ccna pdf labs

ccna pdf labs.Spiders and BandwidthAverage Bandwidth Usage1. Random Early Detection (RED)In order to avoid these problems of tail drop, the network must be set up in Figure 21-2 TCP appears synchronized and the average link utilization is low.Time .Chapter 21 QoS .423 .The standby port drops some packets before it will be congested. RED is a congestion avoidance mechanism that performs packet drops before queue congestion. RED actively drops packets that may cause network congestion. it enables the output bandwidth occupied by a TCP session to be slowly reduced without causing a lot of TCP global synchronization and TCP starvation. it also reduces the average queue length. RED sets two discard thresholds for the queue: the minimum discard threshold and the maximum discard threshold, when the average length of the queue is less than the minimum discard threshold, no packets are discarded; when the average length of the queue is between the minimum discard threshold and the maximum discard threshold, RED starts to discard packets randomly, the longer the average length of the queue, the higher the probability of discarding; when the average length of the queue is greater than the maximum discard threshold, all packets at the end are discarded. all packets at the tail are discarded.2. Weighted Random Early Detection (WRED)The principle of WRED is the same as RED. However, the difference between WRED and RED is that WRED can set different minimum drop thresholds, maximum drop thresholds and drop probabilities according to different IP priority or DSCP values, thus providing different drop characteristics for packets of different priorities. Of course if the minimum drop threshold, maximum drop threshold and drop probability are set to the same for all IP priority or DSCP values, WRED becomes RED.21.3.3 Traffic Supervision and Traffic Shaping