Engineer ofcom Regs voip

Ofcom study into location determining of VoIP callers to emergency Services

Consultants Analysys Mason are conducting a study on behals of Ofcom into determining the location of Voice over IP callers making calls to emergency services. It is is easy to determine the location of a caller is in the old fixed line world because a phone number is recorded based on the location of a piece of copper “plugged” into the local telephone exchange.

This is not the case with VoIP.  A VoIP number could be anywhere on the planet. Anywhere there is a connection to the IP network/internet that is.  Ofcom recognises this and wants to understand whether there is a practical solution.

UK technical standards organisation NICC has published (Jan 2010) a potential solution to the problem though this is complex and also limited to VoIP users using UK ADSL connectivity.

This solution stems really from network architectures familiar to large telcos and my first reaction is that it is very expensive. One might ask what price a life? This is a reasonable question. We all have grannies and nobody wants ours to be the one in the burning building dialing 999 only to find that the fire engine has gone to the other end of the country.

The counter is the same as is used for website blocking. Not only is it expensive but it is going to be fraught with problems. The expense is also going to stifle innovation and prevent new entrants into the market.  Most Internet Telephony Service Providers are still very small companies.

There is more. The system relies on UK IP addresses being used. In calling round some industry contacts to discuss this problem I discovered that the use of non UK IP addresses is quite common. One large telco often uses blocks of IPs that originate in France.   USA based IPs appear in the EU and vice versa.  Bring on IPv6 do I hear you say?.

IPv6 may help. I can see the day when everyone has their own personal IPv6 address/block just like they have their own mobile phone number today. It probably still won’t do enough to provide location data though.

I realise that none of this helps Ofcom. I will be responding to the survey but don’t believe that here is realistically even a medium term solution to this problem.

Trefor Davies

By Trefor Davies

Liver of life, father of four, CTO of, writer, poet,

3 replies on “Ofcom study into location determining of VoIP callers to emergency Services”

Rather than try and figure out where the call is coming from can’t they work on creating an open standard that would let a VoIP phone announce it’s location. In it’s simplest form it could mean a user storing their location details (provided they’re static) when they set up their phone. The phone could have a white list of numbers that it’s allowed to share those details with. If you ever call one of those numbers, the receiver could request that the phone sends the location details, perhaps with DTMF sounds. If the user were on a mobile device it’s becoming more and more likely they’d have GPS that could be used.

The static users aren’t really the problem. We already provide addresses to the Emergency Services mapped to VoIP numbers. The problem lies when the user moves around. The system development work required to map location against an IP address would be huge and almost certainly involve significant manual involvement which ultimately means it would break.

It certainly might be possible to map GPS data though the network overhead to continually update the system would be large. Also people tend to keep GPS switched off on a mobile except when they really need to use it because of the drain on the battery.


Andrew: the framework for this already exists as part of an extension to sip for the 3GPP networks in the use of a P-AccessNetworkInfo header. They key is agreeing to a standardised location format and then getting the device to acutally insert the information. Then there’s trying to get the emergency call centres to use it.

Tref: The technology exists to do this now, but the will doesn’t. Problem is here that it’s unlikely that the will ever will be enough to make it happen because of the costs.

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