The 911 VoIP Myth

A very common concern that is raised about IP Telephony, is E911 services. There’s a widely held belief that 911 services will not work over VoIP. The fact is, that most business class IP Telephony systems from vendors such as Cisco, Avaya and Mitel have addressed most of the challenges associated with 911. In fact many 911 enhancements, relative to traditional TDM based systems, are made possible by IP based systems.

The most serious concern people have, is that it is not possible to reliably determine the location of the 911 caller. This is simply not the case. In fact, in many cases caller location information will be more accurate in IP Telephony systems since the databases that associate a telephone with a location are often updated by automated processes in contrast to many legacy systems that required a manual update. In addition, some IP Telephony systems are capable of providing more precise location information than traditional systems such as “2nd Floor, East Wing”.

IP Telephony systems can also provide 911 related features that are either not possible or rarely implemented in TDM based systems such as:

• Automated database updates of phone location
• More detailed location information
• The ability to trigger other events when someone dials 911. Since, IP Telephony is based on software there’s virtually no limit to the type of events that can be triggered. The most popular is to alert someone of the 911 call such as a security desk for example.
• Do I dial 9 for an external line, then 911 on this phone? Doesn’t matter, dial 9911 or 911 and the IP Telephony system can make the call.
• Depending on the signaling protocol, an IP Telephony system can prevent a caller from disconnecting a call.

On an IP phone with an external speaker, the system can simply switch the phone to speakerphone mode allowing the operator to continue to communicate with the caller. On non-speaker phones, the system can keep the call to the emergency centre active and ring the caller’s phone as soon as they hang up.

Still, there is room for improvement and you should carefully examine the 911 capabilities of your vendor. And while many IP Telephony systems can track phone locations within specific predefined boundaries, there are limitations. That’s because it may be possible, depending on policy and system configurations, to move an IP Telephone to any location in the world. To date, there is no automated way to deal with this issue. While some contend that the solution is to embed GPS receivers in telephone devices, I’m convinced that this approach is not practical. Besides, even if it was possible to track a phone anywhere in the world, what action should a Toronto based IP Telephony system take if it detects that a 911 call has been dialed by one of its subscribers from a hotel room in Tokyo? I don’t expect that we’ll see a solution to this type of scenario in the foreseeable future.

One possible partial solution to handle the issue of the nomadic aspects of IP Telephony is to place the onus on the user. For example, if the IP Telephony system detects that a phone has gone out of service and appears with a different IP subnet address, it would indicate that the phone may have moved. The system could then force the user to inform the system of the new location information before it would allow outgoing calls. There are cons to this approach and it still doesn’t solve the Toronto to Tokyo scenario I previously described.

On the consumer front, the nomadic aspects are even more challenging since there’s no practical way of accurately determining the location of an IP address. The only method is to place the onus on the user to notify the service provider with the correct location information; which is the approach that Vonage has implemented.

Rick McCharles
http://www.ric.ca/