Subject: [AVTCORE] Interpretation of RTCP bandwidth modifiers in SDP offer/answer

From: "Uveges, Balint (NSN - HU/Budapest)" <[email-masked]>
Date: Mon, 12 Sep 2011 14:38:26 +0300

Dear Recipients,

I would like to request clarification regarding the RTCP bandwidth
modifiers [RFC3556] usage in SDP offer/answer model
[RFC3264] in case of unicast streams.

According to RFC3264, during the generation of the (initial) SDP offer:
   If the bandwidth attribute is present for a stream, it indicates the
   desired bandwidth that the offerer would like to receive.

And, during the generation of the SDP answer:
   The answerer MAY include a bandwidth attribute for any media stream;
   this indicates the bandwidth that the answerer would like the offerer
   to use when sending media.

Are the above quoted rules also true for RTCP bandwidth modifiers?

To explain it further, is the following statement true?
   If RS and RR bandwidth modifiers are present in an SDP offer/answer,
it indicates the desired RTCP bandwidth that
   the offerer/answerer would like to receive from active data senders
and from receivers, respectively.

I'm aware of the fact, that RFC3264 was published in 2002 (while RFC3556
in 2003) and the quoted text refers to the 'b=AS:' bandwidth modifier.
Unfortunately RFC3556 does not include Offer-Answer Model consideration
chapter, neither could I find any information on the corresponding
mailing lists regarding this topic.

Thank You for Your help!

Best regards,
-Balint Uveges

Balint Uveges
Nokia Siemens Networks
E-mail: [email-masked]