IMS testing more than just protocols

By Stephen Hardy, editorial director and associate publisher -- IP networking may provide the foundation of IMS, but vendors and carriers alike will discover that traditional IP test tools won't be sufficient to meet their IMS requirements, says at least one test equipment insider.

Stephen Hardy
Editorial director and associate publisher, Lightwave

While the speed with which carriers will adopt IP Multimedia Subsystem (IMS) networking practices remains a matter of debate, both systems developers and network architects are taking the initial steps toward creating and evaluating IMS-friendly equipment. IP networking may provide the foundation of IMS, but vendors and carriers alike will discover that traditional IP test tools won't be sufficient to meet their IMS requirements, says at least one test equipment insider.

IMS comprises a set of specifications designed to enable carriers to implement IP-based networks that can carry services for both wireline and wireless customers simultaneously. In an IMS-enabled world, a user could access the network from almost any device -- from a laptop computer to a mobile phone to a portable video player -- and receive any content that device can support. IMS has its origins in the mobile arena (specifically the 3rd Generation Partnership Project, or 3GPP), with a major assist from the Telecoms & Internet Converged Services & Protocols for Advanced Networks (TISPAN) arm of the European Telecommunications Standards Institute (ETSI).

IMS specification-development has leveraged existing IETF specifications such as Sessions Initiation Protocol (SIP) as much as possible to promote interoperability and to boost adoption. And certainly several carriers have expressed interest in IMS as a platform for fixed/mobile convergence. According to Infonetics Research, sales of voice over IP (VoIP) and IMS equipment grew 19% between 2006 and 2007, to over $3.9 billion.

Yet while the building blocks may be familiar, that doesn't mean that the test platforms engineers have used in the past to exercise their IP system and network designs will prove adequate for IMS, says Alvin Francis, director of product line management at the EXFO Navtel Product Group, formerly Navtel Communications. EXFO Electro-Optical Engineering Inc. (search for EXFO) recently purchased Navtel to serve the growing IMS market.

"The challenge for IMS is not necessarily the protocol itself but the different types of services that the network is supposed to support. In a traditional voice-over-IP space, you're looking at just voice and maybe if you're doing maybe voice telephony a little bit of video," he explains. "You can envision that all these [IMS] networks are supposed to be designed to support all of these [fixed and mobile] services simultaneously, and at the same time provide service guarantees to ensure a good quality of customer experience."

Therefore, testing in an IMS environment is more about the interaction of services rather than how well individual protocols function. "It's easy to test voice in isolation; it's easy to test video in isolation. The complexity comes when you have a multiple of different type of services and you try to understand what's the impact of the IMS network on the services and how do you identify which services are failing, why they're failing, how do you treat it, how do you fix it. It adds a much higher level of complexity when start testing from a service perspective," Francis adds.

Engineers need to be able to see how the demands of one service affect a carrier's ability to support others, Francis asserts, particularly once mobile services are laid on top of a network initially designed to handle wireline services, and vice versa. The fact that IMS specifications also call for encrypted services adds an additional element that may be new to equipment developers and network lab technicians.

The best approach, says Francis, is to be able to simulate an IMS network and evaluate how either the platform under test or the network itself handles the expected traffic load and quality of service requirements. The EXFO Navtel Product Group, in competition with such companies as Spirent Communications (search for Spirent) and Empirix (search for Empirix), provides this capability via its InterWatch chassis and associated SIPFlex and Border Gateway Function test offerings.

Growing interest

Not surprisingly, Francis reports that most of the demand for his group's IMS products comes from systems vendors. He says he sees these vendors incorporating IMS capabilities into existing platforms and building new platforms, such as border gateway controllers, with IMS in mind.

Francis sees evidence that carrier interest in IMS has begun to pick up as well. "We're seeing more and more traction in the network operator labs, especially in the European environment," he says. "There are a lot of field trials going on, evaluation processes going on. We've seen more planning. So we see a few projects coming up, RFPs on the street for IMS equipment coming from the operators."

The European interest doesn't surprise Francis, given the advanced state of mobile services on the continent. He also expects to see significant near-term interest from Asian carriers as well.

"If you look at what's happening in the operator space, the typical requirement is every new deployment has to be IMS compliant. And that's very fuzzy terminology, because what does 'IMS compliant' mean?" Francis concludes. "But moving forward, obviously their focus is to make sure that when they deploy a network, it can support all the different types of services and be compliant moving forward; they won't have to do a forklift upgrade of the network architecture."

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