Thanks for the snapshot.

Here's what is going on:

The Snom phone is attempting to register using the "outbound" mechanism.
(See Internet-Draft draft-ietf-sip-outbound-16,
http://tools.ietf.org/html/draft-ietf-sip-outbound.)  In particular,
"outbound" allows the phone to send its REGISTER message using a TCP
connection and specify that the proxy should send all traffic to the
phone using that same TCP connection.  So the Contact URI provided in
the REGISTER message is not relevant, really.  As part of this, the Snom
phone is not listening for incoming connections on TCP port 5060,
despite that it is giving as its contact
sip:[email protected]:5060;transport=tcp;line=ia8lst43.  (You can see
TCP connection attempts to port 5060 getting RST responses.)

The phone signals that it wants to use "outbound" via the "reg-id" field
parameter on the Contact header:

Contact: 
<sip:[email protected]:5060;transport=tcp;line=ia8lst43>;q=1.0;reg-id=1;audio;mobility="fixed";duplex="full";description="snom320";actor="principal";events="dialog";methods="INVITE,ACK,CANCEL,BYE,REFER,OPTIONS,NOTIFY,SUBSCRIBE,PRACK,MESSAGE,INFO"

However, sipX does not support "outbound".  This is implied by sipX's
response to the REGISTER message, which does not contain "Require:
outbound".  See section 4.2.1:

   The UAC examines successful registration responses for the presence
   of an outbound option-tag in a Require header field value.  Presence
   of this option-tag indicates that the registrar is compliant with
   this specification, and that any edge proxies which needed to
   participate are also compliant.  If the registrar did not support
   outbound, the UA has potentially registered an un-routable contact.
   It is the responsibility of the UA to remove any inappropriate
   Contacts.

Since the phone has been told (implicitly) that the proxy does not
support outbound, it is now responsible for either listening on TCP port
5060 (based on its registered contact URI), or re-registering with a
different contact that indicates a workable method of reaching the
phone.

So the baseline analysis is that the Snom is not correctly detecting and
responding to the fact that sipX does not support "outbound".

A more useful response is that there is probably a configuration setting
on the Snom phone to disable its attempt to use "outbound", and that if
that is set, the phone will work correctly.

Dale


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