Media Termination Points
A Media Termination Point (MTP) software device allows Cisco Unified CallManager to relay calls that are routed through SIP or H.323 endpoints or gateways.
This section covers the following topics:
•Understanding Media Termination Points
•Managing MTPs with the Media Resource Manager
•MTP Types in Cisco Unified CallManager Administration
•MTP System Requirements and Limitations
•MTP Failover and Fallback
•Software MTP Performance Monitoring and Troubleshooting
•Software MTP Configuration Checklist
•Where to Find More Information
Note For information on hardware MTP, which act as transcoders, see the "Transcoders" section on page 22-1.
Understanding Media Termination Points
Media Termination Points extend supplementary services, such as call hold, call transfer, call park, and conferencing, that are otherwise not available when a call is routed to an H.323 endpoint. Some H.323 gateways may require that calls use an MTP to enable supplementary call services, but normally, Cisco IOS gateways do not.
The Cisco IP Voice Media Streaming Application MTP accepts two full-duplex G.711 Coder-Decoder (CODEC) stream connections. MTPs bridge the media streams between two connections. The streaming data that is received from the input stream on one connection passes to the output stream on the other connection and vice versa. In addition, the MTP trancodes a-law to mu-law (and vice versa) and adjusts packet sizes as required by the two connections.
Each MTP belongs to a device pool, which specifies, in priority order, the list of Cisco Unified CallManagers to which the devices that are members of the device pool should attempt to register. This list represents a Cisco Unified CallManager group. The first Cisco Unified CallManager in the list specifies a device primary Cisco Unified CallManager.
An MTP device always registers with its primary Cisco Unified CallManager if that Cisco Unified CallManager is available and informs the Cisco Unified CallManager about how many MTP resources it supports. The Cisco Unified CallManager controls MTP resources. You can register multiple MTPs with the same Cisco Unified CallManager. When more than one MTP is registered with a given Cisco Unified CallManager, that Cisco Unified CallManager controls the set of resources for each MTP. You can also distribute the MTPs across a networked system as desired.
For example, MTP server 1 is configured for 48 MTP resources. The MTP server 2 is configured for 24 resources. If both MTPs register with the same Cisco Unified CallManager, that Cisco Unified CallManager maintains both sets of resources for a total of 72 registered MTP resources.
When the Cisco Unified CallManager determines that a call endpoint requires an MTP, it allocates an MTP resource from the MTP that has the least active streams. That MTP resource gets inserted into the call on behalf of the endpoint. MTP resource use remains invisible to both the users of the system and to the endpoint on whose behalf it was inserted. If an MTP resource is not available when it is needed, the call connects without using an MTP resource, and that call does not have supplementary services.
Make sure that the Cisco IP Voice Media Streaming application is activated and running on the server on which the MTP device is configured.
The Cisco IP Voice Media Streaming application, which is common to the MTP, Conference Bridge, annunciator, and Music On Hold applications, runs as a Windows 2000 service.
You can add an MTP device in two ways:
•You automatically add an MTP device when you activate the Cisco IP Voice Media Streaming Application service from Cisco Unified CallManager Serviceability.
•You can manually install the Cisco IP Voice Media Streaming Application on a networked server and configure an MTP device on that server through Cisco Unified CallManager Administration.
SIP and MTP
Cisco Unified CallManager requires an RFC 2833 DTMF-compliant MTP device to make SIP calls. The current standard for SIP uses inband payload types to indicate DTMF tones, and Cisco components such as SCCP IP phones support only out-of-band payload types. Thus, an RFC 2833-compliant MTP device monitors for payload type and acts as a translator between inband and out-of-band payload types.
With the MTP device, any service that requires a media change (such as call hold) happens transparently. No need exists to send any media update signal to the SIP proxy server.
Managing MTPs with the Media Resource Manager
The Media Resource Manager (MRM), a software component in the Cisco Unified CallManager system, primarily functions for resource registration and resource reservation. Each MTP device that is defined in the database registers with the MRM. The MRM keeps track of the total available MTP devices in the system and of which devices have available resources.
During resource reservation, the MRM determines the number of resources, identifies the media resource type (in this case, the MTP), and the location of the registered MTP device. The MRM updates its shared resource table with the registration information and propagates the registered information to the other Cisco Unified CallManagers within the cluster.
The MRM enhances the Cisco Unified CallManager MTP, Music On Hold, Conference Bridge, and Transcoder devices by distributing the resources throughout the Cisco Unified CallManager cluster, making the features more efficient and economical.
MRM also supports the coexistence of an MTP and transcoder within a Cisco Unified CallManager.
MTP Types in Cisco Unified CallManager Administration
The media termination point types in Table 24-1 exist in Cisco Unified CallManager Administration.
Table 24-1 Media Termination Point Types
Cisco IOS Enhanced Software Media Termination Point
This type supports Cisco 2600XM, Cisco 2691, Cisco 3725, Cisco 3745, and Cisco 3660 Access Routers and the following MTP cases:
•For software-only implementation that does not use DSP but has the same packetization time for devices that support G.711 to G.711 or G.729 to G.729 codecs, this implementation can support up to 500 sessions per gateway.
•For a hardware-only implementation with DSP for devices that use G.711 codec only, 200 sessions can occur per NM-HDV2 and 48 sessions can occur per NM-HD.
This type can support Network Address Translation in a service provider environment to hide the private address.
In Cisco Unified CallManager Administration, ensure that you enter the same MTP name that exists in the gateway Command Line Interface (CLI).
Refer to the "Configuring Enhanced Conferencing and Transcoding for Voice Gateway Routers" section of the Cisco Unified CallManager and Cisco IOS Interoperability Configuration Guide for more information.
Cisco Media Termination Point Software
A single MTP provides a default of 48 MTP (user configurable) resources, depending on the speed of the network and the network interface card (NIC). For example, a 100-MB Network/NIC card can support 48 MTP resources, while a 10-MB NIC card cannot.
For a 10-MB Network/NIC card, approximately 24 MTP resources can be provided; however, the exact number of MTP resources that are available depends on the amount of resources that is being consumed by other applications on that PC, the speed of the processor, network loading, and various other factors.
Planning Your Software MTP Configuration
Provisioning represents a crucial aspect that needs consideration when deploying MTP resources. Provisioning requires attentive analysis of the call load patterns and the network topology.
Consider the following information when you are planning your MTP configuration:
•An improper setting can result in undesirable performance if the workload is too high.
•A single MTP provides a default of 48 MTP (user configurable) resources, depending on the speed of the network and the network interface card (NIC). For example, a 100-MB Network/NIC card can support 48 MTP resources, while a 10-MB NIC card cannot.
•For a 10-MB Network/NIC card, approximately 24 MTP resources can be provided; however, the exact number of MTP resources that are available depends on the amount of resources that is being consumed by other applications on that PC, the speed of the processor, network loading, and various other factors.
Consider the following formula to determine the approximate number of MTPs that are needed for your system, assuming that your server can handle 48 MTP resources (you can substitute 48 for the correct number of MTP resources that are supported by your system):
A number divided by 48 = number of MTP applications needed (n/48 = number of MTP applications).
n represents the number of devices that require MTP support for H.323 and SIP calls.
If a remainder exists, add another server with Cisco IP Voice Streaming Application server with MTP.
•If one H.323 or SIP endpoint requires an MTP, it consumes one MTP resource. Depending on the originating and terminating device type, a given call might consume more than one MTP resource. The MTP resources that are assigned to the call get released when the call terminates.
•Use Performance Monitor to monitor the usage of MTP resources. The Performance Monitor counter, Media TermPoints Out of Resources, increments for each H.323 or SIP call that connects without an MTP resource when one was required. This number can assist you in determining how many MTP resources are required for your callers, and whether you have adequate coverage.
•Identical system requirements apply for the Cisco IP Voice Media Streaming Application and MTP and the Cisco Unified CallManager system.
•Cisco Unified CallManager requires an RFC 2833 DTMF compliant MTP device to make SIP calls.
Software MTP Device Characteristics
The Full Streaming Endpoint Duplex Count, a number of MTP resources that are supported by a specific MTP, represents a device characteristic that is specific to MTP device configuration. Refer to the "Software MTP Configuration Settings" section in the Cisco Unified CallManager Administration Guide for a detailed description of all MTP device settings.
Avoiding Call Failure/User Alert
To prevent call failure or user alert, avoid the following conditions:
•Although the Cisco IP Voice Media Streaming Application service can run on the same PC as the Cisco Unified CallManager, we strongly recommend against this. If the Cisco IP Voice Media Streaming Application is running on the same PC as the Cisco Unified CallManager, it can adversely affect the performance of the Cisco Unified CallManager.
•When you configure the MTP, a prompt asks you to reset MTP before any changes can take effect. This action does not result in disconnection of any calls that are connected to MTP resources. If you choose Reset, as soon as the MTP has no active calls, the changes take effect.
Note When you make updates to the MTP and you choose Restart, all calls that are connected to the MTP get dropped.
MTP System Requirements and Limitations
The following system requirements and limitations apply to software MTP devices:
•You can activate only one Cisco IP Voice Streaming Application per server. To provide more MTP resources, you can activate the Cisco IP Voice Streaming application on additional networked Windows NT servers.
•Each MTP can register with only one Cisco Unified CallManager at a time. The system may have multiple MTPs, each of which may be registered to one Cisco Unified CallManager, depending on how your system is configured.
•Cisco strongly recommends that you do not activate the Cisco IP Voice Streaming Media Application on a Cisco Unified CallManager with a high call-processing load because it can adversely affect the performance of the Cisco Unified CallManager.
•Up to 128 half-duplex streams are configurable.
•With 128 configured streams, 64 full-duplex resources are available for media termination point application.
MTP Failover and Fallback
This section describes how MTP devices failover and fallback when the Cisco Unified CallManager to which they are registered becomes unreachable. This section also explains conditions that can affect calls that are associated with an MTP device, such as MTP reset or restart.
•Active Cisco Unified CallManager Becomes Inactive
•Resetting Registered MTP Devices
Active Cisco Unified CallManager Becomes Inactive
The following description gives the MTP device recovery methods when the MTP is registered to a Cisco Unified CallManager that goes inactive:
•If the primary Cisco Unified CallManager fails, the MTP attempts to register with the next available Cisco Unified CallManager in the Cisco Unified CallManager Group that is specified for the device pool to which the MTP belongs.
•The MTP device reregisters with the primary Cisco Unified CallManager as soon as it becomes available after a failure and is currently not in use.
•The system maintains the calls or conferences that were active in call preservation mode until all parties disconnect. The system does not make supplementary services available.
•If an MTP attempts to register with a new Cisco Unified CallManager and the register acknowledgment is never received, the MTP registers with the next Cisco Unified CallManager.
Resetting Registered MTP Devices
The MTP devices will unregister and then disconnect after a hard or soft reset. After the reset completes, the devices reregister with the Cisco Unified CallManager.
To find what media resource groups a specific media termination point is using, click the Dependency Records link that is provided on the Cisco Unified CallManager Administration Media Termination Point Configuration window. The Dependency Records Summary window displays information about media resource groups that are using the media termination point. To find out more information about the media resource group, click the media resource group, and the Dependency Records Details window displays. If the dependency records are not enabled for the system, the dependency records summary window displays a message.
For more information about Dependency Records, refer to Accessing Dependency Records and Deleting a Media Resource Group in the Cisco Unified CallManager Administration Guide.
Software MTP Performance Monitoring and Troubleshooting
Microsoft Performance Monitor counters for media termination point allow you to monitor the number of media termination points that are currently in use, the number of media termination points that are currently registered with the Cisco Unified CallManager but are not currently in use, and the number of times that a media termination point was requested for a call, but no resources were available. For more information about performance monitor counters, refer to the Cisco Unified CallManager Serviceability System Guide and the Cisco Unified CallManager Serviceability Administration Guide.
Cisco Unified CallManager writes all errors for the media termination point to the Event Viewer. In Cisco Unified CallManager Serviceability, you can set traces for the Cisco IP Voice Media Streaming Application service; to troubleshoot most issues, you must choose the Significant or Detail option for the service, not the Error option. After you troubleshoot the issue, change the service option back to the Error option.
Cisco Unified CallManager generates registration and connection alarms for media termination point in Cisco Unified CallManager Serviceability. For more information on alarms, refer to the Cisco Unified CallManager Serviceability Administration Guide and the Cisco Unified CallManager Serviceability System Guide.
If you need technical assistance, locate and review software MTP logs from C:\Program Files\Cisco\Trace\CMS\cms*.* and C:\Program Files\Cisco\Trace\CCM before you contact your Cisco Partner or the Cisco Technical Assistance Center (TAC).
Software MTP Configuration Checklist
Table 24-2 provides a checklist to configure MTP.
Table 24-2 MTP Configuration Checklist
Procedures and Related Topics
Determine the number of MTP resources that are needed and the number of MTP devices that are needed to provide these resources.
Planning Your Software MTP Configuration
Verify that the Cisco IP Voice Media Streaming Application service is activated and running on the server to which you are adding an MTP.
Cisco Unified CallManager Serviceability Administration Guide
Cisco Unified CallManager Serviceability System Guide
Add and configure the MTPs.
Adding a Media Termination Point, Cisco Unified CallManager Administration Guide
Add the new MTPs to the appropriate media resource groups.
Media Resource Management
Media Resource Group Configuration Settings, Cisco Unified CallManager Administration Guide
Restart the MTP device.
Updating a Media Termination Point, Cisco Unified CallManager Administration Guide
Where to Find More Information
•Media Resource Management
•Transcoders, page 22-1
•Cisco DSP Resources for Transcoding, Conferencing, and MTP
Additional Cisco Documentation
•Media Resource Group Configuration, Cisco Unified CallManager Administration Guide
•Media Resource Group Configuration Settings, Cisco Unified CallManager Administration Guide
•Cisco Unified Communications Solution Reference Network Design
•Cisco Unified CallManager and Cisco IOS Interoperability Configuration Guide