The proliferation of VoIP software and services is one of the industry's most pressing issues right now. Some fear that solutions like Skype could undermine the operators' business model to a catastrophic degree. Others agree, but welcome the prospect. Some network operators, both fixed and mobile, are trying to force their subscribers not to use VoIP, either by blocking ports, filtering traffic or imposing restrictive terms of service.

Some, though, see more of an opportunity in the technology's rise. Richard Appleton of high-reliability computer specialist Stratus Technologies is one of them. In his view, the way forward is to create alliances between network operators and VoIP providers in order to offer an improved service. For example, calls from VoIP terminals to GSM numbers could be handled so the called party sees the caller's GSM phone number, instead of a randomly assigned temporary number as at present.

This, he claims, would lead to an increased volume of returned calls. To make it happen, is more complicated than it might sound. It requires a dedicated server to intercept incoming VoIP traffic requiring routing to a PSTN/GSM number, carry out a lookup of the HLR (or HSS when implemented in an IMS) to determine the phone number, and reroute it as a normal phone call.