Prioritising access to scarce resources: network survivability through policy supported quality of service

Packet-switched networks (such as those using the internet protocol) now support an increasingly heterogeneous mix of applications, generating the need for performance guarantees for each traffic flow, or what is commonly known as quality of service (QoS). We argue that a QoS architecture, supported by the appropriate set of policies, cannot only be used to provide service assurances to performance-sensitive traffic but also to enhance network survivability by prioritising access to scarce resources whenever there is sudden degradation in the underlying network infrastructure. In this paper, we illustrate this idea through representative examples. We also present the taxonomy for various policy based network management architectures and discuss our preliminary results in comparing such architectures through experiments conducted on our network test-bed. The identification of the appropriate policy architectures is an important first step in the implementation of a network system with the desired survivability characteristics.