Hop-by-hop flow control as a method to improve QoS in 802.3 LANs

This paper describes a novel approach to providing high levels of quality of service (QoS) for real-time UDP-based flows transmitted within switched IEEE 802.3 LANs. There are some obvious similarities between controlling congestion and providing high levels of QoS. Hence, some methods invented in order to control congestion may also be applied to support QoS in QoS-aware LANs. Since real-time and elastic traffic have different expectations in relation to the level of service received, the presented scheme grants them different priority levels and also different treatment on a hop-by-hop basis. The modified 802.3x hop-by-hop flow control is advocated as a better congestion control solution than packet dropping. Due to lack of data packet losses, TCP traffic sources need to be provided with the necessary feedback. In the presented scheme this is done by means of an early congestion notification (ECN) mechanism. Simulation results are also presented.