Public ENUM--how important is it? Having an authoritative source translate PSTN and VOIP "numbers" sounds good, but who will build it, secure it, link it with other directories and pay for it?(Voice-Data Convergence)(voice over internet protocol)(electronic number)

The so-called telecom winter in the U.S. seems to be thawing nicely into an election year spring. Money is flowing again, and important telecom policy issues are melting out into view.

Beneath such visible matters as the FCC's planned decision on whether to regulate public VOIP, lurks another policy issue--the matter of U.S. involvement in ENUM, short for the electronic number mapping between PSTN and IP addresses. ENUM isn't getting much high-level attention, for all the usual reasons--it's detailed and complicated and it doesn't lend itself to partisan sound bytes (see "ENUM Essentials"). But ENUM raises important unanswered questions about how "calls" will be made among the end-points served by different IP voice and PSTN service providers. Who decides which addresses map to which? Who makes sure the mapping data are accurate, especially when PSTN numbers can be "ported" to different providers, and IP addresses can take so many different formats? Who will synchronize these databases, and who will protect them from hackers?

The answers so far, at least in the U.S., won't be coming from the federal government. In fact, as discussed below, the FCC, State and Commerce departments are pushing responsibility for ENUM as far away from federal control as possible, while at the same time they are insisting that ENUM implementation(s) adhere to a demanding set of "principles." In more than 20 other countries, however, government regulators have officially "opted in" to implementing ENUM.

ENUM's formula and reference architecture, called the "ENUM tree," have been decided (Figure 1), though implementation is not mandatory. In the U.S., VOIP and PSTN service providers have no direct incentive to push for ENUM. For the time being, they can work around it, and they do. They handle their own address mapping, control their own databases and work out their own arrangements with one another.

Arguably, these workarounds might grow into a complete solution, much as private peering solved the Internet's early growing pains and public email displaced proprietary precursors. But it is potentially just as likely that private databases and mapping workarounds could proliferate to the point that customers would not be sure of their calls getting through to the correct numbers or addresses (Figure 2, p.28). Whose job is it to make sure that doesn't happen?

A Tall Order At Triple-Arms-Length

Government regulators do not want to take direct responsibility for ENUM. Instead, they want an arms-length contractual relationship with an administrative entity, much like their existing relationships with companies like ICANN (for IP address space, top level domain name and root server management); Neustar (for numbering plan and portability management); and VeriSign (for .com and .net registries).

Rather than directly selecting an ENUM contractor, however, they …