At the technical heart of the problems are the basic protocols used to signal VoIP connections, session initiation protocol and H.232. These are evolving standards that have been implemented differently by equipment makers. As a result softswitches and Internet protocol gateways from one vendor may not interoperate with equipment from another. And if the equipment sitting on each network isn't able to talk to each other, then the call can't be completed.
"One can imagine simply taking IP traffic from one network to another," said Joe Aibinder, product marketing director for AT&T. "But there is more to it than that. You have to be using the same type of softswitch with the same software release to make the connection."
A new category of product has been developed to help alleviate this issue. VoIP session controllers can be deployed between two carrier networks to help simplify the protocol conversion. Acme Packet, Ingate Systems, Jasomi Networks, Kagoor Networks, Netrake, NexTone Communications, Ridgeway Systems and Software, and softswitch maker, Sonus, all offer session control products.
But even with session control technology translating the protocols, carriers still need to test and tweak the networks at the interconnection points.
"At this level there's always some sort of testing and certification that must happen," Aibinder said. "But it is becoming easier."
Edward Morche, vice president of soft-switch business development for Level 3 Communications agrees. Level 3, which is considered a carrier's carrier, has been interconnecting IP networks for the past four years. Most of these early deployments required a lot of customisation and tweaking to allow seamless communication between networks. Just recently, the carrier has installed session controllers from Netrake and NexTone Communications to help make this process less labour intensive, so that it's able to offer the solution to more customers.
