NetCri'07 LoST: A Protocol for Mapping Geographic Locations to Public Safety Answering Points Henning Schulzrinne, Hannes Tschofenig, Andrew Newton, Ted Hardie NetCri 2007 (IPCCC) New Orleans, LA April 13, 2007

NetCri'07 Overview Problem: find PSAP for current location –instance of general geographic service location problem LoST architecture Synchronization Implementation Future work

NetCri'07 UA recognition & proxy resolution mapping INVITE urn:service:sos To: urn:service:sos INVITE urn:service:sos To: urn:service:sos Route: (outbound proxy) provider.com LoST

NetCri'07 Problem: Finding the correct PSAP Which PSAP should the e-call go to? –Usually to the PSAP that serves the geographic area –Sometimes to a backup PSAP –If no location, then ‘default’ PSAP –solved by LoST

NetCri'07 LoST functionality Mapping of location to parameters (e.g., URL) Civic as well as geospatial queries –civic address validation Recursive and iterative resolution Pre-querying and caching for efficiency and robustness –query ahead of emergency call (e.g., at boot time for stationary devices) –no re-querying while moving Fully distributed and hierarchical deployment –can be split by any geographic or civic boundary –same civic region can span multiple LoST servers Indicates errors in civic location data  debugging –but provides best-effort resolution Supports overlapping service regions –e.g., contested regions (Kashmir, Palestine, Taiwan,...)

NetCri'07 LoST: Location-to-URL Mapping cluster serves VSP 2 NY US NJ US Bergen County NJ US 123 Broad Ave Leonia Bergen County NJ US cluster serving VSP 1 replicate root information search referral root nodes Leonia NJ US VSP 1 LoST

NetCri'07 LoST Architecture T1 (.us) T2 (.de) T3 (.dk) G G G G G broadcast (gossip) T1:.us T2:.de resolver seeker 313 Westview Leonia, NJ US Leonia, NJ  tree guide

NetCri'07 LoST Properties Minimizes round trips: –caching individual mappings –returns coverage regions (“hinting”) civic (“all of C=US, A1=NY”) or geo (polygon) Facilitates reuse of Transport Layer Security (TLS) Returns emergency service numbers for a region Query for supported Service URN types

NetCri'07 LoST: Query example Uses HTTP or HTTPS <findService xmlns="urn:…:lost1” recursive="true" serviceBoundary="value" > Germany Bavaria Munich Neu Perlach 96 urn:service:sos.police

NetCri'07 LoST “Find Service” response/warning example München Polizei-Abteilung urn:service:sos.police Germany Bavaria Munich

NetCri'07 Validation Determine if civic location is (partially) valid Returns XML tag names of components: –validated and used for mapping –no attempt to validate (and not used) e.g., house number –known to be invalid Return (default) PSAP based on validated elements May return list of guesses for correct addresses, if requested country A1 A3 A6 PC

NetCri'07 Geo support Which geo types should be supported? –Point (3D) –Polygon?  may yield ambiguous answers –more complicated shapes? Current proposal –always include 2D-point –may include other shapes Caching of mappings –return service region –only query again if mobile leaves service region –open issue: “holes” in service region

NetCri'07 Advanced LoST functionality Get list of (emergency) services supported –by server –for a region Obtain service regions –identified by globally-unique tag urn:service:sos urn:service:sos.ambulance urn:service:sos.animal-control

NetCri'07 Server synchronization Synchronization of forest guides and server clusters –push information to peers –get list of new elements and retrieve mappings existing server new server <m sourceId="lost.example" sourceId="abc123" lastUpdated=“..” />...

NetCri'07 Performance of CU LoST server roughly 170 req/sec --> ~17M / day dual-core P4/3.0 GHz Linux Postgresql Tomcat 4.1

NetCri'07 Conclusion LoST = general location-to-service mapping protocol –emergency services: 911 and first-responder directory –AAA, pizza delivery,... Implementations and interoperability tests in progress –Wonsang Song and Yong-Jul Kim (Columbia U.) completed -05 seeker, resolver, authoritative server, FG,... –Krzystof Rzecki, Piotr Blaszcyk, Anna Makarowska, Michael Niedzwiecki (CCNS SA in cooperation with Institute of Telecomputing of CrawcowUniversity of Technology) Future work –server synchronization –extension to non-emergency services (proximity routing?)