Internet E911 System Henning Schulzrinne and Knarig Arabshian

Internet E-911 System Henning Schulzrinne and Knarig Arabshian Department of Computer Science Columbia University {hgs, knarig}@cs. columbia. edu

Overview n n n How E-911 works Emergency call using SIP Internet E-911 Architecture Location Resolution SIPc and SIP-CGI functionality Conclusion

E-911 service Four components needed 1) Universal number such as 911 2) Call routing to an emergency response center-PSAP 1 -212 -9397063 613 CEPSR, Columbia University 3) Caller Identification Who is calling? caller-id to avoid prank call 4) Caller Location Where is he calling from? Address for speedy response

E-911 service How it works? Selective routing database Prefix Emergency Service Number SRDB 212939 xxxx 2345 Emergency Service Number Primary PSAP 2129119345 2345 Secondary PSAP 2129119456 2129119345 Central office 1 -212 -9397063 2129397063 613 CEPSR, 120 th st Broadway Telco and Amsterdam Ave DB

Emergency call using SIP (Legacy PSAP sees the gateway) SIP-PSTN gateway (switch room) ESR DB PSAP SRDB PSTN 939713 x Central office 2129397130 606 CEPSR IP network Sends fire-fighters to the switch room. 128. 59. 19. 61 (multimedia lab) Telco DB

Emergency call using SIP (IP-enabled PSAP is aware of IP telephony) PSAP Outbound Proxy IP Network LAN Richer Communication Envorinment: video to instruct caller in first aid or use sign language, text -based messaging, etc. 128. 59. 19. 61 (multimedia lab)

Architecture for IP telephony Use local switch tables to get the address of the caller PSAP EPAD INVITE sip: sos@example. com SIP/2. 0 Location: Rm. 523, 123 Main Street Centerville, NY 302 Moved Temporarily Contact: tel: +1 -212 -911 -1234 Outbound Proxy INVITE sip: 1 -212 -911 -1234@gw-r-us. com Location: Rm. 523, 123 Main Street Centerville, NY

Location Internet sipd DB Proxy server invokes location resolution module (LRM) Some phones may have address configured. Some phones may not know the location. Sends Location: 613 CEPSR Caller

Location Internet sipd DB Sipd knows IP address of the caller User dials 911 or sos@cs. columbia. edu Caller

Location Internet sipd DB Pings and traceroutes to caller’s IP address to locate last router R 3 R 2 R 1 Caller

Location Internet Uses SNMP to query the ARP table on R 1 to know the MAC address of caller. sipd DB Using switch’s CAM table and recursive query, locate the last port (using CDP). R 3 R 2 R 1 Caller

Location Internet sipd DB Administrative SQL database lookup to map the switch and port to physical address.

Location resolution module n n n The program is capable of identifying CDP participating ports, but SNMP-CDP querying the router for the ARP table (for MAC address) hasn’t been implemented. Unable to test cascading infrastructure or remote vlan scenario. All code in perl, intended to be used within sip-cgi script SNMP-walk program is used to query various CAM tables Traceroute and SNMP query take time n n Pre-fetch and cache this information for all registered users Can also be used with modification at caller’s user agent (in sipc)

Location resolution algorithm

SIPc functionality Click on SOS icon and Call 911 Check to see if home address is configured Location Resolution Module If not, then call Location Resolution Module and insert Location into SIP INVITE

SIP-CGI Internet sipd DB Sends Location: 613 CEPSR Once sipd knows physical address, either using LRM or from INVITE Queries www. geocode. com to message itself get the longitude and latitude information

SIP-CGI Intrado DB Internet sipd Pass longitude/ latitude into to intrado DB to get the nearest PSAP phone. DB

SIP-CGI Internet sipd DB Place the call to the PSAP

Summary n n Internet E-911 system gives us a flexible and robust environment Next generation devices will be interoperable with SIP Location resolution still a topic of research Currently working with Intrado (provider of 911 services and systems) database to implement this system.