F5 BigIP load balancing inside the session

Okay, assuming the internal protocol is HTTP/XML, it's probably also TCP-based. So are these many layer 7 requests inside a single layer TCP session, or multiple (atomic) TCP sessions inside another persistent TCP session? And you've established a TCP session with one server, do you need these internal sessions (layer 4 or 7) to "load balance" to many other servers? Where does the BIG-IP fit into those scenario? Is there any pattern to how the internal sessions should be spread across services, or is it just round robin?