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

Prof. Henning SchulzrinneDept. of Computer Science

Columbia University, New YorkFCC Solutions Summit

March 18, 2004

OverviewOverview

E911 for wireline E911 for wireless (Phase II) Short-term 911 service for VoIP Differences between PSTN and

VoIP Objectives Internet standardization efforts

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 PSAP for

current caller location coarse-grained location currently, ALI and MSAG

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

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 (10

digits) gets complicated if multiple providers

ILEC vs. CLEC multiple wireless providers

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 Corporations and universities

don’t have email carriers, either

voice service provider

(TCP, RTP, SIP)

ISP(IP)

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

Multimedia Integrate alternate modalities such as text (TDD) and video (sign

language) COTS

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, 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

VoIP and 911 – Two stagesVoIP and 911 – Two stages Short term:

work with existing PSAPs may not support nomadic devices

Longer term: upgrades in PSAP CPE opportunity for improved overall architecture support nomadic devices support multimedia provide framework for simpler & cheaper

circuit-switched landline and wireless architecture

Short-term solutionsShort-term solutions Emulate wireline

every subscriber has phone number capture VoIP subscriber address and

enter into ALI DB gateway calls 10-digit number and

provides ANI Emulate wireless

VoIP provider = another wireless carrier use similar dynamic updates for ALI DB

IETF standardization IETF standardization effortsefforts 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

ConclusionConclusion Existing 911 system closely tied to

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

VoIP offers opportunity to increase robustness and decrease costs

Initial international standardization efforts in progress