Emergency services for SIP

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Emergency services for SIP

• Henning Schulzrinne

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Emergency services

• Two types of emergency services
• emergency calls ("911", "112")
• emergency notification ("inverse 911")
• emergency calls are hard
• PSTN gateway dialing 911 may be located anywhere,
  far away from IP phone
• VPNs ? IP address may not reveal network location

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Emergency services

• More than just replicating PSTN
• multimedia
• video monitoring of accident scene or victim
• video instruction in first aid
• better than TTY for hearing-impaired
• transmit biometric data
• Easier to create multiple backup PSAPs

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PSTN emergency calling

• Basic 911 call number, get routed to one Public
  Safety Answering Point (PSAP)
• since 1968 in the United States
• 93 of population covered by 911
• Enhanced 911
• route based on CLID (cannot be suppressed)
• provide user location
• started in 1970s, now 95
• see Bellcore SR4163 for details
• see 47 USC 251 for legal mandate

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Wireless emergency calling

• FCC Phase I caller ID, cell site
• FCC Phase II mandates user location
• Handset-based
• 50 meters for 67 percent of calls
• 150 meters for 95 percent of calls
• Network-based
• 100 meters for 67 percent of calls
• 300 meters for 95 percent of calls

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VoIP emergency calls

• Work for both "legacy" PSAPs and IP-based PSAPs
• Define "sos" universal emergency address
• find location of phone based on
• street address ? geocoding ? long/lat, or
• mobile longitude, latitude
• find appropriate jurisdiction and PSAP
• use national database long/lat ? PSAP
• find ESR (routing number) ? call appears like 911
  call
• convey location to PSAP

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Emergency identifier

• Requirements
• dialable from all SIP devices
• universally recognized
• note SOS ? "save our souls"!
• not quite unassigned consider 112_at_ and 911_at_?
• Also allow "sos.fire" and others for specialized
  emergency services
• Use sipsos_at_home-domain to make handling
  predictable
• intermediate proxies may deflect

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Routing emergency calls
302 Moved Contact sipsos_at_psap.leonia.nj.us Conta
ct tel[phone]
EPAD
REGISTER sipsos Location 07605
INVITE sipsos Location 07605
SIP proxy
INVITE sipsos Location 07605
INVITE sipsos_at_psap.leonia.nj.us Location 07605
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Where is the phone?

• Regular GPS doesn't work well
• doesn't work indoors
• long time to first fix 30"-15'
• assisted GPS (A-GPS)
• HDTV-based
• Landline and 802.11 phones
• LAN jack tracing via traceroute, ARP, Cisco
  Discovery Protocol (CDP) and SNMP vLAN tables
• 802.11 field strength triangulation (e.g.,
  Microsoft, VTT)
• hardware identification
• IR/RF tags
• user data entry

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911 deployment
SIP
0
1
0
c1.leonia.us
IP
UDP, TCP
IP
c2.leonia.us
c1.fortlee.us
IP
0
0
1
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Open issues

• What needs to be standardized?
• Are there any other UA behaviors?
• prevent accidental disconnect
• bypass carrier authentication
• e.g., 3G requirement of REGISTER before calls?
• Myth During PSTN 911 calls, certain features
  (three-way calls, hang-up) are unavailable
• true only for Basic 911

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Emergency notification

• notify public officials and citizens of
  emergencies
• "tornado coming"
• "fugitive alert"
• current systems are typically single-mode (fax,
  telex, phone, TV, loudspeaker)
• don't scale well
• very limited information content
• don't reach citizens outside calling area
• people at work
• hard to authenticate

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SIP-based emergency notification

• SIP has scalable event notification feature
• use for hierarchical notification reflecting
  civil lines of authority
• use XML/WSDL message bodies to semantically
  describe emergency
• location
• type of emergency
• instructions
• ...
• allow automated reaction
• routing to legacy systems (pagers, police radios)
• translation

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Emergency notification