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David Sims - TMCnet CRM Alert Columnist[February 24, 2005]

VoIP and 911 – Part II

By David Sims, TMCnet CRM Alert Columnist


At the ITEXPO in Miami today, two sessions are devoted to the 911 issue with VoIP. Part I of this series mentioned the first session, at 3:00 Thursday titled “The Relationship Between VoIP & E-911.” [See Part I and Part III.]


The second session is a panel discussion titled “What's the Deal With E-911?” at 4:00. It’s a fair question.

Nationwide, an estimated 200 million calls are made to 911 each year. In areas serviced by enhanced 911, the call is routed to the proper local 911 center for the caller location, and the local 911 center has equipment and database information that display the caller’s phone number and address to the call taker. Good so far, right?

Even leaving aside governmental regulatory issues, problems arise with the transition to VoIP and WiFi telephony, since tracing emergency calls and tracking the caller’s location are much bigger problems than with stationary copper-lined home phones.

Enhanced 911 is the industry’s answer so far to the problem of d etermining a caller’s exact location. E 911 sends location information from mobile handsets to more than 6,000 Public Safety Answer Points nationwide. This means the user fills out his personal information and files it with emergency personnel, so the PSAP will have the information needed to dispatch help.

However, if the mobile user is not at the home or business location on file, the system has no way of tracing where she actually is. Emergency responders could be sent to the wrong building or even the wrong city.

Several potential technical solutions have been identified to address the VoIP E 911 challenge, according to Eric Bear, who oversees product strategy for Qovia, Inc. “One of the most basic requires that phone users manually type in their new location, or select it from a drop down list, whenever a VoIP phone is moved and goes through a new Registration,” he says.

Cumbersome, but still, “this method could be acceptable if the user moves between two or three locations on a regular basis. But imagine how inaccurate this method becomes if the user is truly mobile and plugging in at unfamiliar locations.”

So, some form of automation is essential to keep a system updated with correct information. The Simple Network Management Protocol is a promising alternative for communicating with the IP network. As Bear explains, a database stores a physical wiring map of the IP network. SNMP is used to notify a Location Information Server whenever a new device is added. The updates are received and the IP address of the newly added device is compared to a database of known phones and from the call server database for storage in the Location Gateway Server.

Users and their extensions are then tied to the physical location from the wiring map. This information can be updated in the PSAP database so it is automatically ready for the E 911 call. Companies specializing in VoIP monitoring and management tools have already introduced this capability.

Problem solved? “Not quite yet,” Bear says. “Currently, PSAPs accept updates and refresh their databases once every 24 hours and only during the business week. Move the phone on a Friday night and the E 911 capability won’t work until Monday or Tuesday. The PSAPs themselves need more robust update capabilities because, even if the technical tools needed to find phones exist, it does no good unless the information is updated quickly and efficiently.”

Two other potential technical solutions under consideration for tracking IP phone mobility use the Dynamic Host Configuration Protocol and 802.1x protocols.

DHCP is widely used today to assign IP addresses when devices are first plugged into a Local Area Network. 802.1x is a newly proposed security standard for tracking user logins to LANs, dial-up and wireless connections, Bear explains.

Both techniques could work, but would require changes to the software on every existing and new layer 2 IP switch with IP phones attached to it. Both the DHCP and 802.1x approaches would require a Remote Authentication Dial-In User Service security server in the network and changes to the DHCP server software as well.

Another alternative is to place GPS chips inside IP phones and PCs with softphones. That way, Bear says, “whenever a phone is moved to a new location, a technique like the SNMP approach will realize the movement and collect the new GPS coordinates from the phone for updating the PSAP.” However, GPS chips would make the phones more expensive, and many GPS technologies do not work well within buildings.

In Part III, we’ll look at what some vendors are doing to address the issue.


David Sims is contributing editor and CRM Alert columnist for TMCnet.


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