Skype is a web-based service which offers cheap and free phone calls. Explain step by step (in terms of networking technology) what really happens from the point when you initiate a call until the receiver picks up the call.

Marking criteria

1. Correct information about the networking technology used by Skype is provided.

(5 marks)

2. Each step is outlined clearly and precisely. (5 marks)

3. Answer is clear and well written. (5 marks)

4. Appropriate and authentic references have been used. (3 marks)

5. APA reference style has been used correctly. (2 marks)

The user who uses the Skype is known as Skype clients. The server of the Skype authenticates this Skype user and makes its present to others Skype clients. The Skype server also checks the firewall and IP address of the client computer that uses the Skype's.  If a user wants to connect to Skype network the cache of the host computer must contain the valid entry. So in this case TCP connection must be established otherwise login will fail. So the following are the steps that are performed during Skype connection:

Start the Skype connection

Send UDP packet to Host Computer 

 If no response comes within 5 seconds 

Attempts the TCP connection with host computer at port number 80(HTTP).    

If not connected then attempt TCP Connection with Host Computer on port    443(HTTPS)

If not connected again attempt++.

If attempt==5 then fails the connection

else         

Again wait for 6 seconds           

Go to step 2

Again the steps will repeat until it get success