Network Security deals with all aspects related to the protection of the sensitive information assets existing on the network. It covers various mechanisms developed to provide fundamental security services for data communication. This tutorial introduces you to several types of network vulnerabilities and attacks followed by the description of security measures employed against them. It describes the functioning of most common security protocols employed at different networking layers right from application to data link layer. After going through this tutorial, you will find yourself at an intermediate level of knowledge regarding network security.