Re-inventing the Telephone System: The Third Generation

Henning Schulzrinne

Dept. of Computer Science

Columbia UniversityCAT Forum -- October 12, 2004

Overview

1st generation: analog2nd generation: digital circuit switched3rd generation: packet-switched

What is VoIP? Why now? A short history Wireless VoIP Context-aware communications VoIP IM, presence Challenges ahead

Lifecycle of technologies

military corporate consumer

traditional technology propagation:

opex/capex

doesn’t matter;expert support

capex/opex

sensitive, but

amortized;expert support

capex sensitive;amateur

Can it be done? Can I afford it? Can my mother use it?

Internet and networks timeline

1960 1970 1980 1990 2000 2010

theoryuniversityprototypes

production usein research

commercialearly residential

broadbandhome

emailftp

DNSRIPUDPTCP

SMTPSNMPfinger

ATMBGP, OSPF

MboneIPsecHTTPHTMLRTP

100 kb/s 1 Mb/s 10 Mb/s

XMLOWLSIP

Jabber

100 Mb/s 1 Gb/sportspeeds

Internetprotocols

queuingarchitecture

routingcong. control

DQDB, ATMQoSVoD

p2pad-hocsensor

Earlier PSTN changes

starting in 1980s: analog digital transmission in-band out-of-band (SS7) signaling

end systems relatively unaffected few additional services

800# CLASS services (caller ID, call waiting)

customer relationship largely unaffected except CLECs and reselling

Technology evolution of the PSTN

0

10

20

30

40

50

60

70

80

90

100

1980 1985 1987 1990 1995 2000 2001

electromechanalogdigital

SS7: 1987-1997

What is VoIP?

Voice-over-IP = Internet telephony “Internet telephony refers to communications services

—voice, facsimile, and/or voice-messaging applications—that are transported via the Internet, rather than the public switched telephone network (PSTN). The basic steps involved in originating an Internet telephone call are conversion of the analog voice signal to digital format and compression/translation of the signal into Internet protocol (IP) packets for transmission over the Internet; the process is reversed at the receiving end.” (IEC)

Not a single technology, but combination of Internet technologies

Now typically voice only, but easily extended to video

Brief history of packetized voice 1969: ARPAnet, predecessor of modern Internet 1974: real-time packetized voice (early Internet) 1990: primitive version used for transatlantic calls (G.764) 1991: DARTnet (test network) audio experiments using Sun

workstations 1992: first IETF multicast audiocast 1992: RTP (transport) draft 1995: first commercial PC-to-PC voice software (Vocaltec) 1995/1996: first PC-to-PC and PC-to-phone services

(Net2Phone, DialPad, Vocaltec, …) 1996: first version of SIP and H.323 standards ~2000: first service providers ~2002: first large-scale consumer services 2002: 3G wireless specifies Internet multimedia subsystem

How has the industry progressed

TIA, 2003 Telecommunications Market Review and ForecastGartner Dataquest, 2001-2007, United States: Fixed Public Network ServicesGartner Dataquest, 2002 Premises Based Equipment Sales

Softswitch networks carry approximately 2 billion minutes/day vs. 2.3 million in 1999

Services, such as IP-Centrex, are quickly being adopted by enterprises

10% of all international voice traffic to/from U.S. carried on IP primarily prepaid calling cards

IP-enabled handset sales over 4.5 million units in 2002 35% of all total premise sales are IP – enabled IP handset costs drop from $600 in 2001 to $99

today

Jack WatersFall VON 2003

VoIP penetration

0

2

4

6

8

10

12

14

%

YE2003 YE2004 YE2005 YE2006 YE2007 YE2008

Cable

Non-facilities

Glen CampbellTelecom & Cable AnalystMerrill Lynch CanadaMay 2004 (CITI VoIP workshop)

residential & small business

Vonage Subscriber Growth

*Cable Datacom News Round Up, September 1, 2003

-

50.0

100.0

150.0

200.0

250.0

Aug-02

Sep-0

2

Oct

-02

Nov-02

Dec-0

2

Jan-

03

Feb-0

3

Mar

-03

Apr-03

May

-03

Jun-0

3

Jul-0

3

Aug-03

Sept-0

3 (E

)

Feb-0

4

Aug-04

subscribers in thousands

Why has it taken so long?

VoIP technology development since 1995 Web: worked on dial-up, motivated broadband

deployment from 1992 to 2000 VoIP: not usable on dial-up, spurred by residential

broadband More than just protocols needed:

eco-system (management, configuration, OSS, …) interoperability spectrum of products – low to high end interoperation with legacy equipment

Technology introductions

Source: OECD, 2003

Conditions for VoIP

Multimedia PC with low-latency OSearlier Windows versions not suitable

Broadband access for residencemodem adds significant delay

High-speed switched LANs for businesses

only feasible since mid-1990’s

Total high-speed lines

FCC, 2004

DSL usage

DSL Forum, Sept. 2004

DSL penetration

DSL Forum, Sept. 2004

Who provides VoIP service?

voice serviceprovider

(Vonage, Lingo, Packet8)

cableproviders

DSL(ILEC)

long-distancecarrier

(e.g., AT&T, MCI)

service +gateways +IP network

service +gateways

service +gateways +IP network +access

Motivations for VoIP

• access fee• taxes• monopoly rents• local-loop access• separate wiring plant• cheaper services(caller ID, etc.)• higher networkefficiency

• better voice qualitypossible

• user-defined services• video and app. sharing• integration of presence• abundance of identifiers• mobility

• media encryption• signaling encryption• user authentication

financial services security

VoIP models: PBX

LANIP

enterprise

VoIP gateway

call serverproxy server“softswitch”

analogtelephoneadapter

VoIP models: IP Centrex

LANIP

enterprise or residence

serviceprovider

Some differences: VoIP vs. PSTN Separate signaling from

media data path But, unlike SS7, same

network lower call setup delay

Avoid CTI complexity of "remote control"

Mobile and wireline very similar

Any media as session: any media quality

(e.g., TV and radio circuits)

interactive games

No need for telephone company

voice service provider

(RTP, SIP)

ISP(IP, DHCP, DNS)

dark fiberprovider

Yahoo

MC

IN

YSER

NE

T

VoIP components

Re-uses whole Internet protocol architecture and transmission infrastructure IP, UDP for transport TLS and S/MIME for security HTTP for configuration

SIP/SDPH.248MGCPH.323

signaling

ENUMH.350

directories

RTP

transport

provideURI

providedestination

address codecs(G.7xx,H.26x)

SIP trapezoid

SIP trapezoid

outbound proxy

a@foo.com: 128.59.16.1

registrar

1st request

2nd, 3rd, … request

voice trafficRTP

destination proxy(identified by SIP URI domain)

Example SIP phones

about $85

PSTN vs. Internet Telephony

Signaling & Media Signaling & Media

Signaling Signaling

Media

PSTN:

Internettelephony:

China

Belgian customer,currently visiting US

Australia

SIP as service enabler

Rendezvous protocol lets users find each other

by only knowing a permanent identifier

Mobility enabler: personal mobility

• one person, multiple terminals

terminal mobility• one terminal, multiple IP

addresses session mobility

• one user, multiple terminals in sequence or in parallel

service mobility• services move with user

Changes caused by VoIP

Access independence: single-function network to voice-over-any-networkseparation of transport and services

Transition from “polling” service (try until user happens to be available) to “presence” service

Voice special voice just one media among many

(Early) Adulthood

“fully developed and mature”Not quite yet, but no longer a teenagerprobably need another 6 years to be

grown up… Responsibilities:

Dealing with elderly relatives POTSFinancial issues payments, RADIUSFamily emergencies 911

Emerging technologies

Core VoIP technology largely finished deployment largely due to cost savings, not new

services toll and fee bypass integrated infrastructure (LAN & WAN) extend “PBX” reach to home and branch offices

Presence from “polling” to “status report” special case of event notification events as common infrastructure for services location-based services

Integration of IM and VoIP often used in same conference (side channel) IM as initiator of real-time voice/video

Near future: Location-based services Finding services based on location

physical services (stores, restaurants, ATMs, …) electronic services (media I/O, printer, display,

…) not covered here

Using location to improve (network) services communication

• incoming communications changes based on where I am configuration

• devices in room adapt to their current users awareness

• others are (selectively) made aware of my location security

• proximity grants temporary access to local resources

Location-based IM & presence

User service creation

Tailor a shared infrastructure to individual users

traditionally, only vendors (and sometimes carriers)

learn from web models not one “killer application” grass-roots applications not

foreseen by carriers

programmer, carrier

end user

network servers

SIP servlets, sip-cgi

CPL

end system VoiceXML VoiceXML (voice),

LESS

Near future: Multimedia

Wideband audio “better than phone

quality” lectures, discussions, speaker phone

better codecs same bandwidth as existing NB codecs

Video phone itself remains niche application given low incremental

cost, may be viable useful for sign language

Video for group meetings capture whiteboard

Shared applications (WebEx, etc.) still requires

standardization Instant messaging

side channel Better means of

coordination (floor control)

wideband audio

Near future: VoIP over WiFi

Not fundamentally different from landline VoIP combination cellular + WiFi = wide-area +

“cordless” phone Small packet sizes make VoIP over WiFi far

less efficient than nominal data rate Hand-off delay between different base

stations interruptions CU modified hand-off algorithm

Delay jitter with high loads new scheduling algorithms

L3 hand-off across different network types

Challenge: Global interconnect Currently, each VoIP “network”

largely isolated interconnect via PSTN even if

both endpoints are on IP interconnect via few peering

points even if neighbors Long-term solution: ENUM DNS

listing administration appears difficult

Short-term for pure-IP (FWD, etc.): special number prefixes

GW

GWVSP A

Enterprise B

Challenge: CALEA (lawful intercept) Existing models assume congruence of signaling

and voice flows Challenges:

voice service providers outside the US signaling-only providers or no voice providers end-to-end media and signaling encryption (Skype,

SRTP) Intercept IP traffic, not application Assume that long-term, all application traffic (except

browsing of public web pages) will have strong encryption

Challenge: User-programmable and context-aware services Universal reachability control reachability in time

and space by context allow callee to decide reachability (defer and decline

communication) choose appropriate media (text, automated data

response)

time Call Processing Language (CPL), sip-cgi, …

capabilities caller preferences

location location-based call routing

location events

activity/availability presence

sensor data (mood, bio) not yet, but similar to location data

Challenge: Spam prevention

Currently, telemarketing restricted to in-country calling With VoIP, few economical constraints on automated

calls from anywhere Also, SPIM (instant message spam)

Cannot use content-based filtering Public key infrastructure (PKI) for individual

verification has never scaled provide domain-level verification (~ TLS) in signaling blacklists and whitelists

• may depend on local domain policies for user verification

reputation-based systems

Challenge: Service reliability

“QoS” service availability loss of network connection loss of infrastructure components

• DNS, SIP servers, DHCP, … bursts of packet loss cannot be repaired at end

system sustained high packet loss (> 10-15%)

Current service availability probably around 99.5% realistic goal: 99.9% (10h/year) to 99.99% (1h/year)

Challenge: Emergency calling 911 calling system largely unchanged since 1980s

call routing to appropriate destination deliver caller location information

Fundamental differences for VoIP: may not have phone number may be no “phone company” identifier does not describe location location determination more difficult

Also use solution for “311” and other location-based call routing systems

Three stages to VoIP 911

spec. available?

use 10-digit admin. number?

mobility callback

number to PSAP?

caller

location to PSAP?

PSAP

modification

ALI (DB)

modification

new services

I1 now allowed stationary no no no no none

I2 Dec. 2004 no stationary

nomadic

yes yes no (8 or 10 digit)

update none

I3 late 2004 no stationary

nomadic

mobile

yes yes IP-enabled ALI not needed

MSAG replaced by DNS

location in-band

GNP

multimedia

international calls

* gray features in progress.

Prototype

911112

sip:sos@domainw/location or w/out location

geo location

POTS/Wireless Network

IP Network

911

IP Gateway

sip:sos@domainwithout location

Envinsa Server

sip:psap@domainwith location

location

GeoLynx Display

ALI ServerDHCP Server

DNS Server**

DHCP InformMAC Address

Location Info

TCP Socket Telephone Number

PSAP Info

HTTP SOAPLatitude/Longitude

Location Info

VerifiedLocation Info

civil location**

SIPc client receives calls GeoLynx software displays caller location

Call taker setup

Conclusion

VoIP on cusp of widespread deployment: commercial-grade VoIP products mature standards for key components widespread broadband availability better Internet QoS

Focus may shift from “bare-bones” VoIP to context-aware communications

Operational and technical challenges 911, CALEA, network reliability, user-defined

services, multimedia Thus, roughly where PSTN was in 1980