Back-end constrained delegation model

A client can communicate with a middle tier, which can then, in turn, communicate with a back end tier to access information and resources on behalf of the client within the context of a system that can scale well. Each individual back end can establish a policy that defines which computing device can delegate to that back end. That policy can be enforced by a domain controller within the same administrative domain as the particular back end. When a middle tier requests to delegate to a back end, the domain controller to which that request was directed can either apply the policy, or, if the domain controller is in a different domain than the targeted back end, it can direct the middle tier to a domain controller in a different domain and can sign relevant information that the middle tier can utilize when communicating with that different domain controller.