Cable IP Telephony

In addition to offering high-speed Internet access to PCs, cable operators are also working to leverage Docsis cable modem and PacketCable technology to deliver IP telephony services.

The idea of offering competitive residential telephone services has captivated cable operators for years. Although reliable telephony equipment for hybrid fiber-coaxial (HFC) networks is commercially available, economic and technical barriers have discouraged most MSOs in North America from widely deploying it. Two exceptions are Comcast Corp. (Nasdaq: CMCSA, CMCSK) and Cox Communications Inc. , which count more than 2.5 million circuit-switched cable telephone customers. Now, with Internet Protocol (IP) networks emerging as viable platforms for the delivery of voice traffic, many MSOs are using their high-speed data networks to support packet telephone services as an alternative to deploying standalone HFC telephony equipment. The rationale is clear. Deploying separate telephony and high-speed data architectures creates capital, operational, and spectrum inefficiencies, since a cable operator must purchase two hardware platforms, allocate a pair of upstream and downstream channels for each service, integrate two operations support systems, and assign staff to manage each service offering.

Using IP, cable operators hope to create an integrated, multiservice communications platform that operates on a lower cost structure than existing circuit-switched alternatives, enabling aggressive service price discounting without sacrificing margins. Besides undercutting competitors, MSOs hope the flexibility of IP networks will allow them to deliver a host of unique value-added features, such as integrated voice mail and email messaging and the real-time provisioning of additional phone lines without rewiring a home.

However, to make this vision a reality, cable operators needed to overcome a number of hurdles. The first-generation Data Over Cable Service Interface Specification (Docsis) cable modem standard was not specifically designed to support IP telephony and had to be enhanced. Cable packet telephony operations support systems had to be developed to handle customer provisioning, management, and billing. And MSOs are developing required interconnection standards for their IP backbone networks to effectively share packet telephony traffic.

In September 1997 Cable Television Laboratories Inc. (CableLabs) initiated a project on behalf of its North American MSO members, called PacketCable, to address these issues. Most leading networking and telecommunications vendors are participating in the cable IP telephony initiative.

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