Subject: [MMUSIC] SDP multiple packetization time

From: "Willekens, Marc (NSN - BE/Belgium - MiniMD)" <[email-masked]>
Date: Fri, 9 Nov 2007 14:01:23 +0100

Hi,
 
For the SDP, the "ptime" and "maxptime" (packetization time) attributes
are already under discussion for a long time (ca. 10 years). 
 
At last IETF.69, it was discussed with the result that there is a
certain problem with the ptime/maxptime when different media formats are
indicated in the m-line:
The problem indication is described in
http://www.ietf.org/internet-drafts/draft-garcia-mmusic-multiple-ptimes-
problem-00.txt.
 
Some problem statements at IETF.69 were made in the direction of:
- limitations in DSP silicon
- accurate QoS budget calculations
- interworking issues
- codecs implemented in hardware
- ...
 
The IETF first wants to have a clear understanding of the problem and
the requirements before proposing a new standardized solution and/or
before making certain clarifications. So, people having trouble with the
ptime/maxptime now have the chance to indicate their problems and their
wishes for protocol improvements.
 
- Who really needs a ptime/maxptime in function of the codec for what
purpose?  
- What kind of interworking issues were encountered (e.g. during SIPit,
or during real-life deployments)?
- What kind of hardware limitations have you already encountered which
could not be solved with the existing standards?
- Who thinks a clarification can be sufficient?
 
So, if you've any valuable information which could help to proceed with
this long-standing problem, please tell. 
The global VoIP community will appreciate it.
 
Thanks,
Marc.

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