Transcript SIP2005-911 - Columbia University

Emergency Calling in SIP
Henning Schulzrinne
(with Anshuman Rawat, Matthew Mintz-Habib and
Xiaotao Wu)
Dept. of Computer Science
Columbia University
[email protected]
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Emergency calling
1
Overview
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VoIP emergency communications
What makes emergency calling hard?
Stages of deployment
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I1: quick fixes
I2: backward-compatible
I3: end-to-end IP
Initial prototype
NENA + IETF efforts
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Emergency calling
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VoIP emergency communications
emergency call
emergency alert
(“inverse 911”)
dispatch
civic coordination
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Emergency calling
3
Current wireline calls
SUBSCRIBER
1
dial
911,
112
route call to
right PSAP
E911 TANDEM OFFICESRDB
3
2
5
4
END OFFICE
map ANI to
civic location
PSAP
ANI
COMMON
EQUIPMENT
ATTENDENT
POSITIONS
7
ALI
HOST
5
7
6
(Brian Rosen)
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Emergency calling
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Wireless (Phase II) Calls
Ai Di
MSC
Cellsite
E12
(ISUP)
E3
(ANSI-41)
ESNE
(Selective
Router)
CRDB
(ANSI-41)
CAMA
PSAP
E11
(LSP)
PDE
E5
MPC
MSC
MPC
E2
(ESP)
Mobile Switching Center
Mobile Position Center
ESME
(ALI
Database)
CRDB Coordinate Routing Database
PDE
Position Determining Entity
(Brian Rosen)
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Components of emergency calling
Contact well-known
number or identifier
Route call to locationappropriate PSAP
Deliver precise location
to call taker to dispatch
emergency help
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now
transition
all IP
112
911
112
911
dial 112, 911
signal sos@
selective
router
VPC
DNS
phone
number 
location
(ALI lookup)
in-band  key
 location
in-band
Emergency calling
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What makes VoIP 112/911 hard?
POTS
PSTN-emulation VoIP
end-to-end VoIP
(landline) phone number
limited to limited area
landline phone number
anywhere in US (cf. German
180)
no phone number or phone
number anywhere around
the world
regional carrier
national or continent-wide
carrier
enterprise “carrier” or
anybody with a peer-to-peer
device
voice provider = line
provider (~ business
relationship)
voice provider ≠ ISP
voice provider ≠ ISP
national protocols and call
routing
probably North America +
EU
international protocols and
routing
location = line location
mostly residential or small
business
stationary, nomadic, wireless
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Emergency calling
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More than pain…
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Multimedia from the caller
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Data delivery
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e.g., CPR training
Load balancing and redundancy
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caller data: floor plan, hazmat data, medical alerts
measurement data input: automobile crash data, EKGs, …
Delivering video to the caller
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video capture from cell phones
video for sign language
text messaging and real-time text for the deaf
currently only limited secondary PSAP
VoIP can transfer overload calls anywhere
Location delivery
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carry location with forwarded and transferred calls
multiple location objects (civic + geo)
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Core long-term requirements
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Media-neutral
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Work in systems without a voice service provider
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many enterprises will provide their own local voice services
Allow down-stream call data access
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voice (+TDD) first, IM and video later
as well as access to other “tertiary” data about the incident
Globally deployable
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independent of national emergency number (9-1-1, 1-1-2, etc.)
respect jurisdictional boundaries – minimize need for crossjurisdictional coordination
allow usage even if equipment and service providers are not local
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Testable:
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travel, imported equipment, far-flung locations
verifiable civic addresses (“MSAG validation”)
call route validation
Secure and reliable
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Staged deployment
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~6,134 PSAPs in North America
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average 2-3 active call takers each
some serve town, some large parts of a state
only ~30% of PSAPs can receive geo coordinates
30-40% may be voice only
many using 1970s telecom technology
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“CAMA” (operator) trunks
limited to delivering 8 (regional) or 10 digits (national) of information
already facing pressure from supporting cellular services
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Phase I (cell tower and face) and Phase II (caller geo location)
EU: smaller number of PSAPs, but often without location
delivery
Initial version (“I1”):
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dial 10-digit administrative number
like telematics services
does not deliver caller location to PSAP
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Three stages to VoIP 911
spec.
available?
use 10digit
admin.
number?
mobility
callback
number
to
PSAP?
caller
location
to
PSAP?
PSAP
modificatio
n
ALI (DB)
modification
new services
I1
now
allowed
stationary
no
no
no
no
none
I2
June
2005
no
stationary
nomadic
yes
yes
no (8 or 10
digit)
update
none
I3
2005
no
stationary
nomadic
mobile
yes
yes
IP-enabled
ALI not
needed
MSAG
replaced by
DNS
location inband
GNP
multimedia
international
calls
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I1.5: Level 3 ESGW solution
•
•
•
•
uses Level 3 as CLEC to feed ALI information to local ILEC
requires emergency services GW for each tandem
only works for non-ported numbers
does not work for mobile users
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I1.5: Global Crossing VoIP 911 transport
ITSP SoftSw itch does a digit
m anipulation on the 911 call to a
pre-defined 10 digit Pseudo
num ber that represents the
PSAP that needs to receive this
call.
ITSP
SoftSwitch
GW
911
End user
dials 911
Customer
VoIP
Network
TDM
Interconnectio
n
DMS has 300 range Pseudo
num ber assigned to each
individual PSAP circuit. DMS
does Digit Manipulation to
change Pseudo num ber to
w hatever the PSAP expects (e.g.
911)
GX VoIP Network
Route Label to appropriate GSX
w ith DMS IMTs
based on Pseudo number dialed
GSX
Chicago
Originating
GSX
VoIP
Interconnectio
n
IMT
911
DMS
Chicago
Route Label to appropriate GSX
w ith DMS IMTs
IMT
GC ACME
SBC
RL to appropriate GSX
w ith DMS IMTs
GSX
Anaheim
911
DMS
Anaheim
IMT
GSX
Newark
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PSAP Circuits
Emergency calling
PSAP Circuits
911
DMS
Newark
PSAP Circuits
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I2 architecture (draft)
IP domain
Emergency Services
Provider Network
Routing Proxy &
Redirect server(s)
Call server/
proxy server
PSTN
v6
ESGW(s)
v4
v5
v4
v1
IP Domain
E9-1-1
Selective
Router
VPC
VPC
VPC
v0
DHCP
v-e2
ESZ
RDB
LIS
v7
MSAG
VDB DBMS
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routing
database
SRDB
ALI
ALIDB
DB
v8
v3
DNS
PSAP
v2
v2
User
Agent
location
information
service
E9-1-1
Selective
Router
VoIP positioning center
validation
database
Emergency calling
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I2 interfaces
Interface
Participants
Protocol(s)
Description
v0
LIS to UA
DHCP
conveys location to endpoint
v1
UA to CS
SIP (+ others)
recognize emergency call
transport location object
v2
Proxy to VPC
XML query/response
location  ESRN, ESQK
v3
VPC to LIS
?
VPC gets location from location key in
signaling message
v4
CS/routing proxy to
ESGW
SIP
ESRN and ESGW inserted
v5
CS to redirect server
SIP
Redirect server returns call routing
information (ESRN, ESQK) in 3xx
v6
CS to routing proxy
SIP
transport location object
v7
location validation
DNS, ?
LIS requests validation of address
v8
VPC to ERDB
?
VPC sends LO, gets ESQK
ve-2 VPC to ALI-DB
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E2+ (wireless)
Emergency calling
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I3: Location-based call routing –
UA knows its location
GPS
INVITE sips:sos@
48° 49' N 2° 29' E
outbound
proxy server
DHCP
48° 49' N 2° 29' E  Paris fire department
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I3 (long-term) architecture
components
Common URL for emergency calls
1.
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sips:sos@home-domain
Convey local emergency number to devices
Allow devices to obtain their location
2.
3.
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directly via GPS
indirectly via DHCP (MAC  switch port  location
database)
on LAN via LLDP (802.1ab, TIA LLDP-MED)
initially, often through manual configuration
Route calls to right destination
4.
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using look-up in device or proxy
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Location, location, location
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Location  locate right PSAP & speed dispatch
In the PSTN, local 9-1-1 calls remain geographically
local
In VoIP, no such locality for VSPs
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most VSPs have close to national coverage
Thus, unlike landline and wireless, need location
information from the very beginning
Unlike PSTN, voice service provider doesn’t have wire
database information
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VSP needs assistance from access provider (DSL, cable,
WiMax, 802.11, …)
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Columbia/MapInfo prototype
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Goal: build prototype VoIP SIP-based
emergency calling system
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including caller end system
call routing (DNS)
PSAP infrastructure
Use commodity components where
possible
Test reliability and redundancy
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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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Call routing
DHCP Server
DHCP Inform
MAC Address
DNS Server
DNS Query
civil location
Envinsa Server
TCP Socket
Telephone Number
PSAP
Info
Location
Info
ALI Server
HTTP SOAP
geo location
Location
Info
PSAP
Info
PSAP
civil location
geo location
sip:sos@domain1
w/location or
w/out location
911
112
sip:psap@domain2
with location
sip:psap@domain1
without location
IP Network
Local SIP Proxy
PSAP SIP Proxy
civil location
geo location
sip:psap@domain2
with location
sip:rep@domain2
with location
911
POTS/Wireless
Network
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IP Gateway
3PCC Controller
Emergency calling
GeoLynx
Display
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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.us
…
proprietary
TCP-based
protocol
151.algonquin-dr.addison.vt.us.sos-arpa.net
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3rd party call control
7
REFER to
conference
join
conference
6
INVITE to
conference
join
conference
Call Taker 1
8
Hospital
Police
Fire
sipconf
Call Taker 2
5
setup
conference
2
sos
sos
w/location
4
1
Caller
Network
sos calls routed
via normal method
join
conference
Controller
3
PSAP
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Call Taker n
Emergency calling
INVITE to
conference
Call Recorder
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3rd Party Call Control Flow
PSAP UA (Controller)
Caller
Conference instance
Call-taker (SIPC)
Police/Fire/EMS
INVITE w/loc
INVITE w/o loc
200 OK
200 OK
ACK
ACK
INVITE w/loc (no SDP)
200 OK - SDP1
INVITE – SDP1
200 OK – ANS1
ACK
ACK – ANS1
REFER – Police/Fire/EMS URI
200 OK
INVITE w/loc (no SDP)
200 OK – SDP2
INVITE – SDP2
200 OK – ANS2
ACK – ANS2
NOTIFY
200 OK
*SDP can contain A/V
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Call taker setup
SIPc client receives calls
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GeoLynx software displays
caller location
Emergency calling
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GeoLynx displays location
GeoLynx listens for commands
from SIPc
Emergency calling
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Emergency call conferencing
PSAP brings all related
parties into a conference call
Hospital
Fire
department
INVITE
INVITE
Conference
server
Recorder
REFER
3rd party
call control
media
INVITE info
INVITE
INVITE
REFER
REFER
INVITE
media
info
PSAP
Caller
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Scaling
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NENA: “estimated 200 million calls to 91-1 in the U.S. each year”
 approximately 6.3 calls/second
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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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Current standardization efforts
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NENA (National Emergency Number Association)
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ETSI OCG – EMTEL
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exploratory – also emergency notification
NRIC
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I2 and I3 architecture
requirements based on operational needs of PSAPs
goals and long-term architecture
IETF:
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individual and SIPPING drafts for identifier, call routing,
architecture
SIP and DNS usage
possibly new protocols for lookups
ECRIT BOF (pre-WG) at IETF-61 in Washington, DC
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Current IETF documents
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draft-taylor-sippingemerg-scen-01
(expired)
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draft-schulzrinnesipping-emergency-req01
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scenarios, e.g., hybrid
VoIP-PSTN
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overall architecture for
emergency calling
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Emergency calling
“Dynamic Host
Configuration Protocol
Option for Coordinatebased Location
Configuration
Information”
draft-ietf-geopriv-dhcpcivil-04
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new DNS resource
records for location
mapping
RFC 3825
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abstract requirements
and definitions
describes ‘sos’ SIP URI
draft-rosen-dns-sos-01
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draft-schulzrinnesipping-emergencyarch-02
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draft-ietf-sipping-sos-00
DHCP option for civic
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addresses
Conclusion
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Emergency calling services necessary
condition for first-line wireline-replacement
services
US: large numbers of PSAPs financially
exhausted from Phase II wireless support
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often 1970s technology – end of bailing wire
reached
Long-term opportunity for better services
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