[SR-Users] RTPengine: shouldn't SDP <sess-version> be incremented when SDP is updated in-dialog?

Richard Fuchs rfuchs at sipwise.com
Fri May 4 16:51:29 CEST 2018

On 04/11/2018 09:28 AM, George Diamantopoulos wrote:
> Hello all,
> I have the following issue (I think) with RTP engine. An INVITE comes 
> in, and rtpengine will rewrite the SDP accordingly, as configured in 
> kamailio.cfg. After some time a reINVITE is sent out in the opposite 
> direction, for session refresh purposes. As I use rtcp-mux-offer in 
> kamailio.cfg for this direction, RTPengine will inject the rtcp-mux 
> parameter, and this reINVITE is forwarded to the UAC that sent the 
> original INVITE.
> However, the SDP in the reINVITE is exactly the same as the SDP in the 
> 200 OK to the original INVITE, with the exception of the rtcp-mux 
> parameter. Since the SDP offered from the same end has changed, 
> shouldn't session version be incremented as well?
> Does this sound like something that should be reported as a bug to 
> rtpengine? Or am I missing something here?

Technically of course you're correct in that the version counter should 
be incremented if the SDP changed. Currently rtpengine always leaves the 
o= line unchanged, so there can be a discrepancy here in certain cases. 
This should probably be fixed, but this is also the first time I've 
heard of this actually causing an issue.


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