Reinventing the Telephone System: The Third Generation

1
Re-inventing the Telephone System The Third
Generation

• Henning Schulzrinne
• Dept. of Computer Science
• Columbia University
• CAT Forum -- October 12, 2004

2
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

3
Lifecycle of technologies
traditional technology propagation
military
corporate
consumer
opex/capex doesnt 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?
4
Internet and networks timeline
university prototypes
production use in research
commercial early residential
broadband home
theory
1960
1970
1980
1990
2000
2010
port speeds
100 kb/s
1 Mb/s
10 Mb/s
100 Mb/s
1 Gb/s
email ftp
DNS RIP UDP TCP SMTP SNMP finger
ATM BGP, OSPF Mbone IPsec HTTP HTML RTP
XML OWL SIP Jabber
Internet protocols
queuing architecture
routing cong. control
DQDB, ATM QoS VoD
p2p ad-hoc sensor
5
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

6
Technology evolution of the PSTN
SS7 1987-1997
7
What is VoIP?

• Voice-over-IP Internet telephony
• Internet telephony refers to communications
  servicesvoice, facsimile, and/or voice-messaging
  applicationsthat 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

8
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

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How has the industry progressed

• 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

TIA, 2003 Telecommunications Market Review and
Forecast Gartner Dataquest, 2001-2007, United
States Fixed Public Network Services Gartner
Dataquest, 2002 Premises Based Equipment Sales
Jack Waters Fall VON 2003
10
VoIP penetration
residential small business
Glen Campbell Telecom Cable Analyst Merrill
Lynch Canada May 2004 (CITI VoIP workshop)
11
Vonage Subscriber Growth
subscribers in thousands
Cable Datacom News Round Up, September 1, 2003
12
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

13
Technology introductions
Source OECD, 2003
14
Conditions for VoIP

• Multimedia PC with low-latency OS
• earlier Windows versions not suitable
• Broadband access for residence
• modem adds significant delay
• High-speed switched LANs for businesses
• ? only feasible since mid-1990s

15
Total high-speed lines
FCC, 2004
16
DSL usage
DSL Forum, Sept. 2004
17
DSL penetration
DSL Forum, Sept. 2004
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Who provides VoIP service?
voice service provider (Vonage, Lingo, Packet8)
service gateways
long-distance carrier (e.g., ATT, MCI)
service gateways IP network
DSL (ILEC)
cable providers
service gateways IP network access
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Motivations for VoIP
financial
services
security

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

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

• media encryption
• signaling encryption
• user authentication

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VoIP models PBX
analog telephone adapter
call server proxy server softswitch
VoIP gateway
LAN
enterprise
21
VoIP models IP Centrex
service provider
LAN
enterprise or residence
22
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)
Yahoo
ISP (IP, DHCP, DNS)
MCI
dark fiber provider
NYSERNET
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VoIP components

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

?
signaling
SIP/SDP H.248 MGCP H.323
provide destination address
provide URI
codecs (G.7xx, H.26x)
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SIP trapezoid
destination proxy (identified by SIP URI domain)
outbound proxy
1st request
SIP trapezoid
2nd, 3rd, request
a_at_foo.com 128.59.16.1
registrar
voice traffic RTP
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Example SIP phones
about 85
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PSTN vs. Internet Telephony
PSTN
Signaling Media
Signaling Media
China
Internet telephony
Signaling
Signaling
Media
Australia
Belgian customer, currently visiting US
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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

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Changes caused by VoIP

• Access independence single-function network to
  voice-over-any-network
• separation 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

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(Early) Adulthood

• fully developed and mature
• Not quite yet, but no longer a teenager
• probably need another 6 years to be grown up
• Responsibilities
• Dealing with elderly relatives ? POTS
• Financial issues ? payments, RADIUS
• Family emergencies ? 911

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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

31
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

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Location-based IM presence
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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

34
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
35
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

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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
GW
VSP A
Enterprise B
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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

38
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)

39
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

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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 (gt 10-15)
• Current service availability probably around
  99.5
• realistic goal 99.9 (10h/year) to 99.99
  (1h/year)

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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

42
Three stages to VoIP 911
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Prototype
gray features in progress.
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Call taker setup
SIPc client receives calls
GeoLynx software displays caller location
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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 ?