[asterisk-dev] RTCP question!

[Olle E. Johansson]

27 sep 2010 kl. 21.08 skrev David Vossel:

> Howdy,
> 
> I'm dealing with an interoperability issue with X-Lite softphone clients and Asterisk involving RTCP.  Newer X-Lite clients have this setting called RTCP Timeout, which as you would guess times out the call after a certain period of RTCP inactivity.  By default this setting is set to 30 seconds.  The problem I'm dealing with is that during certain scenarios, the X-Lite client will disconnect from Asterisk because of this timeout.  RTCP is always being sent from Asterisk to the X-Lite client, but the X-Lite client will timeout any time Asterisk changes the SSRC field.  Asterisk updates the SSRC field every time it detects the source of the outgoing RTP stream has changed, which makes this a fairly common occurrence.
> 
> I have looked through RFC 3550 to try and determine if Asterisk is doing anything wrong regarding changing the SSRC id, but I have been unable to determine exactly what the behavior is when the SSRC field needs to change.  Should Asterisk send a RTCP Bye message for the old SSRC before sending the new one, or is simply just sending out updates with the new SSRC sufficient?  Also, does it make sense that the X-Lite client is timing out on the SSRC change in the first place?

I've recently noticed this behaviour too, but haven't analyzed further. Test with my pinefrog code to see if there's any difference. We do send CNAME in those RTCP session, which is more permanent than SSRC. I haven't spent any time figuring out when we should change SSRC, but I suspect we do it way too often. guesswork at this level, but it's been used as the medicine for many issues.

Not much help, but at least you have to RTCP implementations to check with.

/O