Nortel plans to put smarts into IP voice

Nortel Networks is working to develop a standardised protocol that would allow the intelligent calling functions of the Signaling System 7 (SS7) network to interoperate with voice traveling over IP networks.

While SS7-related activity has been hot and heavy recently, one analyst noted most vendor initiatives, including Nortel's, are strong on intent but weak on specifics.

"The whole debate on convergence and voice over IP and SS7 has been incredibly superficial," said Tom Nolle, president of Voorhees, New Jersey, consultancy CIMI. "The vendors have not been forthcoming in what they're doing and no one's pushing them on it."

SS7 is a protocol that network elements in the PSTN use to exchange information to set up, control and route voice calls.

What Nortel's initiative, labeled IPS7, aims to do is get the knowledge of the IP network totally integrated into the SS7 network element, said Marcel Chenier, director of technology for Nortel's signaling solutions group.

"From an SS7 network element point of view, the connection and use of IP services would be totally similar (to the PSTN). You'll be able to totally integrate the two networks from an SS7 point of view," Chenier said.

Nortel plans to keep IPS7 fully open and extendible and has already submitted a general definition of the initiative to the IETF, Chenier said.

According to Nolle, vendors such as Nortel aren't looking at the issue of intelligent calling functions on IP networks properly.

"They have to get off SS7," he said. "Anyone who's talking about SS7 to IP is solving the wrong problem."

Instead, Nolle believes, vendors should look at building intelligent network functions into IP in a way that's optimised for the packet space. This is especially true if vendors think the network of the future will be a converged voice/data packet network and the PSTN will fade into oblivion, he said.

Because SS7 was built for the PSTN, it tries to map the devices and protocols of the PSTN into IP, rather than mapping the intelligent functions themselves directly into IP, Nolle explained. So, for instance, an IP router would need to look like a voice switch to an SS7 network element if SS7 was to work in the IP space.

Lyndon Ong, chair of the IETF's signaling transport group and senior architect with Nortel's Bay Networks division, said vendors will eventually look at building intelligent network functions optimized for IP.

But because the PSTN and IP networks coexist for the moment and will probably coexist for many years into the future, "using SS7 as a way to interface between them is a big thing," Ong said.

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