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How To Configure CallRex for Cisco Forked Audio

Introduction

Call recording using Cisco Forked Audio is an elegant solution to replace traditional passive recording methods that use packet sniffing technology. Not only does the new solution provide a tighter integration with Cisco UCM but it also eliminates the need for complicated port mirroring (SPAN) setup on network elements across the organization.

Network Administrators that have configured port mirroring for huge organizations with complicated networks would agree that setting up port mirroring to record all phones can often be a challenging and costly exercise.

Telrex’s implementation of Call Recording using Cisco Forked Audio aims to eliminate this hardship for network administrators to enable devices for recording in an easy and cost effective manner.

Technical Details

The forked audio solution uses a Cisco IP Phone’s internal DSP resource called a built-in-bridge that enables the audio from the phone to be streamed directly to the CallRex Server via a SIP Trunk.

Note that the SIP Trunk to the CallRex Server is setup by the CUCM but the audio flows from the phone in question directly to the CallRex Server. The audio from both the ends of the call are sent separately and simultaneously via two separate SIP sessions. CallRex would also receive call control details via TAPI. The two audio streams are mixed together, tagged with the call control information received and merged into a single recording by the CallRex Server. CallRex supports recording audio in G.711 and G.729A codec formats.

Figure 1 shows the example of recording a PSTN call. Internal call recording would also be similar, as the phone is responsible for forking the audio to the Server.

Configuration

On the CUCM, a directory number is assigned to the CallRex Server and a route pattern is configured for the SIP Trunk pointing to it.

On the CallRex Server, the Cisco TSP application needs to be installed in order to receive TAPI notifications of device specific events. The application user authorized to use the TSP on the CallRex Server should have recording capabilities enabled. It should also have the list of all users that need to be recorded in its list of controlled devices.

For futher details on how to setup the CUCM for Forked Audio Recording, visit the Guide to Configure Silent Monitoring and Recording on Cisco's web site.

CallRex-Specific Configuration to Enable Forked Audio
The following are the necessary steps to equip CallRex 3.9.2 for recording via Cisco Forked Audio:

• Download the cisco TSP from the UCM interface and install it on the CallRex Server
• From the Start Menu, navigate to Control Panel > Phone and Modem Options > Advanced Tab
• Select the appropriate Cisco TSP and select Configure
• In the User tab, enter the username and password of the application user created in UCM interface
• In the CTI Manager tab, enter the IP address of the UCM
• In CallRex, under Services > Call Recording, select Cisco Forked Audio as the PBX type
• In CallRex, under Services > Call Control, select Cisco Forked audio as the PBX type
• IP Addresses for the Users in CallRex need not be added as they are populated during recording

Call Monitoring and On-Demand Recording
CallRex provides the capability to monitor all calls in progress regardless of whether they are being recorded on CallRex or not. Every device in a call in progress that is not set to automatically record will show up as On Phone and the user can monitor or record the call on-demand.

Basic Hardware Requirements

• CPU: 2 GHz Pentium 4 or better -- see the CallRex server specifications on the CallRex datasheet for details
• Operating System: Windows Server 2003 SP2
• CUCM Version: Cisco Unified communications Manager 7.0 or above
• Supported Devices: The following devices are supported according to Cisco: 7906G, 7911G, 7931G, 7941G, 7941G-GE, 7961G, 7961G-GE, 7970G, 7971G-GE and Cisco IP Communicator 7.0 and above.
• Check with Cisco or your hardware vendor for specific devices that have the Built-in-Bridge capability.

See also

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