Integrated Services Mappings for Low Speed Networks
RFC 2688
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
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