Enum registry could revolutionise VoIP

A registry is to be created that could reduce businesses' phone bills by forcing VoIP providers to interconnect their networks.

The so-called Enum (from tElephone NUmber Mapping) registry is to be created by Nominet, the company that already runs the .uk registry, after it won the UK contract on Thursday. 

Currently most VoIP calls pass over the public telephone network, incurring a charge, which is often passed on to the person who makes the call. If VoIP providers connected directly with each other, there would be no additional charge.

The Enum registry could also play a major role in the convergence of traditional telephony and IP telephony, by making standard telephone numbers work for both.

Although it has nothing to do with email, the Enum protocol suite works in a similar way to the domain name system (DNS) that identifies the location of someone's email server. By using Enum, internet telephony servers will be able to translate traditional telephone numbers into domains, which will aid the identification of the server that will handle the call on the other end.

Enum performs this translation through the use of a simple algorithm, which reverses the ordinary telephone number, puts dots between the digits and adds "e164.arpa" onto the end. So the number +44 1234 556677 would become 7.7.6.6.5.5.4.3.2.1.4.4.e164.arpa — a domain that is only meant to be used by a computer.

Jay Daley, director of IT for Nominet, said businesses would be able to avoid the traditional phone network and therefore save costs, if they registered their Enum numbers and published the addresses of their VoIP servers. "Those with VoIP servers will see the immediate gain," said Daley on Tuesday. "Many businesses have a high-speed internet connection and are already moving to internet telephony services. A large supermarket chain might request that all their suppliers use this system."

Daley also suggested that consumers would see a benefit from Enum because it would put pressure on VoIP providers to make their networks interoperable.

"Home consumers already use things like Skype, but the problem with Skype is that you can only talk to [other Skype users] for free," said Daley. "You also don't have a proper telephone number unless you pay for it. [Enum] allows you to go to Skype's competitors, get a proper telephone number from them and then dial any other competitor who wishes to participate for free."

"Many people may move VoIP provider to get a company that does this properly," added Daley. "All these little islands of VoIP providers are going to have to be connected or risk losing their business to companies that are."

According to Daley, the system will go live in spring 2008. Some numbers, such as 0800 freephone numbers, may not be supported, but it is likely that mobile numbers will be supported; a development that could see more widespread implementation of VoIP clients on handsets using Wi-Fi or 3G connectivity.

Once the system goes live, businesses using internet telephony servers will be able to contact their registrar — or possibly their VoIP provider — to register their numbers. The registrar will then use a third party to verify the ownership of the number, before registering the resulting domain name with Nominet.

Nominet will then "publish the details in the same way we publish domains", according to Daley.