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Voice over IP

Posted on 28 Jun 2005 at 12:38

SIP works in a similar way to email and the Web, and it goes a long way to solving the problem of interoperability between different VoIP providers. Ineen and sipgate subscribers, both of which run services using the SIP protocol, can call each other for free by appending the appropriate domain to the end of their subscriber numbers. Therefore, 2003195@ineen.com can speak to 5808085@sipgate.co.uk at no cost, regardless of the fact they have signed up with competing providers.

SIP also allows for direct connections to the outside world at little or no extra cost, using the Electronic Numbering (Enum) system. Enum should eventually unify VoIP and regular telephone networks, and as such is overseen by the International Telecommunication Union, part of the UN. It grew out of the original standard for defining international phone numbers that gave us +44 for the UK, +33 for France, and +1 for Canada and the US. This latest update, Recommendation E.164, makes little distinction between real numbers and those used by VoIP services. By the time it is fully rolled out, you will not need to know if the person you are calling has a landline or a VoIP connection, just as you do not need to know whether your contacts are BT or Telewest subscribers.

So, returning to the example above, that 5808085 sipgate number can now be dialled from a regular telephone by dropping the initial 5 and adding the appropriate UK area code, at which point it will be routed from the regular circuit-switched network to packet-switched VoIP, without the landline caller ever knowing their outbound call has jumped ship onto the Net. Unfortunately, for the time being at least, dialling the number on its own, even from within its own local area, will not connect the call because of the way the system is configured.

The issue of numbering and how VoIP services interface with the regular telephone networks has given regulators cause for concern. In its consultation document for numbering arrangements, Ofcom outlined its belief that 'the use of geographic numbering for [Voice over broadband] services raises a number of concerns, predominantly the impact on the available numbering resource and adequate consumer protection measures'. Its solution is the introduction of a new non-geographic subset of the 05 area code, much like the non-geographic 077 - 079 codes used for mobile phones.

Will Enum survive such intense scrutiny from regulators? Sipgate's Steve Mancour believes so. 'It is always dangerous to make predictions, but I think that Enum has the best chance so far. The SIP protocol is much like the hypertext protocol (http) that the Internet normally uses for web pages... designed to be scalable to huge, multinational networks, while cutting costs to a minimum. It will remain the dominant protocol for VoIP for many years.'

But SIP is by no means the only option. H.323 has been longer established and actually formed the basis of NetMeeting 2, launched in 1998 and since usurped by the largely SIP-based MSN Messenger in the years since XP first appeared. This was one of the earliest standards to define how packet-based telecommunications should work and, in particular, how Internet Protocol and ISDN should converse. It gained widespread acceptance, and H.323-compliant equipment is still available, representing SIP's only realistic high-end, non-proprietary competitor.

Quality and security

So VoIP has taken telecoms away from the established providers, and it does not matter how the underlying technology works. As long as the services can patch you through to a local exchange, the providers can develop them as quickly as they like without recourse to lengthy multinational standards negotiations.