The PPP Multilink Protocol (MP)
RFC 1990

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 12

Network Working Group                                         K. Sklower
Request for Comments: 1990            University of California, Berkeley
Obsoletes: 1717                                                 B. Lloyd
Category: Standards Track                                    G. McGregor
                                                   Lloyd Internetworking
                                                                 D. Carr
                                          Newbridge Networks Corporation
                                                            T. Coradetti
                                                       Sidewalk Software
                                                             August 1996

                    The PPP Multilink Protocol (MP)

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.

Abstract

   This document proposes a method for splitting, recombining and
   sequencing datagrams across multiple logical data links.  This work
   was originally motivated by the desire to exploit multiple bearer
   channels in ISDN, but is equally applicable to any situation in which
   multiple PPP links connect two systems, including async links.  This
   is accomplished by means of new PPP [2] options and protocols.

   The differences between the current PPP Multilink specification (RFC
   1717) and this memo are explained in Section 11.  Any system
   implementing the additional restrictions required by this memo will
   be backwards compatible with conforming RFC 1717 implementations.

Acknowledgements

   The authors specifically wish to thank Fred Baker of ACC, Craig Fox
   of Network Systems, Gerry Meyer of Spider Systems, Dan Brennan of
   Penril Datability Networks, Vernon Schryver of SGI (for the
   comprehensive discussion of padding), and the members of the IP over
   Large Public Data Networks and PPP Extensions working groups, for
   much useful discussion on the subject.

Sklower, et. al.            Standards Track                     [Page 1]
RFC 1990                     PPP Multilink                   August 1996

Table of Contents

   1. Introduction ................................................    2
   1.1. Motivation ................................................    2
   1.2. Functional Description ....................................    3
   1.3. Conventions ...............................................    4
   2. General Overview ............................................    4
   3. Packet Formats ..............................................    7
   3.1. Padding Considerations ....................................   10
   4. Trading Buffer Space Against Fragment Loss ..................   10
   4.1. Detecting Fragment Loss ...................................   11
   4.2. Buffer Space Requirements .................................   12
   5. PPP Link Control Protocol Extensions ........................   13
   5.1. Configuration Option Types ................................   13
   5.1.1. Multilink MRRU LCP option ...............................   14
   5.1.2. Short Sequence Number Header Format Option ..............   15
   5.1.3. Endpoint Discriminator Option ...........................   15
   6. Initiating use of Multilink Headers .........................   19
   7. Closing Member links ........................................   20
   8. Interaction with Other Protocols ............................   20
   9. Security Considerations .....................................   21
   10. References .................................................   21
   11. Differences from RFC 1717 ..................................   22
   11.1. Negotiating Multilink, per se ............................   22
   11.2. Initial Sequence Number defined ..........................   22
   11.3. Default Value of the MRRU ................................   22
   11.4. Config-Nak of EID prohibited .............................   22
   11.5. Uniformity of Sequence Space .............................   22
   11.6. Commencing and Abating use of Multilink Headers ..........   23
   11.7. Manual Configuration and Bundle Assignment ...............   23
   12. Authors' Addresses .........................................   24

1.  Introduction

1.1.  Motivation

   Basic Rate and Primary Rate ISDN both offer the possibility of
   opening multiple simultaneous channels between systems, giving users
   additional bandwidth on demand (for additional cost).  Previous
   proposals for the transmission of internet protocols over ISDN have
   stated as a goal the ability to make use of this capability, (e.g.,
   Leifer et al., [1]).

   There are proposals being advanced for providing synchronization