ECRIT: Emergency Calling Henning Schulzrinne (with Jong Yul Kim, Wonsang Song, Anshuman Rawat, Matthew Mintz-Habib, Amrita Rajagopal and Xiaotao Wu) Dept. of Computer Science Columbia University

SIP 2006 (Paris, February 2006) Introduction Emergency calling is a necessary part of consumer voice service –citizen calls PSAP (public safety answering point) for assistance Existing solutions are insufficient –may deliver call to wrong PSAP particularly for nomadic and mobile users –may not deliver location to PSAP –makes it difficult to move call information around e.g., call location to first responder –voice only (+ TDD)

SIP 2006 (Paris, February 2006) VoIP emergency communications emergency call dispatch civic coordination emergency alert (“inverse 911”)

SIP 2006 (Paris, February 2006) Components of emergency calling Contact well-known number or identifier Route call to location- appropriate PSAP Deliver precise location to call taker to dispatch emergency help nowtransitionall IP dial 112, 911  urn:service:sos selective router VPCDNS phone number  location (ALI lookup) in-band  key  location in-band

SIP 2006 (Paris, February 2006) What makes VoIP 112/911 hard? POTSPSTN-emulation VoIPend-to-end VoIP (landline) phone number limited to limited area landline phone number anywhere in US (cf. German 180) no phone number or phone number anywhere around the world regional carriernational or continent- wide carrier enterprise “carrier” or anybody with a peer- to-peer device voice provider = line provider (~ business relationship) voice provider ≠ ISP national protocols and call routing probably North America + EU international protocols and routing location = line location mostly residential or small business stationary, nomadic, wireless

SIP 2006 (Paris, February 2006) The core problem Voice Service Provider (VSP) sees emergency call but does not know caller location ISP/IAP knows user location but does not handle call

SIP 2006 (Paris, February 2006) Staged deployment ~ 6,134 PSAPs in North America –average 2-3 active call takers each –some serve town, some large parts of a state –only ~30% of PSAPs can receive geo coordinates –30-40% may be voice only –many using 1970s telecom technology “CAMA” (operator) trunks limited to delivering 8 (regional) or 10 digits (national) of information already facing pressure from supporting cellular services –Phase I (cell tower and face) and Phase II (caller geo location) EU: smaller number of PSAPs, but often without location delivery Initial version (“I1”): –dial 10-digit administrative number –like telematics services –does not deliver caller location to PSAP

SIP 2006 (Paris, February 2006) More than pain… Multimedia from the caller –video capture from cell phones –video for sign language –text messaging and real-time text for the deaf Data delivery –caller data: floor plan, hazmat data, medical alerts –measurement data input: automobile crash data, EKGs, … Delivering video to the caller –e.g., CPR training Load balancing and redundancy –currently only limited secondary PSAP –VoIP can transfer overload calls anywhere Location delivery –carry location with forwarded and transferred calls –multiple location objects (civic + geo)

SIP 2006 (Paris, February 2006) Options for location delivery L2: LLDP-MED (standardized version of CDP + location data) –periodic per-port broadcast of configuration information L3: DHCP for –geospatial (RFC 3825) –civic (draft-ietf-geopriv-dhcp-civil) L7: proposals for retrievals –by IP address –by MAC address –by identifier (conveyed by DHCP or PPP)

SIP 2006 (Paris, February 2006) IETF ECRIT working group Emergency Contact Resolution with Internet Technologies Solve four major pieces of the puzzle: –location conveyance (with SIPPING & GEOPRIV) –emergency call identification –mapping geo and civic caller locations to PSAP –discovery of local and visited emergency dial string Not solving –location discovery –inter-PSAP communication and coordination –citizen notification Current status: –finishing general and security requirements –tentative agreement on mapping protocol and identifier –later, to work on overall architecture and UA requirements

SIP 2006 (Paris, February 2006) Emergency identifier requirements Direct user interface, without “dialing” number –but do NOT require user to input this identifier directly –i.e., separate user interface from protocol identifier! Reach emergency help in any country, without knowledge of local numbers –also, universally recognizable by proxies regardless of location of caller Deployable incrementally –even if not all entities support the mechanism Testable without impacting PSAP (human) resources

SIP 2006 (Paris, February 2006) Defining an (emergency) services URN URN = universal resource name –identifies resource, not its network location –translated by protocol (e.g., DNS) into location(s) New: service URN urn:service:service Identifies a generic service, not a specific resource Uses mapping protocol: –{identifier, location}  URL(s) Can be used anywhere a URN or URL is allowed, e.g.: –web pages –result returned by mapping protocol –request and To URI in SIP For emergency services: –urn:service:sos, urn:service:sos.fire, urn:service:sos.police, urn:service:sos.marine, urn:service:sos.mountain, urn:service:sos.rescue, urn:service:sos.poison, urn:service:sos.suicide, urn:service:sos.mental-health Could also be used for other services: urn:service:directory

SIP 2006 (Paris, February 2006) UA recognition & UA resolution INVITE To: urn:service:sos (dial string) mapping INVITE To: urn:service:sos leonianj.gov mapping may recurse location information DHCP LLDP-MED

SIP 2006 (Paris, February 2006) UA recognition & proxy resolution mapping INVITE urn:service:sos To: urn:service:sos INVITE To: urn:service:sos provider.com

SIP 2006 (Paris, February 2006) UA recognition & proxy resolution (proxy location determination) mapping INVITE urn:service:sos To: urn:service:sos INVITE To: urn:service:sos Location: provider.com

SIP 2006 (Paris, February 2006) Proxy recognition & proxy resolution mapping INVITE To: INVITE To: Location: provider.com

SIP 2006 (Paris, February 2006) Emergency dial strings ~60 different dial strings in use –some countries separate fire/police/…, others don’t –some are used for other services PBX, information, prefix, … Needs to support both home and visited dial string when traveling Home = dial string at home location of traveler –traveler may not know local conventions Visited = dial string at visited location –fellow tourist picks up phone –babysitter in ex-pat household Configure –via DHCP –via SIP configuration mechanism –via location mapping

SIP 2006 (Paris, February 2006) LUMP: Mapping service URNs + locations to URLs Common problem: –{geo or civic location, service}  set of URLs –e.g., {Broadway/NY, “911”}  –also applies to anything from towing service to pizza delivery Need to be able to validate addresses ahead of emergency –does this street address resolve to a PSAP? –can the ambulance find the address? Service providers don’t trust each other (fully) –e.g., who gets to include Jerusalem in its map –service may depend which warlord you belong to –can’t wait for UN (or ICANN) to create global emergency services database Suggested approach: new distributed mapping protocol –LUMP: location-to-URL mapping protocol –uses SOAP, but special service URLs

SIP 2006 (Paris, February 2006) LUMP: overview Support global-scale resolution of service identifiers (e.g., service URNs) + locations to other URLs Attempts to be reliable and scalable –borrow concepts, but not protocol limitations, from DNS Architecture: “Forest of trees with a cloud above” –avoid root as only deployment alternative Uses standard web services building blocks

SIP 2006 (Paris, February 2006) LUMP: 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

SIP 2006 (Paris, February 2006) LUMP 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

SIP 2006 (Paris, February 2006) Caching Generally, UA caches lookup results –query: “I’m at (X,Y), what’s my PSAP?” –answer: “Your PSAP is as long as you stay in polygon (X 1,Y 1 ; X 2, Y 2 ; …); this is valid for 12 hours” almost no impact of node mobility on query frequency –same for civic: “as long as you stay on Main Street, your town” civic only relevant for nomadic users –actual PSAP coverage area may be larger  just an optimization Almost always avoids query during emergency call –MAY re-query during call –load distribution via DNS given frequency of calls for one resolver, likely to be no DNS caching anyway Further optimization: query with timestamp (or etag) of last answer –answer: “still the same, thanks for asking”

SIP 2006 (Paris, February 2006) Performance notes US: only about 6 calls/second for whole country –on average, but may spike during mass casualty events Use TCP (or TCP/TLS) for reliability Expect 1-2 queries/day/client Typical: >> 100 queries/second/server –almost all rows will be cached in memory only about 6,000 rows –one server  8,640,000 queries –probably N+1 spared –data center cost: $300/month/server  $0.0003/user/month (1Mq/day)

SIP 2006 (Paris, February 2006) Implementation status Prototype implementation at Columbia University: –includes referrals –both geo and civic coordinates –from draft WSDL (with minor fixes) Server –Axis (Apache) SOAP server –Postgres SQL geo database does polygon intersection Client –Java app (web page) –Tcl (for our SIP client)

SIP 2006 (Paris, February 2006) LUMP geo mapping

SIP 2006 (Paris, February 2006) LUMP: SOAP request

SIP 2006 (Paris, February 2006) Conclusion Opportunity to fundamentally restructure emergency communications –higher reliability with large-scale disasters –lower cost –richer interaction IETF ECRIT working group converging on set of solutions To be done: –finalize mapping protocol additional transport modes? –configuration of dial strings –overall system architecture