Quote:
Originally Posted by emoci
-Which PSTN Access number is the one i question?
-Does your SipPhone have an option to set up STUN?
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I hope it's okay to bring up this older thread, as I'm hitting the issue as well. I cannot hear the PSTN party, but he can hear me. This is via the Toronto, Canada access number, the only city of my interest at this time. STUN is not an option because I am behind a NAT, which is running the DD-WRT router firmware (IP Tables Symmetric NAT), plus the Nokia WiFi phone that I'd like to use at times does not support STUN anyway.
Based on some sniffing, I see the SIP signaling is coming in from IP 204.11.194.10. I am asked via an SDP message to send my RTP stream to that same address, which I do, though I do not receive any RTP traffic from it. A few seconds later, I start receiving RTP data from IP 64.34.164.254, then I am asked (a 2nd SDP) to redirect my RTP stream to this new IP. I honor the redirect.
On the LAN side of things, everything looks solid, but I noticed that the source port number of my 2nd outbound RTP socket was not properly preserved by my router. Somehow it was not preserved even though it is clearly a new socket, yet the disqualification must relate to the fact that the same source port was used with the 1st RTP socket (and which is still active in the router). The lack of port preservation means that the Symmetric RTP relationship has been broken, and I am left stuck with one-sided audio.
Obviously the lack of any easy holistic solution makes this frustrating. But as I think about this, I can't be alone, as there are going to be NAT devices out there that don't always do the right thing (e.g., preserve source ports). Therefore, in the interest in maximizing success for all parties, I wonder if the SIP Broker techs could see if it might be possible to configure the server such that the very first SDP message contains the correct media IP address (64.34.164.254, at least my case), so that there would not need to be any kind of call transfer process once the media has been negotiated.
Thank you for checking!