Route based QoS and the biased early drop algorithm (BED)

DiffServ offers an attractive solution to quality of service (QoS) for mobile ad-hoc networks (MANET)s since the overhead of alternative flow based QoS metrics and signaling is not required. However, within prioritized classes and in the presence of dynamically forming bottlenecks, DiffServ can lead to brittle failure modes in which all flows are highly penalized and subsequently fail rather than maintaining some flows at required QoS levels for latency or packet loss. This problem is particularly difficult for UDP traffic, which does not respond to random early detection (RED) like throttling mechanisms in the presence of congestion. This paper proposes an augmentation of DiffServ QoS over MANET that utilizes metrics available through routing protocols to prevent, and resolve congestion. This is done in a manner that promotes maintenance of some high priority UDP (for example voice over IP) flows in the presence of bottlenecks. The biased early drop (BED) algorithm is introduced to maintain high continuity of UDP flows in the presence of congestion within the same class of service