Multiprotocol Interconnect over Frame Relay
RFC 1490

Document Type RFC - Draft Standard (July 1993; No errata)
Obsoleted by RFC 2427
Obsoletes RFC 1294
Last updated 2013-03-02
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IESG IESG state RFC 1490 (Draft Standard)
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Network Working Group                                        T. Bradley
Request for Comments: 1490               Wellfleet Communications, Inc.
Obsoletes: 1294                                                C. Brown
                                         Wellfleet Communications, Inc.
                                                               A. Malis
                                                   Ascom Timeplex, Inc.
                                                              July 1993

              Multiprotocol Interconnect over Frame Relay

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 describes an encapsulation method for carrying network
   interconnect traffic over a Frame Relay backbone.  It covers aspects
   of both Bridging and Routing.  Additionally, it describes a simple
   fragmentation procedure for carrying large frames over a frame relay
   network with a smaller MTU.

   Systems with the ability to transfer both the encapsulation method
   described in this document, and others must have a priori knowledge
   of which virtual circuits will carry which encapsulation method and
   this encapsulation must only be used over virtual circuits that have
   been explicitly configured for its use.

Acknowledgements

   Comments and contributions from many sources, especially those from
   Ray Samora of Proteon, Ken Rehbehn of Netrix Corporation, Fred Baker
   and Charles Carvalho of Advanced Computer Communications and Mostafa
   Sherif of AT&T have been incorporated into this document. Special
   thanks to Dory Leifer of University of Michigan for his contributions
   to the resolution of fragmentation issues and Floyd Backes from DEC
   and Laura Bridge from Timeplex for their contributions to the
   bridging descriptions. This document could not have been completed
   without the expertise of the IP over Large Public Data Networks
   working group of the IETF.

Bradley, Brown & Malis                                          [Page 1]
RFC 1490             Multiprotocol over Frame Relay            July 1993

1.  Conventions and Acronyms

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

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

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

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

   All drawings in this document are drawn with the left-most bit as the
   high order bit for transmission.  For example, the dawings might be
   labeled as:

              0   1   2   3   4   5   6   7 bits
              +---+---+---+---+---+---+---+

              +---------------------------+
              |    flag (7E hexadecimal)  |
              +---------------------------+
              |       Q.922 Address*      |
              +--                       --+
              |                           |
              +---------------------------+
              :                           :
              :                           :
              +---------------------------+

   Drawings that would be too large to fit onto one page if each octet
   were presented on a single line are drawn with two octets per line.
   These are also drawn with the left-most bit as the high order bit for
   transmission.  There will be a "+" to distinguish between octets as
   in the following example.

Bradley, Brown & Malis                                          [Page 2]
RFC 1490             Multiprotocol over Frame Relay            July 1993

        |---   octet one     ---|---   octet two  ---|
        0  1  2  3  4  5  6  7  0  1  2  3  4  5  6  7
        +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

        +--------------------------------------------+
        | Organizationally Unique                    |
        +--                     +--------------------+
        | Identifier            | Protocol           |
        +-----------------------+--------------------+
        | Identifier            |
        +-----------------------+

   The following are common acronyms used throughout this document.

      BECN - Backward Explicit Congestion Notification
      BPDU - Bridge Protocol Data Unit
      C/R  - Command/Response bit
      DCE  - Data Communication Equipment
      DE   - Discard Eligibility bit
      DTE  - Data Terminal Equipment
      FECN - Forward Explicit Congestion Notification
      PDU  - Protocol Data Unit
      PTT  - Postal Telephone & Telegraph
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