Voice over IP (VoIP) services are growing at a rapid rate and users are now treating them like conventional fixed-line telephone services. VoIP boxes that connect to an Ethernet LAN and support normal telephones add strength to the illusion that VoIP services are no different from normal ones. Unfortunately, VoIP services are different in many ways but let's look at just one difference: the ability to make emergency calls. Many VoIP offerings do not provide access to 999 services, an issue that has been the subject of Ofcom's attention for about three years and has triggered much discussion.

After consulting interested parties and the general public, Ofcom concluded that consumer's interests would be best served by some sort of labelling that would warn users if 999 calls could not be made. Ofcom has now changed its mind and is suggesting that all VoIP services that provide access to the normal public telephone network must be able to connect to the emergency services. A new consultation has just started and anyone who wishes can send comments to Ofcom.

On the face of it, connecting a VoIP network to 999 services ought to be easy, but there is a lot to do and at least one problem is almost intractable. When a normal call arrives at an emergency centre, the operator is presented with a lot of information, particularly the caller's address, or approximate location if calling from a mobile. This information makes it easy to provide help.

In the case of VoIP, there is a much looser tie to a particular location because users can have out-of-area phone numbers or can use the system through an internet connection.

If the VoIP service is used from a fixed location then the provider could pass the address details to the emergency services and the problem would be solved. People who use VoIP when travelling pose a much bigger problem because the only information available would be the IP address in use at the time.

An IP address is not a good indicator of location but, if Ofcom requires the most accurate location that can be squeezed out of an address, there will be consequences for ISPs and companies that use VoIP to connect to the public telephone network. Broadband ISPs generally have location information for their customers but linking that with an IP address and passing the information to the emergency services is not easy. Similar problems will occur with corporate networks where an IP address might be associated with a particular location but the caller could be miles away using a private IP address.

If Ofcom mandates 999 access from VoIP networks and requires location information there will be trouble. Company IT managers should read Ofcom's 100-page consultation and have their say.