Differentiated Services (diffserv)

This Working Group did not meet

NOTE: This charter is a snapshot of the 55th IETF Meeting in Altanta, Georgia USA. It may now be out-of-date.

Last Modifield: 03/29/2002

Brian Carpenter <brian@hursley.ibm.com>
Kathleen Nichols <nichols@packetdesign.com>
Transport Area Director(s):
Scott Bradner <sob@harvard.edu>
A. Mankin <mankin@isi.edu>
Transport Area Advisor:
Scott Bradner <sob@harvard.edu>
Mailing Lists:
General Discussion: diffserv@ietf.org
To Subscribe: diffserv-request@ietf.org
In Body: subscribe your_email_address
Archive: ftp.ietf.org/ietf-mail-archive/diffserv/
Description of Working Group:
There is a clear need for relatively simple and coarse methods of providing differentiated classes of service for Internet traffic, to support various types of applications, and specific business requirements. The differentiated services approach to providing quality of service in networks employs a small, well-defined set of building blocks from which a variety of aggregate behaviors may be built. A small bit-pattern in each packet, in the IPv4 TOS octet or the IPv6 Traffic Class octet, is used to mark a packet to receive a particular forwarding treatment, or per-hop behavior, at each network node. A common understanding about the use and interpretation of this bit-pattern is required for inter-domain use, multi-vendor interoperability, and consistent reasoning about expected aggregate behaviors in a network. Thus, the Working Group has standardized a common layout for a six-bit field of both octets, called the 'DS field'. RFC 2474 and RFC 2475 define the architecture, and the general use of bits within the DS field (superseding theIPv4 TOS octet definitions of RFC 1349).

The Working Group has standardized a small number of specific per-hop behaviors (PHBs), and recommended a particular bit pattern or 'code-point' of the DS field for each one, in RFC 2474, RFC 2597, and RFC 2598. No more PHBs will be standardized until all the current milestones of the WG have been satisfied and the existing standard PHBs have been promoted at least to Draft Standard status.

The WG has investigated the additional components necessary to support differentiated services, including such traffic conditioners as traffic shapers and packet markers that could be used at the boundaries of networks. There are many examples of these in the technical literature.

The WG will define a general conceptual model for boundary devices, including traffic conditioning parameters, and configuration and monitoring data. It is expected that a subset of this will apply to all diffserv nodes. The group will also define a MIB and a PIB for diffserv nodes, and an encoding to identify PHBs in protocol messages. It will document issues involving diffserv through tunnels.

The WG will develop a format for precisely describing various Per-Domain Behaviors (PDBs). A PDB is a collection of packets with the same codepoint, thus receiving the same PHB, traversing from edge to edge of a single diffserv network or domain. Associated with each PDB are measurable, quantifiable characteristics which can be used to describe what happens to packets of that PDB as they cross the network, thus providing an external description of the edge-to-edge quality of service that can be expected by packets of that PDB within that network. A PDB is formed at the edge of a network by selecting certain packets through use of classifiers and by imposing rules on those packets via traffic conditioners.

The description of a PDB contains the specific edge rules and PHB type(s) and configurations that should be used in order to achieve specified externally visible characteristics.

In addition to defining a format for PDB descriptions, specific descriptions of PDBs that can be constructed using the standard PHBs will be developed and reviewed by a design team prior to informational or standards track publication.

The group will continue to analyze related security threats, especially theft of service or denial of service attacks, and suggest counter-measures.

The group will not work on:

o mechanisms for the identification of individual traffic flows

o new signalling mechanisms to support the marking of packets

o end to end service definitions

o service level agreements

Goals and Milestones:
Done  Publish draft of format for BA descriptions
Done  Meet at Adelaide IETF to review tunnels draft, discuss initial PDB descriptions
Done  Solicit PDB descriptions
Done  Finalize tunnels draft, submit to IESG
Done  Finalize PDB format draft, submit to IESG
Done  Meet at Pittsburgh IETF
Done  Meet at San Diego IETF
SEP 01  Finalize model, MIB and PIB drafts, submit to IESG
Done  Submit Informational terminology updates to IESG
  • - draft-ietf-diffserv-pib-09.txt
  • Request For Comments:
    RFC2474 PS Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers
    RFC2475 I An Architecture for Differentiated Services
    RFC2598 PS An Expedited Forwarding PHB
    RFC2597 PS Assured Forwarding PHB Group
    RFC2836 PS Per Hop Behavior Identification Codes
    RFC2983 I Differentiated Services and Tunnels
    RFC3086 I Definition of Differentiated Services Per Domain Behaviors and Rules for their Specification
    RFC3140 PS Per Hop Behavior Identification Codes
    RFC3248 I A Delay Bound alternative revision of RFC2598
    RFC3246 PS An Expedited Forwarding PHB
    RFC3247 I Supplemental Information for the New Definition of the EF PHB
    RFC3260 I New Terminology and Clarification for Diffserv
    RFC3289 PS Management Information Base for the Differentiated Services Architecture
    RFC3290 I An Informal Management Model for Diffserv Routers

    Current Meeting Report

    None received.


    None received.