Is a Session ID generated on the Server-side or Client-side?

Question

This web page http://www.w3schools.com/ASP/prop_sessionid.asp states that a session ID is generated on the ServerSide.

If this is the case, then how does a server kn

Answer 1

The server will generate a session id if none exists. But once it has been generated, the client can pass that id back to the server. If the client modifies that id, you would likely get an error from the server, and a new id generated.