Transcript PowerPoint Presentation - SOS Uniform Resource Identifier (URI

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
Keith Drage
IETF#73
1
[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
2

Proposed solution


In REGISTER request,
append new URI
parameter to AOR in
Contact
Other solutions
considered




Emergency service
identifier in P-PreferredService header
Value in Call-Info header
Emergency GRUU
Priority header set to
emergency value
[REQ 2] Indication of IMS Emergency call
origination



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
Proposed solution

Other solutions considered





3
Append new URI
parameter to Contact in
INVITE
Emergency service
identifier in P-PreferredService 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
[REQ 3] Indicating to the UA that an emergency
call has been initiated

Issue


4
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
[REQ 4] Marking the PSAP call back

Issue


5
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
Priorities




6
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
Backup slides
7
Le (e.g. E2)
P-CSCF adds “sos” URI
parameter in Contact if UE
does NOT detect emergency
session attempt. Service URN
is included in the RequestURI and To header
UE adds “sos” URI
parameter in Contact if UE
detects emergency
session attempt. Service
URN is included in the
Request-URI and To
header
LRF
2. Location &
Routing Function
Ml
PSAP URI added to
Route. “sos” URI
parameter
preserved in
Contact
from PSAP
to PSAP via IP
mutimedia
Network
Mm
UE
Gm
P-CSCF
Mw
1. SIP INVITE
SIP REGISTER
Mw
E-CSCF
Mi/Mg
3. SIP INVITE
or ISUP IAM
to PSAP
(via PSTN
via BGCF/
MGCF)
Registration
Outgoing Call
S-CSCF
Mm/Mw
from PSAP
Callback
Visited Network
2. SIP INVITE
Home Network
8
1. SIP INVITE
PSAP URI as tel URI added
to Request URI (replaces
service URN). BGCF URI
added to Route. “sos” URI
parameter preserved in
Contact