To recognise the Client

Hllo Friends,
I was asked in an interview as to how will the Web Server recognises, i.e distinguishes between the n number of clients it is entertaining. i.e in other words, the sesions are maintained but when the client say C1 again comes back how will the server know that it is C1 and not C2 or C3 ..etc.
Thanks in advance,
Regards,
Milan Doshi

Through the Session objects.

Which are implemented one of two ways...

The server sets a cookie containing the session id and that cookie gets sent with each subsequent request, enabling the server to track who is who.

or if cookies are disabled, the server can use URL rewriting (it writes the session id into the URL), and this way can also keep track of who is who.