I've got a GrandStream 24 FXS port ATA (GXW4024) that I'm trying to get to register to OCS 2007 (not R2). This device supports SIP-over-TCP/TLS and SRTP. In "don't register" mode, I can place a call from the GXW4024 to an OC client, and audio works on both ends. So far, so good...
However, I can't get the GXW4024 to register with OCS. Capturing packets with WireShark on the OCS server machine, I can see the GXW4024 sending a Register, then OCS responding with 401 with: WWW-Authenticate: NTLM WWW-Authenticate: Kerberos
Neither of which the GXW4024 supports. What makes no sense is that there's no "WWW-Authenticate: Digest", which the GXW4024 should be able to respond to. I've triple-checked the "SIP Security" setting on OCS, and it's set to LOW, which according to the help page for that setting, should allow Digest and Basic auth in addition to NTLM and Kerberos. So it seems that:
OCS is ignoring the "SIP Security: LOW" setting, or there's extra undocumented requirements.