While for various reasons I believe that the efforts to enforce E911 requirements on Voice over IP phones are bogus and largely designed to make it harder for smaller players to compete with established companies, there is a legitimate need for ways to give your location to emergency services.
To protect privacy, I suggest that this be done in the endpoints. To assist this, I would propose a set of option extensions to the DHCP protocol to tell an endpoint what the server knows about its location, including address, zip and even what emergency contact center to use. This would start with RFC3825 for geolocation, and move on to other features. The endpoint device, when calling 911 or other emergency services, could include this information in the SIP invite, or provide it on request.
For those who don't know, DHCP is the system which lets a computer connect to an ethernet and ask for an IP address as well as important local network information (such as the addresses of routers, name servers, domain names etc.) Some DHCP servers know exactly who the client device is and effectively act as the client's memory. Some just give the next available address and return information about the local network area.
For example, most people with home networks, and almost all of them who use Voice over IP services like Vonage have a local network with its own DHCP server, built into the home-router they use. That home router could be told the address of the home, and all devices, including VoIP phones, could learn it. For companies, it is the same.
DHCP is also used for ISPs to give addresses to DSL and Cable modem customers who hook up to the internet without a home gateway because they have only one computer. That's pretty rare for VoIP users. In these cases they may or may not know the street address of the computer. DHCP is also very common for people who connect to wireless access points. The AP in a Starbucks could easily tell your device the address of the Starbucks.
As noted, we could start by the device fetching this address and forwarding it on with emergency calls, but not doing so for regular calls. This puts privacy control in the hands of the user, where it should be.
However, we could do even more than just give location as in rfc3825. The DHCP server could publish the direct contact information for the local area for police, fire, ambulance or general emergencies. They could simply include the contact number of a PSAP (Public Service Access Point, the gateway to emergency services) for the location, or in a corporate setting, might direct emergency calls to the corporate security desk, with the PSAP/911 as a fall-back. (There should be laws however about use of such features and protection of privacy. Network owners can already reroute any traffic but we want it to be clear how this might be done.) read more »
