IP Multicast in Differentiated Services (DS) Networks
RFC 3754

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Network Working Group                                           R. Bless
Request for Comments: 3754                            Univ. of Karlsruhe
Category: Informational                                        K. Wehrle
                                                      Univ. of Tuebingen
                                                              April 2004

         IP Multicast in Differentiated Services (DS) Networks

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 (2004).  All Rights Reserved.

Abstract

   This document discusses the problems of IP Multicast use in
   Differentiated Services (DS) networks, expanding on the discussion in
   RFC 2475 ("An Architecture of Differentiated Services").  It also
   suggests possible solutions to these problems, describes a potential
   implementation model, and presents simulation results.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
       1.1.  Management of Differentiated Services. . . . . . . . . .  2
   2.  Problems of IP Multicast in DS Domains . . . . . . . . . . . .  3
       2.1.  Neglected Reservation Subtree Problem (NRS Problem). . .  4
       2.2.  Heterogeneous Multicast Groups . . . . . . . . . . . . . 12
       2.3.  Dynamics of Any-Source Multicast . . . . . . . . . . . . 13
   3.  Solutions for Enabling IP-Multicast in Differentiated
       Services Networks. . . . . . . . . . . . . . . . . . . . . . . 13
       3.1.  Solution for the NRS Problem . . . . . . . . . . . . . . 13
       3.2.  Solution for Supporting Heterogeneous Multicast Groups . 15
       3.3.  Solution for Any-Source Multicast. . . . . . . . . . . . 16
   4.  Scalability Considerations . . . . . . . . . . . . . . . . . . 16
   5.  Deployment Considerations. . . . . . . . . . . . . . . . . . . 17
   6.  Security Considerations. . . . . . . . . . . . . . . . . . . . 18
   7.  Implementation Model Example . . . . . . . . . . . . . . . . . 18
   8.  Proof of the Neglected Reservation Subtree Problem . . . . . . 19
       8.1.  Implementation of the Proposed Solution. . . . . . . . . 20
       8.2.  Test Environment and Execution . . . . . . . . . . . . . 21
   9.  Simulative Study of the NRS Problem and Limited Effort PHB . . 23

Bless & Wehrle               Informational                      [Page 1]
RFC 3754              IP Multicast in DS Networks             April 2004

       9.1.  Simulation Scenario. . . . . . . . . . . . . . . . . . . 24
       9.2.  Simulation Results for Different Router Types. . . . . . 26
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
       11.1. Normative References . . . . . . . . . . . . . . . . . . 31
       11.2. Informative References . . . . . . . . . . . . . . . . . 31
   12. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 33
   13. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 34

1.  Introduction

   This document discusses the problems of IP Multicast use in
   Differentiated Services (DS) networks, expanding on the discussion in
   RFC 2475 ("An Architecture of Differentiated Services").  It also
   suggests possible solutions to these problems, describes a potential
   implementation model, and presents simulation results.

   The "Differentiated Services" (DiffServ or DS) approach [1, 2, 3]
   defines certain building blocks and mechanisms to offer qualitatively
   better services than the traditional best-effort delivery service in
   an IP network.  In the DiffServ Architecture [2], scalability is
   achieved by avoiding complexity and maintenance of per-flow state
   information in core nodes, and by pushing unavoidable complexity to
   the network edges.  Therefore, individual flows belonging to the same
   service are aggregated, thereby eliminating the need for complex
   classification or managing state information per flow in interior
   nodes.

   On the other hand, the reduced complexity in DS nodes makes it more
   complex to use those "better" services together with IP Multicast
   (i.e., point-to-multipoint or multipoint-to-multipoint
   communication).  Problems emerging from this fact are described in
   section 2.  Although the basic DS forwarding mechanisms also work
   with IP Multicast, some facts have to be considered which are related
   to the provisioning of multicast resources.  It is important to
   integrate IP Multicast functionality into the architecture from the
   beginning, and to provide simple solutions for those problems that
   will not defeat the already gained advantages.

1.1.  Management of Differentiated Services

   At least for Per-Domain Behaviors and services based on the EF PHB,
   admission control and resource reservation are required [14, 15].