RFC 5939 on Session Description Protocol (SDP) Capability Negotiation

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        RFC 5939

        Title:      Session Description Protocol (SDP) Capability 
                    Negotiation 
        Author:     F. Andreasen
        Status:     Standards Track
        Stream:     IETF
        Date:       September 2010
        Mailbox:    fandreas@cisco.com
        Pages:      77
        Characters: 188116
        Updates/Obsoletes/SeeAlso:   None

        I-D Tag:    draft-ietf-mmusic-sdp-capability-negotiation-13.txt

        URL:        http://www.rfc-editor.org/rfc/rfc5939.txt

The Session Description Protocol (SDP) was intended to describe
multimedia sessions for the purposes of session announcement, session
invitation, and other forms of multimedia session initiation.  SDP was
not intended to provide capability indication or capability
negotiation; however, over the years, SDP has seen widespread adoption
and as a result it has been gradually extended to provide limited
support for these, notably in the form of the offer/answer model
defined in RFC 3264.  SDP does not define how to negotiate one or more
alternative transport protocols (e.g., RTP profiles) or
attributes.  This makes it difficult to deploy new RTP profiles such as
Secure RTP or RTP with RTCP-based feedback,
negotiate use of different security keying mechanisms, etc.  It also
presents problems for some forms of media negotiation.

The purpose of this document is to address these shortcomings by
extending SDP with capability negotiation parameters and associated
offer/answer procedures to use those parameters in a backwards
compatible manner.

The document defines a general SDP Capability Negotiation framework.
It also specifies how to provide attributes and transport protocols
as capabilities and negotiate them using the framework.  Extensions
for other types of capabilities (e.g., media types and media formats)
may be provided in other documents.  [STANDARDS TRACK]

This document is a product of the Multiparty Multimedia Session Control Working Group of the IETF.

This is now a Proposed Standard Protocol.

STANDARDS TRACK: 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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