Definition of Differentiated Services Per Domain Behaviors and Rules for their Specification
RFC 3086

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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