified.
 b) Each TPRLO parameter page shall be extended by two words as shown
    in Figure 23.

Monia, et al. Standards Track [Page 81] RFC 4172 Internet Fibre Channel Networking September 2005

 c) If word 0, bit 18 (Third Party Originator N_PORT ID validity), in
    the TPRLO flags field has a value of one, then the sender shall
    place the worldwide port name of the fibre channel device's N_PORT
    in the extension words.  The N_PORT ID SHALL be set to 3.
    Otherwise, the contents of the extension words and the Third Party
    Originator N_PORT ID SHALL be set to zero.
 d) The ELS originator SHALL set the SPC bit in the encapsulation
    header of each augmented frame comprising the ELS (see Section
    5.3.1).
 e) If the ELS contains a single TPRLO parameter page, the originator
    SHALL increase the frame length as necessary to include the
    extended parameter page.
 f) If the ELS to be augmented contains multiple TPRLO parameter
    pages, the FC frames created to contain the augmented ELS payload
    SHALL NOT exceed the maximum frame size that can be accepted by
    the destination N_PORT.
    Each fibre channel frame SHALL contain an integer number of
    extended TPRLO parameter pages.  The maximum number of extended
    TPRLO parameter pages in a frame SHALL be limited to the number
    that can be held without exceeding the above upper limit.  New
    frames resulting from the extension of the TPRLO pages to include
    the supplemental data SHALL be created by extending the SEQ_CNT in
    the fibre channel frame header.  The SEQ_ID SHALL NOT be modified.
 The gateway receiving the augmented TPRLO ELS SHALL generate ELS
 frames to be sent to the destination N_PORT by copying word 0 of the
 ELS payload and processing each augmented parameter page as follows:
 a) If word 0, bit 18, has a value of one, create a parameter page by
    copying words 0 through 2 of the augmented parameter page.  The
    Third Party Originator N_PORT ID in word 3 shall be generated by
    referencing the supplemental data as described in Section 7.2.
 b) If word 0, bit 18, has a value of zero, create a parameter page by
    copying words 0 through 3 of the augmented parameter page.
 The size of each frame to be sent to the destination N_PORT MUST NOT
 exceed the maximum frame size that the destination N_PORT can accept.
 The sequence identifier in each frame header SHALL be copied from the
 augmented ELS, and the sequence count SHALL be monotonically
 increasing.

Monia, et al. Standards Track [Page 82] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.1.18. Third Party Logout Accept (TPRLO ACC)

 The format of the TPRLO ACC frame is shown in Figure 24.
 +--------+------------+--------------------+----------------------+
 | Word   |  Bits 0-7  |     Bits 8-15      |     Bits 16 - 31     |
 +--------+------------+--------------------+----------------------+
 | 0      | Cmd = 0x2  | Page Length (0x10) |    Payload Length    |
 +--------+------------+--------------------+----------------------+
 | 1      |          TPRLO Logout Parameter Page 0                 |
 +--------+--------------------------------------------------------+
 | 5      |          TPRLO Logout Parameter Page 1                 |
 +--------+--------------------------------------------------------+
                          ....
 +--------+--------------------------------------------------------+
 |(4*n)+1 |          TPRLO Logout Parameter Page n                 |
 +--------+--------------------------------------------------------+
                Figure 24. Format of TPRLO ACC ELS
 The format of the parameter page and rules for parameter page
 augmentation are as specified in Section 7.3.1.17.

7.3.2. Special FC-4 Link Services

 The following sections define FC-4 link services for which special
 processing is required.

7.3.2.1. FC-4 Link Services Defined by FCP

 The format of FC-4 link service frames defined by FCP can be found in
 [FCP-2].

7.3.2.1.1. FCP Read Exchange Concise (FCP REC)

 The payload format for this link service is identical to the REC
 extended link service specified in Section 7.3.1.8 and SHALL be
 processed as described in that section.  The FC-4 version will become
 obsolete in [FCP-2].  However, in order to support devices
 implemented against early revisions of FCP-2, an iFCP gateway MUST
 support both versions.

Monia, et al. Standards Track [Page 83] RFC 4172 Internet Fibre Channel Networking September 2005

7.3.2.1.2. FCP Read Exchange Concise Accept (FCP REC ACC)

 The payload format for this link service is identical to the REC ACC
 extended link service specified in Section 7.3.1.9 and SHALL be
 processed as described in that section.  The FC-4 version will become
 obsolete in [FCP-2].  However, in order to support devices
 implemented against earlier revisions of FCP-2, an iFCP gateway MUST
 support both versions.

7.4. FLOGI Service Parameters Supported by an iFCP Gateway

 The FLOGI ELS is issued by an N_PORT that wishes to access the fabric
 transport services.
 The format of the FLOGI request and FLOGI ACC payloads are identical
 to the PLOGI request and ACC payloads described in Section 7.3.1.7.
    +------+------------+------------+-----------+----------+
    | Word | Bits 0-7   | Bits 8-15  |Bits 16-24 |Bits 25-31|
    +------+------------+------------+-----------+----------+
    | 0    | Cmd = 0x4  |   0x00     |    0x00   |   0x00   |
    |      | Acc = 0x2  |            |           |          |
    +------+------------+------------+-----------+----------+
    | 1-4  |            Common Service Parameters           |
    +------+------------+------------+-----------+----------+
    | 5-6  |            N_PORT Name                         |
    +------+------------+------------+-----------+----------+
    | 7-8  |            Node Name                           |
    +------+------------+------------+-----------+----------+
    | 9-12 |            Class 1 Service Parameters          |
    +------+------------+------------+-----------+----------+
    |13-17 |            Class 2 Service Parameters          |
    +------+------------+------------+-----------+----------+
    |18-21 |            Class 3 Service Parameters          |
    +------+------------+------------+-----------+----------+
    |22-25 |            Class 4 Service Parameters          |
    +------+------------+------------+-----------+----------+
    |26-29 |            Vendor Version Level                |
    +======+============+============+===========+==========+
         Figure 25. FLOGI Request and ACC Payload Format
 A full description of each parameter is given in [FC-FS].
 This section tabulates the protocol-dependent service parameters
 supported by a fabric port attached to an iFCP gateway.

Monia, et al. Standards Track [Page 84] RFC 4172 Internet Fibre Channel Networking September 2005

 The service parameters carried in the payload of an FLOGI extended
 link service request MUST be set in accordance with Table 9.
    +-----------------------------------------+---------------+
    |                                         | Fabric Login  |
    |          Service Parameter              |    Class      |
    |                                         +---+---+---+---+
    |                                         | 1 | 2 | 3 | 4 |
    +-----------------------------------------+---+---+---+---+
    | Class Validity                          | n | M | M | n |
    +-----------------------------------------+---+---+---+---+
    | Service Options                         |               |
    +-----------------------------------------+---+---+---+---+
    |   Intermix Mode                         | n | n | n | n |
    +-----------------------------------------+---+---+---+---+
    |   Stacked Connect-Requests              | n | n | n | n |
    +-----------------------------------------+---+---+---+---+
    |   Sequential Delivery                   | n | M | M | n |
    +-----------------------------------------+---+---+---+---+
    |   Dedicated Simplex                     | n | n | n | n |
    +-----------------------------------------+---+---+---+---+
    |   Camp On                               | n | n | n | n |
    +-----------------------------------------+---+---+---+---+
    |   Buffered Class 1                      | n | n | n | n |
    +-----------------------------------------+---+---+---+---+
    |   Priority                              | n | n | n | n |
    +-----------------------------------------+---+---+---+---+
    | Initiator/Recipient Control             |               |
    +-----------------------------------------+---+---+---+---+
    |   Clock Synchronization ELS Capable     | n | n | n | n |
    +-----------------------------------------+---+---+---+---+
            Table 9. FLOGI Service Parameter Settings
 Notes:
    1) "n" indicates a parameter or capability that is not supported
       by the iFCP protocol.
    2) "M" indicates an applicable parameter that MUST be supported by
       an iFCP gateway.

Monia, et al. Standards Track [Page 85] RFC 4172 Internet Fibre Channel Networking September 2005

8. iFCP Error Detection

8.1. Overview

 This section specifies provisions for error detection and recovery in
 addition to those in [FC-FS], which continue to be available in the
 iFCP network environment.

8.2. Stale Frame Prevention

 Recovery from fibre channel protocol error conditions requires that
 frames associated with a failed or aborted exchange drain from the
 fabric before exchange resources can be safely reused.
 Since a fibre channel fabric may not preserve frame order, there is
 no deterministic way to purge such frames.  Instead, the fabric
 guarantees that frame the lifetime will not exceed a specific limit
 (R_A_TOV).
 R_A_TOV is defined in [FC-FS] as "the maximum transit time within a
 fabric to guarantee that a lost frame will never emerge from the
 fabric".  For example, a value of 2 x R_A_TOV is the minimum time
 that the originator of an ELS request or FC-4 link service request
 must wait for the response to that request.  The fibre channel
 default value for R_A_TOV is 10 seconds.
 An iFCP gateway SHALL actively enforce limits on R_A_TOV as described
 in Section 8.2.1.

8.2.1. Enforcing R_A_TOV Limits

 The R_A_TOV limit on frame lifetimes SHALL be enforced by means of
 the time stamp in the encapsulation header (see Section 5.3.1) as
 described in this section.
 The budget for R_A_TOV SHOULD include allowances for the propagation
 delay through the gateway regions of the sending and receiving
 N_PORTs, plus the propagation delay through the IP network.  This
 latter component is referred to in this specification as IP_TOV.
 IP_TOV should be set well below the value of R_A_TOV specified for
 the iFCP fabric and should be stored in the iSNS server.  IP_TOV
 should be set to 50 percent of R_A_TOV.
 The following paragraphs describe the requirements for synchronizing
 gateway time bases and the rules for measuring and enforcing
 propagation delay limits.

Monia, et al. Standards Track [Page 86] RFC 4172 Internet Fibre Channel Networking September 2005

 The protocol for synchronizing a gateway time base is SNTP [RFC2030].
 In order to ensure that all gateways are time aligned, a gateway
 SHOULD obtain the address of an SNTP-compatible time server via an
 iSNS query.  If multiple time server addresses are returned by the
 query, the servers must be synchronized and the gateway may use any
 server in the list.  Alternatively, the server may return a multicast
 group address in support of operation in Anycast mode.
 Implementation of Anycast mode is as specified in [RFC2030],
 including the precautions defined in that document.  Multicast mode
 SHOULD NOT be used.
 An SNTP server may use any one of the time reference sources listed
 in [RFC2030].  The resolution of the time reference MUST be 125
 milliseconds or better.
 Stability of the SNTP server and gateway time bases should be 100 ppm
 or better.
 With regard to its time base, the gateway is in either the
 Synchronized or Unsynchronized state.
 When in the synchronized state, the gateway SHALL
 a) set the time stamp field for each outgoing frame in accordance
    with the gateway's internal time base;
 b) check the time stamp field of each incoming frame, following
    validation of the encapsulation header CRC, as described in
    Section 5.3.4;
 c) if the incoming frame has a time stamp of 0,0 and is not one of
    the session control frames that require a 0,0 time stamp (see
    Section 6), the frame SHALL be discarded;
 d) if the incoming frame has a non-zero time stamp, the receiving
    gateway SHALL compute the absolute value of the time in flight and
    SHALL compare it against the value of IP_TOV specified for the IP
    fabric;
 e) if the result in step (d) exceeds IP_TOV, the encapsulated frame
    shall be discarded.  Otherwise, the frame shall be de-encapsulated
    as described in Section 5.3.4.
 A gateway SHALL enter the Synchronized state upon receiving a
 successful response to an SNTP query.

Monia, et al. Standards Track [Page 87] RFC 4172 Internet Fibre Channel Networking September 2005

 A gateway shall enter the Unsynchronized state:
 a) upon power-up and before successful completion of an SNTP query,
    and
 b) whenever the gateway looses contact with the SNTP server, such
    that the gateway's time base may no longer be in alignment with
    that of the SNTP server.  The criterion for determining loss of
    contact is implementation specific.
 Following loss of contact, it is recommended that the gateway enter
 the Unsynchronized state when the estimated time base drift relative
 to the SNTP reference is greater than ten percent of the IP_TOV
 limit.  (Assuming that all timers have an accuracy of 100 ppm and
 IP_TOV equals 5 seconds, the maximum allowable loss of contact
 duration would be about 42 minutes.)
 As the result of a transition from the Synchronized to the
 Unsynchronized state, a gateway MUST abort all iFCP sessions as
 described in Section 5.2.3.  While in the Unsynchronized state, a
 gateway SHALL NOT permit the creation of new iFCP sessions.

9. Fabric Services Supported by an iFCP Implementation

 An iFCP gateway implementation MUST support the following fabric
 services:
     N_PORT ID Value           Description             Section
     ---------------           -----------             -------
     0xFF-FF-FE             F_PORT Server              9.1
     0xFF-FF-FD             Fabric Controller          9.2
     0xFF-FF-FC             Directory/Name Server      9.3
 In addition, an iFCP gateway MAY support the FC broadcast server
 functionality described in Section 9.4.

9.1. F_PORT Server

 The F_PORT server SHALL support the FLOGI ELS, as described in
 Section 7.4, as well as the following ELSs specified in [FC-FS]:
 a) Request for fabric service parameters (FDISC).
 b) Request for the link error status (RLS).
 c) Read Fabric Timeout Values (RTV).

Monia, et al. Standards Track [Page 88] RFC 4172 Internet Fibre Channel Networking September 2005

9.2. Fabric Controller

 The Fabric Controller SHALL support the following ELSs as specified
 in [FC-FS]:
 a) State Change Notification (SCN).
 b) Registered State Change Notification (RSCN).
 c) State Change Registration (SCR).

9.3. Directory/Name Server

 The Directory/Name server provides a registration service allowing an
 N_PORT to record or query the database for information about other
 N_PORTs.  The services are defined in [FC-GS3].  The queries are
 issued as FC-4 transactions using the FC-CT command transport
 protocol specified in [FC-GS3].
 In iFCP, each name server request MUST be translated to the
 appropriate iSNS query defined in [ISNS].  The definitions of name
 server objects are specified in [FC-GS3].
 The name server SHALL support record and query operations for
 directory subtype 0x02 (Name Server) and 0x03 (IP Address Server) and
 MAY support the FC-4 specific services as defined in [FC-GS3].

9.4. Broadcast Server

 Fibre channel frames are broadcast throughout the fabric by
 addressing them to the fibre channel broadcast server at the well-
 known fibre channel address 0xFF-FF-FF.  The broadcast server then
 replicates and delivers the frame to each attached N_PORT in all
 zones to which the originating device belongs.  Only class 3
 (datagram) service is supported.
 In an iFCP system, the fibre channel broadcast function is emulated
 by means of a two-tier architecture comprising the following
 elements:
 a) A local broadcast server residing in each iFCP gateway.  The local
    server distributes broadcast traffic within the gateway region and
    forwards outgoing broadcast traffic to a global server for
    distribution throughout the iFCP fabric.
 b) A global broadcast server that re-distributes broadcast traffic to
    the local server in each participating gateway.

Monia, et al. Standards Track [Page 89] RFC 4172 Internet Fibre Channel Networking September 2005

 c) An iSNS discovery domain defining the scope over which broadcast
    traffic is propagated.  The discovery domain is populated with a
    global broadcast server and the set of local servers it supports.
 The local and global broadcast servers are logical iFCP devices that
 communicate using the iFCP protocol.  The servers have an N_PORT
 Network Address consisting of an iFCP portal address and an N_PORT ID
 set to the well-known fibre channel address of the FC broadcast
 server (0xFF-FF-FF).
 As noted above, an N_PORT originates a broadcast by directing frame
 traffic to the fibre channel broadcast server.  The gateway-resident
 local server distributes a copy of the frame locally and forwards a
 copy to the global server for redistribution to the local servers on
 other gateways.  The global server MUST NOT echo a broadcast frame to
 the originating local server.

9.4.1. Establishing the Broadcast Configuration

 The broadcast configuration is managed with facilities provided by
 the iSNS server by the following means:
 a) An iSNS discovery domain is created and seeded with the network
    address of the global broadcast server N_PORT.  The global server
    is identified as such by setting the appropriate N_PORT entity
    attribute.
 b) Using the management interface, each broadcast server is preset
    with the identity of the broadcast domain.
 During power up, each gateway SHALL invoke the iSNS service to
 register its local broadcast server in the broadcast discovery
 domain.  After registration, the local server SHALL wait for the
 global broadcast server to establish an iFCP session.
 The global server SHALL register with the iSNS server as follows:
 a) The server SHALL query the iSNS name server by attribute to obtain
    the worldwide port name of the N_PORT pre-configured to provide
    global broadcast services.
 b) If the worldwide port name obtained above does not correspond to
    that of the server issuing the query, the N_PORT SHALL NOT perform
    global broadcast functions for N_PORTs in that discovery domain.
 c) Otherwise, the global server N_PORT SHALL register with the
    discovery domain and query the iSNS server to identify all
    currently registered local servers.

Monia, et al. Standards Track [Page 90] RFC 4172 Internet Fibre Channel Networking September 2005

 d) The global broadcast server SHALL initiate an iFCP session with
    each local broadcast server in the domain.  When a new local
    server registers, the global server SHALL receive a state change
    notification and respond by initiating an iFCP session with the
    newly added server.  The gateway SHALL obtain these notifications
    using the iSNS provisions for lossless delivery.
 Upon receiving the CBIND request to initiate the iFCP session, the
 local server SHALL record the worldwide port name and N_PORT network
 address of the global server.

9.4.2. Broadcast Session Management

 After the initial broadcast session is established, the local or
 global broadcast server MAY choose to manage the session in one of
 the following ways, depending on resource requirements and the
 anticipated level of broadcast traffic:
 a) A server MAY keep the session open continuously.  Since broadcast
    sessions are often quiescent for long periods of time, the server
    SHOULD monitor session connectivity as described in Section
    5.2.2.4.
 b) A server MAY open the broadcast session on demand only when
    broadcast traffic is to be sent.  If the session is reopened by
    the global server, the local server SHALL replace the previously
    recorded network address of the global broadcast server.

9.4.3. Standby Global Broadcast Server

 An implementation may designate a local server to assume the duties
 of the global broadcast server in the event of a failure.  The local
 server may use the LTEST message to determine whether the global
 server is functioning and may assume control if it is not.
 When assuming control, the standby server must register with the iSNS
 server as the global broadcast server in place of the failed server
 and must install itself in the broadcast discovery domain as
 specified in steps c) and d) of Section 9.4.1.

10. iFCP Security

10.1. Overview

 iFCP relies upon the IPSec protocol suite to provide data
 confidentiality and authentication services, and it relies upon IKE
 as the key management protocol.  Section 10.2 describes the security
 requirements arising from iFCP's operating environment, and Section

Monia, et al. Standards Track [Page 91] RFC 4172 Internet Fibre Channel Networking September 2005

 10.3 describes the resulting design choices, their requirement
 levels, and how they apply to the iFCP protocol.
 Detailed considerations for use of IPsec and IKE with the iFCP
 protocol can be found in [SECIPS].

10.2. iFCP Security Threats and Scope

10.2.1. Context

 iFCP is a protocol designed for use by gateway devices deployed in
 enterprise data centers.  Such environments typically have security
 gateways designed to provide network security through isolation from
 public networks.  Furthermore, iFCP data may have to traverse
 security gateways in order to support SAN-to-SAN connectivity across
 public networks.

10.2.2. Security Threats

 Communicating iFCP gateways may be subjected to attacks, including
 attempts by an adversary to:
 a) acquire confidential data and identities by snooping data packets,
 b) modify packets containing iFCP data and control messages,
 c) inject new packets into the iFCP session,
 d) hijack the TCP connection carrying the iFCP session,
 e) launch denial-of-service attacks against the iFCP gateway,
 f) disrupt the security negotiation process,
 g) impersonate a legitimate security gateway, or
 h) compromise communication with the iSNS server.
 It is imperative to thwart these attacks, given that an iFCP gateway
 is the last line of defense for a whole fibre channel island, which
 may include several hosts and fibre channel switches.  To do so, the
 iFCP gateway must implement and may use confidentiality, data origin
 authentication, integrity, and replay protection on a per-datagram
 basis.  The iFCP gateway must implement and may use bi-directional
 authentication of the communication endpoints.  Finally, it must
 implement and may use a scalable approach to key management.

Monia, et al. Standards Track [Page 92] RFC 4172 Internet Fibre Channel Networking September 2005

10.2.3. Interoperability with Security Gateways

 Enterprise data center networks are considered mission-critical
 facilities that must be isolated and protected from all possible
 security threats.  Such networks are usually protected by security
 gateways, which, at a minimum, provide a shield against denial-of-
 service attacks.  The iFCP security architecture is capable of
 leveraging the protective services of the existing security
 infrastructure, including firewall protection, NAT and NAPT services,
 and IPSec VPN services available on existing security gateways.
 Considerations regarding intervening NAT and NAPT boxes along the
 iFCP-iSNS path can be found in [ISNS].

10.2.4. Authentication

 iFCP is a peer-to-peer protocol.  iFCP sessions may be initiated by
 either peer gateway or both.  Consequently, bi-directional
 authentication of peer gateways must be provided in accordance with
 the requirement levels specified in Section 10.3.1.
 N_PORT identities used in the Port Login (PLOGI) process shall be
 considered authenticated if the PLOGI request is received from the
 remote gateway over a secure, IPSec-protected connection.
 There is no requirement that the identities used in authentication be
 kept confidential.

10.2.5. Confidentiality

 iFCP traffic may traverse insecure public networks, and therefore
 implementations must have per-packet encryption capabilities to
 provide confidentiality in accordance with the requirements specified
 in Section 10.3.1.

10.2.6. Rekeying

 Due to the high data transfer rates and the amount of data involved,
 an iFCP implementation must support the capability to rekey each
 phase 2 security association in the time intervals dictated by
 sequence number space exhaustion at a given link rate.  In the
 rekeying scenario described in [SECIPS], for example, rekeying events
 happen as often as every 27.5 seconds at a 10 Gbps rate.
 The iFCP gateway must provide the capability for forward secrecy in
 the rekeying process.

Monia, et al. Standards Track [Page 93] RFC 4172 Internet Fibre Channel Networking September 2005

10.2.7. Authorization

 Basic access control properties stem from the requirement that two
 communicating iFCP gateways be known to one or more iSNS servers
 before they can engage in iFCP exchanges.  The optional use of
 discovery domains [ISNS], Identity Payloads (e.g., ID_FQDNs), and
 certificate-based authentication (e.g., with X509v3 certificates)
 enables authorization schemas of increasing complexity.  The
 definition of such schemas (e.g., role-based access control) is
 outside of the scope of this specification.

10.2.8. Policy Control

 This specification allows any and all security mechanisms in an iFCP
 gateway to be administratively disabled.  Security policies MUST
 have, at most, iFCP Portal resolution.  Administrators may gain
 control over security policies through an adequately secured
 interaction with a management interface or with iSNS.

10.2.9. iSNS Role

 iSNS [ISNS] is an invariant in all iFCP deployments.  iFCP gateways
 MUST use iSNS for discovery services and MAY use security policies
 configured in the iSNS database as the basis for algorithm
 negotiation in IKE.  The iSNS specification defines mechanisms for
 securing communication between an iFCP gateway and iSNS server(s).
 Additionally, the specification indicates how elements of security
 policy concerning individual iFCP sessions can be retrieved from iSNS
 server(s).

10.3. iFCP Security Design

10.3.1. Enabling Technologies

 Applicable technology from IPsec and IKE is defined in the following
 suite of specifications:
    [RFC2401] Security Architecture for the Internet Protocol
    [RFC2402] IP Authentication Header
    [RFC2404] The Use of HMAC-SHA-1-96 within ESP and AH
    [RFC2405] The ESP DES-CBC Cipher Algorithm with Explicit IV
    [RFC2406] IP Encapsulating Security Payload

Monia, et al. Standards Track [Page 94] RFC 4172 Internet Fibre Channel Networking September 2005

    [RFC2407] The Internet IP Security Domain of Interpretation for
    ISAKMP
    [RFC2408] Internet Security Association and Key Management
    Protocol (ISAKMP)
    [RFC2409] The Internet Key Exchange (IKE)
    [RFC2410] The NULL Encryption Algorithm and Its Use With IPSEC
    [RFC2451] The ESP CBC-Mode Cipher Algorithms
    [RFC2709] Security Model with Tunnel-mode IPsec for NAT Domains
 The implementation of IPsec and IKE is required according to the
 following guidelines.
 Support for the IP Encapsulating Security Payload (ESP) [RFC2406] is
 MANDATORY to implement.  When ESP is used, per-packet data origin
 authentication, integrity, and replay protection MUST be used.
 For data origin authentication and integrity with ESP, HMAC with SHA1
 [RFC2404] MUST be implemented, and the Advanced Encryption Standard
 [AES] in CBC MAC mode with Extended Cipher Block Chaining SHOULD be
 implemented in accordance with [AESCBC].
 For confidentiality with ESP, 3DES in CBC mode [RFC2451] MUST be
 implemented, and AES counter mode encryption [AESCTR] SHOULD be
 implemented.  NULL encryption MUST be supported as well, as defined
 in [RFC2410].  DES in CBC mode SHOULD NOT be used due to its inherent
 weakness.  Since it is known to be crackable with modest computation
 resources, it is inappropriate for use in any iFCP deployment
 scenario.
 A conforming iFCP protocol implementation MUST implement IPsec ESP
 [RFC2406] in tunnel mode [RFC2401] and MAY implement IPsec ESP in
 transport mode.
 Regarding key management, iFCP implementations MUST support IKE
 [RFC2409] for bi-directional peer authentication, negotiation of
 security associations, and key management, using the IPsec DOI.
 There is no requirement that the identities used in authentication be
 kept confidential.  Manual keying MUST NOT be used since it does not
 provide the necessary keying support.  According to [RFC2409], pre-
 shared secret key authentication is MANDATORY to implement, whereas
 certificate-based peer authentication using digital signatures MAY be
 implemented (see Section 10.3.3 regarding the use of certificates).
 [RFC2409] defines the following requirement levels for IKE Modes:

Monia, et al. Standards Track [Page 95] RFC 4172 Internet Fibre Channel Networking September 2005

    Phase-1 Main Mode MUST be implemented.
    Phase-1 Aggressive Mode SHOULD be implemented.
    Phase-2 Quick Mode MUST be implemented.
    Phase-2 Quick Mode with key exchange payload MUST be implemented.
 With iFCP, Phase-1 Main Mode SHOULD NOT be used in conjunction with
 pre-shared keys, due to Main Mode's vulnerability to man-in-the-
 middle-attackers when group pre-shared keys are used.  In this
 scenario, Aggressive Mode SHOULD be used instead.  Peer
 authentication using the public key encryption methods outlined in
 [RFC2409] SHOULD NOT be used.
 The DOI [RFC2407] provides for several types of Identification
 Payloads.
 When used for iFCP, IKE Phase 1 exchanges MUST explicitly carry the
 Identification Payload fields (IDii and IDir).  Conforming iFCP
 implementations MUST use ID_IPV4_ADDR, ID_IPV6_ADDR (if the protocol
 stack supports IPv6), or ID_FQDN Identification Type values.  The
 ID_USER_FQDN, IP Subnet, IP Address Range, ID_DER_ASN1_DN,
 ID_DER_ASN1_GN Identification Type values SHOULD NOT be used.  The
 ID_KEY_ID Identification Type values MUST NOT be used.  As described
 in [RFC2407], the port and protocol fields in the Identification
 Payload MUST be set to zero or UDP port 500.
 When used for iFCP, IKE Phase 2 exchanges MUST explicitly carry the
 Identification Payload fields (IDci and IDcr).  Conforming iFCP
 implementations MUST use either ID_IPV4_ADDR or ID_IPV6_ADDR
 Identification Type values (according to the version of IP
 supported).  Other Identification Type values MUST NOT be used.  As
 described in Section 5.2.2, the gateway creating the iFCP session
 must query the iSNS server to determine the appropriate port on which
 to initiate the associated TCP connection.  Upon a successful IKE
 Phase 2 exchange, the IKE responder enforces the negotiated selectors
 on the IPsec SAs.  Any subsequent iFCP session creation requires the
 iFCP peer to query its iSNS server for access control (in accordance
 with the session creation requirements specified in Section 5.2.2.1).

10.3.2. Use of IKE and IPsec

 A conforming iFCP Portal is capable of establishing one or more IKE
 Phase-1 Security Associations (SAs) to a peer iFCP Portal.  A Phase-1
 SA may be established when an iFCP Portal is initialized or may be
 deferred until the first TCP connection with security requirements is
 established.

Monia, et al. Standards Track [Page 96] RFC 4172 Internet Fibre Channel Networking September 2005

 An IKE Phase-2 SA protects one or more TCP connections within the
 same iFCP Portal.  More specifically, the successful establishment of
 an IKE Phase-2 SA results in the creation of two uni-directional
 IPsec SAs fully qualified by the tuple <SPI, destination IP address,
 ESP>.
 These SAs protect the setup process of the underlying TCP connections
 and all their subsequent TCP traffic.  The number of TCP connections
 in an IPsec SA, as well as the number of SAs, is practically driven
 by security policy considerations (i.e., security services are
 defined at the granularity of an IPsec SA only), QoS considerations
 (e.g., multiple QoS classes within the same IPsec SA increase odds of
 packet reordering, possibly falling outside the replay window), and
 failure compartmentalization considerations.  Each of the TCP
 connections protected by an IPsec SA is either in the unbound state,
 or bound to a specific iFCP session.
 In summary, at any point in time:
  1. - there exist 0..M IKE Phase-1 SAs between peer iFCP portals,
  1. - each IKE Phase-1 SA has 0..N IKE Phase-2 SAs, and
  1. - each IKE Phase-2 SA protects 0..Z TCP connections.
 The creation of an IKE Phase-2 SA may be triggered by a policy rule
 supplied through a management interface or by iFCP Portal properties
 registered with the iSNS server.  Similarly, the use of a Key
 Exchange payload in Quick Mode for perfect forward secrecy may be
 dictated through a management interface or by an iFCP Portal policy
 rule registered with the iSNS server.
 If an iFCP implementation makes use of unbound TCP connections, and
 such connections belong to an iFCP Portal with security requirements,
 then the unbound connections MUST be protected by an SA at all times
 just like bound connections.
 Upon receipt of an IKE Phase-2 delete message, there is no
 requirement to terminate the protected TCP connections or delete the
 associated IKE Phase-1 SA.  Since an IKE Phase-2 SA may be associated
 with multiple TCP connections, terminating these connections might in
 fact be inappropriate and untimely.
 To minimize the number of active Phase-2 SAs, IKE Phase-2 delete
 messages may be sent for Phase-2 SAs whose TCP connections have not
 handled data traffic for a while.  To minimize the use of SA

Monia, et al. Standards Track [Page 97] RFC 4172 Internet Fibre Channel Networking September 2005

 resources while the associated TCP connections are idle, creation of
 a new SA should be deferred until new data are to be sent over the
 connections.

10.3.3. Signatures and Certificate-Based Authentication

 Conforming iFCP implementations MAY support peer authentication via
 digital signatures and certificates.  When certificate authentication
 is chosen within IKE, each iFCP gateway needs the certificate
 credentials of each peer iFCP gateway in order to establish a
 security association with that peer.
 Certificate credentials used by iFCP gateways MUST be those of the
 machine.  Certificate credentials MAY be bound to the interface (IP
 Address or FQDN) of the iFCP gateway used for the iFCP session, or to
 the fabric WWN of the iFCP gateway itself.  Since the value of a
 machine certificate is inversely proportional to the ease with which
 an attacker can obtain one under false pretenses, it is advisable
 that the machine certificate enrollment process be strictly
 controlled.  For example, only administrators may have the ability to
 enroll a machine with a machine certificate.  User certificates
 SHOULD NOT be used by iFCP gateways for establishment of SAs
 protecting iFCP sessions.
 If the gateway does not have the peer iFCP gateway's certificate
 credentials, then it can obtain them:
 a) by using the iSNS protocol to query for the peer gateway's
    certificate(s) stored in a trusted iSNS server, or
 b) through use of the ISAKMP Certificate Request Payload (CRP)
    [RFC2408] to request the certificate(s) directly from the peer
    iFCP gateway.
 When certificate chains are long enough, IKE exchanges using UDP as
 the underlying transport may yield IP fragments, which are known to
 work poorly across some intervening routers, firewalls, and NA(P)T
 boxes.  As a result, the endpoints may be unable to establish an
 IPsec security association.
 Due to these fragmentation shortcomings, IKE is most appropriate for
 intra-domain usage.  Known solutions to the fragmentation problem
 include sending the end-entry machine certificate rather than the
 chain, reducing the size of the certificate chain, using IKE
 implementations over a reliable transport protocol (e.g., TCP)
 assisted by Path MTU discovery and code against black-holing as per
 [RFC2923], or installing network components that can properly handle
 fragments.

Monia, et al. Standards Track [Page 98] RFC 4172 Internet Fibre Channel Networking September 2005

 IKE negotiators SHOULD check the pertinent Certificate Revocation
 List (CRL) [RFC2408] before accepting a certificate for use in IKE's
 authentication procedures.

10.4. iSNS and iFCP Security

 iFCP implementations MUST use iSNS for discovery and management
 services.  Consequently, the security of the iSNS protocol has an
 impact on the security of iFCP gateways.  For a discussion of
 potential threats to iFCP gateways through use of iSNS, see [ISNS].
 To provide security for iFCP gateways using the iSNS protocol for
 discovery and management services, the IPSec ESP protocol in tunnel
 mode MUST be supported for iFCP gateways.  Further discussion of iSNS
 security implementation requirements is found in [ISNS].  Note that
 iSNS security requirements match those for iFCP described in Section
 10.3.

10.5. Use of iSNS to Distribute Security Policy

 Once communication between iFCP gateways and the iSNS server has been
 secured through use of IPSec, the iFCP gateways have the capability
 to discover the security settings that they need to use (or not use)
 to protect iFCP traffic.  This provides a potential scaling advantage
 over device-by-device configuration of individual security policies
 for each iFCP gateway.  It also provides an efficient means for each
 iFCP gateway to discover the use or non-use of specific security
 capabilities by peer gateways.
 Further discussion on use of iSNS to distribute security policies is
 found in [ISNS].

10.6. Minimal Security Policy for an iFCP Gateway

 An iFCP implementation may be able to disable security mechanisms for
 an iFCP Portal administratively through a management interface or
 through security policy elements set in the iSNS server.  As a
 consequence, IKE or IPsec security associations will not be
 established for any iFCP sessions that traverse the portal.
 For most IP networks, it is inappropriate to assume physical
 security, administrative security, and correct configuration of the
 network and all attached nodes (a physically isolated network in a
 test lab may be an exception).  Therefore, authentication SHOULD be
 used in order to provide minimal assurance that connections have
 initially been opened with the intended counterpart.  The minimal
 iFCP security policy only states that an iFCP gateway SHOULD
 authenticate its iSNS server(s) as described in [ISNS].

Monia, et al. Standards Track [Page 99] RFC 4172 Internet Fibre Channel Networking September 2005

11. Quality of Service Considerations

11.1. Minimal Requirements

 Conforming iFCP protocol implementations SHALL correctly communicate
 gateway-to-gateway, even across one or more intervening best-effort
 IP regions.  The timings with which such gateway-to gateway
 communication is performed, however, will greatly depend upon BER,
 packet losses, latency, and jitter experienced throughout the best-
 effort IP regions.  The higher these parameters, the higher the gap
 measured between iFCP observed behaviors and baseline iFCP behaviors
 (i.e., as produced by two iFCP gateways directly connected to one
 another).

11.2. High Assurance

 It is expected that many iFCP deployments will benefit from a high
 degree of assurance regarding the behavior of intervening IP regions,
 with resulting high assurance on the overall end-to-end path, as
 directly experienced by fibre channel applications.  Such assurance
 on the IP behaviors stems from the intervening IP regions supporting
 standard Quality-of-Service (QoS) techniques that are fully
 complementary to iFCP, such as:
 a) congestion avoidance by over-provisioning of the network,
 b) integrated Services [RFC1633] QoS,
 c) differentiated Services [RFC2475] QoS, and
 d) Multi-Protocol Label Switching [RFC3031].
 One may load an MPLS forwarding equivalence class (FEC) with QoS
 class significance, in addition to other considerations such as
 protection and diversity for the given path.  The complementarity and
 compatibility of MPLS with Differentiated Services is explored in
 [MPSLDS], wherein the PHB bits are copied to the EXP bits of the MPLS
 shim header.
 In the most general definition, two iFCP gateways are separated by
 one or more independently managed IP regions that implement some of
 the QoS solutions mentioned above.  A QoS-capable IP region supports
 the negotiation and establishment of a service contract specifying
 the forwarding service through the region.  Such contract and
 negotiation rules are outside the scope of this document.  In the
 case of IP regions with DiffServ QoS, the reader should refer to
 Service Level Specifications (SLS) and Traffic Conditioning
 Specifications (TCS) (as defined in [DIFTERM]).  Other aspects of a

Monia, et al. Standards Track [Page 100] RFC 4172 Internet Fibre Channel Networking September 2005

 service contract are expected to be non-technical and thus are
 outside of the IETF scope.
 Because fibre channel Class 2 and Class 3 do not currently support
 fractional bandwidth guarantees, and because iFCP is committed to
 supporting fibre channel semantics, it is impossible for an iFCP
 gateway to infer bandwidth requirements autonomously from streaming
 fibre channel traffic.  Rather, the requirements on bandwidth or
 other network parameters need to be administratively set into an iFCP
 gateway, or into the entity that will actually negotiate the
 forwarding service on the gateway's behalf.  Depending on the QoS
 techniques available, the stipulation of a forwarding service may
 require interaction with network ancillary functions, such as
 admission control and bandwidth brokers (via RSVP or other signaling
 protocols that an IP region may accept).
 The administrator of a iFCP gateway may negotiate a forwarding
 service with IP region(s) for one, several, or all of an iFCP
 gateway's TCP sessions used by an iFCP gateway.  Alternately, this
 responsibility may be delegated to a node downstream.  Since one TCP
 connection is dedicated to each iFCP session, the traffic in an
 individual N_PORT to N_PORT session can be singled out by iFCP-
 unaware network equipment as well.
 For rendering the best emulation of fibre channel possible over IP,
 it is anticipated that typical forwarding services will specify a
 fixed amount of bandwidth, null losses, and, to a lesser degree of
 relevance, low latency and low jitter.  For example, an IP region
 using DiffServ QoS may support SLSes of this nature by applying EF
 DSCPs to the iFCP traffic.

12. IANA Considerations

 The IANA-assigned port for iFCP traffic is port number 3420.
 An iFCP Portal may initiate a connection using any TCP port number
 consistent with its implementation of the TCP/IP stack, provided each
 port number is unique.  To prevent the receipt of stale data
 associated with a previous connection using a given port number, the
 provisions of [RFC1323], Appendix B, SHOULD be observed.

13. Normative References

 [AESCBC]  Frankel, S. and H. Herbert, "The AES-XCBC-MAC-96 Algorithm
           and Its Use With IPsec", RFC 3566, September 2003.

Monia, et al. Standards Track [Page 101] RFC 4172 Internet Fibre Channel Networking September 2005

 [AESCTR]  Housley, R., "Using Advanced Encryption Standard (AES)
           Counter Mode With IPsec Encapsulating Security Payload
           (ESP)", RFC 3686, January 2004.
 [ENCAP]   Weber, R., Rajagopal, M., Travostino, F., O'Donnell, M.,
           Monia, C., and M. Merhar, "Fibre Channel (FC) Frame
           Encapsulation", RFC 3643, December 2003.
 [FC-FS]   dpANS INCITS.XXX-200X, "Fibre Channel Framing and Signaling
           (FC-FS), Rev 1.70, INCITS Project 1331D, February 2002
 [FC-GS3]  dpANS X3.XXX-200X, "Fibre Channel Generic Services -3 (FC-
           GS3)", revision 7.01, INCITS Project 1356-D, November 2000
 [FC-SW2]  dpANS X3.XXX-2000X, "Fibre Channel Switch Fabric -2 (FC-
           SW2)", revision 5.2, INCITS Project 1305-D, May 2001
 [FCP-2]   dpANS T10, "Fibre Channel Protocol for SCSI, Second
           Version", revision 8, INCITS Project 1144D, September 2002
 [ISNS]    Tseng, J., Gibbons, K., Travostino, F., Du Laney, C., and
           J. Souza, "Internet Storage Name Service (iSNS)", RFC 4171,
           September 2005.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
           Internet Protocol", RFC 2401, November 1998.
 [RFC2402] Kent, S. and R. Atkinson, "IP Authentication Header", RFC
           2402, November 1998.
 [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
           ESP and AH", RFC 2404, November 1998.
 [RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating Security
           Payload (ESP)", RFC 2406, November 1998.
 [RFC2407] Piper, D., "The Internet IP Security Domain of
           Interpretation for ISAKMP", RFC 2407, N.
 [RFC2408] Maughan, D., Schertler, M., Schneider, M., and J. Turner,
           "Internet Security Association and Key Management Protocol
           (ISAKMP)", RFC 2408, November 1998.

Monia, et al. Standards Track [Page 102] RFC 4172 Internet Fibre Channel Networking September 2005

 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
           (IKE)", RFC 2409, November 1998.
 [RFC2410] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and
           Its Use With IPsec", RFC 2410, November 1998.
 [RFC2451] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher
           Algorithms", RFC 2451, November 1998.
 [RFC793]  Postel, J., "Transmission Control Protocol", STD 7, RFC
           793, September 1981.
 [SECIPS]  Aboba, B., Tseng, J., Walker, J., Rangan, V., and F.
           Travostino, "Securing Block Storage Protocols Over IP", RFC
           3723, April 2004.

14. Informative References

 [AES]     FIPS Publication XXX, "Advanced Encryption Standard (AES)",
           Draft, 2001, Available from
           http://csrc.nist.gov/publications/drafts/dfips-AES.pdf
 [DIFTERM] Grossman, D., "New Terminology and Clarifications for
           Diffserv", RFC 3260, April 2002.
 [FC-AL2]  dpANS X3.XXX-199X, "Fibre Channel Arbitrated Loop (FC-AL-
           2)", revision 7.0, NCITS Project 1133D, April 1999
 [FC-FLA]  TR-20-199X, "Fibre Channel Fabric Loop Attachment (FC-
           FLA)", revision 2.7, NCITS Project 1235-D, August 1997
 [FC-VI] ANSI/INCITS 357:2002, "Fibre Channel Virtual Interface
           Architecture Mapping Protocol (FC-VI)", NCITS Project
           1332-D, July 2000.
 [KEMALP]  Kembel, R., "The Fibre Channel Consultant, Arbitrated
           Loop", Robert W. Kembel, Northwest Learning Associates,
           2000, ISBN 0-931836-84-0
 [KEMCMP]  Kembel, R., "Fibre Channel, A Comprehensive Introduction",
           Northwest Learning Associates Inc., 2000, ISBN
           0-931836-84-0
 [MPSLDS]  Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
           P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
           Protocol Label Switching (MPLS) Support of Differentiated
           Services", RFC 3270, May 2002.

Monia, et al. Standards Track [Page 103] RFC 4172 Internet Fibre Channel Networking September 2005

 [RFC1122] Braden, R., "Requirements for Internet Hosts -
           Communication Layers", STD 3, RFC 1122, October 1989.
 [RFC1323] Jacobson, V., Braden, R., and D. Borman, "TCP Extensions
           for High Performance", RFC 1323, May 1992.
 [RFC1633] Braden, R., Clark, D., and S. Shenker, "Integrated Services
           in the Internet Architecture: an Overview", RFC 1633, June
           1994.
 [RFC2030] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
           for IPv4, IPv6 and OSI", RFC 2030, October 1996.
 [RFC2405] Madson, C. and N. Doraswamy, "The ESP DES-CBC Cipher
           Algorithm With Explicit IV", RFC 2405, November 1998.
 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
           and W. Weiss, "An Architecture for Differentiated Service",
           RFC 2475, December 1998.
 [RFC2625] Rajagopal, M., Bhagwat, R., and W. Rickard, "IP and ARP
           over Fibre Channel", RFC 2625, June 1999.
 [RFC2709] Srisuresh, P., "Security Model with Tunnel-mode IPsec for
           NAT Domains", RFC 2709, October 1999.
 [RFC2923] Lahey, K., "TCP Problems with Path MTU Discovery", RFC
           2923, September 2000.
 [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
           Label Switching Architecture", RFC 3031, January 2001.
 [RFC896]  Nagle, J., "Congestion control in IP/TCP internetworks",
           RFC 896, January 1984.

Monia, et al. Standards Track [Page 104] RFC 4172 Internet Fibre Channel Networking September 2005

Appendix A. iFCP Support for Fibre Channel Link Services

 For reference purposes, this appendix enumerates all the fibre
 channel link services and the manner in which each shall be processed
 by an iFCP implementation.  The iFCP processing policies are defined
 in Section 7.
 In the following sections, the name of a link service specific to a
 particular FC-4 protocol is prefaced by a mnemonic identifying the
 protocol.

A.1. Basic Link Services

 The basic link services are shown in the following table:
                      Basic Link Services
    Name             Description                  iFCP Policy
    ----             -----------                  ----------
    ABTS            Abort Sequence                Transparent
    BA_ACC          Basic Accept                  Transparent
    BA_RJT          Basic Reject                  Transparent
    NOP             No Operation                  Transparent
    PRMT            Preempted                     Rejected
                                                    (Applies to
                                                    Class 1 only)
    RMC             Remove Connection             Rejected
                                                    (Applies to
                                                    Class 1 only)

A.2. Pass-Through Link Services

 As specified in Section 7, the link service requests of Table 10 and
 the associated ACC response frames MUST be passed to the receiving
 N_PORT without altering the payload.
             Name        Description
             ----        -----------
             ADVC         Advise Credit
             CSR          Clock Synchronization Request
             CSU          Clock Synchronization Update
             ECHO         Echo
             ESTC         Estimate Credit
             ESTS         Establish Streaming
             FACT         Fabric Activate Alias_ID
             FAN          Fabric Address Notification

Monia, et al. Standards Track [Page 105] RFC 4172 Internet Fibre Channel Networking September 2005

             FCP_RJT      FCP FC-4 Link Service Reject
             FCP SRR      FCP Sequence Retransmission
                           Request
             FDACT        Fabric Deactivate Alias_ID
             FDISC        Discover F_Port Service
                           Parameters
             FLOGI        F_Port Login
             GAID         Get Alias_ID
             LCLM         Login Control List Management
             LINIT        Loop Initialize
             LIRR         Link Incident Record
                           Registration
             LPC          Loop Port Control
             LS_RJT       Link Service Reject
             LSTS         Loop Status
             NACT         N_Port Activate Alias_ID
             NDACT        N_Port Deactivate Alias_ID
             PDISC        Discover N_Port Service
                           Parameters
             PRLI         Process Login
             PRLO         Process Logout
             QoSR         Quality of Service Request
             RCS          Read Connection Status
             RLIR         Registered Link Incident
                           Report
             RNC          Report Node Capability
             RNFT         Report Node FC-4 Types
             RNID         Request Node Identification
                           Data
             RPL          Read Port List
             RPS          Read Port Status Block
             RPSC         Report Port Speed
                           Capabilities
             RSCN         Registered State Change
                           Notification
             RTV          Read Timeout Value
             RVCS         Read Virtual Circuit Status
             SBRP         Set Bit-Error Reporting
                           Parameters
             SCN          State Change Notification
             SCR          State Change Registration
             TEST         Test
             TPLS         Test Process Login State
             Table 10. Pass-Through Link Services

Monia, et al. Standards Track [Page 106] RFC 4172 Internet Fibre Channel Networking September 2005

A.3. Special Link Services

 The extended and FC-4 link services of Table 11 are processed by an
 iFCP implementation as described in the sections referenced in the
 table.
       Name         Description                    Section
       ----         -----------                    -------
       ABTX         Abort Exchange                 7.3.1.1
       ADISC        Discover Address               7.3.1.2
       ADISC        Discover Address Accept        7.3.1.3
       ACC
       FARP-        Fibre Channel Address          7.3.1.4
       REPLY        Resolution Protocol
                     Reply
       FARP-        Fibre Channel Address          7.3.1.5
       REQ          Resolution Protocol
                     Request
       LOGO         N_PORT Logout                  7.3.1.6
       PLOGI        Port Login                     7.3.1.7
       REC          Read Exchange Concise          7.3.1.8
       REC ACC      Read Exchange Concise          7.3.1.9
                     Accept
       FCP REC      FCP Read Exchange             7.3.2.1.1
                     Concise (see [FCP-2])
       FCP REC      FCP Read Exchange             7.3.2.1.2
       ACC          Concise Accept (see
                     [FCP-2])
       RES          Read Exchange Status           7.3.1.10
                     Block
       RES ACC      Read Exchange Status           7.3.1.11
                     Block Accept
       RLS          Read Link Error Status         7.3.1.12
                     Block
       RRQ          Reinstate Recovery             7.3.1.14
                     Qualifier
       RSI          Request Sequence               7.3.1.15
                     Initiative
       RSS          Read Sequence Status           7.3.1.13
                     Block
       SRL          Scan Remote Loop               7.3.1.16
       TPRLO        Third Party Process            7.3.1.17
                     Logout
       TPRLO        Third Party Process            7.3.1.18
       ACC          Logout Accept
                Table 11. Special Link Services

Monia, et al. Standards Track [Page 107] RFC 4172 Internet Fibre Channel Networking September 2005

Appendix B. Supporting the Fibre Channel Loop Topology

 A loop topology may be optionally supported by a gateway
 implementation in one of the following ways:
 a) By implementing the FL_PORT public loop interface specified in
    [FC-FLA].
 b) By emulating the private loop environment specified in [FC-AL2].
 Private loop emulation allows the attachment of fibre channel devices
 that do not support fabrics or public loops.  The gateway presents
 such devices to the fabric as though they were fabric-attached.
 Conversely, the gateway presents devices on the fabric, whether they
 are locally or remotely attached, as though they were connected to
 the private loop.
 Private loop support requires gateway emulation of the loop
 primitives and control frames specified in [FC-AL2].  These frames
 and primitives MUST be locally emulated by the gateway.  Loop control
 frames MUST NOT be sent over an iFCP session.

B.1. Remote Control of a Public Loop

 A gateway MAY disclose that a remotely attached device is connected
 to a public loop.  If it does, it MUST also provide aliases
 representing the corresponding Loop Fabric Address (LFA), DOMAIN_ID,
 and FL_PORT Address Identifier through which the public loop may be
 remotely controlled.
 The LFA and FL_PORT address identifier both represent an N_PORT that
 services remote loop management requests contained in the LINIT and
 SRL extended link service messages.  To support these messages, the
 gateway MUST allocate an NL_PORT alias so that the corresponding
 alias for the LFA or FL_PORT address identifier can be derived by
 setting the Port ID component of the NL_PORT alias to zero.

Monia, et al. Standards Track [Page 108] RFC 4172 Internet Fibre Channel Networking September 2005

Acknowledgements

 The authors are indebted to those who contributed material and who
 took the time to carefully review and critique this specification
 including David Black (EMC), Rory Bolt (Quantum/ATL), Victor Firoiu
 (Nortel), Robert Peglar (XIOtech), David Robinson (Sun), Elizabeth
 Rodriguez, Joshua Tseng (Nishan), Naoke Watanabe (HDS) and members of
 the IPS working group.  For review of the iFCP security policy, the
 authors are further indebted to the authors of the IPS security
 document [SECIPS], which include Bernard Aboba (Microsoft), Ofer
 Biran (IBM), Uri Elzer (Broadcom), Charles Kunziger (IBM), Venkat
 Rangan (Rhapsody Networks), Julian Satran (IBM), Joseph Tardo
 (Broadcom), and Jesse Walker (Intel).

Monia, et al. Standards Track [Page 109] RFC 4172 Internet Fibre Channel Networking September 2005

Author's Addresses

 Comments should be sent to the ips mailing list (ips@ece.cmu.edu) or
 to the authors.
 Charles Monia
 7553 Morevern Circle
 San Jose, CA 95135
 EMail: charles_monia@yahoo.com
 Rod Mullendore
 McDATA
 4555 Great America Pkwy
 Suite 301
 Santa Clara, CA 95054
 Phone: 408-519-3986
 EMail: Rod.Mullendore@MCDATA.com
 Franco Travostino
 Nortel
 600 Technology Park Drive
 Billerica, MA 01821 USA
 Phone: 978-288-7708
 EMail: travos@nortel.com
 Wayland Jeong
 TROIKA Networks, Inc.
 2555 Townsgate Road, Suite 105
 Westlake Village, CA  91361
 Phone: 805-371-1377
 EMail: wayland@TroikaNetworks.com
 Mark Edwards
 Adaptec (UK) Ltd.
 4th Floor, Howard House
 Queens Ave, UK.  BS8 1SD
 Phone: +44 (0)117 930 9600
 EMail: mark_edwards@adaptec.com

Monia, et al. Standards Track [Page 110] RFC 4172 Internet Fibre Channel Networking September 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
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 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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 made any independent effort to identify any such rights.  Information
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 Copies of IPR disclosures made to the IETF Secretariat and any
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 this standard.  Please address the information to the IETF at ietf-
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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Monia, et al. Standards Track [Page 111]

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