RFC 3290 (rfc3290) - Page 3 of 56
An Informal Management Model for Diffserv Routers
Alternative Format: Original Text Document
RFC 3290 Diffserv Informal Management Model May 2002
1. Introduction
Differentiated Services (Diffserv) [DSARCH] is a set of technologies
which allow network service providers to offer services with
different kinds of network quality-of-service (QoS) objectives to
different customers and their traffic streams. This document uses
terminology defined in [DSARCH] and [NEWTERMS] (some of these
definitions are included here in Section 2 for completeness).
The premise of Diffserv networks is that routers within the core of
the network handle packets in different traffic streams by forwarding
them using different per-hop behaviors (PHBs). The PHB to be applied
is indicated by a Diffserv codepoint (DSCP) in the IP header of each
packet [DSFIELD]. The DSCP markings are applied either by a trusted
upstream node, e.g., a customer, or by the edge routers on entry to
the Diffserv network.
The advantage of such a scheme is that many traffic streams can be
aggregated to one of a small number of behavior aggregates (BA),
which are each forwarded using the same PHB at the router, thereby
simplifying the processing and associated storage. In addition,
there is no signaling other than what is carried in the DSCP of each
packet, and no other related processing that is required in the core
of the Diffserv network since QoS is invoked on a packet-by-packet
basis.
The Diffserv architecture enables a variety of possible services
which could be deployed in a network. These services are reflected
to customers at the edges of the Diffserv network in the form of a
Service Level Specification (SLS - see [NEWTERMS]). Whilst further
discussion of such services is outside the scope of this document
(see [PDBDEF]), the ability to provide these services depends on the
availability of cohesive management and configuration tools that can
be used to provision and monitor a set of Diffserv routers in a
coordinated manner. To facilitate the development of such
configuration and management tools it is helpful to define a
conceptual model of a Diffserv router that abstracts away
implementation details of particular Diffserv routers from the
parameters of interest for configuration and management. The purpose
of this document is to define such a model.
The basic forwarding functionality of a Diffserv router is defined in
other specifications; e.g., [DSARCH, DSFIELD, AF-PHB, EF-PHB].
This document is not intended in any way to constrain or to dictate
the implementation alternatives of Diffserv routers. It is expected
that router implementers will demonstrate a great deal of variability
in their implementations. To the extent that implementers are able
Bernet, et. al. Informational