Definition of Differentiated Services Per Domain Behaviors and Rules for their Specification
RFC 3086
Network Working Group K. Nichols
Request for Comments: 3086 Packet Design
Category: Informational B. Carpenter
IBM
April 2001
Definition of Differentiated Services Per Domain Behaviors
and Rules for their Specification
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
The differentiated services framework enables quality-of-service
provisioning within a network domain by applying rules at the edges
to create traffic aggregates and coupling each of these with a
specific forwarding path treatment in the domain through use of a
codepoint in the IP header. The diffserv WG has defined the general
architecture for differentiated services and has focused on the
forwarding path behavior required in routers, known as "per-hop
forwarding behaviors" (or PHBs). The WG has also discussed
functionality required at diffserv (DS) domain edges to select
(classifiers) and condition (e.g., policing and shaping) traffic
according to the rules. Short-term changes in the QoS goals for a DS
domain are implemented by changing only the configuration of these
edge behaviors without necessarily reconfiguring the behavior of
interior network nodes.
The next step is to formulate examples of how forwarding path
components (PHBs, classifiers, and traffic conditioners) can be used
to compose traffic aggregates whose packets experience specific
forwarding characteristics as they transit a differentiated services
domain. The WG has decided to use the term per-domain behavior, or
PDB, to describe the behavior experienced by a particular set of
packets as they cross a DS domain. A PDB is characterized by
specific metrics that quantify the treatment a set of packets with a
particular DSCP (or set of DSCPs) will receive as it crosses a DS
domain. A PDB specifies a forwarding path treatment for a traffic
aggregate and, due to the role that particular choices of edge and
Nichols & Carpenter Informational [Page 1]
RFC 3086 Diffserv per Domain Behaviors April 2001
PHB configuration play in its resulting attributes, it is where the
forwarding path and the control plane interact. The measurable
parameters of a PDB should be suitable for use in Service Level
Specifications at the network edge.
This document defines and discusses Per-Domain Behaviors in detail
and lays out the format and required content for contributions to the
Diffserv WG on PDBs and the procedure that will be applied for
individual PDB specifications to advance as WG products. This format
is specified to expedite working group review of PDB submissions.
Table of Contents
1. Introduction ................................................ 2
2. Definitions ................................................. 4
3. The Value of Defining Edge-to-Edge Behavior ................. 5
4. Understanding PDBs .......................................... 7
5. Format for Specification of Diffserv Per-Domain Behaviors ...13
6. On PDB Attributes ...........................................16
7. A Reference Per-Domain Behavior .............................19
8. Guidelines for Advancing PDB Specifications .................21
9. Security Considerations .....................................22
10. Acknowledgements ............................................22
References ..................................................22
Authors' Addresses ..........................................23
Full Copyright Statement ....................................24
1 Introduction
Differentiated Services allows an approach to IP Quality of Service
that is modular, incrementally deployable, and scalable while
introducing minimal per-node complexity [RFC2475]. From the end
user's point of view, QoS should be supported end-to-end between any
pair of hosts. However, this goal is not immediately attainable. It
will require interdomain QoS support, and many untaken steps remain
on the road to achieving this. One essential step, the evolution of
the business models for interdomain QoS, will necessarily develop
outside of the IETF. A goal of the diffserv WG is to provide the
firm technical foundation that allows these business models to
develop. The first major step will be to support edge-to-edge or
intradomain QoS between the ingress and egress of a single network,
i.e., a DS Domain in the terminology of RFC 2474. The intention is
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