Session Management in EJB TIer

Hi, have a question about the management of session in EJB Tier.
I wrote (Core J2EE and Blueprints) that in HttpSession there will be just a reference to the EJB (in my case a SFSB).
But using a Business Delgate (with the Service Locator), I will put in HttpSession the ID given by the Service Locator back to Business Delegate
and finally to the Client (an Application Controller).
In this architecture i will have many Business Delegate.

How can I makes different SFSB (behind different Business Delegate) able to talk each other?
In other hand how a SFSB will be able to call another SFSB without going to the Web Tier (Service Locator) ???

Note : I seen in the diagram that show the relation among the patters (Core J2EE Pattrens See Figure 5.2 on page 132.)
[Application Service]- - <<USES>> - ->[Business Delegate]
But if I deploy in different JVM my WEb and EJB Tier ???