Diffserv Policies and Their Combinations in a Policy Server

In policy-based networking, policies sometimes have to be com- bined and applied in cooperation to represent such programmable and customizable network functions as Diffserv. For a policy server called PolicyXpert, we have designed and implemented three types of policies and three types of virtual flow labels (VFLs) to connect the policy rules. The policy combination en- ables the representation of complex Diffserv policies. Policy combination also allows sub-classing of DSCP-based service classes, and the separation of service and subscriber policies. The careful design of Diffserv policies has enabled simple Diffserv policies to be represented in a simple form.