Subject: Re: Lost RTCP packets

From: Stephen Casner <[email-masked]>
Date: Mon, 3 Apr 2000 01:41:54 -0700 (Pacific Daylight Time)

This question is more appropriate for the AVT working group mailing
list rather than the general IETF mailing list, so I have redirected
my response there.

The RTCP packets are designed so that loss of an individual packet is
not critical.  In particular, in the RR packet, cumulative counts are
used rather than deltas so that a difference between the counts can be
calculated for any pair of RTCP packets to determine the delta for the
period between those two packets.

I believe that using TCP would be a bad idea because it can
significantly perturb the timing of the RTCP packets.  Note that the
timestamps in the RTCP SR and RR packets may be used to calculate a
round-trip time.  If the transport for RTCP were different than that
for RTP, the RTT calculation would not be applicable to the RTP
stream.

Not sure what you mean by "adding QoS".  If you mean retransmission,
see the drafts that were discussed at the recent AVT meeting.

							-- Steve

On Fri, 31 Mar 2000, Nikki Cranley wrote:

> Just a thought, what is the procedure when RTCP packets are lost between
> the client and server. These are fairly important bits of information.
> I am experimenting with RTP/RTCP over UDP/IP with a view to adding QoS -
> however I just wondered there if perhaps a hybrid stack should be used
> for example :-
> RTP/UDP/IP & RTCP/TCP/IP.
> Any comments or ideas about this ...
> 
> Thanking you, rgds,
> Nikki