Implementing MGCP Gateways (Examining VoIP Gateways and Gateway Control Protocols) Part 3

Configuring Fax Relay with MGCP Gateways

Figure 5-22 and Example 5-9 show an MGCP configuration of a voice gateway that is configured for T.38 fax support.

Figure 5-22 Fax Pass-Through and Relay with MGCP Gateways Topology

Example 5-9 Fax Pass-Through and Relay with MGCP Gateways Example

This scenario requires a company’s headquarters in San Jose to be able to fax to its Austin office using MGCP. As a network administrator, your responsibility is to configure the gateway to meet the requirements of the network.

Requirements dictate that you

■ Configure a call agent to work with the gateway.

■ Disable Cisco Fax Relay.

■ Enable MGCP on the gateways.

■ Specify additional MGCP package capabilities.

■ Specify the maximum fax rate allowed for MGCP.

■ Adjust the NSE timers for network conditions.

■ Configure the fax machines to negotiate down to G3 speeds.

The following steps describe how to configure fax pass-through with MGCP gateways.

Step 1. Enable the gateway to communicate with Cisco Unified Communications Manager through the MGCP.

This command enables the gateway to communicate with Cisco Unified Communications Manager (UCM) through MGCP. This command also enables control agent redundancy when a backup UCM server is available.

Step 2. Disable the Cisco Fax Relay protocol.

Step 3. Allocate resources for the MGCP.

The port option specifies the UDP port for the MGCP gateway. The UDP port range is from 1025 through 65535. The default is UDP port 2427.

Step 4. Specify the address and protocol of the call agent for MGCP.

Step 5. Specify the FXR package for fax transmissions.

Events specified in the MGCP messages from the call agent must belong to one of the supported packages. Otherwise, connection requests are refused by the gateway.

By default, certain packages are configured as supported on each platform type. Using this command, you can configure additional package capability only for packages that are supported by your call agent. You can also disable support for a package with the no form of this command. Enter each package you want to add as a separate command.

Step 6. Define the maximum fax rate for MGCP T.38 sessions.

Step 7. Define the timeout period for awaiting NSE responses from the dial peer.

The nse-response t38 option sets the timer for awaiting T.38 NSE responses. This timer is configured to tell the terminating gateway how long to wait for an NSE from a peer gateway. The NSE from the peer gateway can either acknowledge the switch and its readiness to accept packets or indicate that it cannot accept T.38 packets.

Step 8. Allow SG3 fax machines to operate at G3 speeds in fax relay mode.

When this command is entered, the DSP fax-relay firmware suppresses the V8 call menu (CM) tone, and the fax machines negotiate down to G3 speeds for the fax stream.

Verifying MGCP

Several show and debug commands provide support for verifying and troubleshooting MGCP. You should be familiar with the information provided from each command and how this information can help you.

Use the output of the show mgcp command, an example of which is provided in Example 5-10, to verify the status of a router’s MGCP parameters. You should see the IP address of the UCM server that you use (10.1.1.101, in this example) and the port you are using to for MGCP. You should also see the administrative and operational states as ACTIVE. All other parameters are left at their default behavior in this example. Also highlighted in the example are the packages supported by the gateway.

Example 5-10 show mgcp Command

 

 

 

 

The show ccm-manager command verifies the active and redundant configured Cisco CallManager servers. It also indicates whether the gateway is currently registered with Cisco Unified Communications Manager. Example 5-11 illustrates sample output from the command.

Example 5-11 show ccm-manager Command

The show mgcp endpoint command displays a list of the voice ports that are configured for MGCP. Example 5-12 illustrates sample output from the command.

Example 5-12 show mgcp endpoint Command

The show mgcp statistics command displays a count of the successful and unsuccessful control commands, as shown in Example 5-13. You should investigate a high unsuccessful count.

Example 5-13 show mgcp endpoint Command

Debug Commands

The following debug commands are useful for monitoring and troubleshooting MGCP:

■ debug voip ccapi inout: This command shows every interaction with the call control application programming interface (API) on the telephone interface and the VoIP side. Watching the output allows users to follow the progress of a call from the inbound interface or VoIP peer to the outbound side of the call. This debug command is very active. Therefore, you should use it sparingly in a live network.

■ debug mgcp [ all I errors I events I packets I parser ]: This command reports all mgcp command activity. You should use this debug command to trace the MGCP request and responses.