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!