User session management : design choices for single-node vs cluster ?

hi , would be gr8 if anyone can throw some light upon a thought of partcular interest. We're just moving from a single-node to a cluster setup. i'm curious to know how u implement session mgmt . Do you ... * layer4 load balance to a named node A ( eg: nodeA.app.com ), following which all links/calls will be made only relative to this nodeA ) * layer4 load balance to top level domain ,but internally could be any one of the nodes , then figure out a way to point user to the same node ( basically another form of persistent load-balance) * only client side cookies with hidden fields * just use querystrings, maybe rewrites * a combination of the above with some state/session shared across a shared db ... ? * have some sort of session data stored in a central db, and message pass between nodes * leave it to a third party s/w to do the dirty work A particular scenario could be one where the user makes an ajax call to the server(load balanced). Perhaps avoiding sending session information in the querystring / javascript and rely more on a strategy that handles cookie/user mgmt from the server side as much as possible. any insights as to what method(s) diff startups / web apps have opted for ? ~B