Thoughts on VoIP and Emergency Calling

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Thoughts on VoIP and Emergency Calling

• Henning Schulzrinne
• Columbia University

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VoIP emergency communications
emergency call
dispatch
emergency alert (inverse 911)
civic coordination
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Reliability issues

• Selective routers can only route to alternate
  (fixed) trunks
• Typically, two
• No MSAG or ALI information for out-of-area
  numbers
• Numbers may not be unique (if 8 digit numbers)
• No GIS information for out-of-area numbers

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Goals

• Any PSAP should be able to back up any other PSAP
  almost instantaneously
• Preferably without prior arrangement
• It should be possible to create a new PSAP in
  short order
• E.g., a university computer lab or a (commercial)
  call center
• Ingredients needed
• Internet bandwidth
• PCs with audio capability
• Call taker staff

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How to achieve these goals?

• Allow every SR and VoIP phone to reach every PSAP
• E.g., via gateway into IP (Internet, ESN)
• Provide mapping independent

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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
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New model

• Clear separation of ISP and VSP roles
• ISP provides location, VSP provides call routing
• IP addresses are not sufficient to locate end
  systems
• Probable regulatory requirement ISPs must
  provide (civic/geo) location information to their
  subscribers even if they do not offer VoIP
  services
• E.g., via DHCP or other standards-based mechanism

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UA recognition proxy resolution
mapping
9-1-1
provider.com
INVITE urnservicesos To urnservicesos ltlocat
iongt
INVITE sippsap_at_leonianj.gov To
urnservicesos ltlocationgt
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UA recognition proxy resolution(proxy location
determination)
mapping
9-1-1
provider.com
INVITE urnservicesos To urnservicesos
INVITE sippsap_at_leonianj.gov To
urnservicesos Location ltlocationgt