PSTN-to-VoIP evolution poses identity, authentication challenges

Going from PSTN to VoIP services, this two-part series looks at the evolution of voice and its challenges, from enabling 911 to user identification.

Editor's note: This two-part series looks at the evolution of voice services away from the public switched telephone network to Voice over Internet Protocol (VoIP) -- and the implications of that migration. In part one below, CIMI Corp. President Tom Nolle discusses how to connect different voice services without the unifying force of plain old telephone service, or POTS, and the challenges of providing 911 emergency services via Internet voice connections. In part two, Nolle addresses the hot-potato issue of how to verify identity and authenticate VoIP users in a non-POTS world to enable legal interception of voice calls over the Internet, not the public switched telephone network.

Few network operators are betting that traditional voice communications based on time-division multiplexing (often called "plain old telephone service" or POTS) will last much longer, given the growth of wireless and over-the-top voice services like Skype. This puts the U.S. Federal Communications Commission in the position of assessing what comes next. The FCC is now supporting trials to determine how to best guide voice evolution for the public good. Looking at voice from that point of view, the technologies most likely to change and the service opportunities for network operators may come as a surprise.

To start, the toughest technical issues in the PSTN to VoIP voice services evolution have nothing to do with voice itself. Voice can easily be encoded and decoded for IP transport at higher-quality levels than those available using TDM. Even delivered over the Internet, voice services are reliable enough for most users.

The big technical questions related to voice evolution are how to create a voice community that provides E911 services and supports lawful intercept and related law-enforcement mandates. Looming over all of the issues is the question of identity and authenticity in the world of voice evolution.

Anyone who uses Skype knows that you can communicate by voice without using telephones or even phone numbers. Users also know that unless they use (and, most often, pay for) Internet voice-service interworking with the public telephone network, they can't communicate with anyone outside their own community. In fact, the only reliable common denominator for voice connection is POTS. OTT voice services like Skype form their own communities, and new messaging services like WhatsApp demonstrate that it's easy to build a communications community around any social-media service.

More on PTSN to VoIP issues

VoIP and wireless E911 services primer

Businesses weigh PSTN vs. VoIP options

How businesses can optimize VoIP over the corporate WAN

So how do all these diverse community services harmonize without POTS? They probably don't, which means that there will always be a technical value to the ENUM-based VoIP activities, and a value for interconnecting through what might be called a "phantom POTS" service. Even if no one made POTS calls at some point in the future, POTS might be the only way to harmonize all of the diverse voice and message services. This means that investments in number portability databases, media conversion tools and ENUM may be of persistent value, to the point where future voice trends make them more important rather than less. Without free intercommunication through something like POTS, no voice service can ever be expected to cover everyone.

The issue of Enhanced 911 or emergency calling is critical for IP voice. With POTS, phone loops terminate at a well-known address, so if an emergency call originates on a given loop, it's possible to determine exactly where the termination is (at least of the public part of the connection) and send help.

For mobile services, a GPS in the device can be used to get an accurate location. For VoIP services, it's possible to get the IP address of the client but more difficult to associate that with a specific location, because IP voice clients rarely have GPS capability. Letting users "register" their location when a client is installed isn't foolproof, although this is one of the options regulators will probably explore. Providing IP phones with an embedded GPS is also an option, and either of these will promote enhanced "look-up" services that can convert GPS coordinates into addresses or validate the correlation between a user's supplied location and the IP address assigned by the access provider.

Next: In part two, we examine how operators could begin to identify and authorize VoIP users.

This was first published in April 2014

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