Six burning VoIP questions

2. VoIP: What really happens when I dial 911?

All corporate IP PBX systems can dial 911 services, but how much critical location data is transmitted during a life-or-death call depends on how the VoIP network and LAN is configured. The issue of IP softphones and mobile voice over Wi-Fi also complicates the issue.

Enhanced 911 service support was a major stumbling block for VoIP when it emerged in the consumer market several years ago. Technical issues, and some well-publicized incidents of failed emergency response from service providers, forced the FCC to step in with special 911 requirements for Internet phone service providers.

Many companies are still dealing with 911 issues and IP telephony deployments, as many IT departments still must manually track the location of phones in corporate offices. The easy portability of IP phones and the emergence of wireless IP handsets are challenges for maintaining an accurate device location database of phone extensions.

Enhanced 911, or E911, requires specific location information to be transmitted from a phone dialing 911 in an emergency, including building number, if a single campus address contains multiple buildings, as well floor numbers directional location (for example north, south, east, west).

"We do support 911 on all of our telephones on our campus," says Scott Mah, assistant vice president for IT infrastructure at the University of Washington in Seattle. "We have policies in place to limit end users from moving their phones around, which helps. But anytime we put a phone into service we basically register that telephone number and its corresponding address with the database."

The database maintained by the school's IT staff is passed to local emergency 911 call centers, or Public Safety Answering Points (PSAP), which links location information to each phone number in the school's system. This Automatic Location Identification (ALI) data is what's relayed to rescuers; if a 911 call is disconnected, emergency responders have information on where to go.

"[E911] is something we care a lot about and it's something we've maintained even without IP-enabled endpoints," Mah says.

There are some ways to automatically update ALI information when IP phones are moved. Some of this involves some planning of the campus network layout. New protocols and software are also available to help. Clever network administrators can setup pools of IP addresses into subnets which correspond to physical locations inside a building or campus. IP phones plugged into ports in these locations would automatically be linked to a building number and floor.

Cisco, Enterasys, Extreme, Nortel and Foundry all have their own proprietary discovery protocols for finding switches, routers and other devices on a network. But getting a Cisco switch to detect, let alone collect location data, on a Nortel IP phone is tricky, if not impossible. The Link Layer Discover Protocol-Media Endpoint Discover (LLDP-MED) is a Telecommunications Industry Association standard supported by Avaya, Extreme and ProCurve by HP, which LAN switches to collect device information and location data from IP phones (as well as other LLDP-MED-compliant devices, such as Wi-Fi access points) when network connections are plugged in. But because wide adoption of a standard discovery or registration protocol for phones is limited, users must work with what they have.

Technology has even emerged recently for tracking location data for IP softphone users. RedSky, which makes E911 software for enterprises and carriers, recently launched its RedSky Softphone Location Determination Application (SLDA), which works with Avaya softphone clients. The software lets users input location data during the logon process for the softphone application, which is then sent if 911 is dialed from the application.

The city of Oakland uses a VoIP system from ShoreTel to support around 2,000 city employees across multiple locations. IT and telecom technicians use a mix of automated and manual database maintenance to deliver E911 ALI data to emergency responders. Ethernet switches in the city's network use virtual LAN (VLAN) tags that are grouped according to buildings. ShoreTel IP phones can also correlate user names and system extensions with IP phone hardware, which is all collected in a database on the system. "This will tell 911 where the call is coming from, what the caller's name is, and what building," says Bob Glaze, CTO for the city. "But to bring it back to the exact location, we enter that information ourselves," into the ShoreTel ALI database, which is passed to local PSAPs.

"The real issues is that people typically feel more comfortable moving VoIP around, whereas they didn't feel like they could terminate their own digital phone in the past," says Drew Depler, Boulder County, Colo., IS director.

Even though the county uses all Cisco switches, CallManager IP PBXs and IP phones, a spreadsheet is used to update location data anytime a phone is moved. Only IT staff are allowed to physically move IP phones, Depler adds. "It's a manual set that we've added to our procedures list."

Depler says the proliferation of softphones and VoWi-Fi handsets is starting to emerge as another challenge for E911 services. "That really starts to become a cost-saving opportunity," Depler says of softphones, which allow county employees to work from home and cut down telecom costs. And in the future, if they're used widely, softphones could also eliminate the need for more costly IP desktop handsets.

But, Depler says, this also raises an issue for mobile workers with softphones. "How do you track where they are. It does have some impacts on 911. There are real tenuous issues as we look at mobility and we look at IP phones moving anywhere."