Multicast Music-on-Hold and IP/TV Configurations
Multicast Music-on-Hold Operation
Cisco CallManager cluster
Music on hold server
CallManager tells IP phone to "join" MMoH group
1000 in call with 2000
1001 in call with 2001
Call is placed on hold
Music is played to 2000 Ext. 2001 gets local copy of MMoH stream
Step 1 Step 2
Extension 1000 is in a call with Extension 2000 (branch office).
Extension 1000 places Extension 2000 on hold. Call Manager signals the IP phone (Extension 2000) via the Skinny protocol to perform an IGMP join for the Multicast MoH group.
The IP phone (Extension 2000) signals to the network that it wishes to receive the multicast stream associated with the MoH group number. PIM is used to forward the stream from the first-hop router for the MoH server, through the WAN, and on to the IP phone at the branch.
Step 4 Step 5
Extension 1001 is on a call with Extension 2001 (same branch office as Extension 2000).
Extension 1001 places Extension 2001 on hold. Call Manager signals the IP phone (Extension 2001) via the Skinny protocol to perform an IGMP join for the same Multicast MoH group.
It is important to make sure that the audio source, region, location and Media Resource Group List (MRGL) are configured properly for the branch office. If not, the wrong MoH audio CODEC may be used and a separate audio stream will be sent to the branch. This defeats the purpose of saving bandwidth with multicast.
The IP phone (Extension 2001) signals the network that it wishes to receive the multicast stream associated with the MoH group number. The local switch and router know, via CGMP/PIM or IGMP snooping, that an existing stream is already being forwarded to Extension 2000. So a copy of the existing stream is forwarded from the local branch office switch.
When the holding phone resumes the call, the held phone sends an IGMP leave to signal that it no longer wants the multicast traffic.
Cisco AVVID Network Infrastructure IP Multicast Design