Internet Telephony completing the transition to IPbased communications

1
Internet Telephony completing the transition to
IP-based communications

• Henning Schulzrinne
• Dept. of Computer Science and Dept. of Electrical
  Engineering
• Columbia University
• "World Wide Web Redux" -- November 8, 2002

2
Overview

• Communications modes
• What makes IP telephony different?
• How long will it take to displace POTS?
• Events as new service enabler
• Making services programmable
• IP telephony for emergency communications

3
Communications services
4
What is Internet telephony?
PSTN phones
soft phones
Ethernet phones
5
VoIP protocol architecture
foo_at_example.com
foo_at_128.59.16.3
SIP proxy
signaling
audio
6
VoIP as natural evolution

• through 1980s signaling and voice in same
  circuit
• special signaling tones ?
• toll fraud, very limited services, slow
• 1987-- special-purpose packet switched signaling
  network (SS7) ? out-of-band signaling
• separate physical circuits (64 kb/s to 1.5 Mb/s)
• 1996-- packet signaling packet media
• physically in-band ? higher speed
• logically out-of-band

7
VoIP motivations

• Bypass LEC charge
• 17c/min in 1984, 0.5c in 2002 (17c in China
  2002)
• cheaper international calls
• VoIP most often invisible as prepay calling cards
• effect Panama outlaws IP telephony
• similar to call back in the 1990s
• cheaper trunks between PBXs
• aggregation into single PSTN termination
• new services
• multimedia conferencing
• integration with Internet services (web, email,
  presence)
• user programmability

8
Two philosophies for voice-over-IP

• carry existing voice services without anybody
  noticing
• Ethernet is cheaper switching fabric
• can share same data pipe
• at best, subset of PSTN services
• make telephone services just another Internet
  service
• integrated with email (forward call to email)
• web ("click-to-dial")
• end system intelligence
• same identifier (alice_at_example.com and
  sipalice_at_example.com)

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IETF VoIP architecture choices

• Mobility is not just for wireless
• terminal mobility change network location
• personal mobility change devices, keep name
• session mobility move sessions to new device
• service mobility services migrate across devices
• SIP identifiers are flexible
• one identifier, many devices
• one person (or function), one or more identifiers
• identifiers are plentiful, cheap and permanent
• independent of provider, device or geographic
  location
• authentication, not identifiers used for privacy
• Proxies are service-transparent ? new services
  can be introduced at the edges
• e.g., IM presence added without proxy changes

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Technology evolution of PSTN
SS7 1987-1997
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VoIP statistics
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Some perspective

• Data volume voice volume
• ATT data passed voice in 1998
• now 5x the volume
• not true for local calls (LANs?)
• Netflix DVD rental 1,500TB/day
• Internet 2,000TB/day
• Total US revenue (in B)

13
Two views of the future

• IP everywhere
• (Vo)IP on cell phones ? 3G/4G
• Internet-based radio and TV
• core transport IP over optical
• IP at the edge
• (Wireless) Ethernet in LANs and home
• edge routers meshed with optical wavelengths

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Programming services

• Web success ? dynamically generated content, not
  (just) static pages
• Content creation small set of specialists ?
  people with other things to do
• similar to audio and video recording
• Service creation for IP telephony
• from few thousand Lucent Nortel programmers to
  every sys-admin
• often uses XML as framework for programming
  languages
• dubious, but designed to be written by machines
  from higher-level specifications
• examples
• sip-cgi for using scripting languages (Perl, Tcl,
  Python, )
• Java SIP servlets
• VoiceXML for voice services
• CPL and LESS for call routing and handling

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Event notification

• Missing service glue
• network management
• alarms "water in level 2"
• email alert
• geographic proximity alert
• "friend Alice is in the area"
• see geopriv work in the IETF ? location object
  with embedded security and privacy policy
• media interaction ? DVR
• "start of show postponed by 30 minutes"
• "semantic SMS"
• have (ab)used email and polling
• email also incurs polling delay
• events are typically infrequent ? overhead
  (wireless)
• can build services one-by-one ? generic platform
  for quick service creation

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Event notification
video
process control
temperature
IR detector
alarms
audio
100
10
1
0.1
0.01
1000
event interval
email
polling
SIP events
RTP
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Controlling devices
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VoIP for emergency communications

• Easier to re-route calls to gateways far away
  from disaster area
• can quickly set up wireless point-to-point links
• gradual degradation 64 kb/s voice ? 5.3 kb/s
  voice ? signaling only ("Subject We're ok")
• work in progress to grant priority to government
  emergency communications

Yale U.
NYC
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Challenges

• QoS as classical topic since 1990's
• but almost no deployment
• technical and business complexity
• really, just the short-term version of
  reliability
• Reliability
• Internet 471 min/year (Labovitz et al.)
• does not count numerous long-loss episodes
• PSTN 5 min/year (Kuhn)
• BGP routing recovery time often several minutes,
  up to 15'
• SONET 50 ms fail-over
• Emergency services ("911")
• Complexity due to interworking, address shortage
• Walled gardens 3G ? no service competition
• Security (privacy, DDOS attacks, spam)

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Conclusion

• Not just an efficient cheap means of
  transporting the same old voice bits
• but different spreading mechanism than web
  (displacement!)
• from vendor/carrier services to user-created
  services
• transition time of 1-2 decades