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Feature Article
November 2004

VoIP Call Recording Goes Mainstream

BY Robert Kapela

The majority of new telephone systems sold today is either IP-based or IP-enabled. Very soon, digital and analog based PBXs will become obsolete as IP PBXs take precedence due to their lower maintenance cost and greater functionality. The rapid adoption of IP PBXs has been the catalyst for the development of a wealth of new technologies and capabilities, among which VoIP call recording is one of the most compelling.

The demand for call recording has increased dramatically in recent years, due to the need of businesses to improve customer service, increase agent productivity, address security concerns, and to comply with new legal requirements. Call recording and monitoring, a capability once available only to big business with big budgets, is now going mainstream.

Lowering Costs
Before the VoIP revolution, recording calls was an expensive proposition. Since most PBXs were either analog or digital, recording calls required the installation of proprietary telephony cards to enable the tapping of telephone lines in order to process the digital signals necessary for recording the calls. The high cost of these proprietary telephony cards, in addition to the ancillary costs of purchasing, installing and maintaining specialized servers, made call recording prohibitive for most businesses.

Today, as IP-enabled PBXs proliferate in the market, price barriers have dropped and call recording is now affordable for most businesses. Recording calls on IP and/or IP-enabled PBXs is significantly less expensive than on analog or digital PBXs because the voice traffic is packetized and travels across the corporate data network (LAN/WAN), not over traditional copper, twisted pair wiring.

To record calls, an IP-based call recording system monitors the corporate data network looking for voice packets as they travel across the corporate (LAN/WAN) to and from the IP PBX. This “packet sniffing” technology allows the call recording system to identify and extract only the voice packets for recording. Packet-sniffing also enables specialized monitoring features, such as the ability to trigger recording when certain conditions are met, or to flag calls by name or value according to particular requirements.

How It Works
In a multi-site VoIP call recording implementation (Figure 1) the IP PBX located at headquarters is connected to the (observe port) on the data switch and the call recording server is connected to the (analysis port) on the data switch. The data switch is enabled for port mirroring, so a copy of every packet going to and from the observe port (IP PBX) is also copied to the analysis port (call recording server). Remote sites are connected to headquarters via a high-speed data connection. The remote site receives dial tone locally or from the headquarters site.

At Remote Site #2, the IP PBX is connected to the observe port on the data switch and port mirroring is enabled on this port. The call recording data collector is connected to the analysis port on the data switch. The switch is configured so a copy of every packet going to and from the observe port (IP PBX) is also copied to the analysis port (call recording data collector). The data collector is configured to record, compress, and send calls in real time back to the main call recording server at headquarters where the calls are stored for later retrieval.

At Remote Site #1, an at-home worker is connected to the IP PBX at headquarters via a high-speed internet connection. As dial tone originates at headquarters, all calls are routed through the headquarters IP PBX and there is no need to install a data collector at the at-home worker remote location.

Key Benefits
Less expensive: VoIP recording/monitoring via packet sniffing is typically two to three times less expensive than digital recording solutions because it is software-based, requiring no station or truck taps or expensive third-party telephony cards.
Simple installation: No complex installation is required with VoIP recording/monitoring. Packet sniffing requires only a customer-supplied server to run the recording software and a data switch enabled for port-mirroring.
Easy maintenance: A VoIP call recording system is managed and maintained like any other software program. No punch-downs, cross-connects, or expensive telephony cards are required. Just point and click.
Record remote sites: With digital recording solutions, the cost of recording remote sites is prohibitive. With VoIP recording solutions, however, the incremental cost of adding remote sites is negligible.
No interference: VoIP call recording/monitoring is completely unobtrusive. As it merely sniffs packets, it will not interfere with the IP PBX or any other mission critical system.
Scalable: VoIP call recording systems are scalable without limit. Digital recording systems are limited in scalability based on the number of telephony cards that can be installed in the server and the number of calls that can be handled by each card.

The real benefit of IP PBXs is the fact that software applications can connect to them across the data network, thus eliminating the need to use expensive and proprietary telephony cards. Now small and medium sized businesses can take advantage of innovative software solutions, like packet-based call recording at price points they can afford. IT

Robert Kapela is a product manager at Telrex. For more information, please visit the company online at

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