Interoperability test completes its mission
Martin Rowe, Senior Technical Editor -- Test & Measurement World, 12/12/2006 5:49:00 AM
On October 27, the MultiService Forum (MSF) completed Global MSF Interoperability 2006 (GMI 2006), a two-week test of networks and their elements that use the IP Multimedia Subsystem (IMS) framework for carrying voice, video, and data over any network. GMI 2006 brought service providers, network-equipment makers, and test-equipment makers together at five locations in four countries around the world.
The locations—Verizon Labs and UNH-IOL in the US, NTT Communications in Japan, British Telecom, and Korea Telecom—kept over 500 engineers busy verifying interoperability of networks and equipment. I spoke on the phone with Andy Huckridge, director of IMS solutions at Spirent Communications. According to Huckridge, interoperability testing among equipment makers is important because “companies can implement communications standards differently, which can lead to incompatibility problems.”
“To test any next-generation network,” said Huckridge, "you need to set up a ‘physical scenario,’ a network that will carry the services. The MSF takes standards from industry standards bodies and takes a look at what exists today that can implement the standards. An industry forum tries to put those standards together and find the practical problems with implementing those standards with real building blocks.”
The standards that Huckridge refers to are called Implementation Agreements (IAs). The IAs, called out in “MSF Project Requirements Document for Global MSF Interoperability,” define how equipment makers must implement IMS. IAs cover topics such as the bandwidth manager for core/edge router and the interface between an access gateway and a call server.
Huckridge explained that testing focused on the quality of the traffic. The type of traffic varied depending on which part of the test network was in use. In most cases, the endpoints of the test network were application servers and the public service telephone network (PSTN). One test might involve a server transporting voice from a server to a simulated PSTN.
Another test involved sending voice and video from a server to a wireless device, which tested wireless access through IMS. In other cases, engineers tested the US Government Emergency Calling System. When the right application server didn’t exist with the test network, engineers could simulate it with a protocol tester.
The four telecom-carrier labs ran tests where traffic traveled between an IMS core and a PSTN, with UNH-IOL adding VoIP to the mix. UNH-IOL also added a link between UNH-IOL, Korea, and Japan which served as the backbone for testing academic networks such as the Abilene Network. INH-IOL also added IPv6 to the mix.
Each lab operated in 12-hour shifts, conducting tests with other labs that were open during overlapping hours. For example, British Telecom engineers would start their day running tests with the labs in Korea and Japan, and then end their day running tests with Verizon and UNH-IOL. Thus, there was always a test running between at least two labs 24 hours a day. In between overlap times, engineers would conduct tests locally.
Although the GMI 2006 players are calling the tests a success, some question the framework’s viability. Interoperability is one of the issues that leaves some doubts. Events such as IMS 2006 may alleviate those doubts.
