E911 for VoIP

Advancements in E911 for VoIP provide the same level of accurate location information to emergency responders we've come to expect from wired phones.

September 27, 2006

6 Min Read
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Errors in the 911 call system have plagued the emergency-services infrastructure in the United States for years. Recent headlines recount the various mistakes: 911 calls routed to the wrong emergency call center, calls sent to administrative offices rather than dispatch offices, and calls put on hold. Problems with voice over IP E911 (Enhanced 911) services compound the troubles of standard 911 service.

Several groups, including the NENA (National Emergency Number Association) and APCO (Association of Public-Safety Communications Officials), are pushing hard for improvements to VoIP E911 service. In particular, NENA recently threw its support behind S.1063, a bill being debated in Congress that would let VoIP providers gain the same access to 911 facilities as those used by wireless and wireline telcos. In addition, bills in Congress and regulations from the FCC are attempting to address VoIP's lack of adequate location services for 911 calls.

According to the FCC, most wireline and wireless services support E911. The goal is for VoIP products, such as IP PBXs and VoIP phones, to provide the same level of location information as a wired phone offers. Some technologies exist to address this need, and we expect the threat of lawsuits will propel private companies to make sure VoIP systems in use at their enterprises support E911. In addition, working groups at the IETF are focused on improving the transmission of location information using protocols such as SIP (Session Initiation Protocol).

The Road to Enhancing 911 Click to enlarge in another window

Can You Hear Me Now?

In August, NENA sent a letter to Senate leaders seeking passage of S.1063, "IP-Enabled Voice Communications and Public Safety Act of 2005," which would require the FCC to mandate that VoIP service providers offer E911; require E911 providers to offer unfettered access to their service by VoIP service providers; extend the same liability protections used by wireless and wireline services to VoIP providers; and give the FCC explicit authority to enforce their provisions. APCO is also lobbying the FCC for more stringent rules surrounding E911 for VoIP, and bills passing through Congress seek similar ends. Title III of HR 5252, "Communications Opportunity, Promotion, and Enhancement Act of 2006," requires VoIP service providers to offer E911 service and requires access to E911 services.

The issues plaguing VoIP services apply equally to enterprises deploying VoIP products. Many states have enacted laws targeted at businesses that deploy VoIP and multiline phone products. There are no federal bills in Congress requiring companies to deploy E911.

Making The StandardsIP PBX solutions by Avaya, Cisco Systems and others can discover the location of a VoIP device based on the IP subnet, switch location or switch/port location. The assumption is that the network topology is relatively fixed. A DHCP range could be assigned to a specific floor of a building, for instance, and a location is mapped in the IP PBX to VoIP phones in that range. Industry standard protocols, such as the Telecommunications Industry Association extension, LLDP-MED (Logical Link Discovery Protocol-Media Endpoint Discovery), to the IEEE 802.1ab Station and Media Access Control Connectivity Discovery document defines methods for an interconnecting switch to notify the VoIP phone about its location based on the assumption that a particular switch port services a specific location. Cisco's CDP (Cisco Discovery Protocol) provides similar features as LLDP-MED for Cisco equipment.

Location Mapping Process Click to enlarge in another window

In the case of LLDP-MED or CDP location discovery, the VoIP phone is responsible for sending its location information to the IP PBX. The IETF's Emergency Context Resolution with Internet Technologies (Ecrit) and Geographic Location/Privacy (Geopriv) working groups are focused on providing a framework to transmit location information using IP-based protocols such as SIP. Neither group addresses how location is determined, just how the information is transmitted. LLDP-MED is a likely candidate for the job. Of the two, the Geopriv work is broader in application, with emergency services just one application, while the Ecrit work focuses on the transmission of the location and interaction with emergency responders.

E911 location service for softphones is spotty, however. Vendor solutions range from advice such as "have a land line handy for 911 calls" to labeling phones as not being 911-capable, which is obviously less than satisfactory. Certainly, expecting users to pick up a softphone to dial 911 may seem silly, but what about company-issued VoIP handsets in the home office?

RedSky Technologies recently announced a software client for Windows called Softphone Location Determination Application (SLDA) that interacts with mobile users to determine their location and then updates the location databases. Locations can be predefined, letting the user determine his location.The focus should be on understanding IP PBX vendors' solutions for E911. You'll need to support E911 for VoIP deployments, and vendor approaches vary greatly. We expect to see wider integration of software packages, such as RedSky's SLDA, to ease the pain of E911 maintenance. However, if the customer pain points are sore enough, IP PBX vendors will likely develop solutions internally.

Mike Fratto is an NWC Senior technology editor based in our Syracuse University Real-world Labs® Write to him at [email protected].

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