Most congestion control and fairness techniques do not work well because they need large queue size for connections with large delay-bandwidth products, require global synchronization, have no isolation against unresponsive flows and are biased towards bursty traffic.
RED algorithm proposed by the authors tries to address these issues. Congestion avoidance is provided by controlling the average queue size. Average queue size is compared between two thresholds. When the average queue size is below minimum threshold no packet is marked while all packets are marked if average queue size is above maximum threshold. When average queue size is between minimum and maximum threshold packets are marked with probability p.
Queue size determines the degree of burstiness allowed by the gateway. Average queue size is calculated with an exponential weighted moving average and this aids in handling burst of packets. RED gets rid of global synchronization by marking packets at a rate that is as low as possible. Fairness is achieved by marking each connections packet based on its share of bandwidth.
I feel that the most challenging aspect of using RED is setting all RED parameters correctly. I am curios to know whether RED has been implemented in routers today? Even if it is implemented in the routers do the routers use this option? It will be interesting to see how RED performs today with such varied type of traffic.
RED algorithm proposed by the authors tries to address these issues. Congestion avoidance is provided by controlling the average queue size. Average queue size is compared between two thresholds. When the average queue size is below minimum threshold no packet is marked while all packets are marked if average queue size is above maximum threshold. When average queue size is between minimum and maximum threshold packets are marked with probability p.
Queue size determines the degree of burstiness allowed by the gateway. Average queue size is calculated with an exponential weighted moving average and this aids in handling burst of packets. RED gets rid of global synchronization by marking packets at a rate that is as low as possible. Fairness is achieved by marking each connections packet based on its share of bandwidth.
I feel that the most challenging aspect of using RED is setting all RED parameters correctly. I am curios to know whether RED has been implemented in routers today? Even if it is implemented in the routers do the routers use this option? It will be interesting to see how RED performs today with such varied type of traffic.
1 comment:
Red is widely implemented, but rarely enabled in operational routers. I think operators have opted for fast links and good provisioning algorithms to avoid congestion issues in their backbones. Setting the RED parameters is indeed a difficult task.
Post a Comment