A Quick Introduction to Voice over Internet Protocol (VoIP)

1
A Quick Introduction to Voice over Internet
Protocol (VoIP)

• PURC Annual Conference 2004
• Chuck Jackson

2
Roadmap

• Basics of packet communications as used in the
  Internet
• How voice is transmitted over packet networks
  such as the Internet.
• Examples of VoIP uses and systems
• Concluding thoughts

3
Internet Basics

• The basic building block of networks is the IP
  datagram.
• Analogy to datagramsa postcard with
• Destination address
• Return address
• A small amount of text
• A postcard might inform you of a friends holiday
  travels or remind you of a dentists appointment.
• The postal service doesnt care which application
  (friend or dentist) sent the postcardit just
  carries processed wood pulp with black marks.

4
Protocol Layering
Applications (e.g., email, web pages)
TCP
UDP
IP (Internet Protocol)
Physical Transport (e.g, Cable Modem)
A Typical IP Datagram
Email Data (1000 bytes)
TCP Header (20 bytes)
IP Header (20 bytes)
5
The Hourglass Figure
Source Steve Deering, IETF 51
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VoiceAnother Application over IP

• Voice requires about 10,000 to 100,000 bits per
  second.
• Can send those bits over IPjust as we send web
  pages or email.

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Alternative VoIP Architectures

• PC to PC

Internet
8
Alternative VoIP Architectures

• Phone to Phone via the Internet

Internet
9
Alternative VoIP Architectures

• Phone to Internet to Gateway to PSTN

Internet
GATEWAY
PSTN
10
Alternative VoIP Architectures

• PSTN to Gateway to Internet to Gateway to PSTN

Internet
GATEWAY
GATEWAY
PSTN
PSTN
11
VoIP Examples

• Xbox Voice
• Windows messenger
• AOL Instant Messenger
• Motorola Phone Adapter (Vonage)
• Cisco Phone
• Cox Cable in Hampton Roads, Virginia

12
Xbox Live
http//www.xbox.com/en-US/live/about/StarterKit-Re
tailers.htm
13
Microsofts Explanation of the Benefits of Voice
with Xbox
http//www.xbox.com/en-US/live/about/Article-Top10
GetLive.htm.htm
14
Microsoft Windows Messenger
15
AOL Instant Messenger
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The Motorola Box Used by Vonage
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Vonage Uses this Archtecture

• Phone to Internet to Gateway to PSTN

Internet
GATEWAY
PSTN
18
Motorola Box in Vonage Architecture
Internet
GATEWAY
PSTN
19
Cisco 7970 IP Phone
20
Cox Cable in Hampton Roads, Virginia
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Concluding Thoughts

• VoIP is one of many higher-level communications
  capabilites among devices connected to the
  Internet.
• VoIP is not an application.
• VoIP is a capability that is part of many
  applications.
• VoIP capabilities are already pervasive.
• Microsoft Windows Messenger (part of XP)
• AOL Instant Messenger
• Xbox and Sony Playstation