Dell Force10 E600i FTOS Version 8.4.1.5 Configuration Guide for ExaScale - Page 809

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 44-3, "Default Bandwidth Weights for C-Series and S-Series," in Quality of Service 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 44-3. 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. Table 44-4, "Assigning Bandwidth Weights for the C-Series and S-Series," in Quality of Service shows an example of choosing bandwidth weights for all four queues to achieve a target bandwidth allocation. Table 44-4. Assigning Bandwidth Weights for the C-Series and S-Series Queue 0 1 2 3 Weight 1 64 128 32 Equivalent Percentage 0.44% 28.44% 56.89% 14.22% Target Allocation 1% 25% 60% 14% Quality of Service | 809