http://www.rfc-editor.org/rfc/rfc7006.txt
RFC 7006: Miscellaneous Capabilities Negotiation in the Session Description Protocol (SDP), M. Garcia-Martin, S. Veikkolainen, R. Gilman2013-09-01T23:00:00-00:00This memo extends the SDP capability negotiation framework to allow endpoints to negotiate three additional SDP capabilities. In particular, this memo provides a mechanism to negotiate bandwidth ("b=" line), connection data ("c=" line), and session or media titles ("i=" line for each session or media).