are SESSION's necessary or can Auth keep track of a user

[eluser]jtingato[/eluser]
I couldn't possibly remember that! ha ha. I didn't know that. What a newb.

Sessions aren't always available, are they? If cookies are disabled...
Also, on refresh of a page, don't session vars get cleansed?
Also, looking at the CI log, it appears that CI cleanses the Session vars?

Are these true statements.

My original thought was to session_start() then store the sessionID within the cart table along with any items added to the cart. But on refresh, a new sessionID is assigned. the other issue is that the cart table will fill up fast, without a way to clean it out.

Bottom line, what is the best way to go about this? Is it possible to create a cart environment without sessions? Or is it best to use sessions?

If so, do you recommend PHP sessions or CI sessions?
Once again, I do apologize for my ignorance.