Dialogic DMG VoIP Gateway Drops Lync Calls Placed on Hold

We are implementing a pilot of Microsoft Lync 2010 and we've been running in to a few little quirks.

We are using a Dialogic DMG VoIP gateway to interface with our legacy telephony equipment to receive calls from the PSTN.

Here is the current quirk that was encountered: any call that originated from the PSTN to a Lync user that was placed on hold would disconnect after exactly 90 seconds. The following information was observed in a Lync trace of the call:

ms-diagnostics-public: 10047;reason="Unexpected call termination from gateway side, request has an unexpected reason header or cause code format";component="MediationServer";sip-reason="E.182;text="Transport Failure""
Reason: E.182;text="Transport Failure"

The same behavior was exhibited in a call originating from the PSTN to a Lync user who then merged the PSTN call with another 1-to-1 call or a conference call that the Lync user was already in - the PSTN call would drop after exactly 90 seconds.

After some tracing and trying to change settings in Lync as well as the Dialogic, we found that the gateway was terminating the call because it thought the call was no longer active.

Setting the

Monitor Call Connections setting in

Config > VoIP > General to


resolved our issues.

While I'm not sure this change is the long-term fix, it solved our problems. Hope this helps someone out there.