[SR-Users] question regarding rtpengine and ICE candidate selection

[Richard Fuchs]

On 04/12/2020 13.10, Andrew Chen wrote:
> So from a SIP point of view, the 200 OK should of sent the final 
> negotiation of SDP once the client ACK's it right?

The requirement to send an updated offer once ICE has completed with the 
final negotiated candidates existed in the original ICE RFC, but I 
believe it has been removed in the newer ICE RFC (I'm not 100% sure 
about that though). For rtpengine that requirement certainly doesn't 
exist and it's happy to negotiate and conclude ICE without a final 
updated offer. Also rtpengine itself cannot trigger such an updated 
offer since it's not directly in the SIP path, so that would have to be 
left up to the clients. So in short, a single offer/answer exchange is 
enough to get ICE started and it can complete negotiation out of band 
without further signalling.

Cheers