A Transport Independent Bandwidth Modifier for the Session Description Protocol (SDP)
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From: The IESG <email@example.com> To: IETF-Announce <firstname.lastname@example.org> Cc: Internet Architecture Board <email@example.com>, RFC Editor <firstname.lastname@example.org>, mmusic mailing list <email@example.com>, mmusic chair <firstname.lastname@example.org> Subject: Protocol Action: 'A Transport Independent Bandwidth Modifier for the Session Description Protocol (SDP)' to Proposed Standard The IESG has approved the following document: - 'A Transport Independent Bandwidth Modifier for the Session Description Protocol (SDP) ' <draft-ietf-mmusic-sdp-bwparam-07.txt> as a Proposed Standard This document is the product of the Multiparty Multimedia Session Control Working Group. The IESG contact persons are Jon Peterson and Cullen Jennings. A URL of this Internet-Draft is: http://www.ietf.org/internet-drafts/draft-ietf-mmusic-sdp-bwparam-07.txt
Technical Summary Although the Session Description Protocol (SDP) already has a "bandwidth" parameter(the b= line) to characterize the amount of bandwidth a particular session will require, it is difficult for the receiver of an SDP message to know what values the creator of SDP used to factor the overhead into the total session bandwidth value. This becomes especially problematic in the presence of middleboxes that convert between IPv4 and IPv6. The use of session header compression (such as cRTP) on a per-hop basis at the sender side can also confuse recipients of SDP, since the assessment of total bandwidth on the sender side will assume header compression that probably isn't available at the receiver side. Similar problems exist for calculating RTCP bandwidth. Accordingly, this document defines a Transport Independent Application Specific Maximum (TIAS) bandwidith modifier that can appear in the b= line o SDP, and a new attribute, "maxrate", that is correlated with SDP media (m=) lines. Together, these two parameters enable recipients of SDP to make a muc more exact and universal assessment of the bandwidth that a session will require. Working Group Summary This MMUSIC Working Group supported the advancement of this specification. Protocol Quality This document has been reviewed for the IESG by Jon Peterson.