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October 2009 | Volume 12 / Number 10
Ask the SIP Trunk Expert

Cable Companies Leveraging SIP Trunks

There’s a new market turning its eye toward SIP trunking: cable companies. Recent announcements by some of the large players indicate that SIP trunking has become a significant way to leverage IP communications to shave costs.

Like service providers and end users, cable companies are using SIP trunking as a simplified way to offer their customers VoIP capability. This can be a boon for their business customers, who can consolidate bills and eliminate toll telephony costs. For the cable operators, SIP trunking offers a means of generating revenue from business customers who, in turn, will benefit from the savings and flexibility of this service.

Like other service providers, one of the problems for cable providers is interoperability between their telephony switches and the PBX (News - Alert) at the customer premises. To be truly effective – and secure – every customer’s IP PBX must work seamlessly with the SIP trunk service. Achieving certification with every vendor is a costly and time-consuming process – but a very necessary one.

The workaround: utilizing an Enterprise Session Border Controller (E-SBC) at the edge of the network, which serves as a normalization engine – or “universal adapter” — connecting the PBX to the SIP trunk and supporting requirements for authentication and signaling. With a single E-SBC, the cable company is instantly, truly interoperable with the IP PBX, offering their customers the reliability of a proven interop solution. Massive interoperability testing is no longer needed, further reducing costs for the cable company.

The E-SBC also provides other critical functions:

Demarcation point: Many service providers want a clear hand-off point between their network and the end customer. The E-SBC serves this important function, delivering health and quality statistics while establishing a security boundary.

Security and NAT traversal: When connecting enterprises to SIP trunks directly via the Internet, issues created by the enterprise firewall and the NAT must be resolved while also maintaining security. An enterprise border element provides the necessary functionality to resolve these problems.

Advanced Security: In addition to inspecting the SIP signaling and controlling the media ports, the E-SBC can add encryption to signaling and media (using TLS and SRTP), creating greater privacy.

SIP trunking is gaining ground with cable companies looking to build their business today and generate future revenue. With an E-SBC, the connection can be assured to be both interoperable and secure. IT

Steven Johnson is president of Ingate Systems (News - Alert).

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