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September 2007 | Volume 10 / Nuber 9
The Next Wave Redux

Phone Numbers and Our Evolving Communications Identity

ENUM and P2P VoIP are focus topics for this month’s issue, but while they both pertain to Internet Telephony, it’s also true that apples and hamburgers are both food. The conjunction does prompt one to reflect on how telecom identities are evolving and where it will lead.

Ten years ago, our telecom identity was one or a few PSTN telephone numbers that represented places where we spent time - home, work, etc. With mobile telephony, people acquired personal PSTN numbers. They also acquired handsets that remove the need to remember phone numbers and largely remove the need to even deal with a phone number more than once - the first time you call a new person or business. Now you can address someone by their name or a “handle” of their or your devising.

The advent of VoIP introduced new addressing schemes, but also an interest in communicating between the new, small (VoIP) networks and the vast majority of existing telephones, i.e. to connect with the PSTN. Proprietary approaches have emerged and the IETF has developed a specification for ENUM that facilitates the use of PSTN numbers for VoIP services.

ENUM leverages the Internet’s Domain Name System (DNS) to provide a way to translate PSTN telephone numbers to SIP addresses. Since DNS is a centrally managed, system with hierarchical delegation, ENUM inherits those characteristics. That’s exactly opposite the way Peer to Peer (P2P) system attempt to work - they endeavor to avoid any central components. However, since PSTN telephone numbers are centrally assigned (by national authorities, with country codes assigned by the ITU) it’s not unreasonable that ENUM be centrally managed as well.

The advent of the Internet has enabled many new communications services - email, instant messaging, blogging, social networking - and, so far, each new service comes with its own, new, centrally managed, addressing scheme. These addresses are typically names or “handles,” not purely numbers, but they serve the same purpose. Where briefly it seemed we were moving to one number per person (your mobile phone number), it’s now clear we’re moving to rich identities with dozens of context-dependent identifiers per person.

How does P2P VoIP play in this? So far, the P2P community has not focused on issues of identity. For example, Skype has a completely distributed approach for telephone and text chat connections, but like other services, they centrally manage their address space, requiring you to obtain new names from their central registration server.

There are theoretical approaches to completely distributed identity and there are examples of distributed identities for documents in the form of Globally Unique Identifiers (GUIDs). Typically these schemes rely on numbers, chosen randomly, that are so large the chance of two people choosing the same number is negligible. There are even proposals for public key encrypted GUIDs which would allow you to identify (and screen) incoming communications requests thus addressing the problem of spam. But, so far, these proposals remain largely theoretical.

The real activity is in interconnecting communications networks, P2P or otherwise. Any communications network becomes more valuable when it reaches more people. For P2P VoIP, that means reaching PSTN subscribers, using existing PSTN numbers. In fact, despite all the new addressing schemes that have appeared with email, IM and P2P VoIP, PSTN numbers remain the mainstay of voice telephony. Today, most individual VoIP networks are too small to justify VoIP peering, so calls from one VoIP network to another VoIP network go through the PSTN. As VoIP networks get larger, that will change but the use of PSTN numbers will last for many decades - at least as long as the PSTN remains the largest telephone network in the world.

What will be most interesting is the evolving user interface as we seek new ways to manage the diverse “handles” that we, and those we communicate with, are accumulating. The mobile handset has given us an easy way to organize our PSTN contacts without remembering their specific phone numbers. But we need new user interfaces that are as automatic in coupling our chosen contact list to each of the communications clients we use including PSTN, VoIP, IM, email and social networks. This will be no small venture as, today, each communications application seems to have its own set of identifiers and relatively few provide open APIs.

Looking forward, we can expect rapid technological change, many new communications applications and a profusion of new identities. The client that wraps all this complexity in one simple user interface will do extremely well. IT

Brough Turner is Senior VP of Technology, CTO and Co-Founder of NMS Communications. For more information, please visit the company online at

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