[Sipping] draft-ietf-sipping-media-policy-dataset: Bandwidth limitations

["Worley, Dale R (Dale)" <[e-mail]>]

The media-policy-dataset provides 3 different bandwidth limitations:

max-bw
max-session-bw
max-stream-bw

Comparing the description of these (section 7.3 et seq.) with the description of
the b= line in SDP (RFC 4566 section 5.8) turns up a lot of ambiguity in the
definitions.

It seems to me to be clear that the max-stream-bw number corresponds to the "b=AS:..." line
in an SDP media description -- the bandwidth used by one direction of one media
stream.

The max-session-bw seems to correspond to the "b=AS:..." line in the *session* description,
the total bandwidth used (in one direction) by the whole session.

The max-bw number is less clear.  It seems to be intended to limit the total bandwidth used
by an agent (across all of the sessions it participates in).  As such, it can't be translated to
an SDP attribute.

Conversely, the "b=CT:..." line in an SDP session description seems to be intended to
describe the total bandwidth used by a "conference" (whatever that is).  It's not clear
what the significance of that is exactly, since the agent in question may not be the conference
focus, and indeed, the session may not be part of a "conference".

Thoughts?

Dale