[Zope] maintaining session variables using zeocluster

Hellol, We are using a zeocluster with six clients and use pound for load balancing betwwen them. However I am having problems using session variables. I think that session variables are maintained separately for each client i.e a value set to sesssion variable when pound sends a request to one client cannot be retreived when a request is sent to some other client. What can be done in such a situation ? Thanks in advance Rajiv Nair