rfc2625.txt

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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



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      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



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      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



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   (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:

      - Other FARP mechanisms that directly build IPv4 address and FC
        Port Identifier (Port_ID) associations.
      - 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.




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   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:

        - A format definition and encapsulation mechanism for IPv4
          and ARP packets over FC
        - 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.










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         +------+--------+-----------+----//-------+------+------+
         | 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]:

     - Network_Header (16-bytes)
     - Association_Header (32-bytes)
     - Device_Header (up to 64-bytes).