A communications protocol which would provide users with a single number for both telephony and Internet services has sparked the release of a new discussion paper by the Australian Communications Authority (ACA).

The electronic numbering, or ENUM, protocol was originally developed by the Internet Engineering Task Force (IETF) as a means of solving multidomain Voice over IP (VoIP) addressing by converting telephone numbers into a uniform resource identifier (URI) that can be recognised and verified by a domain name server (DNS).

Approved as an interim standard by the Internet Advisory Board and already being considered for trials in Europe and the US, the ACA is now calling for comments on the practical implementation of the ENUM protocol in Australia.

While the ACA suggests the ENUM protocol could be beneficial in enhancing the integration of IP-based telephony networks, it concedes discussions are still in the early stages, and there are a variety of questions and issues which need to be addressed. Some of these include what processes should be introduced to ensure the authenticity of the user, what number should be used (fixed geographical number versus mobile number for example), who should maintain the DNS registry, and details on a proposed trial of the ENUM service.

One of the major challenges is how to tackle regulatory issues when creating an ENUM database of user numbers. Storing numbers in a large ENUM registry could present risks to the user's privacy, the ACA report states.

According to the paper, "unless strict authentication procedures are developed, the introduction of ENUM may provide opportunities for some service providers to insert telephone numbers in the DNS without an end-user's consent".

"This would allow service providers to collect transit revenues illegally," the report stated.

Despite the ACA's technical concerns, Gartner vice president and research director Geoff Johnson says the question consumers and businesses should be asking is why to adopt such a protocol.

"The ENUM technology debate is academic," he said.

"Any universal messaging system (which combines, say, voicemail via fixed line phone or mobile or e-mail) in our recent history has ended up with trivial market shares and revenues and falls into the 'not particularly compelling category'," he said.

"Interesting concept, but don't hold your breath for an uptake of unified messaging."

Johnson said he expects ENUM will be used in specialist situations and niche markets where "tight directory management has large pay-offs". For example, some corporates, operational agencies such as police force or military, or companies with sales representatives out in the field could benefit from employing one number across all of their devices.

"The probability of this hitting the mainstream is less than 20 per cent," he said.

Johnson added users will generally not want to pay a premium for using the same number for both telephony and Internet services.

"I don't think this [ENUM] is a big cash cow for carriers."

The ENUM protocol takes a telephone number and reverses it, with each digit separated by a full stop. A domain code or number, such as E.164, is then assigned on the end of the address. This domain code allows the DNS to identify the number as an IP address.

With practical implementations of ENUM at least two years away, Johnson said ENUM directory services and management are more likely to be provided by non-traditional service providers interested in the enterprise market, such as Novell, Lucent, Nortel or IBM. These companies will then sell the technology on to carriers to pass on to their subscribers.

Nevertheless, the technology has already generated interest from various carriers and Internet service providers. Bob Bowden, a consultant for Primus Telecommunications, says Primus is planning to contribute to the ACA paper, but has not yet formed a decision as to whether ENUM could contribute positively or negatively to their business.

From a small carrier's point of view, it makes a lot of sense to have one all-embracing number, Bowden said.

"Anything which represents increased opportunities for competition, they [small carriers] are generally in favour of," he said.

Likewise, RequestDSL managing director Phil Sykes says although RequestDSL will not be issuing a comment on ENUM to the ACA, he will be watching the protocol's progress "with interest".

"We want to see how we can apply it in our business," he said.

Sykes said privacy concerns over the use of a single number would wind up no worse than the breaches users currently experience with e-mail service.

"We could spend and put a lot of resources into this to get it 100 per cent, but we have a reasonable system in place with e-mail today. [ENUM] privacy isn't any more severe an issue," he said.

Users could employ filters, such as those used to separate spam e-mails from their Inbox, to validate calls and e-mails, he said.

Submissions to the ACA on the ENUM protocol are due by 11 November.