Dell PowerSwitch S4820T 9.50.1 Configuration Guide for the S4820T System - Page 307

Step 1 Task Enter global configuration mode to create a DCB map or edit PFC and ETS settings. Command dcb-map name Command Mode CONFIGURATION 2 Configure the PFC setting (on or off) and the priority-group DCB MAP ETS bandwidth percentage allocated to traffic in each priority group, or whether the priority group traffic should be handled with strict priority scheduling. You can enable PFC on a group_num {bandwidth percentage | strictpriority} pfc {on | off} maximum of two priority queues on an interface. Enabling PFC for dot1p priorities makes the corresponding port queue lossless. The sum of all allocated bandwidth percentages in all groups in the DCB map must be 100%. Strict-priority traffic is serviced first. Afterwards, bandwidth allocated to other priority groups is made available and allocated according to the specified percentages. If a priority group does not use its allocated bandwidth, the unused bandwidth is made available to other priority groups. Example: priority-group 0 bandwidth 60 pfc off priority-group 1 bandwidth 20 pfc on priority-group 2 bandwidth 20 pfc on priority-group 4 strict-priority pfc off Repeat this step to configure PFC and ETS traffic handling for each priority group. 3 Specify the dot1p priority-to-priority group priority-pgid DCB MAP mapping for each priority. Priority-group range: 0 to 7. All priorities that map to the same queue must be in the same priority group. dot1p0_group_num dot1p1_group_num dot1p2_group_num dot1p3_group_num Leave a space between each priority group number. For example: priority-pgid 0 0 0 1 2 4 4 4 in which priority group 0 maps to dot1p priorities 0, 1, and 2; priority group 1 maps to dot1p priority 3; priority group 2 maps to dot1p4_group_num dot1p5_group_num dot1p6_group_num dot1p7_group_num dot1p priority 4; priority group 4 maps to dot1p priorities 5, 6, and 7. Important Points to Remember • If you remove a dot1p priority-to-priority group mapping from a DCB map (no priority pgid command), the PFC and ETS parameters revert to their default values on the interfaces on which the DCB map is applied. By default, PFC is not applied on specific 802.1p priorities; ETS assigns equal bandwidth to each 802.1p priority. As a result, PFC and lossless port queues are disabled on 802.1p priorities, and all priorities are mapped to the same priority queue and equally share the port bandwidth. • To change the ETS bandwidth allocation configured for a priority group in a DCB map, do not modify the existing DCB map configuration. Instead, first create a new DCB map with the desired PFC and Data Center Bridging (DCB) 307