A prototype i3 VoIP PSAP implementation

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A prototype i3 VoIP PSAP implementation

• Henning Schulzrinne, Anshuman Rawat, Matthew
  Mintz-Habib, Xiaotao Wu and Ron Shacham
• Dept. of Computer Science
• Columbia University
• NENA JTCM Meeting
• Atlanta, GA
• September 2004

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Overview

• A quick review of I3 assumptions
• Goals of project
• Prototype architecture and experiences
• Scaling and robustness
• Next steps

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Our I3 assumptions

• VoIP (SIP) capable end systems
• SIP-capable PSAP
• Location inserted by origin
• outbound proxy
• originating device (e.g., via DHCP)
• either geospatial or civic location

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Goals of prototype

• Provide a platform for quick experimentation
• Determine easy vs. hard parts of problem
• Experiment with redundancy and robustness
• Use off-the-shelf components where possible
• Modes
• Phase II wireless (based on ALI lookup)
• I3 VoIP end-to-end, with in-band location
  information

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Components
sipd SIP proxy server
database-backed DNS server
SIP phone
web server
SQL database for call routing
sipc SIP user agent
geo-coding, PSAP boundaries
GIS software for call location plotting
No endorsement implied other components likely
will work as well
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Prototype
gray features in progress.
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Demo prototype
Ft. Wayne, IN August 17, 2004
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Call routing

• PSAP lookup depends on location type
• DNS for civic locations
• Mapinfo Envinsa for geo location

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Detail I3 - DNS-based resolution
DHCP INFORM
psap.state.vt.gov
SIP w/location
MAC ? loc
Perl sip-cgi script
psap.state.vt.gov
DNS NAPTR addison.vt.us algonquin-dr.addison.vt.u
s
proprietary TCP-based protocol
151.algonquin-dr.addison.vt.us.sos-arpa.net
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Call taker setup
SIPc client receives calls
GeoLynx software displays caller location
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sipc receives call
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GeoLynx displays location
GeoLynx receives commands and displays location.
Caller location displayed on map.
Caller information displayed in GUI.
GeoLynx listens for commands from SIPc
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Demo Ft. Wayne, IN (August 17, 2004)
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White PSAP
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Red PSAP
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Blue PSAP
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Close-up of PSAP call taker station
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Using IP phones for voice
redundant sipds
XML display shows caller location
Apache web server
XML display with HTTP retrieval
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Emergency call conferencing
PSAP brings all related parties into a
conference call
Hospital
Fire department
INVITE
Conference server
Recorder
3rd party call control
PSAP
Caller
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Scaling

• NENA estimated 200 million calls to 9-1-1 in
  the U.S. each year
• ? approximately 6.3 calls/second
• if 3 minute call, about 1,200 concurrent calls
• typical SIP proxy server (e.g., sipd) on 1 GHz PC
  can handle about 400 call arrivals/second
• thus, unlikely to be server-bound

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Next steps for our prototype

• Custom user interface for call taker
• Add voice recording and conferencing
• using our software conference server
• Data mining
• collect and display statistical data about calls
• Integration of police/fire/EMS
• direct transmission of call-related data via
  simple IM application ? requires only Internet
  access

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Difficulties

• Difficult to get good test environment
• access to PDE
• IP access to ALI (often, jury-rigged telnet
  interfaces)
• access to MSAG and ALI data
• friendly PSAPs one option
• but open, network-accessible test lab would be
  better
• longer-term may need plug fests
• see SIPit effort vendors collaborating in
  friendly, non-public interop test efforts ? rapid
  elimination of protocol and implementation
  problems

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Conclusion

• A first prototype of I3 PSAP
• integrates Phase II wireless call delivery
• Shown that it is possible to integrate existing
  GIS applications with I3
• Based on COTS technology, with modest
  modifications
• Additional operational support in progress