What service allows users to authenticate to a network?

There are different ways for a network to ensure the person is who he is suppose to be, ie. authenticate. The most common way is to ask for a user name and passWord for authentication. This is not set up by a service, but rather by the network administrator. He/she has permission to go into control panel/User Groups and set up the authentication process is for that software.

Another way is by registering the MAC address of the computer in the network.