A Family of QoS Aware Congestion Control Protocols

Providing guaranteed end-to-end quality of service (QoS) is important for real-time applications such as Voice-over-IP. In this paper, a family of optimal, distributed, QoS- aware, end-to-end congestion control laws is derived. It enables a set of class of services (CoSs) including Assured Forwarding Service (AFS), Minimum Rate Guaranteed Service (MRGS), and Minimum Rate Guaranteed and Upper Bounded Rate Service (MRGUBS). These control laws maximize the same utility function as the TCP congestion control protocol does. As a result, they are by design TCP friendly. These control laws are implemented as window-based congestion control protocols, similar to the window-based TCP congestion control protocol. The performance of these protocols is tested based on ns-2 simulation. The results indicate that these protocols are indeed TCP friendly and can provide end-to-end service assurance as long as the percentage of network bandwidth consumed by the flows using these protocols is moderately small. Consequently, this family of QoS-aware control protocols has the potential to be used to provide end-to-end QoS guaranteed services for low- bandwidth applications, such as Voice-over-IP.