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
datatracker.ietf.org