Integrated Services Mappings for Low Speed Networks
RFC 2688

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Network Working Group                                       S. Jackowski
Request for Comments: 2688                        Deterministic Networks
Category: Standards Track                                     D. Putzolu
                                                 Intel Architecture Labs
                                                              E. Crawley
                                                          Argon Networks
                                                                B. Davie
                                                           Cisco Systems
                                                          September 1999

          Integrated Services Mappings for Low Speed Networks

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 (1999).  All Rights Reserved.

Abstract

   A set of companion documents describe an architecture for providing
   integrated services over low-bitrate links, such as modem lines, ISDN
   B-channels, and sub-T1 links [1, 2, 3, 4]. The main components of the
   architecture are: a set of real-time encapsulation formats for
   asynchronous and synchronous low-bitrate links, a header compression
   architecture optimized for real-time flows, elements of negotiation
   protocols used between routers (or between hosts and routers), and
   announcement protocols used by applications to allow this negotiation
   to take place.

   This document defines the service mappings of the IETF Integrated
   Services for low-bitrate links, specifically the controlled load [5]
   and guaranteed [6] services.  The approach takes the form of a set of
   guidelines and considerations for implementing these services, along
   with evaluation criteria for elements providing these services.

Jackowski, et al.           Standards Track                     [Page 1]
RFC 2688      Integrated Services Mappings Low Speed Nets September 1999

1. Introduction

   In addition to the "best-effort" services the Internet is well-known
   for, other types of services ("integrated services") are being
   developed and deployed in the Internet. These services support
   special handling of traffic based on bandwidth, latency, and other
   requirements that cannot usually be met using "best-effort" service.

   This document defines the mapping of integrated services "controlled
   load" [5] and "guaranteed" [6] services on to low-bandwidth links.
   The architecture and mechanisms used to implement these services on
   such links are defined in a set of companion documents. The
   mechanisms defined in these documents include both compression of
   flows (for bandwidth savings) [4,10] and a set of extensions to the
   PPP protocol which permit fragmentation [2] or suspension [3] of
   large packets in favor of packets from flows with more stringent
   service requirements.

1.1.  Specification Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [11].

2. Issues for Providing Controlled and Guaranteed Service

   Unlike other link layers, the links referred to in this document
   operate only over low speed point to point connections.  Examples of
   the kinds of links addressed here include dial-up lines, ISDN
   channels, and low-speed (1.5Mbps or less) leased lines.  Such links
   can occur at different positions within the end-to-end path:

   - host to directly connected host.
   - host to/from network access device (router or switch).
   - Edge device (subnet router or switch) to/from router or switch.
   - In rare circumstances, a link from backbone router to backbone
     router.

   These links often represent the first or last wide area hop in a true
   end to end service.  Note that these links may be the most bandwidth
   constrained along the path between two hosts.

   The services utilized in mapping integrated services to these links
   are only provided if both endpoints on the link support the
   architecture and mechanisms referenced above. Support for these
   mechanisms is determined during the PPP negotiation.  The non-shared

Jackowski, et al.           Standards Track                     [Page 2]
RFC 2688      Integrated Services Mappings Low Speed Nets September 1999

   nature of these links, along with the fact that point-to-point links
   are typically dual simplex (i.e., the send and receive channels are
   separate) allows all admission control decisions to be made locally.

   As described in [2] and [3], for systems that can exert real time