Which Algorithm r v following in network security?
Is it RSA?

Where exactly? There are different algorithms used for different purposes. Any book on network security might be able to throw light on this. Your textbook would be good for some elementary knowledge. If you like Network Security and are planning to get your hands dirty, I would like to recommend books by Bruce Schneierr, the most famous one being "Practical Cryptography".

If there any specific things that you would like to know about RSA, please post the question here. If I am unable to answer, I can get one of my friends working in RSA to reply to you.

Thanks. How the security is maintained in online shopping?which algorithm they are following?