[OpenSER-Devel] [Serdev] Possible bug in the tm module in the presence of packet loss/branches

[Dan Pascu]

On Thursday 13 March 2008, Anatoly Pidruchny wrote:
> The NACK may work, but it would be a very big and fundamental RFC
> change. And it would be very disruptive, because it is not compatible
> with the current RFC.

It is probably one of the simplest ways to solve the conflict. About how 
disruptive it is, I would say that is just an extension. If a device 
doesn't support it it can ignore it, as it doesn't change any other call 
flows, it only fixes one that the current RFC specs can't.

>
> How about my proposal to stop resending INVITE and start resending
> CANCEL in a proxy if a provisional response is not received? May be I
> am wrong, but I think it can help and it is really a minor change in
> RFC that in fact preserves compatibility.

This still doesn't resolve the conflict between the CANCEL and 200 OK. 
Even if you start transmitting a CANCEL, still a 200 OK for the initial 
INVITE can come after that because there is packet loss or the 200 OK was 
already send before you started to transmit the CANCEL and then you can't 
handle the situation using the current mechanisms the RFC provides.

-- 
Dan