Batteling the Mediation server (or; this time we blame Cisco)

I'm sorry I haven't posted in a wile. But I have been busy doing other implementations. The two last days however, have been more quiet (Easter is almost upon us in Norway). I have now tried to install a mediation server, and connect the OCS world to the rest of the world through a SIP trunk to CUCM (v7).

Installing the mediation server, adding a certificate, and configuring dialing rules and routes was pretty easy. I've made one simple rule for internal dialing with 4 extensions, and one for the rest of the world (for testing purposes limited to dialing the Norwegian dial plan).

Setting up the trunk on CUCM seemed fairly easy to, but I do however have on problem with the configuration I set up. And if any of you out there have a solution to it, please let me know :)

Dialing from a Cisco phone to a pure MOCS extension is working with RTP in both directions. But when dialing from MOCS and out, all calls are blocked with a 503 (Service unavailable) message from the CUCM. I can see the call in CUCM's traces), and I see the same when tracing on the Mediation server.

I've searched around, and tried to figure out what is wrong. The only thing I think might be it is a problem related to how the OCS uses + in front of numbers when calling. There is a fix for this in OCS 2007, but it is not released for R2 (at least yet).

I have verified translation patterns, css and partitons on CUCM. And the digit analyzer is giving me an OK.

Does anyone out there know the reason for the 503 error code? (The SIP trunk is unsecured and is set to use MTP)