Dell Force10 S25N-S50N FTOS Configuration Guide FTOS 8.4.2.7 E-Series TeraScal - Page 863

Configure policy-based rate shaping Rate shape egress traffic using the command rate-shape from QOS-POLICY-OUT mode. Output QoS policy can be applied to an output policy map with a policy aggregate or to an specific queue. Per queue rate shaping is supported on C-Series and S-Series only; see Create Output Policy Maps on page 868. FTOS#conf t FTOS(conf)#qos-policy-output QosShape FTOS(conf-qos-policy-out)# rate-shape 4 10 FTOS(conf-qos-policy-out)#show config ! qos-policy-output QosShape rate-shape 4 10 FTOS(conf-qos-policy-out)#exit Allocate bandwidth to queue The E-Series schedules unicast, multicast, and replication traffic for egress based on the Weighted Fair Queuing algorithm. The C-Series and S-Series schedule packets for egress based on Deficit Round Robin (DRR). These strategies both offer a guaranteed data rate. To allocate an amount bandwidth to a queue using the command bandwidth-percentage on the E-Series. To allocate bandwidth to queues on the C-Series and S-Series, assign each queue a weight ranging from 1 to 1024, in increments of 2n, using the command bandwidth-weight. Table 41-3 shows the default bandwidth weights for each queue, and their equivalent percentage which is derived by dividing the bandwidth weight by the sum of all queue weights. Table 41-3. Default Bandwidth Weights for C-Series and S-Series Queue Default Weight 0 1 1 2 2 4 3 8 Equivalent Percentage 6.67% 13.33% 26.67% 53.33% There are two key differences between allocating bandwidth by weight on the C-Series and S-Series and allocating bandwidth by percentage on the E-Series: 1. Assigning a weight to one queue affects the amount of bandwidth that is allocated to other queues. Therefore, whenever you are allocating bandwidth to one queue, Dell Force10 recommends that you evaluate your bandwidth requirements for all other queues as well. 2. Because you are required to choose a bandwidth weight in increments of 2n you may not be able to achieve exactly a target bandwidth allocation. Quality of Service | 863