Network Working Group                                Magnus Westerlund
INTERNET-DRAFT                                                Ericsson
Expires: March 2007                                     Stephan Wenger
                                                                 Nokia

                                                    September 17, 2006

                             RTP Topologies
                   draft-ietf-avt-topologies-01.txt>


Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document disucsses multi-endpoint topologies commonly used in
   RTP based environments.  In particular, centralized topologies
   commonly employed in the video conferencing industry are mapped to
   the RTP terminology.







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TABLE OF CONTENTS

Status of this Memo................................................1
Copyright Notice...................................................1
Abstract...........................................................1
TABLE OF CONTENTS..................................................2
1. Introduction....................................................3
2. Definitions.....................................................3
  2.1. Glossary...................................................3
  2.2. Terminology................................................3
  2.3. Topologies.................................................4
     2.3.1. TOPO10: Point to Point................................4
     2.3.2. TOPO20: Point to Multi-point using Multicast..........4
     2.3.3. TOPO30: Point to Multipoint using the RFC 3550
     translator...................................................5
     2.3.4. TOPO40: Point to Multipoint using the RFC 3550 mixer
     model........................................................8
     2.3.5. TOPO50: Point to Multipoint using video switching MCU 10
     2.3.6. TOPO60: Point to Multipoint using RTCP-terminating MCU11
     2.3.7. Combining Topologies.................................12
3. Security Considerations........................................13
4. IANA Considerations............................................13
5. Acknowledgements...............................................13
6. References.....................................................14
  6.1. Normative references......................................14
  6.2. Informative references....................................14
7. Authors' Addresses.............................................14
8. List of Changes relative to previous drafts....................15
RFC Editor Considerations.........................................16























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.  Introduction

   When working on the Codec Control Messages [CCM], we noticed a
   considerable confusion in the community with respect to terms such
   as MCU, mixer, and translator.  In the process of writing, we
   became increasingly unsure of our own understanding, and therefore
   added what became the core of this draft to the CCM draft.  Later,
   it was found that this information has its own value, and was
   "outsourced" from the CCM draft into the present memo.

   It could be argued that this document clarifies and explains
   sections of the RTP spec [RFC3550], and is therefore of
   informational nature.  In this case, the present memo may end up
   as an informational RFC.

   When the Audio-Visual Profile with Feedback (AVPF) [AVPF] was
   developed, the main emphasis lied in the efficient support of
   point-to-point and small multipoint scenarios without centralized
   multipoint control.  However, in practice, many small multipoint
   conferences operate utilizing devices known as Multipoint Control
   Units (MCUs).  MCUs comprise mixers and translators (in RTP
   [RFC3550] terminology), but also signalling support



.  Definitions


2.1.    Glossary

   ASM    - Asynchronous Multicast
   AVPF   - The Extended RTP Profile for RTCP-based Feedback
   MCU    - Multipoint Control Unit
   PtM    - Point to Multipoint
   PtP    - Point to Point


2.2.    Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   RFC 2119 [RFC2119].







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