Quality of Service (QoS) Mechanism Selection in the Session Description Protocol (SDP)
RFC 5432

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Network Working Group                                            J. Polk
Request for Comments: 5432                                   S. Dhesikan
Category: Standards Track                                  Cisco Systems
                                                            G. Camarillo
                                                                Ericsson
                                                              March 2009

             Quality of Service (QoS) Mechanism Selection
               in the Session Description Protocol (SDP)

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.

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Polk, et al.                Standards Track                     [Page 1]
RFC 5432             QoS Mechanism Selection in SDP           March 2009

Abstract

   The offer/answer model for the Session Description Protocol (SDP)
   assumes that endpoints somehow establish the Quality of Service (QoS)
   required for the media streams they establish.  Endpoints in closed
   environments typically agree out-of-band (e.g., using configuration
   information) regarding which QoS mechanism to use.  However, on the
   Internet, there is more than one QoS service available.
   Consequently, there is a need for a mechanism to negotiate which QoS
   mechanism to use for a particular media stream.  This document
   defines such a mechanism.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. SDP Attributes Definition .......................................3
   4. Offer/Answer Behavior ...........................................4
      4.1. Offerer Behavior ...........................................4
      4.2. Answerer Behavior ..........................................4
      4.3. Resource Reservation .......................................5
      4.4. Subsequent Offer/Answer Exchanges ..........................5
   5. Example .........................................................5
   6. IANA Considerations .............................................6
      6.1. Registration of the SDP 'qos-mech-send' Attribute ..........6
      6.2. Registration of the SDP 'qos-mech-recv' Attribute ..........6
      6.3. Registry for QoS Mechanism Tokens ..........................7
   7. Security Considerations .........................................7
   8. Acknowledgements ................................................7
   9. References ......................................................8
      9.1. Normative References .......................................8
      9.2. Informative References .....................................8

Polk, et al.                Standards Track                     [Page 2]
RFC 5432             QoS Mechanism Selection in SDP           March 2009

1.  Introduction

   The offer/answer model [RFC3264] for SDP [RFC4566] does not provide
   any mechanism for endpoints to negotiate the QoS mechanism to be used
   for a particular media stream.  Even when QoS preconditions [RFC3312]
   are used, the choice of the QoS mechanism is left unspecified and is
   up to the endpoints.

   Endpoints that support more than one QoS mechanism need a way to
   negotiate which one to use for a particular media stream.  Examples
   of QoS mechanisms are RSVP (Resource Reservation Protocol) [RFC2205]
   and NSIS (Next Steps in Signaling) [QoS-NSLP].

   This document defines a mechanism that allows endpoints to negotiate