how linux virtual server identify the connection?

["Kilmer Yang" <yangqi@xxxxxxxxxxxxxxxx>]

Help:    
        I plan to install the Linux Virtual Server for web. but I don't know if 
the Linux Virtual Server could keep the same session going to the same real 
server. we use the session to track the user so we need the service will not 
interrupt for the load balancing of Linux Virtual Server. If Linux Virtual 
Server can not . what else can?
         By the way, who can tell me how Linux Virtual Server identify the same 
connection. is it done by user's IP?
           Waiting for your response,Thanks a lot!