Transmission of IP and ARP over FDDI Networks
RFC 1390

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Network Working Group                                           D. Katz
Request for Comments: 1390                          cisco Systems, Inc.
STD: 36                                                    January 1993

             Transmission of IP and ARP over FDDI Networks

Status of this Memo

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

Abstract

   This memo defines a method of encapsulating the Internet Protocol
   (IP) datagrams and Address Resolution Protocol (ARP) requests and
   replies on Fiber Distributed Data Interface (FDDI) Networks.

   This RFC is the product of the IP over FDDI Working Group of the
   Internet Engineering Task Force (IETF).

Acknowledgments

   This memo draws heavily in both concept and text from RFC 1042 [3],
   written by Jon Postel and Joyce K. Reynolds of USC/Information
   Sciences Institute.  The author would also like to acknowledge the
   contributions of the IP Over FDDI Working Group of the IETF, members
   of ANSI ASC X3T9.5, and others in the FDDI community.

Conventions

   The following language conventions are used in the items of
   specification in this document:

      "Must," "Shall," or "Mandatory"--the item is an absolute
      requirement of the specification.

      "Should" or "Recommended"--the item should generally be followed
      for all but exceptional circumstances.

      "May" or "Optional"--the item is truly optional and may be
      followed or ignored according to the needs of the implementor.

Katz                                                            [Page 1]
RFC 1390                      IP Over FDDI                  January 1993

Introduction

   The goal of this specification is to allow compatible and
   interoperable implementations for transmitting IP datagrams [1] and
   ARP requests and replies [2].

   The Fiber Distributed Data Interface (FDDI) specifications define a
   family of standards for Local Area Networks (LANs) that provides the
   Physical Layer and Media Access Control Sublayer of the Data Link
   Layer as defined by the ISO Open System Interconnection Reference
   Model (ISO/OSI).  Documents are in various stages of progression
   toward International Standardization for Media Access Control (MAC)
   [4], Physical Layer Protocol (PHY) [5], Physical Layer Medium
   Dependent (PMD) [6], and Station Management (SMT) [7].  The family of
   FDDI standards corresponds to the IEEE 802 MAC layer standards [8, 9,
   10].

   The remainder of the Data Link Service is provided by the IEEE 802.2
   Logical Link Control (LLC) service [11].  The resulting stack of
   services appears as follows:

        +-------------+
        |   IP/ARP    |
        +-------------+
        |  802.2 LLC  |
        +-------------+-----+
        |  FDDI MAC   | F   |
        +-------------+ D S |
        |  FDDI PHY   | D M |
        +-------------+ I T |
        |  FDDI PMD   |     |
        +-------------+-----+

   This memo describes the use of IP and ARP in this environment.  At
   this time, it is not necessary that the use of IP and ARP be
   consistent between FDDI and IEEE 802 networks, but it is the intent
   of this memo not to preclude Data Link Layer interoperability at such
   time as the standards define it.

   It is the explicit intent of this memo to allow the interoperability
   of IP and ARP between stations on FDDI networks and stations on
   Ethernet networks via translational bridges.

   The FDDI standards define both single and dual MAC stations.  This
   document describes the use of IP and ARP on single MAC stations
   (single-attach or dual-attach) only.

Katz                                                            [Page 2]
RFC 1390                      IP Over FDDI                  January 1993

Packet Format

   IP datagrams and ARP requests and replies sent on FDDI networks shall
   be encapsulated within the 802.2 LLC and Sub-Network Access Protocol
   (SNAP) [12] data link layers and the FDDI MAC and physical layers.
   The SNAP must be used with an Organization Code indicating that the
   SNAP header contains the EtherType code (as listed in Assigned
   Numbers [13]).

   802.2 LLC Type 1 communication (which must be implemented by all
   conforming 802.2 stations) is used exclusively.  All frames must be
   transmitted in standard 802.2 LLC Type 1 Unnumbered Information
   format, with the DSAP and the SSAP fields of the 802.2 header set to
   the assigned global SAP value for SNAP [11].  The 24-bit Organization
   Code in the SNAP must be zero, and the remaining 16 bits are the
   EtherType from Assigned Numbers [13] (IP = 2048, ARP = 2054).

      ...--------+--------+--------+
                 MAC Header        |                           FDDI MAC