Multiprotocol Interconnect over Frame Relay
RFC 2427

Document Type RFC - Internet Standard (September 1998; No errata)
Obsoletes RFC 1490, RFC 1294
Also known as STD 55
Authors Andy Malis  , Caralyn Brown 
Last updated 2013-03-02
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IESG IESG state RFC 2427 (Internet Standard)
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Network Working Group                                          C. Brown
Request for Comments: 2427                                   Consultant
STD: 55                                                        A. Malis
Obsoletes: 1490, 1294                       Ascend Communications, Inc.
Category: Standards Track                                September 1998

              Multiprotocol Interconnect over Frame Relay

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 (1998).  All Rights Reserved.


   This memo describes an encapsulation method for carrying network
   interconnect traffic over a Frame Relay backbone.  It covers aspects
   of both Bridging and Routing.

   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.


   This document could not have been completed without the support of
   Terry Bradley of Avici Systems, Inc..  Comments and contributions
   from many sources, especially those from Ray Samora of Proteon, Ken
   Rehbehn of Visual Networks, Fred Baker and Charles Carvalho of Cisco
   Systems, 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 (though
   it was deleted in the final version) and Floyd Backes and Laura
   Bridge of 3Com 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 and the IP over NBMA working
   groups of the IETF.

Brown & Malis               Standards Track                     [Page 1]
RFC 2427             Multiprotocol over Frame Relay       September 1998

1.  Conventions and Acronyms

   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
   document, are to be interpreted as described in [16].

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

        |---   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

Brown & Malis               Standards Track                     [Page 2]
RFC 2427             Multiprotocol over Frame Relay       September 1998

      DE   - Discard Eligibility bit
      DTE  - Data Terminal Equipment
      FECN - Forward Explicit Congestion Notification
      PDU  - Protocol Data Unit
      PTT  - Postal Telephone & Telegraph
      SNAP - Subnetwork Access Protocol

2.  Introduction

   The following discussion applies to those devices which serve as end
   stations (DTEs) on a public or private Frame Relay network (for
   example, provided by a common carrier or PTT.  It will not discuss
   the behavior of those stations that are considered a part of the
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