Traditional Centrex services offered businesses fixed-line private branch exchange (PBX) functionality delivered by a carrier, without the need for an actual PBX on their premises.

It enjoyed considerable success during the nineties in the US and reasonable take-up in the UK, but virtually none in continental Europe, which some observers have ascribed to a cultural difference whereby companies in that region prefer the DIY approach of owning their PBX. It may also be because carriers in those countries believed less in Centrex than their US and UK counterparts, or simply that it was wrongly priced to attract sufficient customers.

Whatever the reason for Centrex’s only partial success, Petri Seppanen, director of IP Multimedia Subsystems (IMS) for Espoo, Finland-based Nokia, argued that there is a fundamental difference that makes IP Centrex a more compelling proposition for carriers, regardless of the geography. This is the ability, with an IMS architecture in the core of a carrier’s network, to offer FMC to enterprise customers.

Wikipedia defines IMS as an open, standardized, operator-friendly, next-generation network (NGN) multimedia architecture for mobile and fixed services, adding that it’s a VoIP implementation based on a 3GPP variant of SIP, and runs over the standard Internet protocol (IP). As such, it is used by telecom operators in NGN networks (which combine voice and data in a single packet switched network), to offer network controlled multimedia services.

As an architecture, an IMS offering will usually come from a telecoms equipment provider like Nokia, Ericsson and Alcatel, with Cisco also seeking to leverage its clout in IP to break into this market, and will comprise a number of server software packages for its various functions. Seppanen said Nokia began developing its IMS portfolio in 2000/2001, with its first release coming to market in 2004.

This entailed two core servers, a Call State Control Function (CSCF) product called the Connection Processing Server and a Home Subscriber Server (HSS) called the IP Multimedia Registrar, plus the first application server to interact with them, namely the Nokia Push-to-Talk Server.

At the beginning of this year, there was a second release, Seppanen recalled. The thrust of that release was integration with a product group that already existed as a standalone offering outside IMS, namely the Media Softswitch Server (MSS). Its component parts are the Media Gateway and Media Gateway Controller, the purpose of which is to handle PSTN break-in and break-out, i.e. connections between the VoIP and legacy PSTN worlds.

It was in June, he said, that Nokia launched its IP Centrex Application Server, which when deployed in conjunction with the MSS in a combination called the Business Communication Solution enables the hosted business comms offering by carriers for cellular, WLAN and fixed-line IPT, said Seppanen.

It is Nokia’s belief in the brighter future for IP Centrex than its TDM predecessor had which underscores the exec’s remark that we are currently not intending to have an IP PBX offering.

Not that Nokia doesn’t see a demand for the so-called PBX extension flavour of enterprise FMC. This is where companies adopt a DIY approach by putting VoIP clients on mobile phones so that they can be treated as a regular extension to a PBX, with other employees being able to call them using four-digit dialling. Indeed, it has relationships with leading IP PBX vendors like Cisco and Avaya for this very purpose.

However, it is on IP Centrex that Nokia is putting its money for enterprise FMC, not least because it will entail no clients on phones. Indeed, the main challenge involved would appear to be for the carriers, which must work out how to bill corporate customers for a service where some of their calls will be going over their own IP infrastructure rather than over a cellular network, and thus could conceivably be free.

Of course, the decision not to go into IP PBX in its own right, even though it has an Enterprise Solutions business unit, can also be seen Nokia choosing carefully on which fronts it wants to fight in private telephony. After all, the PBX market is already carved up among Avaya, Nortel and Alcatel, with Cisco as the main challenger as the market moves towards IP. Nokia’s neutral position enables it to partner with all and any of these for PBX extension while preaching the IP Centrex gospel.

This stance also helps explain why Nokia agreed to merge its carrier networking business with that of Siemens AG and run the resulting entity yet shunned the offer of doing the same with Siemens’ enterprise comms business, which is a second-tier competitor in the PBX market.

Interestingly, Seppanen declined to talk about what Siemens might or might not have in terms of an IMS offering of its own, and how the two business unit’s integration into Nokia Siemens Networks would impact the two portfolios. He argued that he would only be able to comment in January, when they actually start to operate as a single, merged company.