Congestion Avoidance In DiffServ-aware MPLS Networks

With the increase of traffic amount and traffic type, providing QoS in Internet is becoming more and more important. DiffServ-aware MPLS network is put forward to provide QoS. But the existence of congestion counteracts it. We must seek some policies to avoid network congestion to provide QoS.In this thesis, several congestion avoidance mechanisms are studied aiming at different reasons in DiffServ-aware MPLS networks. Our objective is to utilize limited network resources effectively and improve QoS.Firstly, Dynamic Load Balancing algorithm is proposed to solve the imbalance in utilization of network resources and to avoid congestion, we use probing packets to obtain delay of multiple LSPs, then compute the average delay and distribute traffic among the LSPs. The simulation results show that our approach improves the throughput, reduces the end-to-end delay and the packet drop rate. Secondly, Traffic Shaping algorithm is proposed aiming at the congestion caused by unresponsive flows. The information about network congestion is transported from core routers to ingress routers so that the ingress routers can shape the unresponsive flows by dropping the "undelivered packets" beforehand and avoid the congestion in core routers. The simulation results illustrate that the shaping algorithm effectively controls unresponsive flows while fairness is kept.