Later calls may not work when Audio/Video (A/V) Edge Server is specified in the Mediation Server properties for Audio/Video Edge Authentication purposes in an integrated Exchange server 2007 and Office Communication Server 2007 environment

The Auto-Attendant feature or the System-Attendant feature can be configured on a Microsoft Exchange 2007 Unified Messaging (UM) server through integration with Microsoft Office Communication Server (OCS) 2007. The first Auto-Attendant call or the first System-Attendant call from an external PSTN device works, and you can hear the voice prompts. However, later calls may not work when Audio/Video (A/V) Edge Server is specified in the Mediation Server properties for Audio/Video Edge Authentication purposes.

Note If you want to change these A/V Edge Server settings, use the Office Communications Server 2007 administrative snap-in to view or to update the settings. You can find this snap-in in Office Communications Server Global Properties in the OCS console.

To resolve this issue, check whether there is a firewall that is blocking the traffic from the Exchange UM server to OCS A/V Edge Server.

When Exchange 2007 UM and OCS 2007 are installed together, and Interactive Connectivity Establishment is configured in the topology, the Exchange 2007 UM traffic may flow through the Audio/Video Edge server. The traffic can flow only if the endpoint of OCS 2007 is located outside the firewall. For this to occur, Exchange 2007 UM must obtain a token from the A/V Authentication Service that is servicing the corresponding OCS 2007 pool.

The A/V Authentication Service is an OCS 2007 service that runs on the A/V Edge server. Exchange 2007 UM receives the A/V Authentication Service token at the time that it receives the first incoming call from that OCS 2007 pool. If the firewall breaks the token, the calls do not work.