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Session Description Protocol (SDP) Simple Capability Declaration (RFC3407)

IP.com Disclosure Number: IPCOM000010082D
Original Publication Date: 2002-Oct-01
Included in the Prior Art Database: 2002-Oct-17
Document File: 11 page(s) / 21K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

F. Andreasen: AUTHOR

Abstract

This document defines a set of Session Description Protocol (SDP) attributes that enables SDP to provide a minimal and backwards compatible capability declaration mechanism. Such capability declarations can be used as input to a subsequent session negotiation, which is done by means outside the scope of this document. This provides a simple and limited solution to the general capability negotiation problem being addressed by the next generation of SDP, also known as SDPng.

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Network Working Group� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � F. Andreasen

Request for Comments: 3407� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � Cisco Systems

Category: Standards Track� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � October 2002

� � Session Description Protocol (SDP) Simple Capability Declaration

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 (2002).� All Rights Reserved.

Abstract

� � This document defines a set of Session Description Protocol (SDP)

� � attributes that enables SDP to provide a minimal and backwards

� � compatible capability declaration mechanism.� Such capability

� � declarations can be used as input to a subsequent session

� � negotiation, which is done by means outside the scope of this

� � document.� This provides a simple and limited solution to the general

� � capability negotiation problem being addressed by the next generation

� � of SDP, also known as SDPng.

1. Conventions Used in this Document

� � 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 [2].

2. Introduction

� � The Session Description Protocol (SDP) [3] describes multimedia

� � sessions for the purposes of session announcement, session

� � invitation, and other forms of multimedia session initiation.� SDP

� � was not intended to provide capability negotiation.� However, as the

� � need for this has become increasingly important, work has begun on a

� � "next generation SDP" (SDPng) [4,5] that supports both session

� � description and capability negotiation.� SDPng is not anticipated to

� � be backwards compatible with SDP and work on SDPng is currently in

� � the early stages.� However, several other protocols, e.g. SIP [6] and

� � Media Gateway Control Protocol (MGCP) [7], use SDP and are likely to

Andreasen� � � � � � � � � � � � � � � � � � Standards Track� � � � � � � � � � � � � � � � � � � � [Page 1]

RFC 3407� � � � � � � � � � SDP Simple Capability Declaration� � � � � � � October 2002

� � continue doing so for the foreseeable future.� Nevertheless, in many

� � cases these signaling protocols have an urgent need for some limited

� � form of capability negotiation.

� � For example, an endpoint may support G.711 audio (over RTP) as well

� � as T.38 fax relay (over UDP or TCP).� Unless the endpoint is willing

� � to support two media streams at the same time, this cannot currently

� � be expressed in SDP.� Another example involves supp...