Part I: Real-life interop testing highlights IMS drawbacks

The MultiService Forum's (MSF) fourth massive interoperability testing of next generation network (NGN) components which spans three continents is underway.

The focus of this event is looking at IP Multimedia System (IMS) and its role in network service integration and in particular to validate MSF Release 4 architectural framework and, crucially, its supporting implementation agreements (IAs). The service attracting the most attention is IPTV - see the six scenarios below.

There are 22 vendors and operators working together to test 225 devices in six network test scenarios specified by the carriers. Some 82 basic test cases are being carried out across the six scenarios*, with almost 500 permutations, Over 600 pages of test plans that took two years to prepare have kept a team of 125 engineers working around the clock.

David Hutton of Vodafone commented, "Standards are about functional architecture and we sometimes find issues in implementing lower level standards. This is a rare chance for operators to try out real life scenarios in multi-vendor networks."

By half way through GMI, more than 7180 tests had been carried out at BT's Adastral Park in the UK, according to BT's Ken Mills, involving 11 vendors and up to 45 test engineers.

Interoperability testing is first carried out in each lab, then between the five labs, which in the US are based at Verizon, National Communication System (responsible for ensuring emergency numbers can be used on IP networks, among other things) and the University of New Hampshire InterOperability Lab. BT/Vodafone form the European leg with China Mobile representing Asia.

What big lessons have been learned so far‾ According to a spokesperson at the Verizon centre, "IMS is the weakest link. We have three to four vendors with an IMS core and it's a point of contention. The other challenge is how long it takes to configure the IMS core platform for the next test. IMS slowed down execution beyond our expectations, yet we want to do IPTV via a common IMS core."

He added, "With the IPTV testing, channel change is not yet SIP-based - SIP is used for signalling - so we still have a hybrid architecture, which means having to test both."

Ian Jennings, BT Innovate's chief voice strategist remarked, "IMS is  mature - a common control, so with each new test you do have to reset the whole lot, unlike changing just one bit in the old stove pipe network set-up. One of the big issues is how to make it work with existing broadband and run services on the top and speed up time to market."

However, John Frieslaar, CTO, key accounts, Huawei disagreed saying, "IMS is still in the definition phase of what it's going to be. It could be great for IPTV, for service control. We need to know what happens next with mash-ups on the platform. What is needed in a business context‾ IPTV is a single application with a lot of market buzz, yet look at the rotten quality transmission today [at the press conference today which linked to all the sites] and you've got to wonder how we are going to manage IPTV in an HD world. The size and scale of IMS has yet to be defined."

*The six scenarios are:


"¢ end-to-end session control accounts for two physical scenarios, with QoS for access technologies - including baseband, broadband, 3GPP, WiMAX 3gPP2 and TD-SCDMA - over a converged core network;

"¢ IPTV with the emphasis on specifications developed by the Alliance for Telecommunications Solutions (ATIS) IIF - it is the first time standardised IPTV is being tested in a network to validate automatic configuration of set-top boxes and user experience;

"¢ locations-based services, including routing and privacy issues;

"¢ service orientated architecture (SOA) integrating IMS with web-based services;

"¢ management issues, especially online management of IPTV set-top boxes and collection of IPTV stats to avoid truck-roll.