911 services: wireline, 911 services: wireline, wireless and VoIPwireless and VoIP

Prof. Henning SchulzrinneDept. of Computer Science

Columbia University, New Yorkhgs@cs.columbia.edu

VoIP Roundtable, Washington, DCJune 24, 2004

OverviewOverview

E911 for wireline E911 for wireless (Phase II) Differences between phone system

and VoIP Requirements and opportunities Internet standardization efforts Funding and regulation challenges

Components of emergency Components of emergency callingcalling

Three core components that need to be replicated – everything else are implementation details

1. identifying emergency calls (“911”)2. determining the right emergency call

center (PSAP) for current caller location coarse-grained location currently, two main databases: ALI for number-

to-location mapping and MSAG for address verification

3. deliver caller location to PSAP fine-grained location

E911 for wirelineE911 for wireline

CO Switch Tandem Switch(911 Selective Router)

LECnetwork

555-1234313 Main St

ALIMSAG

100-500 Main Street ESN 1789 555-1234 PSAP #1, 313 Main St

CAMA or PRIdelivers ANI(555-1234)CAMA or SS7

ANI: 555-1234 313 Main

555-1234 PSAP #1

PSAP #1

verify addressvalidity

provisionedupdates

privatedata link

Wireless 911Wireless 911 Phase I (April 1998)

Route all call to the appropriate PSAP based on call sector

Provide cell/sector location data to PSAP

Provide call back number to PSAP

Phase II (October 2001)

Phase I + latitude and longitude

67% 95%

handset 50m 150m

network 100m

300m

Wireless 911: Phase 2Wireless 911: Phase 2

y N e t r s

r

ti

i

l

S

t

w .a p .c o

Wireless Tower

ALI

PDE

A-GPS, UTDOA, …

MPC/SCP

ESRK or ESRD coordinatescallback number

pANI(ESRD or ESRK)

ISUP

LECselective router

MSC

E2

ESRK = unique for callESRD = unique for location

dynamicupdates

Problems with existing 911 Problems with existing 911 systemsystem 1970s technology:

CAMA trunks induce long call setup delays limited in ability to transfer information (8-10 digits) sometimes, 2,400 baud modems for database access

increases call setup delays gets complicated if multiple providers

ILEC vs. CLEC multiple wireless providers in one state

tied to ILEC rate centers and other PSTN routing artifacts

hard to move PSAPs on short notice (e.g., emergency evacuation)

can’t just plug into any network termination

PSTN vs. Internet PSTN vs. Internet TelephonyTelephony

Signaling & Media Signaling & Media

Signaling Signaling

Media

PSTN:

Internettelephony:

China

Belgian customer,currently visiting US

Australia

How does VoIP differ from How does VoIP differ from landline and wireless PSTN?landline and wireless PSTN? All devices are nomadic

new location, but same identifier Telephone companies are no

longer needed there are still carriers for DSL

and cable “IP dial tone” but unaware of type of data

carried (voice, web, IM, …) VSP may be in another state or

country anybody can be their own “VSP”

Corporations and universities don’t have email carriers, either

voice service provider[VSP]

(TCP, RTP, SIP)

ISP(IP, DHCP)

dark fiberprovider

(λ)

Yahoo

MC

IN

YSER

NE

T

The role of phone numbers The role of phone numbers and identifiersand identifiers Wireline line, device, subscriber &

location Wireless device, but not location VoIP (phone number and URIs):

mostly identifies person, not device multiple devices located in different states can share

the same number however, may not have a phone number if it does, area code may be from different state

than customer billing address multiple devices device can move, while number stays the same not related to ISP

Why is VoIP ≠ wireless?Why is VoIP ≠ wireless?

VoIP devices may not have phone numbers as lookup keys

e.g., sip:hgs@cs.columbia.edu Location information for devices is civil, not

longitude/latitude e.g., service address for VSPs GPS not available (nor functional) on indoor devices

plus, accuracy of 50 m (67%) or 150 m spans many buildings…

no floor information Cell phones don’t work in our building…

so A-GPS is unlikely to work there, either Plus, wireless E911 complexity due to old signaling

mechanism expensive and complicated to connect to multiple

wireless operators proposals to use IP-based solutions

50m

Objectives for IP-based Objectives for IP-based 911911 International

devices must work anywhere

independent of local emergency number

international roaming Multimedia

integrate alternate modalities such as text (TDD) and video (sign language)

COTS (commercial off-the-shelf)

re-use standard protocols (SIP, DNS, DHCP, HTTP, XML, …)

avoid repeat of CAMA trunks Resilient

easily re-route calls to any number of backup PSAPs

Testable users can test operation

without tying up operator resources

Secure integrity, privacy and

confidentiality, protection against denial-of-service attacks

Technology-independent do not depend on (e.g.,)

specific wireless or link technology

Pro-competitive does not require carriers or

gatekeepers

Opportunities for I911Opportunities for I911 More robust

multiple networks and interfaces increase disaster resiliency

operations can be moved easily to any network-connected location

Additional services multimedia

text chat replacing TTY video and images for

situational awareness and instructions to civilians at scene of accident

additional data hazmat data accident data (impact

velocity, airbags, fuel spill, …)

Better integration with first responders and public safety

integration with telematics providers

general awareness of call volume, origin and type

information flow back to PSAP

see 9/11 evacuation hand off call data, not just

remote printing of address alerts and notifications to

public safety and the public Cheaper to build and operate

currently, small niche expensive equipment, specialized circuits, slow upgrades

should be able to leverage almost existing technology lower risk

Three stages to VoIP 911: I1 Three stages to VoIP 911: I1 I2 I2 I3 I3 I1:

may use administrative line to deliver call no location delivery

I1 & I2: no modification to PSAP calls delivered to PSAP via existing technology delivers location information

I3: deliver calls to PSAP via VoIP including circuit-switched calls

I1, I2 and I3 will likely co-exist for some time design to allow local upgrades, without national or

state-wide coordination

Three stages to VoIP 911Three stages to VoIP 911when deployable?

use 10-digit admin. number?

mobility callerlocation conveyed to PSAP?

PSAPmodification

ALI (DB)modification

new services

I1 now allowed stationary no no no none

I2 December 2004

no stationarynomadic

yes no (10-digit)

yes none

I3 specified by late 2004

no stationarynomadicmobile

yes IP-enabled replaced by DNS

global number portabilitymultimediainternational calls

IETF and NENA I3 IETF and NENA I3 standardization effortsstandardization efforts

IETF = Internet Engineering Task Force = international open standardization body

provide location (civil

or geo)

includecivil and/or

geo

sip:sos@“911”

911 sos112 sos

sip:psap@leonia.nj.gov

cn=us, a1=nj, a2=bergen

DHCP

Regulatory challengesRegulatory challenges Uniform technology

but avoid things that don’t work internationally Distributed responsibility:

VSP does not know location Residential user may have any number of VSPs

like prepaid calling cards and may use any one of them for calling 911

ISP does not know VSP and whether call is voice or not

ISP needs to provide location information to end user regulatory mandate!

Funding challengesFunding challenges Existing line/number model

does not work longer term, no more

“lines” and numbers every person may have

multiple identifiers Short-term vs. long-term

options Even small VSPs have a

national footprint number assigned may not

match location of customer VoIP has built-in global

number portability can’t require to keep track

of 6,000 different county 911 fees and recipients

Funding collector should have direct customer

relationship know accurately where

customer lives have regional footprint have modest collection and

distribution costs Some options:

facilities-based (broadband) ISP

local & state taxes non-telecom utilities (water,

gas, electric) that reflect residency

collect directly from household

like home owners insurance

ConclusionConclusion Existing 911 system closely tied to phone

system history number as universal identifier close affiliation with telephone switches incremental, constrained evolution

VoIP offers opportunity to increase robustness, offer new services and decrease costs

Initial international and US standardization efforts in progress

IETF and NENA collaboration combines 911 and Internet expertise

Initial prototypes and demonstration systems in development

Additional I1 and I2 Additional I1 and I2 informationinformation

Example I1 solution #1Example I1 solution #1

Mark Lewis

Broadband Network

LANIP Phone

End OfficeSwitch

SS7

End OfficeSwitch

SelectiveRouter

PSAP

MediaGateway

SignalingGateway

Softswitch

Customer

POP

CLEC #1

CLEC #2

1 2 3

4 5 6

7 8 9

* 8 #

Call Taker

Example: VoxPath

I1 Solution #2I1 Solution #2CustomerSoftswitch PSTN

E911Tandem

IP Phones

ALIDB

ACD

PSAP

PBX(emergency lines)

End Users

Level 3 911 Softswitch

Network

Dedicated 911 trunks

Public Internet or

Private IP Network

E911Tandem

Mark Lewis

Level3

Possible I2 architecture Possible I2 architecture

Selective Router

Selective Router

ALI

ALI

Local

National

PAM

CAMA

Emergency Services N/WVoice N/Ws

IP

ISUP

E2+ ESP

ALI-FE

ALI-FE

PSTN

based on slideby Martin Dawson

MGMG

SIPPUBLISH

ESRK, DN loc

INVITE sos