What is VoIP? 4. What is VoIP? VoIP = “Voice over Internet Protocol”. Basically, VoIP means Voice transmitted over a Digital Network”. Also called IP Telephony.

1. The Future of Voice
over Internet Protocol

2. Introduction
• What is Voice Over Internet Protocol (VoIP)?
• The two-way transmission of audio over a
packet-switched IP network.
• When used in a private intranet or WAN, it is
generally known as 'voice over IP,' or 'VoIP.'
• When the transport is the public Internet or the
Internet backbone from a major carrier, it is
generally called 'Internet telephony’.

3. Introduction
• Voice Over Internet Protocol (VoIP)
– History
– Implementation
– Service Types
– Benefits
– Drawbacks
– Current and Projected Use

4. History of VoIP
• Network Voice Protocol
– Created in 1973 by Danny Cohen at USC
– Project Goals
• Wanted to create digital high-quality, low-bandwidth,
secure voice handling capability
– Control Protocol
– Data Transport Protocol

5. Circuit Switching
•
•
•
•
Current Phone Systems
Dedicated line with a constant connection
Originally very expensive
Each call transmits at 64 kilobits per second
– 64 kbps x 2 directions = 128 kbps
– 128 kbps = 16 kilobytes per second
– During a 10 minute call, about 10 MB
– Highly inefficient

6. Circuit Switching
• Example: Circuit Switching

7. Packet Switching
• VoIP Phone Systems
• Connection only long enough to send a
packet of information
• Thousands of possible paths for packet to go
• Network uses cheapest and least congested
paths
• Quality of Service (QoS)
• A 10 minute call transfers only about 2 MB

8. Packet Switching
• Example: Packet Switching

9. Quality of Service (QoS)
• Defined in the International
Telecommunication Union standard X.902
• A set of quality requirements on the
collective behavior of one or more objects.
• Control mechanisms to provide different
priorities to different users or data flows
• Important for real-time streaming applications

10. VoIP Implementation
• Sender picks up the phone
• Analog telephone adapter (ATA)
– Data converted by a codec
• Soft Switch
• Receiver picks up ringing phone
• Data transfer during calls is handled by
current internet infrastructure

11. Analog Telephone Adapter (ATA)
• Converts audio between analog and digital
signals
• Need one on each end of the call
• Sends signal to handle connect and
disconnect

12. Codecs
• Coder-decoder or codecs
• Conversion from analog audio signal to
digital signal
• Most common codec is the G.729A
– sampling rate of 8,000 times per second
• Conjugate-structure Algebraic-code-excited
Linear Prediction algorithm (CS-ACELP)
• Responsible for the large gap in performance

13. Soft Switches
• Database mapping program
• Endpoint-to-Endpoint
– Location
– Phone Number
– IP address
• Allows phones, computers, and WiFi phones
to work together

14. Industry Protocol Standards
• H.323 Protocol Suite
• Main flaw – not designed for VoIP

15. Industry Protocol Standards
• Session Initiation Protocol (SIP)
– Smaller, more efficient
– Designed specifically for VoIP
• Handles
– User location
– User capabilities
– User availability
– Call setup
– Call handling

16. VoIP Service Types
• Home Phones
– Requires an ATA
– Usually provided for free
• IP Phones
– ATA technology built in
– Ethernet Phones
– WiFi Phones
• Computer-to-Computer calls

17. Computer-to-Computer VoIP
• Simplest and cheapest way to use VoIP
• Requires
– Microphone
– Speaker
– Sound card
– Broadband internet
• Costs: Software and ISP service
• Calls: Free
• Example: Skype Download Service

18. Benefits
• Uses technology already in common use
• Cost
• Bundled Services
– Caller ID
– Voice Mail
– Call Waiting
– Call Forwarding
– Many Others
• Long Distance and International Rates

19. Benefits
Cost of Calls Made from US to Foreign Countries

20. Drawbacks
•
•
•
•
•
911 Emergency Calls
Dependence on Wall Power
Latency issues, jitter, and packet loss
Viruses, worms, and hackers
Integration with land-line dependant
hardware
– DVRs, digital television service, and home
security systems

21. Drawbacks
•
•
•
•
•
Security
Problems sending faxes
Dependence on Internet Service Providers
Requirement of broadband connectivity
WiFi hotspot dependence

22. Current and Projected Use
• Roughly 6 million in US in 2006
• Expected to climb to 24 million by the end of
2008
• Increase in service providers
– Traditional phone companies
• At&T, Sprint, Nextel, Time Warner
– VoIP companies
• Skype, Vonage, VoIP Inc.

23. Conclusion
• VoIP will be a dominate force in the 21st
century
• Probably at least another 10 years before
possibly replacing current phone systems
• If the current flaws are fixed sooner rather
than later, it could be much sooner than a
decade