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Sunday, October 3, 2010

Is there any way to have the MOH server as the local gateway of the users?

We have branches gateways connected as H323 to a call manager cluster. We are using centralized call processing for all the users in branches. We want to configure MOH for the branch phones and wondering what to do. Note that our ISP does not support multicast and we are using G729 over the WAN.Is there any way to have the MOH server as the local gateway of the users? What is recommended for this scenario? Is the CUCM server support G711 and G729

Cisco SRST gateways can be configured to multicast Real-Time Transport Protocol (RTP) packets from flash memory during fallback and normal Cisco CallManager operation. To make this happen, Cisco CallManager must be configured for multicast MOH in such a way that the audio packets do not cross the WAN. Instead, audio packets are broadcast from the flash memory of Cisco SRST gateways to the same multicast MOH IP address and port number configured for Cisco CallManager multicast MOH. IP phones at remote sites are able to pick up RTP packets that are multicast from the local branch gateways instead of from the central Cisco CallManager.

Even if you do g729 across the WAN, the region between your MOH server and this gateway should be set to g711, so that when the call is placed on hold, CM switches the codec to g711. The reason for this is because the audio file is recorded in g711 format, so the call needs to be in g711 during hold. Since no MOH traverses the WAN (MOH will be local at this site to the phones or PSTN connection) it doesn't use any more bandwidth.

Set it up like you would to have g711 multicast MOH across your WAN, and then just limit your hop count. Add a file to flash, configure the moh route to include the IP phone subnet and a loopback interface IP (latter is needed for PSTN call holds). Apply multicast routing and PIM to the IP phone interface and the loopback interface, and you should be good to go. Place a call on hold across the PSTN and use 'sh ccm music' and make sure the IP and port match what you have configured in the 'multicast moh' line.

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