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Understand Media Resource Groups and Group

Lists
Document ID: 45525

Introduction
Prerequisites
Requirements
Components Used
Conventions
Media Resource Groups and Media Resource Group Lists
The Media Resource Manager
Media Resource Manager Interfaces
Configure Media Resource Groups/Media Resource Group Lists
Configuration Procedure
Troubleshoot
Problem
Solution
Problem − Fast Busy is Received When Remote Location is Called
Solution
NetPro Discussion Forums − Featured Conversations
Related Information

Introduction
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).

Prerequisites
Requirements
Cisco recommends that you have knowledge of Cisco CallManager Fundamentals.

Components Used
The information in this document is based on Cisco CallManager 3.1x and later.

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.

Cisco − Understand Media Resource Groups and Group Lists
Conventions
Refer to the Cisco Technical Tips Conventions for more information on document conventions.

Media Resource Groups and Media Resource Group Lists
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.

• CM1 and CM2 belong to the same cluster.
• Cisco CallManager uses the MRGL concept in order to select resources. The selection depends on the
geographical assignment of the resources.

The Media Resource Manager
The Media Resource Manager manages these media resource types:

• MOH server.
• Unicast conference bridge (CFB).
• Media streaming application server (software media termination point).
• Transcoder (XCODE).

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 user preferences.

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

Cisco − Understand Media Resource Groups and Group Lists
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 resources.

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 deallocation.

Media Resource Manager Interfaces
The Media Resource Manager interfaces with these major components:

• Call Control
• Media Control
• Media Termination Point Control
• Unicast Bridge Control
• MOH Control

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 features.

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 cluster.

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

Cisco − Understand Media Resource Groups and Group Lists
audio sources.

Configure Media Resource Groups/Media Resource Group
Lists
• 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 MRG.
• 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 default pool.
• 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 MTP.
• 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.

♦ If a device has an MRGL configured at the device pool level as well as on the device itself,
the MRGL configured at the device level is searched first, followed by the MRGL on the
device pool.
• 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.

Configuration Procedure
Complete these steps in order to configure your MRG/MRGLs after you have your media resources
configured within Cisco CallManager.

1. Login to the Cisco CallManager Administration page and select Service > Media Resource > Media
Resource Group.

Cisco − Understand Media Resource Groups and Group Lists
2. Select Add a New Media Resource Group.

Cisco − Understand Media Resource Groups and Group Lists
A list of all the configured media resources displays.

3. 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.

Cisco − Understand Media Resource Groups and Group Lists
Cisco − Understand Media Resource Groups and Group Lists
4. 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 group.

5. Select all the necessary resources and click Insert.

Cisco − Understand Media Resource Groups and Group Lists
6. Select Service > Media Resource > Media Resource Group List in order to create an MRGL to
associate the MRG(s).

Cisco − Understand Media Resource Groups and Group Lists
7. Click Add a New Media Resource Group List.

Cisco − Understand Media Resource Groups and Group Lists
Four MRGLs are created in this example.

a. MRG Dallas_MRGL for the main site resources.

b. MRG SanJose_MRGL for the remote site resources.

Cisco − Understand Media Resource Groups and Group Lists
c. 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.

Cisco − Understand Media Resource Groups and Group Lists
8.

d. 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.
9. For the Dallas_Redundant_MRGL, the Dallas_MRG is first in the list and SanJose_MRG is the
second.

Cisco − Understand Media Resource Groups and Group Lists
10. For the SanJose_Redundant_MRGL, the SanJose_MRG is first in the list and Dallas_MRG is the
second.

Cisco − Understand Media Resource Groups and Group Lists
11. When you perform a search on Media Resource Group Lists, you see all four lists that are created.

Cisco − Understand Media Resource Groups and Group Lists
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.

Cisco − Understand Media Resource Groups and Group Lists
12.

13. 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.

Cisco − Understand Media Resource Groups and Group Lists
Troubleshoot
Problem
This error message appears in the Event Viewer:

Error: ConferenceNoMoreResourcesAvailable − No more Conference Resources available

Solution
Complete these steps in order to check if all the hardware conference bridges are registered with the Cisco
CallManager.

1. Go to the CallManager Admin page and choose Service > Media Resource > Conference Bridge.
2. Click Find and check if all the bridges are listed.

Note: Distribute Media Resources in an optimal manner under the Device Pool configuration.

Problem − Fast Busy is Received When Remote Location is Called
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.

Cisco − Understand Media Resource Groups and Group Lists
Solution
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).

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Updated: Jul 20, 2007 Document ID: 45525

Cisco − Understand Media Resource Groups and Group Lists