Thanks for replying! I was afraid this list might be very empty. See below...

On Sat, Jan 14, 2012 at 1:46 AM, Mikael Magnusson <mikma...@gmail.com> wrote:
> On 01/14/2012 12:36 AM, Chris Tilt wrote:
>> Hello.
>> Please forgive my ignorance on the subject of SIP, but I am looking
>> for a solution to the SIP + NAT problem with a slightly twisted use
>> case that involves establishing connections based not on phone
>> numbers, but rather on unique ids of computer hosts. I am an
>> experienced Erlang programmer, which is what drew me to Yxa in the
>> first place, so making the extensions myself should not be a problem.
>> However, I would like your opinion on the feasibility before I start
>> work.
>> I'd like to use UDIDs or a hash of them in place of phone numbers
>> because these computers do not have phone numbers. Next, in order to
>> short-circuit the not-so-rare case that the two computers are behind
>> the same firewall, I'd like to include the local/private IP addresses
>> in the INVITE message so that the invitee can notice a peer on an
>> internal network and avoid routing packets through the firewall
>> needlessly. Perhaps this is better done once the "call" is established
>> via a secondary protocol message, but it seems like adding headers is
>> straight forward in SIP. Am I crazy to think this?
> If you want to set up a direct connection between the peers I think you
> should use SDP as usual in SIP INVITEs.
Ok, that makes sense. SDP is quite simple as I see now; I could just
add the private IP address as a tag there.
>> The application is remote login from a client to a host where both
>> systems sit behind firewalls and know only some agreed-upon public
>> name such as u...@well-known-domain.net. The incoming proxy and SIP
>> router are good candidates for connection establishment through the
>> NATs, with public domain at incomingproxy.well-known-domain.net. One
>> more question... I noticed that STUN was added to Yxa. Do the STUN
>> packets and SIP packets come out through the same port of the NAT
>> (with respect to the internal side of the NAT)? If so, then it seems
>> this would be a good thing to assist with NAT traversal. If not, then
>> how do SIP routed messages pass into the NAT of the invitee (from
>> internet side to private network side) since there would not be an
>> open port? Or does this require opening of the SIP port (5060?) on the
>> NAT/firewall of the peer networks?
> The NATed peers will need to keep the hair pin opened in the NAT router
> by regularly sending traffic to the Yxa proxy. There are several
> solutions to the NAT problem. One is to put a SBC in front of the Yxa
> server, another is to use ICE.

I agree that hole must be maintained with some sort of keep-alive, but
what I was asking is wether the STUN and SIP packets use the same
port? That seems critical in order for the SIP packets to even make it
through the firewall. I can use the SBC on the server side with little
problem, but I can not require one on the client. Is that a usable

I guess it's time to dig into the code :-) The oldest version of
Erlang that is still available is just one version newer than the one
required by the config file. Hopefully that will do.

> /Mikma
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Cheers, Chris
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