Made by: Yuzhao LiStudent ID:u3035801

Skype A case study of VoIP applications

How many of you are using Skype, or have ever used Skype?

Do you know what the VoIP is?

Warming-up questions

Voice over Internet Protocol

A general term for a family of methodologies, communication protocols, and transmission technologies for delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet.

VoIP

People’s voice or other sounds record by the computer as samples

Then the samples are send as packets over IP network to another computer and played there.

How does VoIP work

Different from traditional Public Switched Telephony Network, VoIP has several advantages

Cost saving

Flexibility

Better voice quality

Advantages of VoIP services

A software application that provides telephone service using VoIP technology facilitating voice communication over the internet.

Available free for both PC and Macintosh platforms as well as Linux and pocket PC’s

Skype

Founded in 2003 by the Swedish entrepreneur Niklas Zennstro, and a Dane Janus Friis

In October 2005, eBay purchased Skype

In October 2006, Skype 2.0 for Mac was released

In 2009, Skype 4.0 was released

On October 14 2010, Skype 5.0 for Windows was released with a slew of improvements and feature additions

History of Skype

01020304050

active user (in mil-lions)

active user (in millions)

Usage and market share

Skype13% MSN

11%some other VoIP service companies

76%

percentage of market share (2010)

Skype offers a number of features to its users, such as:

Features

a) Rate control mechanism

b) Voice codec

c) Error-resilience mechanism

d) Better relaying mechanism to go through NAT servers or firewalls

Reasons of Skype improvement

Can find and locate users

Highly scalable

Strong NAT/ firewall traversal capability

Security feature

Integrated buddy list, presence information, chat, and audio conferencing

Highlights of Skype

Quality of service

Susceptibility to power failure

Still difficult to make a emergency calls

Lack of redundancy

The security issues

Challenges

MSN sends smaller packets with higher sending rate than Skype

MSN has higher variance in packet’s inter-arrival time while Skype sends packets in a stable fashion

Skype has better performance than MSN in MOS score

Skype can increase its throughput to recover missed data when suffering from higher loss rate, but MSN can’t

Skype has better mechanisms to go through NAT than MSN

Skype vs. MSN

Clarity

Reliable

Can call any phone, local or international, not just computers

Quality of voice

Have many different options

Why people use Skype?

Skype have a lot of impacts on its users, and also may influenced people’s daily life.

For example, its impact on teaching and learning. It opens up numerous options to teacher and

students interactions and the Skype offers can potentially revolutionize the teaching and learning process. So that teachers can envision students exchanging ideas, cultures, and information using the free Skype to Skype feature from one classroom to another or one student to another.

Impacts on users

Weicheng Xiao. (2006). A performance Study of VoIP Applications: Skype vs. MSN. National Taiwan University

Lani Rexius. (2007). Skype- An Emerging Technology. London: Oxford University

About Skype. (2010). Retrieved October 26, 2010. from http://about.skype.com/

History of Skype. (2010).Retrieved October 26,2010. from http://en.wikipedia.org/wiki/Skype

References:

Thank you for listening!And hope you enjoy this presentation!