In typical Cisco CallManager configurations, voice calls and Music on
Hold (MoH) streams that must traverse a low-speed WAN link use the G.729 codec
in order to save bandwidth. The use of the G.729 codec for voice or MoH traffic
over a WAN link is still recommended. However, in some situations G.729 does
not provide adequate quality for MoH streams. This is due to the fact that
G.729 codec is optimized for speech. Therefore, it typically provides only
marginal audio fidelity for MoH.
In situations where it is determined that G.729 MoH is unacceptable,
you can force MoH to use G.711 while you still maintain voice calls at G.729.
This is done through the use of the 'region' configuration in Cisco
CallManager. When you place the MoH server in a Cisco CallManager region by
itself, you can specify what codecs are used between the MoH server and other
regions when a user is placed on hold or during network hold. Consequently,
voice calls can still use G.729 while MoH is streamed using G.711. This results
in better audio quality. This document demonstrates how to achieve this.
Note: This is only supported in centralized Cisco CallManager deployments.
There are no specific requirements for this document.
The information in this document is based on Cisco CallManager
4.0(1)sr2, but the concept applies to any Cisco CallManager release where
regions can be created.
The information in this document was created from the devices in a
specific lab environment. All of the devices used in this document started with
a cleared (default) configuration. If your network is live, make sure that you
understand the potential impact of any command.
For more information on document conventions, refer to the
Technical Tips Conventions.
In order to focus on the specific configurations needed, assume that
you have a central site named HQ. HQ is where the Cisco CallManager server is.
You also have one remote site named Remote. The MoH server is configured on the
Cisco CallManager itself at the central site.
Note: Media Resource Group configuration and Media Resource Group Lists
configuration in Cisco CallManager is beyond the scope of this document. For
the purpose of this document, the default SampleAudioSource is used as an audio
These steps are required:
Create three regions called HQ, Remote, and
Specify the codecs for each
Create three device pools called HQ_DP,
Remote_DP, and MoHServer_DP.
Specify the region that corresponds to each
device pool. For example, the region for device pool 'HQ_DP' is 'HQ'.
Place the IP phones in their equivalent device
pool. For example, at the HQ, IP phones are placed in the HQ_DP device
Place the MoH server in the MoHServer_DP device
Ensure that the correct codecs are selected in
the supported MoH codecs in the Cisco IP Voice Media Streaming
Select System > Region > Add a New Region in
order to create each of these regions:
For the MoH region, specify these codecs:
For the HQ region, specify these codecs:
For the Remote region, specify these codecs:
Select System > Device Pool > Add a New Device
Pool in order to create these three device pools:
For the MoHServer_DP device pool, specify MoH as the
Note: The default SampleAudioSource is used as an audio source that is used
by the MoH server.
For the HQ_DP device pool, specify HQ as the
For the Remote_DP device pool, specify Remote as the
Based on the assumption that you have IP Communicator at the Remote
region and a Cisco 7960 IP phone at the HQ region, place the IP Communicator in
device pool Remote_DP.
Place the Cisco 7960 in HQ_DP.
Select Service > Media Resource and select the MoH
In the Device Pool field select
Select Service > Service Parameters and choose
Cisco IP Voice Media Streaming App from the Service pull down
Under Clusterwide Parameters, select the codecs that you want supported
Although G.729 is selected here, you only need G.711. When you select
multiple codecs, hold down the CRTL key and use the mouse to select multiple
codecs from the list.
Place a call from the Cisco 7960 to the IP Communicator. Once the call
is answered, double-click the ? in the IP Communicator screen
to view Call Statistics.
Note: The codec used here is G.729.
From the Cisco 7960, place the user (IP Communicator phone) on hold and
view Call Statistics.
Note: The codec is now G.711. This is used for the MoH transmission:
There is currently no specific troubleshooting information available
for this configuration.