Getting Edgy: IMS Needs to Expand Beyond the Core

Call it a case of core values. After years of hype, IMS is becoming reality, but the transition to a converged IP architecture mostly is happening in the core, creating lonely islands of IP in a sea of legacy interconnection. This lack of IP at the edge creates operational and competitive issues for operators exchanging traffic while trying to maintain control over quality, expose their networks to open application environments, deliver services in a mobile environment, and roll out SIP-based services.

The emerging need to unite different operators' IMS islands has motivated the GSM Association to launch extensive real-world trials this year of the IP eXchange (IPX). The goal of IPX is to create a private, service-aware global IP network that — through the support of end-to-end QoS and the principle of cascading interconnect payments — will provide fixed and mobile service providers with a secure commercial platform to exchange IP-based traffic.

“A lot of this is being developed as we speak, and folks are now looking at the IPX, a packet exchange to connect the islands together,” said Ajay Joseph, CTO at wholesale carrier iBasis. “The purpose today is, when mobile operator A is taking traffic from 700 to 800 operators, direct connections become cumbersome and expensive. So they need something that can provide a QoS backbone, billing, security, and can do service differentiation. Eventually, this will be important for fixed carriers too.”

The idea is that 20 to 30 IPX carriers will step in and provide a cloud of interconnection. To keep a firm hold on quality, no more than two IPX carriers will be included in any link between service providers on the edge. Of course, there already are neutral IP data centers and Internet exchange services out there. But the IPX aims to take a universal approach to service quality and traffic metrics, which will be standardized throughout. That’s an important point when it comes to SIP addressing and address resolution, peering point discovery and the need to discover the best transit network for a particular link, and efficient, real-time billing and other back-office functions. The IPX also will take care of differentiating service traffic, maintaining SLAs, and generally guaranteeing QoS and consistency for the services riding along its backbone.

Several companies, like iBasis, are taking part in the trials, which are, for now, focused on getting voice running across an IPX backbone and doing it with standards and specs.

The TDM Torrent

Increasingly, TDM is the barrier to new services. Kevin Mitchell, director of solutions marketing at session border controller vendor Acme Packet explained that when there’s TDM in the middle of two IP links, it makes a big difference in the subscriber experience. “Take VoIP for instance,” he said, “in addition to eliminating unnecessary transcoding, which adds latency and possibly degrades call quality, using IP interconnects also allows service providers to make use of hi-fidelity codecs, which offer better quality than standard PSTN codecs. “

And quality, especially when it comes to new services, is something operators cannot afford to sacrifice in an era of fickle customers and slim margins. Interest in new revenue-generating services hinges on the customer experience — a fact not lost on carriers.

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