HP Network Direr Software Products manual RFC Definitions, RFC Number Title

Useful Information and References 653

DiffServ Codepoint The DiffServ Codepoint field, defined in the IETF (Internet Engineering Field Task Force) RFC 2474, allows information about the quality of service

requirements of a packet to be carried with the packet as it traverses the network.

There are no restrictions on what any of the codepoint values mean as it is the choice of the network manager or the network management tool to decide the local meanings, although there are recommended uses for some of the values. The codepoint meanings can extend beyond simple traffic priority to more precise specifications such as latency and jitter requirements.

Information about the field, its use and the recommended values are available in the IETF RFCs listed in Table 102.

Table 102 RFC Definitions

RFC Number Title

RFC 2474 Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers

RFC 2475 An Architecture for Differentiated Services

RFC 2597 Assured Forwarding PHB Group

RFC 3246 An Expedited Forwarding PHB

RFC 3247 Supplemental Information for the New Definition of the EF PHB

RFC 3260 New Terminology and Clarification for DiffServ

All of these RFCs are freely available from the IETF website:

http://www.ietf.org/

The RFCs listed in Table 102 do not include all of the RFCs relevant to

DiffServ. Additional RFCs can be located on the Differentiated Services

Working Group’s page on the IETF website.

As the DiffServ codepoint field is only present in IP packets, this restricts the use of this marking mechanism to IP packets only. This means that the information about the importance of non-IP traffic cannot be conveyed from a complex classification device to a simple classification device using this marking mechanism.