SOS Uniform Resource Identifier (URI) parameter for marking of Session Initiation Protocol (SIP) requests related to emergency services draft-patel-ecrit-sos-parameter-01.txt

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SOS Uniform Resource Identifier (URI) parameter
for marking of Session Initiation Protocol (SIP)
requests related to emergency servicesdraft-patel
-ecrit-sos-parameter-01.txt

• Keith Drage
• IETF73

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REQ 1 Indication in REGISTER request

• Issue
• 3GPP needs to distinguish an emergency
  registration from ordinary registration
• Allows UE to get its associated tel-URI for
  things like callback
• Allows barred public user identities (e.g.
  pre-pay expired) to be used which are not
  included in a normal registration
• UE performs emergency registration if not
  otherwise registered or is roaming
• Previously had an emergency public user identity
  which has issues so removed

• Proposed solution
• In REGISTER request, append new URI parameter to
  AOR in Contact
• Other solutions considered
• Emergency service identifier in
  P-Preferred-Service header
• Value in Call-Info header
• Emergency GRUU
• Priority header set to emergency value

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REQ 2 Indication of IMS Emergency call
origination

• Proposed solution
• Append new URI parameter to Contact in INVITE
• Other solutions considered
• Emergency service identifier in
  P-Preferred-Service header
• Value in Call-Info header
• Value in History-Info when service URN in Request
  URI is replaced
• Provide service URN as last entry in Route header
• Priority header set to emergency value

• Issue
• Some routeing proxies remove the Request-URI and
  replace it with PSAP address, e.g. in order to
  get through an existing PSTN gateway. Still need
  an indication that it is an emergency call

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REQ 3 Indicating to the UA that an emergency
call has been initiated

• Issue
• It is possible for a 3GPP UA to initiate a call
  without realising that the number dialled is an
  emergency number. Subsequently recognised in
  network
• UA ideally needs to learn that the call is now an
  emergency call, e.g. to suppress services in the
  UA

• Proposed solution
• Append new URI parameter to Contact in 1xx/2xx
  response
• Other solutions considered
• Value in Call-Info header
• Priority header set to emergency value
• 181 response code

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REQ 4 Marking the PSAP call back

• Issue
• Need for an indicator for suppression of network
  based services
• Need for an indicator that services in the UE are
  to be suppressed

• Proposed solution
• Append new URI parameter to Contact in INVITE

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Priorities

• Callbacks do not yet form part of 3GPP release so
  can defer REQ-4 (to an extent).
• Because REQ-1 is release 7, and because it is
  essential to make emergency calls operate, it is
  imperative to have a rapid solution to this.
• REQ-2 and REQ-3 are desirable to fix, but not
  quite so urgent as REQ-1.
• Therefore WG requested to charter work at least
  to include a solution to REQ-1

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Backup slides
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P-CSCF adds sos URI parameter in Contact if UE
does NOT detect emergency session attempt.
Service URN is included in the Request-URI and To
header
PSAP URI added to Route. sos URI parameter
preserved in Contact
UE adds sos URI parameter in Contact if UE
detects emergency session attempt. Service URN is
included in the Request-URI and To header
PSAP URI as tel URI added to Request URI
(replaces service URN). BGCF URI added to Route.
sos URI parameter preserved in Contact