Subject: [AVT] RE: Structure of compound BYE packet

From: Vavilapalli Srikanth-A19563 <[email-masked]>
Date: Tue, 29 Mar 2005 21:58:49 +0530

Thanks Magnus. Please find my comments inline

-----Original Message-----
From: Magnus Westerlund [mailto:[email-masked]] 
Sent: Tuesday, March 29, 2005 2:55 AM
To: Vavilapalli Srikanth-A19563
Cc: [email-masked]
Subject: Re: Structure of compound BYE packet

Hi,

The usage of SR or RR as first RTCP packet type is dependent on the 
normal rules, also in the case of RTCP BYE packets. So if you have sent 
RTP packets in the last two RTCP reporting intervalls it shall send SR 
packet.

The reason for this is so that any receiver also get the reporting on 
the sent packets.

[Srikanth Vavilapalli] This can be achieved with RR packets also if I am
right.

 Benefits of doing this, even if leaving session, is so 
that the receivers can learn if the lost any trailing packets. As packet 
loss is undetected until a RTP packet with higher sequence number or a 
RTCP packet with an SR indicating that a higher sequence number has been 
sent.

[Srikanth Vavilapalli] This makes sense. So far I was thinking the uses of
'sender info' in SR packet is for inter media synchronization originating
from that source, which is anyway no more required when that participant
leaves the session. 
But in such case are you saying that the cumulative loss field in the report
block shall account the sender's sent packet count as expected number of
packets? According to the RFC: "The number of packets expected is defined to
be the extended last sequence number received less the initial sequence
number received" which never account the trailing lost packets

 It also will tell the receivers what was the last packet sent. 
This provides explicitness when a stream ends. Which can be helpfull and 
avoiding going into concealment unnecessary.

Hope this answers your question

Magnus

Vavilapalli Srikanth-A19563 wrote:
> Hi
> 
>  
> 
> Can anyone tell me that if it is mandated to include a SR packet rather a
RR
> packet as the first packet of RTCP BYE compound packet when a 'RTP sender
> (Who has sent some RTP data since the last RTCP packet and this BYE
packet)'
> wants to leave the session? If so can you tell me what are the advantages
> with that SR packets to the remaining receivers of that session? 
> 
>  
> 
> Regards
> 
> Srikanth
> 
> 

-- 

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: [email-masked]

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt