Registering asterisk with Microsoft OCS as sip client

Trying to register asterisk with MS OCS as a sip client. I’m not getting a response. I think this is due in part to OCS wanting an initial REGISTER with no credentials so it can do an NTLM challenge?

Anyway, this is what is in my sip.conf:

The following is the REGISTER message being sent. I’ve replaced the IPs in the SIP header. ==
my asterisk server ==

REGISTER 10 headers, 0 lines Reliably Transmitting (no NAT) to REGISTER SIP/2.0 Via: SIP/2.0/TLS;branch=z9hG4bK0c1fbb6d Max-Forwards: 70 From: <>;tag=as3d8b8c33 To: <> Call-ID: 7f26d5ce62a8745716a9ed2a62917fd2@ CSeq: 104 REGISTER User-Agent: Asterisk PBX Expires: 120 Contact: <sip:from-ocs@;transport=TLS> Content-Length: 0

And finally, the error message itself.

[Apr 14 16:48:05] NOTICE[16267]: chan_sip.c:12232 sip_reg_timeout: -- Registration for '' timed out, trying again (Attempt #3) Really destroying SIP dialog '7f26d5ce62a8745716a9ed2a62917fd2@' Method: REGISTER

Microsoft’s OCS / LCS / Lync implementation is not compliant with the SIP RFC. Any successful connection between the two will be a hack.

Google turns up a few threads specific to this topic.

Good luck!