Landline, Mobile Operators Said Increasingly Deploying E-Numbering for Cheaper Call-Routing
The idea of mapping telephone numbers to Internet Protocol addresses on the public Internet flopped but e-numbering (ENUM) technology is evolving into a key -- and lower cost -- way for mobile and fixed telecom carriers to route calls, sources said. The plan to have telephone numbers resolve in e.164.arpa faltered for several reasons, but carriers increasingly use ENUM telephone number translation to send calls within their own networks or to other providers’ networks, they said.
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In its original form, known as “public” ENUM, the idea was to mimic the domain name system, which has proved a very successful model, said Eli Katz, CEO of XConnect, which provides ENUM services to telecom carriers. But the idea “died a miserable death, slowly” because the world of phone numbers and telecom carriers differs from that of Internet Protocol addresses and the Internet, he said.
Public ENUM was intended to allow end-users to have phone numbers tied to Internet addresses, but it faced several challenges, Katz said. People didn’t understand it so they wouldn’t pay for it. Some might have been willing to take the leap if it meant they could contact others, but that also didn’t happen, he said. The organizations best placed to speed ENUM adoption, the telecom companies, resisted because it meant making naming and addressing information available publicly and giving users control of it, he said. Despite trials in the U.K., Austria, the U.S. and elsewhere, the idea never took off, he said.
But the concept was clearly important so some alternate use of the technology was needed, Katz said. What emerged was “carrier ENUM,” which allows service providers and network operators to query the ENUM database in order to route calls for interconnection. Most queries go through the Session Initiation Protocol (SIP), which allows for richer queries than those in the DNS, he said. Data can include not only the telephone number, but what kind of data is being transmitted and where it’s coming from, he said. Carrier ENUM can also handle services beyond voice, such as video, HD video and mobile money, which typically use phone numbers as unique identifiers, he said.
Nearly all voice traffic from U.S. cable companies is now routed over ENUM to avoid termination charges, said Richard Shockey, a private telecom consultant who chairs the SIP Forum board. Fixed operators no longer use the publicly switched telephone network for routing, but they don’t like talking about it because all-IP routing gives them a huge competitive advantage, he told us.
The GSM Association is running a carrier ENUM service on behalf of mobile operators that delivers information to help route calls between mobile networks, Katz said. The Pathfinder service is still in its early days, primarily because mobile operators are slow to transition to new technologies, he said. In addition, the i3 Forum, a group of 37 telecom operators which is developing industry recommendations for transitioning voice services to IP, is looking at using ENUM-based queries to identify the service provider of record in order to route a particular call, Shockey said.
Eventually, all interconnections between operators, land and mobile, will be IP-based, Shockey said. The question now is whether carriers have the money to pay for it, he said. Much of the capital expenditure of mobile operators and domestic carriers is being sucked up by mobile data, he said.
Is ENUM-based IP routing the end of the PSTN? No, said Shockey, but it does signal the death of analog telephony switching. LTE architecture is all-IP, and as it rolls out more widely beginning later this year, using ENUM for number translation, the analog “plain old telephone service” will collapse, he said. Because the PSTN is a regulatory concept that is somewhat technology-agnostic, landline will survive, he said.
There is another growing use for ENUM, Katz said. “Private” ENUM is being deployed to optimize call-routing within networks, he said. Around 40-50 telecom operators worldwide use the technology as part of their routing mechanisms, he said. The translation service is becoming a necessary tool in many day-to-day operations, said Alexander Mayrhofer, research and development team leader at nic.at/enum.at, which operates the registry and domain name system server for the commercial use of ENUM in Austria.