Decentralized Control and Optimization of Networks with QoS-Constrained Services

We consider data networks in which real-time/near real-time applications require not only successful transmission of packets from source to destination, but also specific end-to-end delay bounds, such as voice over IP. Although there is a well-developed general theory for control of best-effort packet traffic in data networks (elastic traffic), little is known about decentralized control mechanisms that ensure end-to-end performance bounds (inelastic traffic). In this paper we propose and analyze a simple, distributed and self-stabilizing rate control scheme that uses only end-to-end delay feedback to ensure QoS while using the network resources efficiently. In particular, we show that while for short paths (up to two hops long) the proposed scheme guarantees end-to-end delay budgets for all node pairs and also maximizes the total network throughput, when there are long paths in the network the resulting solution, even though still self-stabilizing and QoS-compliant, can deviate from the global network throughput. We present numerical results and conclude with a discussion of possible implementations of the proposed scheme in multi-service networks involving a mixture of best-effort and QoS-constrained services.