在ESB上实现ACL的最佳方法

I am currently trying to implement an ACL on an ESB (Camel apps on Servicemix) which will enable each service artifact to decide if current user is a valid user and if it has required priviledge to access the service. I have decided to use the RBAC (Please, kindly recommend if there are superior models) model. My actual headache is how to implement the model, service call vs in memory. Making a network service call for each verification/authentication is definately too much for this as the ACL server (Which has the business logic) will be implement as a service to other artifacts for re-usability. The alternate is to implement locally and verify from database or memory. What are the popular ways this type of problems are being solved?I am currently trying to implement an ACL on an