Voice Over Internet Protocol

Voice over Internet Protocol Presenter: Devesh Patidar

August 2, 2009

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’.

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

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

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

Circuit Switching • Example: Circuit Switching

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

Packet Switching • Example: Packet Switching

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

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

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

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

Soft Switches • Database mapping program • Endpoint-to-Endpoint – Location – Phone Number – IP address

• Allows phones, computers, and WiFi phones to work together

Industry Protocol Standards • H.323 Protocol Suite

• Main flaw – not designed for VoIP

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

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

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

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

Benefits

Cost of Calls Made from US to Foreign Countries

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

Drawbacks • • • • •

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

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, Reliance info.

– VoIP companies • Skype, Vonage, VoIP Inc.

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

Thank you