[asterisk-users] SIP header challenge

[Mr. Jones]

This is essentially a follow-up to my previous email on the 404 I was
seeing with my DIDs.

I think it maybe more involved with the SIP headers I'm receiving from
the company providing my origination.

Here's what's interesting.

I have inbound 800 service and outbound termination from provider A.
This is working great. I don't have anything specific configured in
sip.conf, and the dialed 800 number matches an entry in
extensions.conf - everything works great.

With provider B who is providing my nationwide origination I'm having
some challenges. I'm having to extract the SIP header and modify it
then pass it into a macro to actually route it to extensions. Its not
so pretty.

In digging into the SIP headers I've noticed the following.

The first sample is from Provider "A" and works:

To: <sip:8005551212 at 66.123.123.6:5060>;tag=as6519d118

I also noticed the "Contact" header seems to be filled in:

Contact: <sip:8005551212 at 66.123.123.6>

>From provider B:

To: <sip:3125551212 at 66.123.123.6;user=phone>;tag=as7154d7ed

Contact: <sip:s at 66.123.123.6>

So I guess my question is two fold:

1. What sets the "Contact" field - Asterisk, or the sending machine?
2. Would the ;user=phone and the lack of a port number be causing
Asterisk not to set the exten properly?

TIA