RFC 2597 (rfc2597) - Page 1 of 11

Assured Forwarding PHB Group

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Network Working Group                                        J. Heinanen
Request for Comments: 2597                                 Telia Finland
Category: Standards Track                                       F. Baker
                                                           Cisco Systems
                                                                W. Weiss
                                                     Lucent Technologies
                                                           J. Wroclawski
                                                                 MIT LCS
                                                               June 1999


                      Assured Forwarding PHB Group

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

   This document defines a general use Differentiated Services (DS)
   [Blake] Per-Hop-Behavior (PHB) Group called Assured Forwarding (AF).
   The AF PHB group provides delivery of IP packets in four
   independently forwarded AF classes.  Within each AF class, an IP
   packet can be assigned one of three different levels of drop
   precedence.  A DS node does not reorder IP packets of the same
   microflow if they belong to the same AF class.

1. Purpose and Overview

   There is a demand to provide assured forwarding of IP packets over
   the Internet.  In a typical application, a company uses the Internet
   to interconnect its geographically distributed sites and wants an
   assurance that IP packets within this intranet are forwarded with
   high probability as long as the aggregate traffic from each site does
   not exceed the subscribed information rate (profile).  It is
   desirable that a site may exceed the subscribed profile with the
   understanding that the excess traffic is not delivered with as high
   probability as the traffic that is within the profile.  It is also





Heinanen                    Standards Track
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