IMS spans carrier networks – in labs, if not yet reality

The NGN IMS Forum today said its last plugfest lab test successfully demonstrated a working IP Multimedia Subsystem (IMS) network spanning two simulated operator networks and lab locations on four continents, showing advanced capabilities like user roaming and distributed authentication.

Plugfest 6 was held January 12-16 with network locations in the US, France, Israel and China. In addition to setting up the core IMS networks, the tests included several different IMS CPE/clients as well as advanced charging, billing and policy servers operating in support of IP applications. The core network was set up in a day and a half and was built to support up to 250,000 user sessions, said Manuel Vexler, chair of the IMS Technical Working Groups.

“This was the first time we tested what was essentially an environment with two service providers and a variety of commercial user equipment connected to the network,” Vexler said. “It let us test complex scenarios, such as roaming to other [IMS] networks and real-time billing for services.”

The goal of the NGN IMS Forum – like any lab-based group – is to test capabilities out ahead of commercial deployment. Across its six plugfests, the forum has tested core gear and interface interoperability that is now paying dividends in real-world IMS deployments, which are growing – albeit cautiously – across the globe.

Testing cross-domain IMS roaming – which is akin to, though more complex than, today’s wireless network roaming – is certainly ahead of commercial reality. Most IMS networks today are focused on supporting single services on a single network. And though IMS clients are emerging, they are not so widespread on real-world devices that cross-network interoperability is a big issue – at least yet.

Indeed, exactly when there will be multiple, commercial IMS networks that require a user to register themselves and their services in order to seamlessly roam between networks is the “$64,000 question,” admitted John Lenns, associate vice president of business development at Tekelec, which participated in the plugfest.

“What was good to see was the increasing sophistication of testing two networks -- a subscriber’s home network and a visiting network,” Lenns said. “What it means for our CSCF [call session control function server] is that we were able to show it interoperating not only in those scenarios but also with more third-party products – more HSSs [home subscriber servers], instant messaging servers, rating interfaces. We saw no real problems [in the testing].”

IMS roaming starts with simple tasks – the client registers and authenticates with the visiting network, shares profiles via an HSS, etc. – but in a complex IMS environment can expand quickly to include federated security and service- and role-based policy control, Vexler said.

To demonstrate such scenarios, the plugfest tested a variety of end-to-end charging scenarios (on- and offline billing), including interoperability of Diameter and SIP interfaces, as well as interfaces for charging, policy and application servers. Among the applications tested were voice over IP, video over IP and picocell network access.

Vendors involved in the testing included Acision, HP, Inexbee, Marben-Products, Mu Dynamics, NTT AT, Radvision, Sonus Networks, Starent Networks and Tekelec.