Emergency Calling for VoIP

1
Emergency Calling for VoIP

• Wonsang Song, Jong Yul Kim,
• and Henning Schulzrinne

2
Overview

• Project introduction
• Architecture and implementation
• References
• Demo

3
Introduction

• Emergency call is necessary for voice service.
• People expect to reach PSAP when dials 911.
• Many people use VoIP as primary telephone.
• Traditional 9-1-1 system does not work well with
  VoIP
• Identity Line number, Location billing
  address
• Covering limited area
• National protocols and routing
• Three (related) fundamental problems
• Where is the caller?
• To which PSAP should the call go to?
• How to identify the emergency call?

4
Project Goals

• Develop a prototype system that routes emergency
  calls over SIP based VoIP networks.
• Implement requirements for IP-based PSAP
• Provide opportunities to enhance 911 system
• Multimedia (audio, video, text)
• Data delivery (floor plan, medical information)
• Delivering video (CPR how-to)
• Load balancing and redundancy
• Location delivery (location with forwarded,
  transferred calls)

5
Four Phases of Emergency Calls
Phase 4
Phase 1
Phase 2
Phase 3
6
System Components
phase1
phase1
phase2
phase3
phase4
phase3
7
Phase1 Determining Location

• Purpose
• To get the visited emergency dial strings
  (Phase2)
• To resolve the correct PSAP URL (Phase3)
• To present the callers location on the call
  takers screen using mapping software (Phase4)
• Solution
• UA can be stationary, nomadic or mobile -gt apply
  different methods
• GPS, CDP (LLDP-MED), DHCP and Manual Entry
• The result location information is either civic
  address or geospatial coordinates.
• The location information will be included in the
  INVITE request as PIDF-LO.

8
DHCP for Location

• modified ISCs dhcpd to generate location
  information
• use MAC address back-tracing to get location
  information

9
CDP for Location

• Cisco Discovery Protocol (Layer2)
• Cisco switches broadcast switch/port ID
  periodically.
• A Switch covers a floor, a port leads to a jack
  in a room
• -gt room-level accuracy

10
SIP message for Location Info.
------- _ZGY1NTFlZDJkMDkxY2FkMTIxMWI2MzIzNjE1M2U0
OTY MIME-Version 1.0 Content-Type
application/pidfxml Content-Transfer-Encoding
8bit lt?xml version"1.0" encoding"ISO-8859-1"?gt
ltpresence xmlns"urnietfparamsxmlnspidf"
xmlnsgp"urnietfparamsxmlnspidfgeopriv10"
xmlnscl" urnietfparamsxmlnspidfgeopriv1
0civilLoc" xmlnsgml"urnopengisspecificati
ongmlschema-xsdfeaturev3.0"
entity"sipcalltaker_ny2_at_irt.cs.columbia.edu"gt
lttuple id"28185"gt ltstatusgt ltgpgeoprivgt
ltgplocation-infogt ltclcivilAddressgt
ltclcountrygtuslt/clcountrygt
ltclA1gtnylt/clA1gt ltclA2gtnew
yorklt/clA2gt ltclA3gtnew yorklt/clA3gt
ltclA6gtamsterdamlt/clA6gt
ltclHNOgt1214lt/clHNOgt lt/clcivilAddressgt
lt/gplocation-infogt ltgpmethodgtManuallt/gp
methodgt lt/gpgeoprivgt lt/statusgt
ltcontact priority"0.8"gtsipeddie_at_160.39.54.70506
0lt/contactgt lttimestampgt2005-09-26T155734-040
0lt/timestampgt lt/tuplegt lt/presencegt -------
_ZGY1NTFlZDJkMDkxY2FkMTIxMWI2MzIzNjE1M2U0OTY--
INVITE urnservicesos SIP/2.0
request line
To urnservicesos Call-ID 763782461_at_192.168.1.1
06 Via SIP/2.0/TCP 192.168.1.1064064rport Conte
nt-Type multipart/mixed boundary From
sipcaller_at_irt.cs.columbia.edu Contact
ltsipeddie_at_160.39.54.705060gt CSeq 1
INVITE Content-Length 1379
header fields
------ _ZGY1NTFlZDJkMDkxY2FkMTIxMWI2MzIzNjE1M2U0O
TY MIME-Version 1.0 content-Type
application/sdp Content-Transfer-Encoding
8bit v0 oeddie 1127764654 1127764654 IN IP4
192.168.1.106 sSIPC Call cIN IP4
160.39.54.70 t0 0 maudio 10000 RTP/AVP 0
3 mvideo 20000 RTP 31
SDP
PIDF-LO
11
Phase2 Identifying SOS

• Purpose
• For UA To send callers location information
• For Proxies To handle the emergency call
  specially
• Emergency Identifier (Emergency Service URN)
• Service URN identifies a generic service, not a
  specific resource
• For emergency
• urnservicesos
• urnservicesos.ambulance
• urnservicesos.fire
• urnservicesos.police
• Can be used in request URI and To header.
• Will be resolved into PSAP URL using mapping
  service (phase3)

12
Emergency Dial Strings

• Different emergency dial strings
• different in countries (e.g., 911 for North
  America, 112 for Europe)
• some countries uses separate numbers for
  ambulance/police/fire
• Required to support both home and visited
  emergency dial strings
• e.g., for an American traveler who is visiting
  Europe, both 911 and 112 should be recognized as
  emergency
• For the home emergency dial strings
• User can set his/her home country through
  configuration.
• In initial time, UA gets the home emergency dial
  strings using mapping protocols.
• For the visited emergency dial strings
• Whenever current location is changed, UA gets the
  visited emergency dial strings using mapping
  protocols.
• UA keeps all emergency dial strings in the local
  dial plans
• e.g., 911 -gt urnservicesos

13
Phase3 Routing to Correct PSAP

• Which PSAP should the call go to?
• Usually to the PSAP that covers the area
• Sometimes to a backup PSAP
• If no location, then default PSAP
• PSAP determination
• mapping problem
• Works in progress for standardization
• LoST A Location-to-Service Translation Protocol

14
LoST (Location-to-Service Translation)

• For mapping a service identifier and location
  information to PSAP URL emergency dial-string
• Supports both civic and geo location information
• Uses web service (SOAP base) as underlying
  protocol

ltmappinggt ltresponse expires"2006-03-09T01
5333.396Z"gt ltservicegturnservicesoslt/s
ervicegt ltdisplayNamegtNew York City
PSAPlt/displayNamegt lturigtsippsap_ny_at_irt.c
s.columbia.edult/urigt ltcivicMatchgt
ltgplocation-infogt
ltclcivicAddressgt
ltclcountrygtUSlt/clcountrygt
ltclA1gtNYlt/clA1gt ltclA3gtNew
Yorklt/clA3gt ltclA6gtAmsterdamlt/clA
6gt ltclHNOgt1214lt/clHNOgt
lt/clcivicAddressgt
lt/gplocation-infogt lt/civicMatchgt
ltdialstringgt911lt/dialstringgt
lt/responsegt lt/mappinggt
ltmappinggt ltrequestgt
ltoperationgtrecurselt/operationgt
ltservicegturnservicesoslt/servicegt
ltgplocation-infogt ltclcivicAddressgt
ltclcountrygtUSlt/clcountrygt
ltclA1gtNYlt/clA1gt ltclA3gtNew
Yorklt/clA3gt ltclA6gtAmsterdamlt/clA6gt
ltclHNOgt1214lt/clHNOgt
lt/clcivicAddressgt lt/gplocation-infogt
lt/requestgt lt/mappinggt
request
response
LoST Server
15
Phase4 Call Presentation in PSAP
16
Calltakers Screen

• SIPc as SIP UA
• Mapping software to display callers location
• Geolynx
• Google Maps

17
Web Interface

• Manage PSAP systems
• Show call logs, details, incident information and
  statistics

18
Scenario 1 Normal Case(UA recognition, UA
resolution)
Mapping Server
SOS caller
SIP proxy
call taker
19
Scenario 2 No Location from UA(UA recognition,
Proxy resolution)
Mapping Server
DHCP Server
(5)
(4)
PSAP URL
Location Service Identifier
(3)
Location
(1)
INVITE urnservicesos To urnservicesos
(2)
dial 911 or push emergency button
SIP proxy
SOS caller
call taker
20
Scenario 3 Backward Compatible(Proxy
recognition, Proxy resolution)
Mapping Server
DHCP Server
(5)
(4)
PSAP URL
Location Service Identifier
(3)
Location
(1)
INVITE sip911_at_domain To sip911_at_domain
(2)
INVITE PSAP URL To urnservicesos ltLocationgt
(6)
SOS caller
dial 911
SIP proxy
call taker
21
References

• SIP Session initiation protocol, RFC 3261
• Requirements for Emergency Context Resolution
  with Internet Technologies, draft-ietf-ecrit-requi
  rements-04
• Dynamic Host Configuration Protocol (DHCPv4 and
  DHCPv6) Option for Civic Addresses Configuration
  Information, draft-ietf-geopriv-dhcp-civil-07
• Dynamic Host Configuration Protocol Option for
  Coordinate-based Location Configuration
  Information, RFC 3825
• A Presence-based GEOPRIV Location Object Format,
  RFC 4119
• A Uniform Resource Name (URN) for Services,
  draft-ietf-ecrit-service-urn-01
• LoST A Location-to-Service Translation Protocol,
  draft-hardie-ecrit-lost-00
• Best current practices for third party call
  control (3pcc) in the session initiation protocol
  (SIP), RFC 3725

22
Demo