A Bandwidth represents the b= fields contained within either a MediaDescription or a
This specifies the proposed bandwidth to be used by the session or media, and is optional. Multiple
bandwidth specifiers of different types may be associated with the same SessionDescription. Each
consists of a token type and an integer value measuring bandwidth in kilobits per second.
RFC 2327 defines two bandwidth types (or modifiers):
Conference Total: An implicit maximum bandwidth is associated with each TTL on the Mbone or
within a particular multicast administrative scope region (the Mbone bandwidth vs. TTL limits are given
in the MBone FAQ). If the bandwidth of a session or media in a session is different from the
bandwidth implicit from the scope, a 'b=CT:...' line should be supplied for the session giving the
proposed upper limit to the bandwidth used. The primary purpose of this is to give an approximate
idea as to whether two or more conferences can co-exist simultaneously.
Application-Specific Maximum: The bandwidth is interpreted to be application-specific, i.e., will be the
application's concept of maximum bandwidth. Normally this will coincide with what is set on the
application's "maximum bandwidth" control if applicable.
Note that CT gives a total bandwidth figure for all the media at all sites. AS gives a bandwidth figure for a
single media at a single site, although there may be many sites sending simultaneously.
Please refer to IETF RFC 2327 for a description of SDP.