Since the release of Cisco CallManager 3.1x, Media Resource Groups
(MRGs) and Media Resource Group Lists (MRGLs) are now used in order to allow an
administrator to allocate media resources to particular devices. The most
common use of MRGs and MRGLs is to restrict media resource usage on a
geographic basis. For example, if you have conference resources at a remote
location, you can create an MRGL for the IP phones at the remote location that
only allows them to access their local conference bridge resources. This
ensures that the conference calls that an IP phone creates at the remote
location do not have to use WAN bandwidth for conferencing within the same
site. You can also configure the MRGL to have secondary, tertiary resources
(and so forth), so that if the conference bridge at a remote location is out of
resources or is unavailable, resources from another site can be used as a
backup. You can use MRGs and MRGLs for any other media resource (for instance,
Music On Hold Servers (MOH), and Transcoding resources).
Cisco recommends that you have knowledge of Cisco CallManager
The information in this document is based on Cisco CallManager 3.1x and
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.
Refer to the
Technical Tips Conventions for more information on document
An MRGL provides a prioritized grouping of MRGs. An application selects
the required media resource, such as an MOH server, from among the available
media resources based on the priority order defined in an MRGL.
Media resource management provides access to media resources for all
Cisco CallManagers in a cluster. Every Cisco CallManager contains a software
component called a Media Resource Manager. The Media Resource Manager locates
the necessary media resource in order to connect media streams to complete a
feature (for example, MOH, Conferencing, and so forth). The Cisco CallManager
uses the Skinny protocol in order to interface to these media resources.
The Media Resource Manager manages these media resource types:
These reasons explain why resources are shared:
In order to allow both hardware and software devices to coexist
within a Cisco CallManager.
In order to enable Cisco CallManager to share and access resources
available within the cluster.
In order to enable Cisco CallManager to perform load distribution
within a group of similar resources.
In order to enable Cisco CallManager to allocate resources based on
Initialization of Cisco CallManager creates a Media Resource Manager.
Each Media Termination Point, MOH, Transcoder, and Conference Bridge device
defined in the database registers with the Media Resource Manager. The Media
Resource Manager obtains a list of provisioned devices from the database and
constructs and maintains a table in order to track these resources. The Media
Resource Manager uses this table in order to validate registered devices. The
Media Resource Manager keeps track of the total devices available in the
system. The Media Resource Manager also tracks the devices that have available
When a media device registers, Cisco CallManager creates a controller
in order to control this device. After the device is validated, the system
advertises its resources throughout the cluster. This mechanism allows the
resource to be shared throughout the cluster.
Resource reservation takes place based on search criteria. The given
criteria provide the resource type and the MRGL. When the Cisco CallManager no
longer needs the resource, resource deallocation occurs. Cisco CallManager
updates and synchronizes the resource table after each allocation and
The Media Resource Manager interfaces with these major components:
The Call Control software component performs call processing, this
includes setup and tear down of connections. Call Control interacts with the
feature layer in order to provide services like transfer, hold, conference, and
so forth. Call Control interfaces with the Media Resource Manager when it needs
to locate a resource in order to set up a conference call and/or MOH
The Media Control software component manages the creation and teardown
of media streams for the endpoint. Whenever a request for media to be connected
between devices is received, Media Control sets up the proper interface in
order to establish a stream, which depends on the type of endpoint.
The media layer interfaces with the Media Resource Manager when it
needs to locate a resource in order to set up a Media Termination Point. Media
Termination Point Control provides the capability to bridge an incoming H.245
stream to an outgoing H.245 stream. Media Termination Point maintains an H.245
session with an H.323 endpoint when the streaming from its connected endpoint
stops. Media Termination Point currently supports only codec G.711 and can also
transcode a-law to mu-law.
For each Media Termination Point device defined in the database, Cisco
CallManager creates a Media Termination Point Control process. This Media
Termination Point Control process registers with the Media Resource Manager
when it initializes. The Media Resource Manager keeps track of these Media
Termination Point resources and advertises their availability throughout the
Unicast Bridge Control provides the capability to mix a set of incoming
unicast streams into a set of composite output streams. Unicast Bridge provides
resources in order to implement ad hoc and meet-me conferencing in the Cisco
CallManager. For each Unicast Bridge device defined in the database, Cisco
CallManager creates a Unicast Control Process. This Unicast Control Process
registers with the Media Resource Manager when it initializes. The Media
Resource Manager tracks Unicast stream resources and advertises their
availability throughout the cluster.
MOH provides the capability to redirect a party on hold to an audio
server. For each MOH server device defined in the database, Cisco CallManager
creates an MOH control process. This MOH Control Process registers with the
Media Resource Manager when it initializes. The Media Resource Manager tracks
MOH resources and advertises their availability throughout the cluster. MOH
supports both Unicast and Multicast audio sources.
MRGs are logical groupings of media resources. A single MRG can
contain hardware conference resources, software conference resources,
transcoder resources, MOH servers, and software Media Termination Points. An
MRG has no user-defined order. All resources in an MRG are considered equal.
Therefore, Cisco CallManager loads share between resources of each type in one
When transcoding is used with a conference, the transcoder is
selected based on the MRGL of the Conference Bridge.
Note: You cannot explicitly configure an MRGL for a Conference Bridge.
Therefore, the MRGL is taken first from the Device Pool, and then from the MRG
When a phone is put on hold, the MRGL of the device that it put on
hold (could be a gateway for offnet calls) determines which MOH server is used
to play music to the held device.
Conference Bridges are chosen based on the MRGL of the conference
controller (the party that initiates the conference).
If a call goes out through a gateway, and Media Termination Point
(MTP) is required. The MRGL of the gateway is then used to select the
MRGLs are an ordered list of MRGs. All resources in one MRG must be
exhausted before Cisco CallManager attempts to use a media resource from
another MRG in the same MRGL.
MRGLs can be associated on a per-device basis, which means that you
can give specific devices access to media resources on an individual basis. A
second MRGL can also be configured at the device pool level.
The last MRGL is the default MRGL. A media resource that is not
assigned to an MRG is automatically assigned to the default MRGL. The default
MRGL is always searched and it is the last resort if no resources are available
in the device-based MRGL and the device pool MRGL or if no MRGLs are configured
at any level.
Complete these steps in order to configure your MRG/MRGLs after you
have your media resources configured within Cisco CallManager.
Login to the Cisco CallManager Administration page and select
Service > Media Resource >
Media Resource Group.
Select Add a New Media Resource Group.
A list of all the configured media resources displays.
Enter a name for the MRGs. Select the resources that you want to
associate with this MRG and then click Insert.
Note: In this example, two MRGs are created. One for Main Site
resources and one for Remote Site resources.
Create another MRG for the remote site resources. In this example,
a copy is made of the first group and the Name is changed to reflect the new
Select all the necessary resources and click
Select Service > Media
Resource > Media Resource Group List in order to
create an MRGL to associate the MRG(s).
Click Add a New Media Resource Group List.
Four MRGLs are created in this example.
MRG Dallas_MRGL for the main site resources.
MRG SanJose_MRGL for the remote site resources.
MRG Dallas_Redundant_MRGL for redundancy if the server that the
Dallas office devices are honed to goes down. If media resources are not
available at this site, they failover to the remote site resources so that
calls do not fail.
MRG SanJose_Redundant_MRGL for redundancy if the server that the
San Jose office devices are honed to goes down. If media resources are not
available at the remote site, they failover to the main site resources so that
calls do not fail.
For the Dallas_Redundant_MRGL, the Dallas_MRG is first in the list
and SanJose_MRG is the second.
For the SanJose_Redundant_MRGL, the SanJose_MRG is first in the
list and Dallas_MRG is the second.
When you perform a search on Media Resource Group
Lists, you see all four lists that are created.
Associate the MRGL with either the Device Pool for all users or
through configuration on the device itself.
In this example, the redundant MRGL is configured for both the
Dallas Location and San Jose location.
The next example shows the configuration of the MRGL on the device
itself. When an MRGL is configured directly on the device, that MRGL takes
precedence over the Device Pool configuration.
This error message appears in the Event Viewer:
Error: ConferenceNoMoreResourcesAvailable - No more Conference Resources available
Complete these steps in order to check if all the hardware conference
bridges are registered with the Cisco CallManager.
Go to the CallManager Admin page and choose
Service > Media Resource >
Click Find and check if all the bridges are
Note: Distribute Media Resources in an optimal manner under the Device Pool
When you call the IP Contact Center (IPCC) remote location, the phone
rings at the remote location, but when the user picks up the phone, a fast busy
signal is received.
In order to resolve the issue, create separate Media Resource Groups
(MRGs) for the software transcoder resources and hardware transcoder resources
and make sure that the hardware transcoder resource MRG has first priority in
the Media Resource Group List (MRGL).