You can track your visitors using their IP addresses. As visitor types in his id, link it with the visitor's ip address and store in a table on the server.

On each page request check if the ip address is on the table, with no cookies involved.

Something like this I use on my web site (PHP & MySQL). It is fast enough, does not feel any slower comparing to using cookies.

One problem exists: many internet connections have dynamic ip addresses assigned, and some of them are, I would say, too dynamic. A visitor may have his ip address reassigned three times in, say, five minutes. Which makes him enter his id again and again.

As well several LAN computers may use same public IP address.

A combination of both cookies and table-based identification may work better.