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rfc:rfc2625

Network Working Group M. Rajagopal Request for Comments: 2625 R. Bhagwat Category: Standards Track W. Rickard

                                                      Gadzoox Networks
                                                             June 1999
                   IP and ARP over Fibre Channel

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 (1999).  All Rights Reserved.

Abstract

 Fibre Channel (FC) is a high speed serial interface technology that
 supports several higher layer protocols including Small Computer
 System Interface (SCSI) and Internet Protocol(IP). Until now, SCSI
 has been the only widely used protocol over FC. Existing FC standards
 [3] do not adequately specify how IP packets may be transported over
 FC and how IP addresses are resolved to FC addresses. The purpose of
 this document is to specify a way of encapsulating IP and Address
 Resolution Protocol(ARP) over Fibre Channel and also to describe a
 mechanism(s) for IP address resolution.

Table of Contents

 1. Introduction ...............................................  3
 2. Problem Statement ..........................................  5
 3. IP and ARP Encapsulation ...................................  5
    3.1 FC Frame Format ........................................  5
    3.2 MTU ....................................................  7
        3.2.1 IP MTU ...........................................  7
        3.2.2 Maximally Minimum IPv4 packet ....................  8
        3.2.3 ARP MTU ..........................................  8
        3.2.4 FC Data Field containing FARP Packet .............  9
    3.3 FC Port and Node Network Addresses .....................  9
    3.4 FC Sequence Payload Format ............................. 10
    3.5 Bit and Byte Ordering .................................. 12
 4. ARP ........................................................ 12

Rajagopal, et al. Standards Track [Page 1] RFC 2625 IP and ARP over Fibre Channel June 1999

    4.1 Address Resolution  .................................... 12
    4.2 ARP Packet Format ...................................... 13
    4.3 ARP Layer Mapping and Operation ........................ 15
    4.4 ARP Broadcast in a Point-to-Point Topology ............. 16
    4.5 ARP Broadcast in a Private Loop Topology ............... 16
    4.6 ARP Broadcast in a Public Loop Topology ................ 16
    4.7 ARP Operation in a Fabric Topology ..................... 17
 5. FARP ....................................................... 18
    5.1 Scope .................................................. 18
    5.2 FARP Overview .......................................... 18
    5.3 FARP Command Format .................................... 20
    5.4 Match Address Code Points .............................. 22
    5.5 Responder Flags ........................................ 23
    5.6 FARP Support Requirements .............................. 24
 6. Exchange Management ........................................ 25
    6.1 Exchange Origination ................................... 25
    6.2 Exchange Termination ................................... 25
 7. Summary of Supported Features .............................. 25
    7.1 FC-4 Header ............................................ 25
    7.2 R_CTL .................................................. 26
    7.3 F_CTL .................................................. 27
    7.4 Sequences .............................................. 28
    7.5 Exchanges .............................................. 29
    7.6 ARP  and InARP ......................................... 30
    7.7 Extended Link Services (ELS) ........................... 31
    7.8 Login Parameters ....................................... 31
        7.8.1 Common Service Parameters  - FLOGI ............... 32
        7.8.2 Common Services Parameters - PLOGI ............... 32
        7.8.3 Class Service Parameters - PLOGI ................. 32
 8. Security Considerations .................................... 32
    8.1 IP and ARP Related ..................................... 32
    8.2 FC Related ............................................. 32
 9. Acknowledgements ........................................... 33
 10. References ................................................ 33
 11. Authors' Addresses ........................................ 35
 Appendix A: Additional Matching Mechanisms in FARP ............ 36
 Appendix B: InARP ............................................. 40
    B.1 General Discussion ..................................... 40
    B.2 InARP Protocol Operation ............................... 40
    B.3 InARP Packet Format .................................... 40
    B.4 InARP Support Requirements ............................. 41
 Appendix C: Some Informal Mechanisms for FC Layer Mappings .... 42
    C.1 Login on cached Mapping Information .................... 42
    C.2 Login on ARP parsing ................................... 42
    C.3 Login to Everyone ...................................... 43
    C.4 Static Table ........................................... 43
 Appendix D: FC Layer Address Validation........................ 44
    D.1 General Discussion ..................................... 44

Rajagopal, et al. Standards Track [Page 2] RFC 2625 IP and ARP over Fibre Channel June 1999

    D.2 FC Layer Address Validation in a Point-to-Point Topology 45
    D.3 FC Layer Address Validation in a Private Loop Topology . 45
    D.4 FC Layer Address Validation in a Public Loop Topology .. 45
    D.5 FC layer Address Validation in a Fabric Topology ....... 46
 Appendix E: Fibre channel Overview ............................ 47
    E.1 Brief Tutorial ......................................... 47
    E.2 Exchange, Information Unit, Sequence, and Frame ........ 48
    E.3 Fibre Channel Header Fields ............................ 49
    E.4 Code Points for FC Frame ............................... 52
         E.4.1 Code Points with IP and ARP Packet .............. 52
         E.4.2 Code Points with FARP Command ................... 54
 Appendix F: Fibre Channel Protocol Considerations.............. 58
    F.1 Reliability in Class 3 ................................. 58
    F.2 Continuously Increasing SEQ_CNT ........................ 58
 Appendix G: Acronyms and Glossary of FC Terms ................. 60
 Full Copyright Statement ...................................... 63

1. Introduction

 Fibre Channel (FC) is a gigabit speed networking technology primarily
 used for Storage Area Networking (SAN). FC is standardized under
 American National Standard for Information Systems of the National
 Committee for Information Technology Standards (NCITS) and has
 specified a number of documents describing its protocols, operations,
 and services.
 Need:
 Currently, Fibre Channel is predominantly used for communication
 between storage devices and servers using the SCSI protocol, with
 most  of the servers still communicating with each other over LANs.
 Although, there exists a Fibre Channel Standard [3] that has
 architecturally defined support for IP encapsulation and address
 resolution, it is inadequately specified. ([3] prohibits broadcasts,
 thus loops are not covered; [10] has no support for Class 3).
 This has lead to a nonstandard way of using IP over FC in the past.
 Once such a standard method is completely specified, servers can
 directly communicate with each other using IP over FC, possibly
 boosting performance in Server host-to-host communications.  This
 technique will be especially useful in a Clustering Application.
 Objective and Scope:
 The major objective of this specification is to promote interoperable
 implementations of IPv4 over FC. This specification describes a
 method for encapsulating IPv4 and Address Resolution Protocol (ARP)
 packets over FC. This specification accommodates any FC topology

Rajagopal, et al. Standards Track [Page 3] RFC 2625 IP and ARP over Fibre Channel June 1999

 (loop, fabric, or point-to-point) and any FC class of service (1, 2
 or 3).  This specification also describes a FC Address Resolution
 Protocol(FARP) for associating World Wide Port Names (MAC addresses)
 and FC Port identifiers.
 A secondary objective of this specification is to describe other
 optional address resolution mechanisms:
  1. Other FARP mechanisms that directly build IPv4 address and FC

Port Identifier (Port_ID) associations.

  1. Inverse ARP (InARP) that allows learning the IP address of a

remote node given its World Wide Port Name (WW_PN) and Port_ID.

 "Multicasting" in Fibre Channel is defined as an optional service
 [11] for FC Classes 3 and 6 only, with no definition for Classes 1
 and 2. Currently, there are no vendor implementations of this service
 for either Class of service. Broadcast service available within Fibre
 Channel can be used to do multicasting, although less efficiently.
 Presently, there appears to be no IP applications over Fibre Channel
 that require support for IP multicasting. This specification
 therefore does not support IP Multicasting.
 Organization:
 Section 2 states the problem that is solved in this  specification.
 Section 3 describes the techniques used for encapsulating  IP and ARP
 packets in a FC sequence. Section 4 discusses the ARP protocol(IP
 address to WW_PN). Section 5 discusses the FARP protocol used in FC
 Layer mappings (WW_PN to Port_ID).  Section 6 describes the
 "Exchange" Management in FC. Section 7 is a summary section and
 provides a quick reference to FC header settings, FC Link Service
 Commands, supported features in ARP, FARP, InARP, FC Sequences, FC
 Exchanges, and FC Login Parameters.  Section 8 discusses security.
 Section 9 acknowledges the technical contributors of this document.
 Section 10 provides a list of references, and Section 11 provides the
 authors' addresses.
 Appendix A discusses other optional FARP mechanisms. Appendix B
 discusses the Inverse ARP protocol(WW_PN to IP address) as an
 alternate and optional way of building MAC and IP address
 associations. Appendix C lists some informal mechanisms for FC Layer
 Mappings.  Appendix D provides a discussion on validation of the FC-
 layer mappings for the different FC topologies.  Appendix E provides
 a brief overview of the FC Protocols and Networks.  Appendix F
 addresses reliability in Class 3 and Sequence Count FC Protocol
 issues.  Appendix G provides a list of acronyms and a glossary of FC
 Terms used in this specification.

Rajagopal, et al. Standards Track [Page 4] RFC 2625 IP and ARP over Fibre Channel June 1999

 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 RFC 2119 [19].

2. Problem Statement

 This specification addresses two problems:
  1. A format definition and encapsulation mechanism for IPv4

and ARP packets over FC

  1. Mechanisms for Address Resolution
 As noted earlier, the existing FC Standard [3] ([10]) is inadequate
 to solve the above problems. A solution to both problems was first
 proposed by the Fibre Channel Association (FCA)[1]. FCA is an
 industry consortium of FC vendor companies and not a Standards Body.
 This specification is based on the proposed solution in [1] and
 builds on it.
 Address Resolution is concerned with resolving IP addresses to WW_PN
 (MAC address) and WW_PN to FC Port Identifiers (Port_ID). ARP
 provides a solution to the first resolution problem and FARP the
 second.
 An optional FARP mechanism resolves IP address directly to FC
 Port_IDs. This is useful in some upper layer applications.
 InARP is another optional mechanism that resolves WW_PN and Port_ID
 to an IP address.  InARP is useful when a node after performing a
 PLOGI with another node, knows its WW_PN and Port_ID, but not its IP
 address.

3. IP and ARP Encapsulation

3.1 FC Frame Format

 All FC frames have a standard format much like LAN 802.x protocols.
 (See Appendix E and F).  However, the exact size of each frame varies
 depending on the size of the variable fields.  The size of the
 variable field ranges from 0 to 2112-bytes as shown in the FC Frame
 Format in Fig. 1.

Rajagopal, et al. Standards Track [Page 5] RFC 2625 IP and ARP over Fibre Channel June 1999

       +------+--------+-----------+----//-------+------+------+
       | SOF  |Frame   |Optional   |  Frame      | CRC  |  EOF |
       | (4B) |Header  |Header     | Payload     | (4B) | (4B) |
       |      |(24B)   |<----------------------->|      |      |
       |      |        | Data Field = (0-2112B)  |      |      |
       +------+--------+-----------+----//-------+------+------+
                        Fig. 1 FC Frame Format
 The Start of Frame (SOF) and End of Frame (EOF) are both 4-bytes long
 and act as frame delimiters.
 The CRC is 4-bytes long and uses the same 32-bit polynomial used in
 FDDI and is specified in ANSI X3.139 Fiber Distributed Data
 Interface.
 The Frame Header is 24-bytes long and has several fields that are
 associated with the identification and control of the payload. Some
 of the values and options for this field that are relevant to the IP
 and ARP payloads are discussed in Section 7.
 Current FC Standards allow up to 3 Optional Header fields [11]:
  1. Network_Header (16-bytes)
  2. Association_Header (32-bytes)
  3. Device_Header (up to 64-bytes).
 The IP and ARP FC Sequences SHALL carry only the Network_Header field
 which is 16-bytes long. Other types of optional headers SHALL NOT be
 used.  The Network_Header is REQUIRED in all ARP packets and in the
 first frame of a logical sequence carrying an IP payload as described
 below.
 An application level payload such as IP is called an Information Unit
 at the FC-4 Level. Lower FC levels map this to a FC Sequence.  (See
 Appendix E.2 for a description of Sequences and Information Units.)
 Typically, a Sequence consists of more than one frame. Larger user
 data is segmented and reassembled using two methods: Sequence Count
 and Relative Offset [18]. With the use of Sequence Count, data blocks
 are sent using frames with increasing sequence counts (modulo 65536)
 and it is quite straightforward to detect the first frame that
 contains the Network_Header.  When Relative Offset is used, as frames
 arrive, some computation is required to detect the first frame that
 contains the Network_Header. Sequence Count and Relative Offset field
 control information, is carried in the FC Header.
 In FC, the physical temporal ordering of the frames as it arrives at
 a destination can be different from that of the order sent because of
 traversing through a FC Network.

Rajagopal, et al. Standards Track [Page 6] RFC 2625 IP and ARP over Fibre Channel June 1999

 When IP forms the FC Payload then only the first frame of the logical
 Sequence SHALL include the FC Network_Header. Fig. 2 shows the
 logical First Frame and logical subsequent frames. Since frames may
 arrive out of order, detection of the first frame of the logical FC
 Sequence is necessary.
 ARP packets map to a single frame FC Sequence and SHALL always carry
 the FC Network_Header.
 Note the definition of FC Data Field and FC Frame Payload in Fig. 1.
 FC Data Field includes the FC Frame Payload and the FC Optional
 Header, that is, Frame Payload definition does not include the FC
 Optional Header. One or more Frame Payloads together make the FC
 Sequence Payload as shown in Fig 2 and discussed further in Sections
 3.2 and 3.4. FC Sequence Payload includes the mapped IP or ARP packet
 along with the LLC/SNAP headers.
               First Frame of a Logical FC Sequence

—+————+—————————+———-———-+— | FC Header | FC Network_Header | FC Sequence Payload | —+————+—————————+——————–+—

            Subsequent Frames of a Logical FC Sequence
        --+-----------+--------------//----------------+--
          | FC Header | Additional FC Sequence Payload |
        --+-----------+-------------//-----------------+--
           Fig. 2 FC Network_Header in a Frame Sequence
 The SOF, CRC, EOF control fields of the FC frame and other optional
 headers have been omitted in the figure for clarity.

3.2 MTU

3.2.1 IP MTU

 An FC Information Unit specific to each protocol such as IP is
 defined in FC-4. This defines the upper bound on the size of the
 information that can be transported.
 Each IP or ARP Packet is mapped to a single FC Information Unit,
 which in turn is mapped to a single FC Sequence. There is a one-to-
 one mapping between an IP or ARP packet and a FC Sequence.
 Fibre Channel limits the size of a single Information Unit to 2^32-1,
 which is very large [2].  However, since the Maximum Transmission
 Unit (MTU) size of an IPv4 packet does not exceed 65,536-bytes, the
 mapped IPv4 size is far below the 2^32-1 limit.

Rajagopal, et al. Standards Track [Page 7] RFC 2625 IP and ARP over Fibre Channel June 1999

 IPv4 Packet definition includes the IP Payload and IP Headers - both
 fixed and optional.  The corresponding FC Sequence Payload includes
 the LLC/SNAP Header and the IPv4 packet.
 As noted above, the greatest length allowed for an IPv4 Packet
 including any optional headers and independent of this standard is
 65,536-bytes. However, limiting the IP MTU size to 65,280-bytes helps
 in buffer resource allocation at N_Ports and also allows for up to
 256-bytes of overhead. Since the FC Network_Header requires 16-bytes
 and the IEEE 802.2 LLC/SNAP header requires 8 bytes, it leaves 232
 bytes for future use.
 All implementations SHALL restrict the IP MTU size to 65,280 bytes
 and the corresponding FC Sequence Payload size to 65536-bytes.

3.2.2 Maximally Minimum IPv4 Packet

 In order for IP fragmentation and reassembly to work properly it is
 necessary that every implementation of IP be capable of transporting
 a maximally minimum size IP packet without fragmentation. A maximally
 minimum size IP Packet is defined as an IP Packet with an 8-byte
 payload (the smallest possible non-zero payload size for a fragment)
 and a 60-byte header (the largest possible header consisting of a
 20-byte fixed part and a maximum size option field of 40-bytes) [17].
 All implementations SHALL support a FC Data Field of 92-bytes, which
 is required to support 68-bytes of the maximally minimum sized IP
 Packet, 16-bytes of the FC Network_Header, and 8-bytes of the
 LLC/SNAP Header.

3.2.3 ARP MTU

 The ARP packet has a fixed size of 28-bytes. All implementations
 SHALL support a FC Data Field size of 52-bytes, which is required to
 support 28-bytes of an ARP Packet, 16-bytes of the FC Network_Header,
 and 8-bytes of the LLC/SNAP Header. Note that the minimum MTU
 requirement for ARP is already covered by the minimum MTU requirement
 for IP but it is mentioned here for completeness.
 The InARP packet is identical in size to the ARP and the same MTU
 requirements apply.

Rajagopal, et al. Standards Track [Page 8] RFC 2625 IP and ARP over Fibre Channel June 1999

3.2.4 FC Data Field containing FARP Packet

 The FARP Command is a FC Extended Link Service (ELS) command and maps
 directly to the FC Data Field without the LLC/SNAP or the FC
 Network_Header. The FARP Command has a fixed size of 76-bytes.
 Because FARP operates purely in the FC space, it places no special
 MTU requirements in this specification.

3.3 FC Port and Node Network Addresses

 FC devices are identified by Nodes and their Ports. A Node is a
 collection of one or more Ports identified by a unique nonvolatile
 64-bit World Wide Node name (WW_NN). Each Port in a node, is
 identified with a unique nonvolatile 64-bit World Wide Port name
 (WW_PN), and a volatile Port Identifier (Port_ID).
 Port_IDs are 24-bits long. A FC frame header carries a Source Port_ID
 (S_ID) and a Destination Port_ID (D_ID). The Port_ID of a given port
 is volatile. (The mechanism(s) by which a Port_ID may change in a FC
 topology is outside the scope of this document. See Appendix D).
 The FC Network_Header is normally optional in FC Standards, but
 REQUIRED in this specification.  A FC Network_Header carries source
 and destination WW_PNs. A WW_PN consists of a 60-bit Network Address
 and a upper 4-bit Network Address Authority (NAA) field as shown in
 Fig. 3.  The 4-bit NAA field is used to distinguish between the
 various name registration authorities used to define the Network
 Address [2].
 In this specification, both the Source and Destination 4-bit NAA
 identifiers SHALL be set to binary '0001' indicating that an IEEE
 48-bit MAC address is contained in the lower 48 bits of the network
 address fields. The high order 12 bits in the network address fields
 SHALL be set to 0x0000. The NAA field value equal to binary '0001'
 allows FC networks to be bridged with other FC networks or
 traditional LANs.

Rajagopal, et al. Standards Track [Page 9] RFC 2625 IP and ARP over Fibre Channel June 1999

       +--------+---------------------------------------+
       | D_NAA  |Network_Dest_Address (High-order bits) |
       |(4 bits)|              (28 bits)                |
       +--------+---------------------------------------+
       |      Network_Dest_Address (Low-order bits)     |
       |                       (32 bits)                |
       +--------+---------------------------------------+
       | S_NAA  |Network_Source_Address(High-order bits)|
       |(4 bits)|              (28 bits)                |
       +--------+---------------------------------------+
       |      Network_Source_Address (Low-order bit)    |
       |                       (32 bits)                |
       +--------+---------------------------------------+
            Fig. 3 Format of the Network_Header Field

3.4 FC Sequence Payload Format

 FC Payload with IP:
 An FC Sequence Payload carrying an IP and ARP packet SHALL use the
 formats shown in Figs. 4 and 5 respectively. Both formats use the
 8-byte LLC/SNAP header.

+—————–+———–+————+————-———-+ | LLC/SNAP Header | IP Header | Opt.IP Hdr.| IP Data | | (8 bytes) | (20 bytes)| (40 bytes | (65280 -IP Header | | | | Max) | - Opt. IP Hdr.) bytes | +—————–+———–+————+————-———-+

         Fig. 4 Format of FC Sequence Payload carrying IP
 FC Sequence Payload with ARP:
 As noted earlier, FC frames belonging to the same Sequence may be
 delivered out of order over a Fabric. If the Relative Offset method
 is used to identify FC Sequence Payload fragments, then the IP Header
 MUST appear in the frame that has a relative offset of 0.
             +-----------------+-------------------+
             | LLC/SNAP Header |   ARP Packet      |
             |   (8 bytes)     |   (28 bytes)      |
             +-----------------+-------------------+
        Fig. 5 Format of FC Sequence Payload carrying ARP

Rajagopal, et al. Standards Track [Page 10] RFC 2625 IP and ARP over Fibre Channel June 1999

 FC Sequence Payload with FARP:
 FARP Protocol commands are directly mapped to the Frame Sequence
 Payload and are 76-bytes long. No LLC/SNAP Header or FC
 Network_Header is used and therefore the FC Data Field size simply
 consists of the FC Sequence Payload.
 LLC:
 A Logical Link Control (LLC) field along with a Sub Network Access
 Protocol (SNAP) field is a method used to identify routed and bridged
 non-OSI protocol PDUs and is defined by IEEE 802.2 and applied to IP
 in [8]. In LLC Type 1 operation (i.e., unacknowledged connectionless
 mode), the LLC header is 3-bytes long and consists of a 1-byte
 Destination Service Access Point (DSAP)field, a 1-byte Source Service
 Access Point (SSAP)field, and a 1-byte Control field as shown in Fig.
 6.
                +----------+----------+----------+
                |   DSAP   |   SSAP   |   CTRL   |
                | (1 byte) | (1 byte) | (1 byte) |
                +----------+----------+----------+
                           Fig. 6 LLC Format
 The LLC's DSAP and SSAP values of 0xAA indicate that an IEEE 802.2
 SNAP header follows. The LLC's CTRL value equal to 0x03 specifies an
 Unnumbered Information Command PDU. In this specification the LLC
 Header value SHALL be set to 0xAA-AA-03. Other values of DSAP/SSAP
 indicate support for other protocols and SHALL NOT be used in this
 specification.
 SNAP:
 The SNAP Header is 5-bytes long and consists of a 3-byte
 Organizationally Unique Identifier (OUI) field and a 2-byte Protocol
 Identifier (PID) as shown in Fig. 7
                 +------+------+-------+------+------+
                 |         OUI         |     PID     |
                 |      ( 3 bytes)     |  (2 bytes)  |
                 +------+------+-------+------+------+
                       Fig. 7 SNAP Format
 SNAP was invented to "encapsulate" LAN frames within the payload.
 The SNAP OUI value equal to 0x00-00-00 specifies that the PID is an
 EtherType (i.e., routed non-OSI protocol).
 The SNAP OUI value equal to 0x00-80-C2 indicates Bridged Protocols.

Rajagopal, et al. Standards Track [Page 11] RFC 2625 IP and ARP over Fibre Channel June 1999

 With the OUI value set to 0x00-00-00, the SNAP PID value equal to
 0x08-00 indicates IP and a PID value equal to 0x08-06 indicates ARP
 (or InARP).
 The complete LLC/SNAP Header is shown in Fig. 8.

+———–+———-+———-+——-+——-+——-+——-+——+

DSAP SSAP CTRL OUI PID
(1 byte) (1 byte) (1 byte) ( 3 bytes) (2 bytes

+———–+———-+———-+——-+——-+——-+——-+——+

                        Fig. 8 LLC/SNAP Header

3.5 Bit and Byte Ordering

 IP or ARP Packets are mapped to FC-4 Level using the big endian byte
 ordering, which corresponds to the standard network byte order or
 canonical form [20]. FC-4 Payload maps with no change in order to the
 FC-2 Level.
 FC-1 Level defines the method used to encode data prior to
 transmission and subsequently decode the data upon reception. The
 method encodes 8-bit bytes into 10-bit transmission characters to
 improve the transmission characteristics of the serial data stream.
 In Fibre Channel, data fields are aligned on word boundaries. See
 Appendix E.  A word in FC is defined as 4 bytes or 32 bits. The
 resulting transmission word after the 8-bit to 10-bit encoding
 consists of 40 bits.
 Data words or Ordered Sets (special FC-2 Level control words) from
 the FC-2 Level map to the FC-1 Level with no change in order and the
 bytes in the word are transmitted in the Most Significant Byte first
 to Least Significant Byte order. The transmission order of bits
 within each byte is the Least Significant Bit to the Most Significant
 Bit.

4. ARP

4.1 Address Resolution

 Address Resolution in this specification is primarily concerned with
 associating IP addresses with FC Port addresses. As described
 earlier, FC device ports have two types of addresses:
  1. a non-volatile unique 64-bit address called World Wide Port_Name

(WW_PN)

  1. a volatile 24-bit address called a Port_ID

Rajagopal, et al. Standards Track [Page 12] RFC 2625 IP and ARP over Fibre Channel June 1999

 The Address Resolution mechanism therefore will need two levels of
 mapping:
    1. A mapping from the IP address to the WW_PN (i.e., IEEE
       48-bit MAC address)
    2. A mapping from the WW_PN to the Port_ID (see Appendix G for a
       definition of Port_ID)
 The address resolution problem is compounded by the fact that the
 Port_ID is volatile and the second mapping MUST be valid before use.
 Moreover, this validation process can be different depending on the
 network topology used. Appendix D provides a discussion on validation
 for the different FC topologies.
 Architecturally, the first level of mapping and control operation is
 handled by the Address Resolution Protocol (ARP), and the second
 level by the FC Address Resolution Protocol (FARP). FARP is described
 in Section 5.
 Other optional mechanisms in FARP that directly map an IP address to
 a Port_ID, or WW_NN to a Port_ID are described in Appendix A.
 The Inverse Address Resolution Protocol (InARP) is yet another
 optional mechanism that resolves WW_PN and Port_IDs to IP addresses.
 InARP is described in Appendix B.

4.2 ARP Packet Format

 The Address Resolution Protocol (ARP) given in [9] was designed to be
 a general purpose protocol, and to work with many network
 technologies, and with many upper layer protocols. Fig 9 shows the
 ARP packet format based on [9], where the upper layer protocol uses a
 4 octet protocol (IP) address and the network technology uses six-
 octet hardware (MAC) address.
 The ARP uses two packet types - Request and Reply - and each type of
 packet is 28 -bytes long in this specification. The ARP Packet fields
 are common to both ARP Requests and ARP Replys.
 The LLC/SNAP encapsulated ARP Request Packet is mapped to a FC
 Broadcast Sequence and the exact mechanism used to broadcast a FC
 Sequence depends on the FC topology. This is discussed later in this
 section. Compliant ARP Request Broadcasts SHALL include
 Network_Headers.

Rajagopal, et al. Standards Track [Page 13] RFC 2625 IP and ARP over Fibre Channel June 1999

 The LLC/SNAP encapsulated ARP Reply Packet is mapped to a FC
 Sequence. Compliant ARP Replys SHALL include Network_Headers.
 Note that in all discussions to follow, the WW_PN and the 48-bit MAC
 address conceptually mean the same thing.
 The 'HW Type' field SHALL be set to 0x00-01.
 Technically, the correct HW Type value should be set to 0x00-06
 according to RFC 1700 indicating IEEE 802 networks. However, as a
 practical matter a HW Type value of 0x00-06 is known to cause
 rejections from some Ethernet end stations when FC is bridged to
 Ethernet. Translational bridges are normally expected to change this
 field from Type 6 to 1 and vice versa under these configurations, but
 many do not. It is because of this reason that the Type Code is set
 to 1 rather than 6. However, both HW Type values of 0x00-01 and
 0x00-06 SHALL be accepted.
 The 'Protocol' field SHALL be set to 0x08-00 indicating IP protocol.
 The 'HW Addr Length' field SHALL be set to 0x06 indicating 6-bytes of
 HW address.
 The 'Protocol Addr Length' field SHALL be set to 0x04 indicating 4-
 bytes of IPv4 address.
 The 'Operation' Code field SHALL be set as follows:
          0x00-01 for ARP Request
          0x00-02 for ARP Reply
 The 'HW Addr of Sender' field SHALL be the 6-byte IEEE MAC address of
 the sender. It is either the Requester (ARP Request) or the Responder
 (ARP Reply) address.
 The 'Protocol Addr of Sender' field SHALL be the 4-byte IP address of
 the Requester (ARP Request) or that of the Responder (ARP Reply).
 The 'HW Addr of Target' field SHALL be set to zero during an ARP
 Request and to the 6-byte MAC address of the Requester (ARP Request)
 in an ARP Reply.
 The 'Protocol Addr of Target' field SHALL be set to the 4-byte IP
 address of the Responder (ARP Reply) in a ARP Request, and to the
 4-byte IP address of the Requester (ARP Request) in an ARP Reply.

Rajagopal, et al. Standards Track [Page 14] RFC 2625 IP and ARP over Fibre Channel June 1999

                   +-------------------------+
                   | HW Type                 | 2 bytes
                   +-------------------------+
                   | Protocol                | 2 bytes
                   +-------------------------+
                   | HW Addr Length          | 1 byte
                   +-------------------------+
                   | Protocol Addr Length    | 1 byte
                   +-------------------------+
                   | Op Code                 | 2 bytes
                   +-------------------------+
                   | HW Addr of Sender       | 6 bytes
                   +-------------------------+
                   | Protocol Addr of Sender | 4 bytes
                   +-------------------------+
                   | HW Addr of Target       | 6 bytes
                   +-------------------------+
                   | Protocol Addr of Target | 4 bytes
                   +-------------------------+
                                        Total 28 bytes
                    Fig. 9 ARP Packet Format

4.3 ARP Layer Mapping and Operation

 Whenever a FC port wishes to send IP data to another FC port, then
 the following steps are taken:
    1. The source port should first consult its local mapping tables to
       determine the <destination IP address, destination WW_PN>.
    2. If such a mapping is found, then the source sends the IP
       data to the port whose WW_PN address was found in the table.
    3. If such a mapping is not found, then the source sends an
       ARP Request broadcast to its connected FC network in
       anticipation of getting a reply from the correct destination
       along with its WW_PN.
    4. When an ARP Request Broadcast frame is received by a node with
       the matching IP address, it generates an ARP Reply.  Since the
       ARP Reply must be addressed to a specific destination Port_ID,
       the FC layer mapping between the WW_PN and Port_ID (of the ARP
       Request orginator) MUST be valid before the reply is sent.
    5. If no node has the matching IP address, the result is a silent
       behavior.

Rajagopal, et al. Standards Track [Page 15] RFC 2625 IP and ARP over Fibre Channel June 1999

4.4 ARP Broadcast in a Point-to-Point Topology

 The ARP Request (Broadcast) and Reply mechanism described above still
 apply, although there is only one node that receives the ARP Request.

4.5 ARP Broadcast in a Private Loop Topology

 In a private loop, the ARP Request Broadcast frame is sent using the
 broadcast method specified in the FC-AL [7]standard.
    1. The source port first sends an Open Broadcast Replicate
       primitive (OPN(fr))Signal forcing all the ports in the loop
       (except itself), to replicate the frames that they receive
       while examining the frame header's Destination_ID field.
    2. The source port then removes this OPN(fr) signal when it
       returns to it.
    3. The loop is now ready to receive the ARP broadcast.  The source
       now sends the ARP Request as a single-frame Broadcast Sequence
       in a Class 3 frame with the following FC Header D_ID field and
       F_CTL bits setting:
  Destination ID <Word 0, bit 0:23>: D_ID = 0xFF-FF-FF
  Sequence Initiative <Word 2, bit23>: SI=0
  Last Sequence <Word 2, bit 20>: LS=1
  End Sequence <Word 2, bit 19>: ES=1.
    4. A compliant ARP Broadcast Sequence frame SHALL include the
       Network_Header with destination MAC address set to 0xFF-FF-FF-
       FF-FF-FF and with NAA = b'0001'
    5. The destination port recognizing its IP address in the ARP
       Request packet SHALL respond with an ARP Reply.

4.6 ARP Broadcast in a Public Loop Topology

 The following steps will be followed when a port is configured in a
 public loop:
    1. A public loop device attached to a fabric through a FL_Port
       MUST NOT use the OPN(fr) signal primitive. Rather, it sends the
       broadcast sequence to the FL_Port at AL_PA = 0x00.

Rajagopal, et al. Standards Track [Page 16] RFC 2625 IP and ARP over Fibre Channel June 1999

    2. A FC Fabric propagates the broadcast to all other ports
       including the FL_Port which the broadcast arrived on. This
       includes all F_Ports, and other FL_Ports.
    3. On each FL_Port, the fabric propagates the broadcast by first
       using the primitive signal OPNfr, in order to prepare the loop
       to receive the broadcast sequence.
    4. A Broadcast Sequence is now sent on all ports (all FL_ports,
       F_Ports) in Class 3 frame with:
  Destination ID <Word 0, bit 23:0>: D_ID = 0xFF-FF-FF
  Sequence Initiative <Word 2, bit23>: SI=0
  Last Sequence <Word 2, bit 20>: LS=1
  End Sequence <Word 2, bit 19>: ES=1.
    5. A compliant ARP Broadcast Sequence frame SHALL include the
       Network_Header with destination MAC address set to 0xFF-FF-FF-
       FF-FF-FF and with NAA = b'0001'
    6. The destination port recognizing its IP address in the ARP
       Request packet SHALL respond with an ARP Reply.

4.7 ARP Operation in a Fabric Topology

    1. Nodes directly attached to fabric do not require the OPN(fr)
       primitive signal.
    2. A Broadcast Sequence is now sent on all ports (all FL_ports,
       F_Ports) in Class 3 frame with:
           Destination ID <Word 0, bit 23:0>: D_ID = 0xFF-FF-FF
           Sequence Initiative <Word 2, bit23>: SI=0
           Last Sequence <Word 2, bit 20>: LS=1
           End Sequence <Word 2, bit 19>: ES=1.
    3. A compliant ARP Broadcast Sequence frame SHALL include the
       Network_Header with destination MAC address set to
       0xFF-FF-FF-FF-FF-FF and with NAA = b'0001'
    4. The destination port recognizing its IP address in
       the ARP packet SHALL respond with an ARP Reply.

Rajagopal, et al. Standards Track [Page 17] RFC 2625 IP and ARP over Fibre Channel June 1999

5. FARP

5.1 Scope

 FC Layer Mapping between the WW_PN and the Port_ID is independent of
 the ARP mechanism and is more closely associated with the details of
 the FC protocols. Name Server and FC Address Resolution Protocol
 (FARP) are two formal mechanisms that can be used to create and
 maintain WW_PN to Port_ID tables.
 FARP is a method using Extended Link Service (ELS) commands that
 resolves <WW_PN, Port_ID> mappings. The WW_PN to Port_ID address
 resolution using FARP is especially useful in instances where the
 Login table entries at a node expire and a Name Server is not
 available.  It is outside the scope of this document to describe Name
 Server. (See [14].)
 Additional address matching mechanisms that resolve <WW_NN, Port_ID>
 and <IP addr., Port_ID> mapping have been added to FARP. These
 additional mechanisms are optional and described in Appendix A.
 Direct IP address to Port_ID mapping is useful in applications where
 there is no visibility of the MAC address.
 Other less formal FC Layer Mapping mechanisms are described in
 Appendix C.
 Since Port_IDs are volatile, all mapped Port_IDs  at all times MUST
 be valid before use. There are many events that can invalidate this
 mapping. Appendix D discusses conditions when such a validation is
 required.

5.2 FARP Overview

 The FARP protocol uses two ELS commands - FARP-REQ and FARP-REPLY.
 Note: In the following discussion 'Requester' means the node
    issuing the FARP-REQ ELS message; 'Responder' means the
    node replying to the request by sending the FARP-REPLY
    command.
 The FARP-REQ ELS Broadcast Request command is used to retrieve a
 specific node's current Port_ID given its unique WW_PN. This Port_ID
 is sent in a FARP-REPLY unicast command.
 The FARP-REQ may indicate that the Responder:

Rajagopal, et al. Standards Track [Page 18] RFC 2625 IP and ARP over Fibre Channel June 1999

  1. Perform only a Login with it (Requester) or,
  2. Send only a FARP-REPLY or,
  3. Perform a Login and send a FARP-REPLY.
 No sequence initiative is transferred with the FARP-REQ and therefore
 no Reply (ACCEPT or REJECT) follows this command.
 Since a Sequence Initiative is transferred with the FARP-REPLY,
 either a ACCEPT or REJECT follows this command as a response.
 Reception of a FARP-REQ requires a higher level entity at the
 responding node to send a FARP-REPLY or perform a Port Login.
 You do not have to be logged in to issue a FARP Request. Also, you do
 not have to be logged in to the FARP Requester to issue a FARP-REPLY.
 The FARP Protocol Steps:
      FARP-REQ (ELS broadcast) Request Sequence
           (No Reply Sequence)
      FARP-REPLY (ELS command) Sequence
           Accept/Reject Reply Sequence
 The FARP Protocol Format [2] and Size:
        FT_1, 76-bytes fixed size
 The FARP Protocol Addressing:
  1. In a FARP-REQ, the S_ID in the FC Header designates the

Requester's Port ID. The D_ID in the FC Header is the broadcast

    identifier 0xFF-FF-FF.
  1. In a FARP-REPLY, the S_ID in the FC Header designates the

Responder's Port_ID. The D_ID in the FC Header is the Requester's

    Port_ID.

Rajagopal, et al. Standards Track [Page 19] RFC 2625 IP and ARP over Fibre Channel June 1999

5.3 FARP Command Format

 FARP-REQ and FARP-REPLY commands have identical formats (76-bytes
 fixed size) and fields but use different command codes. See tables
 below.

+———————————————————————+ | FARP-REQ Command | +————————————-+———+———————+ | Field | Size | Remarks | | | (Bytes) | | +————————————-+———+———————+ | 0x54-00-00-00 | 4 | Request Command Code| +————————————-+———+———————+ | Match Address Code Points | 1 | Indicates Address | | | | Matching Mechanism | +————————————-+———+———————+ | Port_ID of Requester | 3 | Supplied by | | | | Requester = | | | | S_ID in FC Header | +————————————-+———+———————+ | Responder Flags | 1 | Response Action to | | | | be taken | +————————————-+———+———————+ | Port_ID of Responder | 3 | Set to 0x00-00-00 | +————————————-+———+———————+ | WW_PN of Requester | 8 |Supplied by Requester| +————————————-+———+———————+ + WW_NN of Requester | 8 |OPTIONAL; | | | |See Appendix A | +————————————-+———+———————+ | WW_PN of Responder | 8 |Supplied by Requester| +————————————-+———+———————+ | WW_NN of Responder | 8 |OPTIONAL; see App. A | +————————————-+———+———————+ | IP Address of Requester | 16 |OPTIONAL; see App. A | +————————————-+———+———————+ | IP Address of Responder | 16 |OPTIONAL; see App. A | +————————————-+———+———————+

Rajagopal, et al. Standards Track [Page 20] RFC 2625 IP and ARP over Fibre Channel June 1999

+———————————————————————+ | FARP-REPLY Command | +————————————-+———+———————+ | Field | Size | Remarks | | | (Bytes) | | +————————————-+———+———————+ | 0x55-00-00-00 | 4 | Reply Command Code | +————————————-+———+———————+ | Match Address Code Points | 1 | Not Used and | | | | Unchanged from the | | | | FARP-REQ | +————————————-+———+———————+ | Port_ID of Requester | 3 | Extracted from | | | | FARP-REQ | +————————————-+———+———————+ | Responder Flags | 1 | Not Used and | | | | Unchanged from the | | | | FARP-REQ | +————————————-+———+———————+ | Port_ID of Responder | 3 | Supplied by | | | | Responder = | | | | S_ID in FC Header | +————————————-+———+———————+ |WW_PN of Requester | 8 |Supplied by Requester| +————————————-+———+———————+ |WW_NN of Requester | 8 |OPTIONAL; see App. A | +————————————-+———+———————+ |WW_PN of Responder | 8 |Supplied by Requester| +————————————-+———+———————+ |WW_NN of Responder | 8 |OPTIONAL; see App. A | +————————————-+———+———————+ |IP Add. of Requester | 16 |OPTIONAL; see App. A | +————————————-+———+———————+ |IP Address of Responder | 16 |OPTIONAL; see App. A | +————————————-+———+———————+

 Following is a description of the address fields in the FARP
 Commands.
 Port_ID of Requester:
 It is the 24-bit Port_ID used in the S_ID field of the FC Header of a
 FARP-REQ.  It is supplied by the Requester in a FARP-REQ and retained
 in a FARP-REPLY.

Rajagopal, et al. Standards Track [Page 21] RFC 2625 IP and ARP over Fibre Channel June 1999

 Port_ID of Responder:
 It is the 24-bit Port_ID used in the S_ID field of the FC Header of a
 FARP-REPLY.  It SHALL be set to 0x00-00-00 in a FARP-REQ. It is
 supplied by the Responder in a FARP-REPLY.
 WW_PN:
 This address field is used with the b'001', b'011', b'101, b'111',
 Match Address Code Points. See Match Address Code Point Table below.
 The Requester supplies the unique 8-byte WW_PN of the Requester and
 the Responder. It is retained in a FARP-REPLY.
 WW_NN:
 The WW_NN address field is used with Match Address Code Points
 b'010', b'011', b'110', and b'111', which are all optional. Its usage
 is fully described in Appendix A. When the WW_NN field is not used it
 SHALL be either set to '0' or a valid non-zero address.
 IPv4:
 The IPv4 address field is used with the Match Address Code Points
 b'100', b'101', b'110', and b'111', which are all optional. Its usage
 is fully described in Appendix A. When the IP Address field is not
 used it SHALL be either set to '0' or a valid IP address. A valid IP
 address consists of the 32-bit IPv4 Address with the upper 96 bits
 set to '0'.

5.4 Match Address Code Points

 For each receipt of the FARP-REQ Broadcast ELS, the recipients match
 one or more addresses based on the encoded bits of the "FARP Match
 Address Code Points" field shown in the table below. FARP operation
 with the Match Address Code Point equal to b'001' is described in
 this section. Other code points are OPTIONAL and are discussed in
 Appendix A. The upper 5 bits of the Match Address Code Point byte are
 unused and their use is not currently defined.

Rajagopal, et al. Standards Track [Page 22] RFC 2625 IP and ARP over Fibre Channel June 1999

+——————————————————————+ | Match Address Code Points | +——————————————————————+ | LSBits | Bit name | Action | +———–+——————–+———————————+ | 000 | Reserved | | +———–+——————–+———————————+ | 001 | MATCH_WW_PN | If 'WW_PN of Responder' = | | | | Node's WW_PN then respond | +———–+——————–+———————————+ | 010 | MATCH_WW_NN | OPTIONAL; see Appendix A | +———–+——————–+———————————+ | 011 | MATCH_WW_PN_NN | OPTIONAL; see Appendix A | +———–+——————–+———————————+ | 100 | MATCH_IPv4 | OPTIONAL; see Appendix A | +———–+——————–+———————————+ | 101 | MATCH_WW_PN_IPv4 | OPTIONAL; see Appendix A | +———–+——————–+———————————+ | 110 | MATCH_WW_NN_IPv4 | OPTIONAL; see Appendix A | +———–+——————–+———————————+ | 111 | MATCH_WW_PN_NN_IPv4| OPTIONAL; see Appendix A | +———–+——————–+———————————+

 When a node receives a FARP-REQ with Code Point b'001', it checks its
 WW_PN against the one set in 'WW_PN of Responder' field of the FARP-
 REQ command.  If there is a match, then the node issues a response
 according to the action indicated by the FARP Responder Flag.  See
 table below.
 WW_NN and IPv4 address fields are not used with the b'001' Code Point
 operation.  They SHALL be set to '0' or a valid address either by the
 Requester or the Requester and the Responder.
 Note that there can be utmost one FARP-REPLY per FARP-REQ.

5.5 Responder Flags

 The Responder Flags define what Responder action to take if the
 result of the Match Address Code Points is successful. 'Responder
 Flags' is an 8-bit field (bits 0-7) and is defined in the table
 below. This field is used only in a FARP-REQ.  This field is retained
 unchanged in a FARP-REPLY. If no bits are set, the Responder will
 take no action.

Rajagopal, et al. Standards Track [Page 23] RFC 2625 IP and ARP over Fibre Channel June 1999

+———-+——————————————————-+ | | FARP Responder Flag | +———-+—————-+————————————–+ | Bit | Bit Name | Action | | Position | | | +———-+—————-+————————————–+ | 0 | INIT_P_LOGI | Initiate a P_LOGI to the Requester | +———-+—————-+————————————–+ | 1 | INIT_REPLY | Send FARP_REPLY to Requester | +———-+—————-+————————————–+ | 2 to 7 | Reserved | | +———-+—————-+————————————–+

 If INIT_P_LOGI bit is set then, a Login is performed with the port
 identified by "Port_ID of Requester" field.
 If INIT_REPLY is set then, a FARP-REPLY is sent to the Port
 Identified by "Port_ID of Requester" field.
 If both bits are set at the same time, then both Actions are
 performed.
 All other bit patterns are undefined at this time and are reserved
 for possible future use.

5.6 FARP Support Requirements

 Responder action - FARP-REPLY and/or Port Login - for a successful
 MATCH_WW_PN is always REQUIRED. If there is no address match then a
 silent behavior is specified.
 Support for all other Match Address Code Points is OPTIONAL and a
 silent behavior from the Responder is valid when it is not supported.
 Recipients of the FARP-REQ ELS SHALL NOT issue a Service Reject
 (LS_RJT) if FARP OPTIONAL mechanisms are not supported.
 In all cases, if there are no matches, then a silent behavior is
 specified.
 If an implementation issues a FARP-REQ with a Match Address Code
 Point that is OPTIONAL, and fails to receive a response, and the
 implementation has not obtained the Port_ID of the Responder's port
 by other means (e.g., prior FARP-REQ with other Code Points), then
 the implementation SHALL reattempt the FARP-REQ with the MATCH_WW_PN
 Code Point.

Rajagopal, et al. Standards Track [Page 24] RFC 2625 IP and ARP over Fibre Channel June 1999

 Getting multiple FARP Replies corresponding to a single FARP-REQ
 should normally never occur.  It is beyond the scope of this document
 to specify conditions under which this error may occur or what the
 corrective action ought to be.

6. Exchange Management

6.1 Exchange Origination

 FC Exchanges shall be established to transfer data between ports.
 Frames on IP exchanges shall not transfer Sequence Initiative. See
 Appendix E for a discussion on FC Exchanges.

6.2 Exchange Termination

 With the exception of the recommendations in Appendix F, Section F.1,
 "Reliability in Class 3", the mechanism for aging or expiring
 exchanges based on activity, timeout, or other method is outside the
 scope of this document.
 Exchanges may be terminated by either port. The Exchange Originator
 may terminate Exchanges by setting the LS bit, following normal FC
 standard FC-PH [2] rules. This specification prohibits the use of the
 NOP ELS with LS set for Exchange termination.
 Exchanges may be torn down by the Exchange Originator or Exchange
 Responder by using the ABTS_LS protocol. The use of ABTS_LS for
 terminating aged Exchanges or error recovery is outside the scope of
 this document.
 The termination of IP Exchanges by Logout is discouraged, since this
 may terminate active Exchanges on other FC-4s.

7. Summary of Supported Features

 Note: 'Settable' means support is as specified in the relevant
 standard; all other key words are as defined earlier in this
 document.

7.1 FC-4 Header

+——————————————————————–+ | Feature | Support | Notes | +——————————————————————–+ | Type Code ( = 5) ISO8802-2 LLC/SNAP | REQUIRED | 2 | | Network_Headers | REQUIRED | 3 | | Other Optional Headers | MUST NOT | | +——————————————————————–+

Rajagopal, et al. Standards Track [Page 25] RFC 2625 IP and ARP over Fibre Channel June 1999

 Notes:
    1. This table applies only to FC-4 related data, such as IP and
       ARP packets. This table does not apply to link services and
       other non-FC-4 sequences (PLOGI, for example) that must occur
       for normal operation.
    2. The TYPE field in the FC Header (Word 2 bits 31-24) MUST
       indicate ISO 8802-2 LLC/SNAP Encapsulation (Type 5). This
       revision of the document focuses solely on the issues related
       to running IP and ARP over FC. All other issues are outside
       the scope of this document, including full support for IEEE
       802.2 LLC.
    3. DF_CTL field (Word 3, bits 23-16 of FC-Header) MUST indicate
       the presence of a Network_Header (0010 0000) on the First
       logical Frame of FC-4 Sequences.  It should not indicate the
       presence of a Network_Header on any subsequent frames of the
       Sequence.

7.2 R_CTL

 R_CTL in FC-Header: Word 0, bits 31-24

+——————————————————————–+ | Feature | Support | Notes | +——————————————————————–+ | Information Category (R_CTL Routing): | | | | | | | | FC-4 Device Data | REQUIRED | 1 | | Extended Link Data | REQUIRED | | | FC-4 Link Data | MUST NOT | | | Video Data | MUST NOT | | | Basic Link Data | REQUIRED | | | Link Control | REQUIRED | | | | | | | R_CTL information : | | | | | | | | Uncategorized | MUST NOT | | | Solicited Data | MUST NOT | | | Unsolicited Control | REQUIRED | | | Solicited Control | REQUIRED | | | Unsolicited Data | REQUIRED | 1 | | Data Descriptor | MUST NOT | | | Unsolicited Command | MUST NOT | | | Command Status | MUST NOT | | +——————————————————————–+

Rajagopal, et al. Standards Track [Page 26] RFC 2625 IP and ARP over Fibre Channel June 1999

 Notes:
    1. This is REQUIRED for FC-4 (IP and ARP) packets
  1. Routing bits of R_CTL field MUST indicate Device Data

frames (0000)

  1. Information Category of R_CTL field MUST indicate

Unsolicited Data (0100)

7.3 F_CTL

 F_CTL in FC-Header: Word 2, bits 23-0

+——————————————————————–+ | Feature | Support | Notes | +——————————————————————–+ | Exchange Context | Settable | | | Sequence Context | Settable | | | First / Last / End Sequence (FS/LS/ES) | Settable | | | Chained Sequence | MUST NOT | | | Sequence Initiative (SI) | Settable | 1 | | X_ID Reassigned / Invalidate | MUST NOT | | | Unidirectional Transmit | Settable | | | Continue Sequence Condition | REQUIRED | 2 | | Abort Seq. Condition -continue and single Seq.| REQUIRED | 3 | | Relative Offset - Unsolicited Data | Settable | 4 | | Fill Bytes | Settable | | +——————————————————————–+

 Notes
    1. For FC-4 frames, each N_Port shall have a dedicated OX_ID for
       sending data to each N_Port in the network and a dedicated
       RX_ID for receiving data from each N_Port as well. Exchanges
       are used in a unidirectional mode, thus setting Sequence
       Initiative is not valid for FC-4 frames. Sequence Initiative is
       valid when using Extended Link Services.
    2. This field is required to be 00, no information.
    3. Sequence error policy is requested by an exchange originator in
       the F_CTL Abort Sequence Condition bits in the first data frame
       of the exchange. For Classes 1 and 2, ACK frame is required to
       be "continuous sequence".
    4. Relative offset prohibited on all other types (Information
       Category) of frames.

Rajagopal, et al. Standards Track [Page 27] RFC 2625 IP and ARP over Fibre Channel June 1999

7.4 Sequences

+———————————————————————+ | Feature | Support |Notes | +———————————————————————+ | Class 2 open Sequences / Exchange | 1 | 1 | | Length of Seq. not limited by end-to-end credit | REQUIRED | 2 | | IP and ARP Packet and FC Data Field sizes | REQUIRED | 3 | | Capability to receive Sequence of maximum size | OPTIONAL | 4 | | Sequence Streaming | MUST NOT | 5 | | Stop Sequence Protocol | MUST NOT | | | ACK_0 support | OPTIONAL | 6 | | ACK_1 support | REQUIRED | 6 | | ACK_N support | MUST NOT | | | Class of Service for transmitted Sequences | Class | 7 | | | 1, 2, or 3 | | | Continuously Increasing Sequence Count | OPTIONAL | 8, 9 | +———————————————————————+

 Notes:
    1. Only one active sequence per exchange is optional.
    2. A Sequence Initiator shall be capable of transmitting Sequences
       containing more frames than the available credit indicated by a
       Sequence recipient at Login. FC-PH [2] end-to-end flow control
       rules will be followed when transmitting such Sequences.
    3.  a) IP MTU size is 65280-bytes and resulting FC Sequence
           Payload size is 65536-bytes.
        b) Maximally Minimum IP Packet size is 68-bytes and resulting
           FC Data Field size is 92-bytes.
        c) ARP (and InARP) Packet size is 28-bytes and resulting FC
           Data Field size is 52-bytes.
    4. Some OS environments may not handle the max Sequence Payload
       size of 65536. It is up to the administrator to configure the
       Max size for all systems.
    5. All class 3 sequences are assumed to be non-streamed.
    6. Only applies for Class 1 and 2. Use of ACK_1 is default, ACK_0
       used if indicated by Sequence recipient at Login.
    7. The administrator configured class of service is used, except
       where otherwise specified (e.g. Broadcasts are always sent in
       Class 3).

Rajagopal, et al. Standards Track [Page 28] RFC 2625 IP and ARP over Fibre Channel June 1999

    8. Review Appendix F, "Reliability in Class 3".
    9. The first frame of the first sequence of a new Exchange must
       have SEQ_CNT = 0 [2].

7.5 Exchanges

+——————————————————————–+ | Feature | Support | Notes | +——————————————————————–+ | X_ID interlock support | OPTIONAL | 1 | | OX_ID=FFFF | MUST NOT | | | RX_ID=FFFF | OPTIONAL | 2 | | Action if no exchange resources available | P_RJT | 3 | | Long Lived Exchanges | OPTIONAL | 4 | | Reallocation of Idle Exchanges | OPTIONAL | | +——————————————————————–+

 Notes:
    1. Only applies to Classes 1 and 2, supported by the Exchange
       Originator. A Port SHALL be capable of interoperating with
       another Port that requires X_ID interlock. The Exchange
       Originator facility within the Port shall use the X_ID
       Interlock protocol in such cases.
    2. An Exchange Responder is not required to assign RX_IDs. If a
       RX_ID of FFFF is assigned, it is identifying Exchanges based on
       S_ID / D_ID / OX_ID only.
    3. In Classes 1 and 2, a Port shall reject a frame that would
       create a new Exchange with a P_RJT containing reason code
       "Unable to establish Exchange". In Class 3, the frame would be
       dropped.
    4. When an Exchange is created between 2 Ports for IP/ARP data, it
       remains active while the ports are logged in with each other.
       An Exchange SHALL NOT transfer Sequence Initiative (SI).
       Broadcasts and ELS commands may use short lived Exchanges.

Rajagopal, et al. Standards Track [Page 29] RFC 2625 IP and ARP over Fibre Channel June 1999

7.6 ARP and InARP

+——————————————————————–+ | Feature | Support | Notes | +——————————————————————–+ | ARP Server Support | MUST NOT | 1 | | Response to ARP requests | REQUIRED | 2 | | Class of Service for ARP requests | Class 3 | 3 | | Class of Service for ARP replies | Class | 4 | | | 1, 2, or 3 | | | Response to InARP requests | OPTIONAL | | | Class of Service for InARP requests/replies | Class | | | | 1, 2 or 3 | 5 | +——————————————————————–+

Notes:

    1. Well-known Address FFFFFC is not used for ARP requests. Frames
       from Well-known address FFFFFC are not considered to be ARP
       frames. Broadcast support is REQUIRED for ARP.
    2. The IP Address is mapped to a specific MAC address with ARP.
    3. An ARP request is a Broadcast Sequence, therefore Class 3
       is always used.
    4. An ARP reply is a normal Sequence, thus the administrator
       configured class of service is used.
    5. An InARP Request or Reply is a normal Sequence, thus an
       administrator configured class of service is used.

Rajagopal, et al. Standards Track [Page 30] RFC 2625 IP and ARP over Fibre Channel June 1999

7.7 Extended Link Services (ELS)

+——————————————————————–+ | Feature | Support | Notes | +——————————————————————–+ | Class of service for ELS commands / responses | Class | | | | 1,2 or 3 | 1 | | Explicit N-Port Login | REQUIRED | | | Explicit F-Port Login | REQUIRED | | | FLOGI ELS command | REQUIRED | | | PLOGI ELS command | REQUIRED | | | ADISC ELS command | REQUIRED | | | PDISC ELS command | OPTIONAL | 2 | | FAN ELS command | REQUIRED | 5 | | LOGO ELS command | REQUIRED | | | FARP-REQ/FARP-REPLY ELS commands | REQUIRED | 3 | | Other ELS command support | OPTIONAL | 4 | +———————————————–+————+——-+

 Notes:
    1. The administrator configured class of service is used.
    2. PDISC shall not be used as a Requester; ADISC shall be used
       instead. As a Responder, an implementation may need to respond
       to both ADISC and PDISC for compatibility with other
       specifications.
    3. Responder Action - FARP-REPLY and/or Port Login - for a
       successful MATCH_WW_PN is always REQUIRED.
       Support for all other match Address Codes Points is a silent
       behavior from the Responder is valid when it is not supported.
       Recipients of the FARP-REQ ELS shall not issue a Service Reject
       (LS_RJT) if FARP is not supported.
    4. If other ELS commands are received an LS_RJT may be sent. NOP
       is not required by this specification, and shall not be used as
       a mechanism to terminate exchanges.
    5. Required for FL_Ports

7.8 Login Parameters

 Unless explicitly noted here, a compliant implementation shall use
 the login parameters as described in [4].

Rajagopal, et al. Standards Track [Page 31] RFC 2625 IP and ARP over Fibre Channel June 1999

7.8.1 Common Service Parameters - FLOGI

  1. FC-PH Version, lowest version may be 0x09 to indicate

'minimum 4.3'.

  1. Can't use BB_Credit=0 for N_Port on a switched Fabric

(F_Port).

7.8.2 Common Service Parameters - PLOGI

  1. FC-PH Version, lowest version may be 0x09 to indicate

'minimum 4.3'.

  1. Can't use BB_Credit=0 for N_Port in a Point-to-Point

configuration

  1. Random Relative Offset is optional.
  1. Note that the 'Receive Data Field Size' fields specified in

the PLOGI represent both optional headers and payload.

  1. The MAC Address can therefore be extracted from the 6 lower

bytes of the WW_PN field (when the IEEE 48-bit Identifier

   format is chosen as the NAA) during PLOGI or ACC payload
   exchanged during Fibre Channel Login [2].
  1. The MAC Address can also be extracted from the WW_PN field in

the Network_Header during ADISC (and ADISC ACC), or PDISC

   (and PDISC ACC).

7.8.3 Class Service Parameters - PLOGI

  1. Discard error policy only.

8. Security Considerations

8.1 IP and ARP Related

 IP and ARP do not introduce any new security concerns beyond what
 already exists within the Fibre Channel Protocols and Technology.
 Therefore IP and ARP related Security does not require special
 consideration in this document.

8.2 FC Related

 FC Standards [11] specify a Security Key Server (independent of IP
 and ARP) as an optional service. However, there are no known
 implementations of this server yet. Also, the previously defined [2]
 use of a Security Header has been discontinued [11].

Rajagopal, et al. Standards Track [Page 32] RFC 2625 IP and ARP over Fibre Channel June 1999

9. Acknowledgement

 This specification is based on FCA IP Profile, Version 3.3.  The FCA
 IP Profile was a joint work of the Fibre Channel Association (FCA)
 vendor community.  The following organizations or individuals have
 contributed to the creation of the FCA IP Profile: Adaptec, Ancor,
 Brocade, Clariion, Crossroads, emf Associates, Emulex, Finisar,
 Gadzoox, Hewlett Packard, Interphase, Jaycor, McData, Migration
 Associates, Orca Systems, Prisa, Q-Logic, Symbios, Systran,
 Tektronix, Univ. of Minnesota, Univ. of New Hamshire. Jon Infante
 from Emulex deserves special mention for his contributions to the
 FARP Protocol. The authors extend their thanks to all who provided
 comments and especially to Lansing Sloan from LLNL for his detailed
 comments.

10. References

 [1] FCA IP Profile, Revision 3.3, May 15, 1997
 [2] Fibre Channel Physical and Signaling Interface (FC-PH) , ANSI
     X3.230-1994
 [3] Fibre Channel Link Encapsulation (FC-LE), Revision 1.1, June 26,
     1996
 [4] Fibre Channel Fabric Loop Attachment (FC-FLA), Rev. 2.7, August
     12, 1997
 [5] Fibre Channel Private Loop SCSI Direct Attach (FC-PLDA),
     Rev. 2.1, September 22, 1997
 [6] Fibre Channel Physical and Signaling Interface-2 (FC-PH-2),
     Rev. 7.4, ANSI X3.297-1996
 [7] Fibre Channel Arbitrated Loop (FC-AL), ANSI X3.272-1996
 [8] Postel, J. and J. Reynolds, "A standard for the Transmission of
     IP Datagrams over IEEE 802 Networks", STD 43, RFC 1042, February
     1988.
 [9] Plummer, D. "An Ethernet Address Resolution Protocol -or-
     Converting Network Addresses to 48-bit Ethernet Address for
     Transmission on Ethernet Hardware", STD 37, RFC 826, November
     1982.
 [10] FCSI IP Profile, FCSI-202, Revision 2.1, September 8, 1995

Rajagopal, et al. Standards Track [Page 33] RFC 2625 IP and ARP over Fibre Channel June 1999

 [11] Fibre Channel Physical and Signaling Interface -3 (FC-PH-3),
      Rev. 9.3, ANSI X3.303-199x
 [12] Fibre Channel-The Basics, "Gary R. Stephens and Jan V. Dedek",
      Ancot Corporation
 [13] Fibre Channel -Gigabit Communications and I/O for Computers
      Networks "Alan Benner", McGraw-Hill, 1996, ISBN 0-07-005669-2
 [14] Fibre Channel Generic Services -2 (FC-GS-2), Rev. 5.2
      X3.288-199x
 [15] Bradley, T. and C. Brown, "Inverse Address Resolution Protocol",
      RFC 1293, January 1992.
 [16] Bradley, T., Brown, C. and A. Malis, "Inverse Address Resolution
      Protocol", RFC 2390, August 1992.
 [17] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981.
 [18] The Fibre Channel Consultant: A Comprehensive Introduction,
      "Robert W. Kembel", Northwest Learning Associates, 1998
 [19] Bradner, S., "Key Words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
 [20] Narten, T. and C. Burton, "A Caution on The Canonical Ordering
      of Link-Layer Addresses",  RFC 2469, December 1998.

Rajagopal, et al. Standards Track [Page 34] RFC 2625 IP and ARP over Fibre Channel June 1999

11. Authors' Addresses

 Murali Rajagopal
 Gadzoox Networks, Inc.
 711 Kimberly Avenue, Suite 100
 Placentia, CA 92870
 Phone: +1 714 577 6805
 Fax: +1 714 524 8508
 EMail: murali@gadzoox.com
 Raj Bhagwat
 Gadzoox Networks, Inc.
 711 Kimberly Avenue, Suite 100
 Placentia, CA 92870
 Phone: +1 714 577 6806
 Fax: +1 714 524 8508
 EMail: raj@gadzoox.com
 Wayne Rickard
 Gadzoox Networks, Inc.
 711 Kimberly Avenue, Suite 100
 Placentia, CA 92870
 Phone: +1 714 577 6803
 Fax: +1 714 524 8508
 EMail: wayne@gadzoox.com

Rajagopal, et al. Standards Track [Page 35] RFC 2625 IP and ARP over Fibre Channel June 1999

Appendix A: Additional Matching Mechanisms in FARP

 Section 5 described the FC Layer mapping between the WW_PN and the
 Port_ID using the FARP Protocol. This appendix describes other
 optional criteria for address matching and includes:
  1. WW_NN
  1. WW_PN & WW_NN at the same time
  1. IPv4
  1. IPv4 & WW_PN at the same time
  1. IPv4 & WW_NN at the same time
  1. IPv4 & WW_PN & WW_NN at the same time
 Depending on the Match Address Code Points, the FARP protocol
 fundamentally resolves three main types of addresses to Port_IDs and
 is described in table below.
  1. For Match Address Code Point b'001': WW_PN Names fields are

used to resolve the WW_PN names to Port_IDs. WW_NN and IP

      address fields are not used with these Code Points and SHALL be
      set to either '0' or valid addresses by Requester or Requester
      and Responder.
  1. For Match Address Code Point b'010': WW_NN Names fields are

used to resolve the WW_NN names to Port_IDs. WW_PN and IP

      address fields are not used with these Code Points and SHALL be
      set to either '0' or valid addresses by Requester or Requester
      and Responder.
  1. For Match Address Code Point b'100': IPv4 fields are used to

resolve the IPv4 addresses to Port_IDs. WW_PN and WW_NN fields

      are not used with these Code Points and SHALL be set to either '
      0' or valid addresses by Requester or Requester and Responder.
  1. For all other Match Address Code Points b'011', b'101',b'110',

b'111', depending on set bits one or more addresses are jointly

      resolved to a Port_ID. See table below. If fields are not used,
      then they are set either to '0' or valid addresses.
 The Responder Flags remain the same as before. Note that there can be
 utmost one FARP-REPLY per FARP-REQ.

Rajagopal, et al. Standards Track [Page 36] RFC 2625 IP and ARP over Fibre Channel June 1999

 Tables showing FARP-REQ and FARP-REPLY and address fields setting are
 given below:

+——————————————————————–+ | Match Address Code Points | +——————————————————————–+ | LSBits| Bit name | Action | +——-+——————–+—————————————+ | 000 | Reserved | | +——-+——————–+—————————————+ | 001 | MATCH_WW_PN | If 'WW_PN of Responder' = | | | | Node's WW_PN then respond | +——-+——————–+—————————————+ | 010 | MATCH_WW_NN | If 'WW_NN of Responder' = | | | | Node's WW_NN then respond | +——-+——————–+—————————————+ | 011 | MATCH_WW_PN_NN | If both 'WW_PN of Responder' & | | | | 'WW_NN of Responder' = | | | | Node's WW_PN & WW_NN then respond | +——-+——————–+—————————————+ | 100 | MATCH_IPv4 | If 'IPv4 Address of Responder' = | | | | Node's IPv4 Address then respond | +——-+——————–+—————————————+ | 101 | MATCH_WW_PN_IPv4 | If 'WW_PN & IPv4 of Responder' = | | | | Node's WW_PN and IPv4 then respond | +——-+——————–+—————————————+ | 110 | MATCH_WW_NN_IPv4 | If both 'WW_NN of Responder' & | | | | 'IPv4 Address of Responder' = | | | | Node's WW_NN & IPv4 then respond | +——-+——————–+—————————————+ | 111 |MATCH_WW_PN_NN_IPv4 | If 'WW_PN of Responder' & | | | | 'WW_NN of Responder' & | | | | 'IPv4 Address of Responder' = | | | | Nodes' WW_PN & WW_NN & IPv4 | | | | then respond | +——-+——————–+—————————————+

Rajagopal, et al. Standards Track [Page 37] RFC 2625 IP and ARP over Fibre Channel June 1999

+———————————————————————+ | FARP-REQ Command | +——————————-+———+—————————+ | Field | Size | Remarks | | | (Bytes) | | +——————————-+———+—————————+ | 0x54-00-00-00 | 4 | Request Command Code | +——————————-+———+—————————+ | Match Address Code Points | 1 | Indicates Address | | | | Matching Mechanism | +——————————-+———+—————————+ | Port_ID of Requester | 3 |Supplied by Requester | +——————————-+———+—————————+ | Responder Flags | 1 |Response Action to be taken| +——————————-+———+—————————+ | Port_ID of Responder | 3 | Set to 0x00-00-00 | +——————————-+———+—————————+ |WW_PN of Requester | 8 | Supplied by Requester | +——————————-+———+—————————+ |WW_NN of Requester | 8 |OPTIONAL; | | | |Supplied by Requester | +——————————-+———+—————————+ |WW_PN of Responder | 8 |Supplied by Requester | +——————————-+———+—————————+ |WW_NN of Responder | 8 |OPTIONAL ;Supplied by | | | |Requester or Responder | +——————————-+———+—————————+ |IP Add. of Requester | 16 |OPTIONAL; Supplied by | | | |Requester | | | |IPv4 Add.=low 32 bits | +——————————-+———+—————————+ |IP Address of Responder | 16 |OPTIONAL; Supplied by | | | |Requester or Responder | | | |IPv4 Add.=low 32 bits | +——————————-+———+—————————+

Rajagopal, et al. Standards Track [Page 38] RFC 2625 IP and ARP over Fibre Channel June 1999

+———————————————————————+ | FARP-REPLY Command | +——————————-+———+—————————+ | Field | Size | Remarks | | | (Bytes) | | +——————————-+———+—————————+ | 0x55-00-00-00 | 4 |Reply Command Code | +——————————-+———+—————————+ | Match Address Code Points | 1 | Not Used and unchanged | | | |from the FARP-REQ | +——————————-+———+—————————+ | Port_ID of Requester | 3 |Supplied by Requester | +——————————-+———+—————————+ | Responder Flags | 1 | Not Used and unchanged | | | |from the FARP-REQ | +——————————-+———+—————————+ | Port_ID of Responder | 3 |Supplied by Responder | +——————————-+———+—————————+ |WW_PN of Requester | 8 |Supplied by Requester | +——————————-+———+—————————+ |WW_NN of Requester | 8 |OPTIONAL; Supplied by | | | |Requester | +——————————-+———+—————————+ |WW_PN of Responder | 8 |Supplied by Requester | +——————————-+———+—————————+ |WW_NN of Responder | 8 |OPTIONAL; Supplied by | | | |Requester or Responder | +——————————-+———+—————————+ |IP Add. of Requester | 16 |OPTIONAL; Supplied by | | | |Requester | | | |IPv4 Add.=low 32 bits | +——————————-+———+—————————+ |IP Address of Responder | 16 |OPTIONAL; Supplied by | | | |Requester or Responder | | | |IPv4 Add.=low 32 bits | +——————————-+———+—————————+

Rajagopal, et al. Standards Track [Page 39] RFC 2625 IP and ARP over Fibre Channel June 1999

Appendix B: InARP

B.1 General Discussion

 Inverse ARP (InARP) is a mechanism described in RFC 1293/2390 [15,
 16], which is useful when a node desires to know the protocol address
 of a target node whose hardware address is known. Situations where
 this could occur are described in [15, 16]. The motivation for using
 InARP in FC is to allow a node to learn the IP address of another
 node with which it has performed a Port Login (PLOGI).  PLOGI is a
 normal FC process that happens between nodes, independent of this
 standard. PLOGI makes it possible for a node to discover the WW_PN
 and the Port_ID of the other node but not its IP address. A node in
 this way may potentially obtain the IP address of all nodes with
 which it can PLOGI.
 Note that the use of the InARP mechanism can result in resolving all
 WW_PN to IP addresses and ARP may no longer be required. This can be
 beneficially applied in cases where a particular FC topology makes it
 inefficient to send out an ARP broadcast.

B.2 InARP Protocol Operation

 InARP uses the same ARP Packet format but with different 'Op Codes',
 one for InARP Request and another for InARP Reply.
 The InARP protocol operation is very simple. The requesting node
 fills the hardware address (WW_PN) of the target device and sets the
 protocol address to 0x00-00-00-00. Because, the request is sent to a
 node whose WW_PN and Port_ID are known, there is no need for a
 broadcast. The target node fills in its Protocol address (IP address
 in this case) and sends an InARP Reply back to the sender.  A node
 may collect, all such WW_PN and IP addresses pairs in a similar way.

B.3 InARP Packet Format

 Since the InARP protocol uses the same packet format as the ARP
 protocol, much of the discussion on ARP formats given in Section 4
 applies here.
 The InARP is 28-bytes long in this application and uses two packet
 types:  Request and Reply. Like ARP, the InARP Packet fields are
 common to both InARP Requests and InARP Replies.
 InARP Request and Reply Packets are encapsulated in a single frame FC
 Sequence much like ARP. Compliant InARP Request and Reply FC
 Sequences SHALL include Network_Headers.

Rajagopal, et al. Standards Track [Page 40] RFC 2625 IP and ARP over Fibre Channel June 1999

 The 'HW Type' field SHALL be set to 0x00-01.
 The 'Protocol' field SHALL be set to 0x08-00 indicating IP protocol.
 The 'HW Addr Length' field SHALL be set to 0x06 indicating 6-bytes of
 HW address.
 The 'Protocol Addr Length' field SHALL be set to 0x04 indicating
 4-bytes of IP address.
 The 'Operation' Code field SHALL be set as follows:
         0x00-08 for InARP Request
         0x00-09 for InARP Reply
 The 'HW Addr of Sender' field SHALL be the 6-byte IEEE MAC address of
 the Requester (InARP Request) or Responder (InARP Reply).
 The 'Protocol Addr of Sender' field SHALL be the 4-byte IP address of
 the Requester (InARP Request) or Responder (InARP Reply).
 The 'HW Addr of Target' field SHALL be set to the 6-byte MAC address
 of the Responder in an InARP Request and to the 6-byte MAC address of
 the Requester in an InARP Reply.
 The 'Protocol Addr of Target' field SHALL be set to 0x00-00-00-00 in
 an InARP Request and to the 4-byte IP address of the Requester in an
 InARP Reply.

B.4 InARP Support Requirements

 Support for InARP is OPTIONAL. If a node does not support InARP and
 it receives an InARP Request message then a silent behavior is
 specified.

Rajagopal, et al. Standards Track [Page 41] RFC 2625 IP and ARP over Fibre Channel June 1999

APPENDIX C: Some Informal Mechanisms for FC Layer Mappings

 Each method SHALL have some check to ensure PLOGI has completed
 successfully before data is sent. A related concern in large networks
 is limiting concurrent logins to only those ports with active IP
 traffic.

C.1 Login on Cached Mapping Information

 This method insulates the level performing Login from the level
 interpreting ARP. It is more accommodating of non-ARP mechanisms for
 building the FC-layer mapping table.
    1. Broadcast messages that carry a Network_Header contain the S_ID
       on the FC-header and WW_PN in the Network-Header.  Caching this
       information provides a correlation of Port_ID to WW_PN. If the
       received Broadcast message is compliant with this
       specification, the WW_PN will contain the MAC Address.
    2. The WW_PN is "available" if Login has been performed to the
       Port_ID and flagged. If Login has not been performed, the WW_PN
       is "unavailable".
    3. If an outbound packet is destined for a port that is
       "unavailable", the cached information (from broadcast) is used
       to look up the Port_ID.
    4. After sending an ELS PLOGI command (Port Login) to the Port
       (from a higher level entity at the host), waiting for an
       outbound packet before sending this Port Login conserves
       resources for only those ports which wish to establish
       communication.
    5. After Port Login completes (ACC received), the outbound packet
       can be forwarded. At this point in time, both ends have the
       necessary information to complete their <IP address, MAC
       Address, Port_ID> association.

C.2 Login on ARP Parsing

 This method performs Login sooner by parsing ARP before passing it up
 to higher levels for IP/MAC Address correlation. It requires a low-
 level awareness of the IP address, and is therefore protocol-
 specific.
    1. When an ARP Broadcast Message is received, the S_ID is
       extracted from the FC-header and the corresponding
       Network_Source_Address from the Network_Header.

Rajagopal, et al. Standards Track [Page 42] RFC 2625 IP and ARP over Fibre Channel June 1999

    2. The ARP payload is parsed to determine if
       (a) this host is the target of the ARP request (Target IP
           Address match), and
       (b) if this host is currently logged in with the port
           (Port_ID = S_ID) originating the ARP broadcast.
    3. The ARP is passed to a higher level for ARP Response
       generation.
    4. If a Port Login is required, an ELS PLOGI command (Port Login)
       is sent immediately to the Port originating the ARP Broadcast.
    5. After Port Login completes, an ARP response can be forwarded.
       Note that there are two possible scenarios:
  1. The ACC to PLOGI returns before the ARP reply is processed

and the ARP Reply is immediately forwarded.

  1. The ARP reply is delayed, waiting for ACC (successful

Login).

    6. At this point in time, both ends have the necessary
       information to complete their
       <IP address, MAC Address, Port_ID> association.

C.3 Login to Everyone

 In Fibre Channel topologies with a limited number of ports, it may be
 efficient to unconditionally Login to each port. This method is
 discouraged in fabric and public loop environments.
 After Port Login completes, the MAC Address to Port_ID Address tables
 can be constructed.

C.4 Static Table

 In some loop environments with a limited number of ports, a static
 mapping from a MAC Address to Port_ID (D_ID or AL_PA) may be
 maintained.  The FC layer will always know the destination Port_ID
 based on the table. The table is typically downloaded into the driver
 at configuration time. This method scales poorly, and is therefore
 not recommended.

Rajagopal, et al. Standards Track [Page 43] RFC 2625 IP and ARP over Fibre Channel June 1999

Appendix D: FC Layer Address Validation

D.1 General Discussion

 At all times, the <WW_PN, Port_ID> mapping MUST be valid before use.
 There are many events that can invalidate this mapping.  The
 following discussion addresses conditions when such a validation is
 required.
 After a FC link interruption occurs, the Port_ID of a port may
 change.  After the interruption, the Port_IDs of all other ports that
 have previously performed PLOGI (N_Port Login) with this port may
 have changed, and its own Port_ID may have changed.
 Because of this, address validation is required after a LIP in a loop
 topology [7] or after NOS/OLS in a point-to-point topology [6].
 Port_IDs will not change as a result of Link Reset (LR),thus address
 validation is not required.
 In addition to actively validating devices after a link interruption,
 if a port receives any FC-4 data frames (other than broadcast
 frames), from a port that is not currently logged in, then it shall
 send an explicit Extended Link Service (ELS) Request logout (LOGO)
 command to that port.
 ELS commands (Requests and Replies) are used by an N_Port to solicit
 a destination port (F_Port or N_Port) to perform some link-level
 function or service.) The LOGO Request is used to request
 invalidation of the service parameters and Port_ID of the recipient
 N_Port.
 The level of initialization and subsequent validation and recovery
 reported to the upper (FC-4) layers is implementation-specific.
 In general, an explicit Logout (LOGO) SHALL be sent whenever the FC-
 Layer mapping between the Port_ID and WW_PN of a remote port is
 removed.
 The effect of power-up or re-boot on the mapping tables is outside
 the scope of this specification.

Rajagopal, et al. Standards Track [Page 44] RFC 2625 IP and ARP over Fibre Channel June 1999

D.2 FC Layer Address Validation in a Point-to-Point Topology

 No validation is required after LR. In a point-to-point topology,
 NOS/OLS causes implicit Logout of each port and after a NOS/OLS, each
 port must perform a PLOGI [2].

D.3 FC Layer Address Validation in a Private Loop Topology

 After a LIP, a port SHALL not transmit any link data to another port
 until the address of the other port has been validated. The
 validation consists of completing either ADISC or PDISC. (See
 Appendix G.)
 ADISC (Address Discovery) is an ELS command for discovering the hard
 addresses - the 24-bit identifier- of NL_Ports [5], [6].
 PDISC (Discover Port) is an ELS command for exchanging service
 parameters without affecting Login state [5], [6].
 As a requester, this specification prohibits PDISC and requires
 ADISC.
 As a responder, an implementation may need to respond to both ADISC
 and PDISC for compatibility with other FC specifications.
 If the three addresses, Port_ID, WW_PN, WW_NN, exactly match the
 values prior to the LIP, then any active exchanges may continue.
 If any of the three addresses have changed, then the node must be
 explicitly Logged out [4], [5].
 If a port's N_Port ID changes after a LIP, then all active Port-ID to
 WW_PN mappings at this port must be explicitly Logged out.

D.4 FC Layer Address Validation in a Public Loop Topology

 A FAN (Fabric Address Notification) ELS command is sent by the fabric
 to all known previously logged in  ports following an initialization
 event. Therefore, after a LIP, hosts may wait for this notification
 to arrive or they may perform a FLOGI.
 If the WW_PN and WW_NN of the fabric FL_Port contained in the FAN ELS
 or FLOGI response exactly match the values before the LIP, and if the
 AL_PA obtained by the port is the same as the one before the LIP,
 then the port may resume all exchanges. If not, then FLOGI (Fabric
 Login) must be performed with the fabric and all nodes must be
 explicitly Logged out.

Rajagopal, et al. Standards Track [Page 45] RFC 2625 IP and ARP over Fibre Channel June 1999

 A public loop device will have to perform the private loop
 authentication to any nodes on the local loop which have an Area +
 Domain Address == 0x00-00-XX

D.5 FC Layer Address Validation in a Fabric Topology

 No validation is required after LR (link reset).
 After NOS/OLS, a port must perform FLOGI. If, after FLOGI, the S_ID
 of the port, the WW_PN of the fabric, and the WW_NN of the fabric are
 the same as before the NOS/OLS, then the port may resume all
 exchanges. If not, all nodes must be explicitly, Logged out [2].

Rajagopal, et al. Standards Track [Page 46] RFC 2625 IP and ARP over Fibre Channel June 1999

APPENDIX E: Fibre Channel Overview

E.1 Brief Tutorial

 The FC Standard [2] defines 5 "levels" (not layers) for its protocol
 description: FC-0, FC-1, FC-2, FC-3, and FC-4. The first three levels
 (FC-0, FC-1, FC-2) are largely concerned with the physical formatting
 and control aspects of the protocol. FC-3 has been architected to
 provide a place holder for functions that might need to be performed
 after the upper layer protocol has requested the transmission of an
 information unit, but before FC-2 is asked to deliver that piece of
 information by using a sequence of frames [18]. At this time, no FC-3
 functions have been defined.  FC-4 is meant for supporting profiles
 of Upper Layer Protocols (ULP) such as IP and Small Computer System
 Interface (SCSI), and supports a relatively small set compared to LAN
 protocols such as IEEE 802.3.
 FC devices are called "Nodes", each of which has at least one "Port"
 to connect to other ports. A Node may be a workstation, a disk drive
 or disk array, a camera, a display unit, etc.  A "Link" is two
 unidirectional paths flowing in opposite directions and connecting
 two Ports within adjacent Nodes.
 FC Nodes communicate using higher layer protocols such as SCSI and IP
 and are configured to operate using Point-to-Point, Private Loop,
 Public Loop (attachment to a Fabric), or Fabric network topologies.
 The point-to-point is the simplest of the four topologies, where only
 two nodes communicate with each other. The private loop may connect a
 number of devices (max 126) in a logical ring much like Token Ring,
 and is distinguished from a public loop by the absence of a Fabric
 Node participating in the loop. The Fabric topology is a switched
 network where any attached node can communicate with any other. For a
 detail description of FC topologies refer to [18].
 Table below summarizes the usage of port types depending on its
 location [12]. Note that E-Port is not relevant to any discussion in
 this specification but is included below for completeness.

Rajagopal, et al. Standards Track [Page 47] RFC 2625 IP and ARP over Fibre Channel June 1999

+-----------+-------------+-----------------------------------------+
| Port Type |  Location   |      Topology Associated with           |
+-----------+-------------+-----------------------------------------+
| N_Port    |   Node      |      Point-to-Point or Fabric           |
+-----------+-------------+-----------------------------------------+
| NL_Port   |   Node      |In N_Port mode -Point-to-Point or Fabric |
|           |             |In NL_Port mode - Arbitrated Loop        |
+-----------+-------------+-----------------------------------------+
| F_Port    |   Fabric    |                   Fabric                |
+-----------+-------------+-----------------------------------------+
| FL_Port   |   Fabric    | In F_Port mode - Fabric                 |
|           |             | In FL_Port mode - Arbitrated Loop       |
+-----------+-------------+-----------------------------------------+
| E_Port    |   Fabric    |     Internal Fabric Expansion           |
+-----------+-------------+-----------------------------------------+

E.2 Exchange, Information Unit, Sequence, and Frame

 The FC 'Exchange' is a mechanism used by two FC ports to identify and
 manage an operation between them [18]. An Exchange is opened whenever
 an operation is started between two ports. The Exchange is closed
 when this operation ends.
 The FC-4 Level specifies data units for each type of application
 level payload called 'Information Unit' (IU). Each protocol carried
 by FC has a defined size for the IU. Every operation must have at
 least one IU.  Lower FC levels map this to a FC Sequence.
 Typically, a Sequence consists of more than one frame. Larger user
 data is segmented and reassembled using two methods: Sequence Count
 and Relative Offset [18]. With the use of Sequence Count, data blocks
 are sent using frames with increasing sequence counts (modulo 65536)
 and it is quite straightforward to detect the first frame that
 contains the Network_Header.  When Relative Offset is used, as frames
 arrive, some computation is required to detect the first frame that
 contains the Network_Header. Sequence Count and Relative Offset field
 control information, is carried in the FC Header.
 The FC-4 Level makes a request to FC-3 Level when it wishes it to be
 delivered.  Currently, there are no FC-3 level defined functions, and
 this level simply converts the Information Unit delivery request into
 a 'Sequence' delivery request and passes it on to the FC-2 Level.
 Therefore, each FC-4 Information Unit corresponds to a FC-2 Level
 Sequence.
 The maximum data carried by a FC frame cannot exceed 2112-bytes [2].
 Whenever, the Information Unit exceeds this value, the FC-2 breaks it
 into multiple frames and sends it in a sequence.

Rajagopal, et al. Standards Track [Page 48] RFC 2625 IP and ARP over Fibre Channel June 1999

 There can be multiple Sequences within an Exchange. Sequences within
 an Exchange are processed sequentially. Only one Sequence is active
 at a time. Within an Exchange information may flow in one direction
 only or both. If bi-directional then one of the ports has the
 initiative to send the next Sequence for that Exchange. Sequence
 Initiative can be passed between the ports on the last frame of
 Sequence when control is transferred. This amounts to half-duplex
 behavior.
 Ports may have more than one Exchange open at a time. Ports can
 multiplex between Exchanges. Exchanges are uniquely identified by
 Exchange IDs (X_ID). An Originator OX_ID and a Responder RX_ID
 uniquely identify an Exchange.

E.3 Fibre Channel Header Fields

 The FC header as shown in the diagrams below contains routing and
 other control information to manage Frames, Sequences, and Exchanges.
 The Frame-header is sent as 6 transmission words immediately
 following an SOF delimiter and before the Data Field.
 D_ID and S_ID:
    FC uses destination address routing [12], [13]. Frame routing in a
    point-to-point topology is trivial.
    For the Arbitrated Loop topology, with the destination NL_Port on
    the same AL, the source port must pick the destination port,
    determine its AL Physical Address, and "Open" the destination
    port. The frames must pass through other NL_Ports or the FL_Port
    on the loop between the source and destination, but these ports do
    not capture the frames. They simply repeat and transmit the frame.
    Either communicating port may "Close" the circuit.
    When the destination port is not on the same AL, the source
    NL_Port must open the FL_Port attached to a Fabric. Once in the
    Fabric, the Fabric routes the frames again to the destination.
    In a Fabric topology, the Fabric looks into the Frame-header,
    extracts the destination address (D_ID), searches its own routing
    tables, and sends the frame to the destination port along the path
    chosen. The process of choosing a path may be performed at each
    fabric element or switch until the F_Port attached to the
    destination N_Port is reached.

Rajagopal, et al. Standards Track [Page 49] RFC 2625 IP and ARP over Fibre Channel June 1999

Fibre Channel Frame Header, Network_Header, and Payload carrying IP Packet

+—+—————-+—————-+—————-+————–+ |Wrd| <31:24> | <23:16> | <15:08> | <07:00> | +—+—————-+—————-+—————-+————–+ |0 | R_CTL | D_ID | +—+—————-+—————-+—————-+————–+ |1 | CS_CTL | S_ID | +—+—————-+—————-+—————-+————–+ |2 | TYPE | F_CTL | +—+—————-+—————-+—————-+————–+ |3 | SEQ_ID | DF_CTL | SEQ_CNT | +—+—————-+—————-+—————-+————–+ |4 | OX_ID | RX_ID | +—+——–+——-+—————-+—————-+————–+ |5 | Parameter (Control or Relative Offset for Data ) | +—+—————————————————————–+ |6 | NAA | Network_Dest_Address (Hi order bits) | +—+——–+——-+—————-+—————-+————–+ |7 | Network_Dest_Address (Lo order bits) | +—+——–+——-+—————-+—————-+————–+ |8 | NAA | Network_Src_Address (Hi order bits) | +—+——–+——-+—————-+—————-+————–+ |9 | Network_Src_Address (Lo order bits) | +—+—————-+—————-+—————-+————–+ |10 | DSAP | SSAP | CTRL | OUI | +—+—————-+—————-+—————-+————–+ |11 | OUI | PID | +—+—————-+—————-+—————-+————–+ |12 | IP Packet Data … | +—+—————-+—————-+—————-+————–+

 R_CTL (Routing Control) and TYPE(data structure):
    Frames for each FC-4 can be easily distinguished from the others
    at the receiving port using the R_CTL (Routing Control) and TYPE
    (data structure) fields in the Frame-header.
    The R_CTL has two sub-fields: Routing bits and Information
    category. The Routing bits sub-field has specific values that mean
    FC-4 data follows and the Information Category tells the receiver
    the "Type" of data contained in the frame. The R_CTL and TYPE code
    points are shown in the diagrams.

Rajagopal, et al. Standards Track [Page 50] RFC 2625 IP and ARP over Fibre Channel June 1999

 Other Header fields:
    F_CTL (Frame Control) and SEQ_ID (Sequence Identification),
    SEQ_CNT (Sequence Count), OX_ID (Originator exchange Identifier),
    RX_ID (Responder exchange Identifier), and Parameter fields are
    used to manage the contents of a frame, and mark information
    exchange boundaries for the destination port.
 F_CTL(Frame Control):
    The FC_CTL field is a 3-byte field that contains information
    relating to the frame content. Most of the other Frame-header
    fields are used for frame identification. Among other things, bits
    in this field indicate the First Sequence, Last Sequence, or End
    Sequence. Sequence Initiative bit is used to pass control of the
    next Sequence in the Exchange to the recipient.
 SEQ_ID (Sequence Identifier) and SEQ_CNT (Sequence Count):
    This is used to uniquely identify sequences within an Exchange.
    The <S_ID, D_ID, SEQ_ID> uniquely identifies any active Sequence.
    SEQ_CNT is used to uniquely identify frames within a Sequence to
    assure sequentiality of frame reception, and to allow unique
    correlation of link control frames with their related data frames.
 Originator Exchange Identifier (OX_ID) and Responder Exchange
 Identifier (RX_ID):
    The OX_ID value provides association of frames with specific
    Exchanges originating at a particular N_Port. The RX_ID field
    provides the same function that the OX_ID provides for the
    Exchange Originator. The OX_ID is meaningful on the Exchange
    Originator, and the RX_ID is meaningful on the Responder.
 DF_CTL (Data Field Control):
    The DF_CTL field specifies the presence or absence of optional
    headers between the Frame-header and Frame Payload
 PARAMETER:
    The Parameter field has two meanings, depending on Frame type.
    For Link Control Frames, the Parameter field indicates the
    specific type of Link Control frame. For Data frames, this field
    contains the Relative Offset value. This specifies an offset from
    an Upper Layer Protocol buffer from a base address.

Rajagopal, et al. Standards Track [Page 51] RFC 2625 IP and ARP over Fibre Channel June 1999

E.4 Code Points for FC Frame

E.4.1 Code Points with IP and ARP Packets

 The Code Points for FC Frames with IP and ARP Packets are very
 similar with the exception of PID value in Word 11 which is set to
 0x08-00 for IP and 0x08-06 for ARP. Also, the Network_Header appears
 only in the first logical frame of a FC Sequence carrying IP. In the
 case, where FC frames carry ARP packets it is always present because
 these are single frame Sequences.
             Code Points for FC Frame with IP packet Data

+—+—————-+—————-+—————-+————+ |Wrd| <31:24> | <23:16> | <15:08> | <07:00> | +—+—————-+—————-+—————-+————+ | 0 | 0x04 | D_ID | +—+—————-+—————-+—————-+————+ | 1 | 0x00 | S_ID | +—+—————-+—————-+—————-+————+ | 2 | 0x05 | F_CTL | +—+—————-+—————-+—————-+————+ | 3 | SEQ_ID | 0x20 | SEQ_CNT | +—+—————-+—————-+—————-+————+ | 4 | OX_ID | RX_ID | +—+—————-+—————-+—————-+————+ | 5 | 0xXX-XX-XX-XX Parameter Relative Offset | +—+——+——————————————————–+ | 6 | 0001 | 0x000 | Dest. MAC (Hi order bits) | +—+——+———+—————-+—————-+————+ | 7 | Dest. MAC (Lo order bits) | +—+——+———-+—————-+—————————-+ | 8 | 0001 | 0x000 | Src. MAC (Hi order bits) | +—+——+———+—————-+—————-+————+ | 9 | Src. MAC (Lo order bits) | +—+—————-+—————-+—————-+————+ |10 | 0xAA | 0xAA | 0x03 | 0x00 | +—+—————-+—————-+—————-+————+ |11 | 0x00-00 | 0x08-00 | +—+—————-+—————-+—————-+————+ |12 | IP Packet Data | +—+—————-+—————-+—————-+————+ |13 | … | +—+—————-+—————-+—————-+————+

Rajagopal, et al. Standards Track [Page 52] RFC 2625 IP and ARP over Fibre Channel June 1999

            Code Points for FC Frame with ARP packet Data

+—+—————-+—————-+—————-+————+ |Wrd| <31:24> | <23:16> | <15:08> | <07:00> | +—+—————-+—————-+—————-+————+ | 0 | 0x04 | D_ID | +—+—————-+—————-+—————-+————+ | 1 | 0x00 | S_ID | +—+—————-+—————-+—————-+————+ | 2 | 0x05 | F_CTL | +—+—————-+—————-+—————-+————+ | 3 | SEQ_ID | 0x20 | SEQ_CNT | +—+—————-+—————-+—————-+————+ | 4 | OX_ID | RX_ID | +—+—————-+—————-+—————-+————+ | 5 | 0xXX-XX-XX-XX Parameter Relative Offset | +—+——+——————————————————–+ | 6 | 0001 | 0x000 | Dest. MAC (Hi order bits) | +—+——+———+—————-+—————-+————+ | 7 | Dest. MAC (Lo order bits) | +—+——+———-+—————-+—————————-+ | 8 | 0001 | 0x000 | Src. MAC (Hi order bits) | +—+——+———+—————-+—————-+————+ | 9 | Src. MAC (Lo order bits) | +—+—————-+—————-+—————-+————+ |10 | 0xAA | 0xAA | 0x03 | 0x00 | +—+—————-+—————-+—————-+————+ |11 | 0x00-00 | 0x08-06 | +—+—————-+—————-+—————-+————+ |12 | ARP Packet Data | +—+—————-+—————-+—————-+————+ |13| … | +—+—————-+—————-+—————-+————+

 The Code Points for a FARP-REQ for a specific Match Address Code
 Point MATCH_WW_PN_NN ( b'011') is shown below. In particular, note
 the IP addresses field of the Requester set to a valid address and
 that of the responder set to '0'. Note also the setting of the D_ID
 address and the Port_ID of the Responder.
 The corresponding code point for a FARP-REPLY is also shown below.
 In particular, note the setting of the Port_ID of Responder and the
 IP address setting of the Responder.

Rajagopal, et al. Standards Track [Page 53] RFC 2625 IP and ARP over Fibre Channel June 1999

E.4.2 Code Points with FARP Command

   Code Points for FC Frame with FARP-REQ Command for MATCH_WW_PN_NN

+—+—————-+—————-+—————-+————+ |Wrd| <31:24> | <23:16> | <15:08> | <07:00> | +—+—————-+—————-+—————-+————+ | 0 | 0x04 | D_ID = | | | | 0xFF 0xFF 0xFF | +—+—————-+—————-+—————-+————+ | 1 | 0x00 | S_ID | +—+—————-+—————-+—————-+————+ | 2 | 0x05 | F_CTL | +—+—————-+—————-+—————-+————+ | 3 | SEQ_ID | 0x20 | SEQ_CNT | +—+—————-+—————-+—————-+————+ | 4 | OX_ID | RX_ID | +—+—————-+—————-+—————-+————+ | 5 | 0xXX-XX-XX-XX Parameter Relative Offset | +—+—————-+—————-+—————-+————+ | 6 | 0x54 | 0x00 | 0x00 | 0x00 | +—+—————-+—————-+—————-+————+ | 7 | Port_ID of Requester = S_ID |Match Addr. | | | |Code Points | | | | xxxxx011 | +—+—————-+—————-+—————-+————+ | 8 | Port_ID of Responder = |Responder | | | 0x00 0x00 0x00 |Flags | +—+—————-+—————-+—————-+————+ | 9 | 0001 | 0x000 |WW_PN Src. MAC(Hi order bits)| +—+——+———+—————-+—————-+————+ |10 | WW_PN Src. MAC (Lo order bits) | +—+——+———-+—————+—————————–+ |11 | 0001 | 0x000 |WW_NN Src. MAC(Hi order bits)| +—+——+———+—————-+—————-+————+ |12 | WW_NN Src. MAC (Lo order bits) | +—+—————-+—————-+—————-+————+ |13 | 0001 | 0x000 |WW_PN Src. MAC(Hi order bits)| +—+——+———+—————-+—————-+————+ |14 | WW_PN Dest. MAC (Lo order bits) | +—+——+———-+—————+—————————–+ |15 | 0001 | 0x000 |WW_NN Dest.MAC(Hi order bits)| +—+——+———+—————-+—————-+————+ |16 | WW_NN Dest. MAC (Lo order bits) | +—+—————-+—————-+—————-+————+ |17 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |18 | 0x00-00-00-00 | +——————–+—————-+———+——————-+

Rajagopal, et al. Standards Track [Page 54] RFC 2625 IP and ARP over Fibre Channel June 1999

|19 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |20 | set to a valid IPv4 Address by Requester if Available | +——————–+—————-+———+——————-+ |21 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |22 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |23 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ | | 0x00-00-00-00 | |24 | set to a valid IPv4 Address of Responder if available | +——————–+—————-+———+——————-+

Rajagopal, et al. Standards Track [Page 55] RFC 2625 IP and ARP over Fibre Channel June 1999

          Code Points for FC Frame with FARP-REPLY Command

+—+—————-+—————-+—————-+————+ |Wrd| <31:24> | <23:16> | <15:08> | <07:00> | +—+—————-+—————-+—————-+————+ | 0 | 0x04 | D_ID | +—+—————-+—————-+—————-+————+ | 1 | 0x00 | S_ID | +—+—————-+—————-+—————-+————+ | 2 | 0x05 | F_CTL | +—+—————-+—————-+—————-+————+ | 3 | SEQ_ID | 0x20 | SEQ_CNT | +—+—————-+—————-+—————-+————+ | 4 | OX_ID | RX_ID | +—+—————-+—————-+—————-+————+ | 5 | 0xXX-XX-XX-XX Parameter Relative Offset | +—+—————-+—————-+—————-+————+ | 6 | 0x55 | 0x00 | 0x00 | 0x00 | +—+—————-+—————-+—————-+————+ | 7 | Port_ID of Requester = D_ID | xxxxx011 | +—+—————-+—————-+—————-+————+ | 8 | Port_ID of Responder = S_ID |Resp. Flag | +—+—————-+—————-+—————-+————+ | 9 | 0001 | 0x000 |WW_PN Src. MAC(Hi order bits)| +—+——+———+—————-+—————-+————+ |10 | WW_PN Src. MAC (Lo order bits) | +—+——+———-+—————+—————————–+ |11 | 0001 | 0x000 |WW_NN Src. MAC(Hi order bits)| +—+——+———+—————-+—————-+————+ |12 | WW_NN Src. MAC (Lo order bits) | +—+—————-+—————-+—————-+————+ |13 | 0001 | 0x000 |WW_PN Src. MAC(Hi order bits)| +—+——+———+—————-+—————-+————+ |14 | WW_PN Dest. MAC (Lo order bits) | +—+——+———-+—————+—————————–+ |15 | 0001 | 0x000 |WW_NN Dest.MAC(Hi order bits)| +—+——+———+—————-+—————-+————+ |16 | WW_NN Dest. MAC (Lo order bits) | +—+—————-+—————-+—————-+————+ |17 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |18 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |19 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |20 | set to a valid IPv4 Address by Requester | +——————–+—————-+———+——————-+ |21 | 0x00-00-00-00 | +——————–+—————-+———+——————-+

Rajagopal, et al. Standards Track [Page 56] RFC 2625 IP and ARP over Fibre Channel June 1999

|22 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |23 | 0x00-00-00-00 | +——————–+—————-+———+——————-+ |24 | set to a valid IPv4 Address by Responder | +——————–+—————-+———+——————-+

Rajagopal, et al. Standards Track [Page 57] RFC 2625 IP and ARP over Fibre Channel June 1999

APPENDIX F: Fibre Channel Protocol Considerations

F.1 Reliability In Class 3

 Problem: Sequence ID reuse in Class 3 can conceivably result in
 missing frame aliasing, which could result in delivery of corrupted
 (incorrectly-assembled) data, with no corresponding detection at the
 FC level.
 Prevention: This specification requires one of the following methods
 if Class 3 is used.
  1. Continuously increasing Sequence Count (new Login Bit) - both

sides must set When an N_Port sets the PLOGI login bit for

        continuously increasing SEQ_CNT, it is guaranteeing that it
        will transmit all frames within an Exchange using a
        continuously increasing SEQ_CNT (see description in Section
        B.1 below).
      - After using all SEQ_IDs (0-255) once, must start a new
        Exchange. It is recommended that a minimum of 4 Exchanges be
        used before an OX_ID can be reused.
      - Note: If an implementation is not checking the OX_ID when
        reassembling Sequences, the problem can still occur. Cycling
        through some number of SEQ_IDs, then jumping to a new Exchange
        does not solve the problem. SEQ_IDs must still be unique
        between two N_Ports, even across Exchanges.
      - Use only single-frame Sequences.

F.2 Continuously Increasing SEQ_CNT

 This method allows the recipient to check incoming frames, knowing
 exactly what SEQ_CNT value to expect next. Since the SEQ_CNT will not
 repeat for 65,536 frames, the aliasing problem is significantly
 reduced.
 A Login bit (PLOGI) is used to indicate that a device always uses a
 continuously increasing SEQ_CNT, even across transfers of Sequence
 Initiative. This bit is necessary for interoperability with some
 devices, and it provides other benefits as well.
 In the FC-PH-3 [11], the following is supported:
       Word 1, bit 17 - SEQ_CNT (S)
       0 = Normal FC-PH rules apply
       1 = Continuously increasing SEQ_CNT

Rajagopal, et al. Standards Track [Page 58] RFC 2625 IP and ARP over Fibre Channel June 1999

 Any N_Port that sets Word 1, Bit 17 = 1, is guaranteeing that it will
 transmit all frames within an Exchange using a continuously
 increasing SEQ_CNT. Each Exchange SHALL start with SEQ_CNT = 0 in the
 first frame, and every frame transmitted after that SHALL increment
 the previous SEQ_CNT by one, even across transfers of Sequence
 Initiative. Any frames received from the other N_Port in the Exchange
 shall have no effect on the transmitted SEQ_CNT.

Rajagopal, et al. Standards Track [Page 59] RFC 2625 IP and ARP over Fibre Channel June 1999

Appendix G: Acronyms and Glossary of FC Terms

 It is assumed that the reader is familiar with the terms and acronyms
 used in the FC protocol specification [2]. The following is provided
 for easy reference.
 First Frame: The frame that contains the SOFi field. This means a
 logical first and may not necessarily be the first frame temporally
 received in a sequence.
 Code Point: The coded bit pattern associated with control fields in
 frames or packets.
 PDU: Protocol Data Unit
 ABTS_LS: Abort Sequence Protocol - Last Sequence. A protocol for
 aborting an exchange based on the ABTS recipient setting the
 Last_Sequence bit in the BA_ACC ELS to the ABTS
 ADISC: Discover Address. An ELS for discovering the Hard Addresses
 (the 24 bit NL_Port Identifier) of N_Ports
 D_ID: Destination ID
 ES: End sequence. This FCTL bit in the FC header indicates this frame
 is the last frame of the sequence.
 FAN: Fabric Address Notification. An ELS sent by the fabric to all
 known previously Logged in ports following an initialization event.
 FLOGI: Fabric Login.
 LIP: Loop Initialization. A primitive Sequence used by a port to
 detect if it is part of a loop or to recover from certain loop
 errors.
 Link: Two unidirectional paths flowing in opposite directions and
 connecting two Ports within adjacent Nodes.
 LOGO: Logout.
 LR: Link reset. A primitive sequence transmitted by a port to
 initiate the link reset protocol or to recover from a link timeout.
 LS: Last Sequence of Exchange. This FCTL bit in the FC header
 indicates the Sequence is the Last Sequence of the Exchange.

Rajagopal, et al. Standards Track [Page 60] RFC 2625 IP and ARP over Fibre Channel June 1999

 Network Address Authority: A 4-bit field specified in Network_Headers
 that distinguishes between various name registration authorities that
 may be used to identify the WW_PN and the WW_NN. NAA=b'0001'
 indicates IEEE-48-bit MAC addresses
 Node: A collection of one or more Ports identified by a unique World
 Wide Node Name (WW_NN).
 NOS: Not Operational. A primitive Sequence transmitted to indicate
 that the port transmitting this Sequence has detected a link failure
 or is offline, waiting for OLS to be received.
 OLS: Off line. A primitive Sequence transmitted to indicate that the
 port transmitting this Sequence is either initiating the link
 initialization protocol, receiving and recognizing NOS, or entering
 the offline state.
 PDISC: Discover Port. An ELS for exchanging Service Parameters
 without affecting Login state.
 Primitive Sequence: A primitive Sequence is an Ordered Set that is
 transmitted repeatedly and continuously.
 Private Loop Device: A device that does not attempt Fabric Login
 (FLOGI) and usually adheres to PLDA.  The Area and Domain components
 of the NL_Port ID must be 0x0000. These devices cannot communicate
 with any port not in the local loop.
 Public Loop Device: A device whose Area and Domain components of the
 NL_Port ID cannot be 0x0000. Additionally, to be FLA compliant, the
 device must attempt to open AL_PA 0x00 and attempt FLOGI. These
 devices communicate with devices on the local loop as well as devices
 on the other side of a Fabric.
 Port: The transmitter, receiver and associated logic at either end of
 a link within a Node. There may be multiple Ports per Node. Each Port
 is identified by a unique Port_ID, which is volatile, and a unique
 World Wide Port Name (WW_PN), which is unchangeable. In this
 document, the term "port" may be used interchangeably with NL_Port or
 N_Port.
 Port_ID: Fibre Channel ports are addressed by unique 24-bit Port_IDs.
 In a Fibre Channel frame header, the Port_ID is referred to as S_ID
 (Source ID) to identify the port originating a frame, and D_ID to
 identify the destination port. The Port_ID of a given port is
 volatile (changeable).
 PLOGI: Port Login.

Rajagopal, et al. Standards Track [Page 61] RFC 2625 IP and ARP over Fibre Channel June 1999

 SI: Sequence Initiative
 World Wide Port_Name (WW_PN): Fibre Channel requires each Port to
 have an unchangeable WW_PN. Fibre Channel specifies a Network Address
 Authority (NAA) to distinguish between the various name registration
 authorities that may be used to identify the WW_PN. A 4-bit NAA
 identifier, 12-bit field set to 0x0 and an IEEE 48-bit MAC address
 together make this a 64-bit field.
 World Wide Node_Name (WW_NN): Fibre Channel identifies each Node with
 a unchangeable WW_NN. In a single port Node, the WW_NN and the WW_PN
 may be identical.

Rajagopal, et al. Standards Track [Page 62] RFC 2625 IP and ARP over Fibre Channel June 1999

Full Copyright Statement

 Copyright (C) The Internet Society (1999).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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

Rajagopal, et al. Standards Track [Page 63]

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