Impacts of QoS queue configuration on GMB operation

The section Configuring GMB for outbound traffic assumes the ports on the switch offer eight prioritized, outbound traffic queues. This may not always be the case, however, because the switch supports a QoS queue configuration feature that allows you to reduce the number of outbound queues from eight (the default) to four queues, or two.

Changing the number of queues affects the GMB commands (interface bandwidth-min and show bandwidth output) such that they operate only on the number of queues currently configured. If the queues are reconfigured, the guaranteed minimum bandwidth per queue is automatically re-allocated according to the following percentages:

Default GMB percentage allocations per QoS queue configuration
802.1p priority 8 queues (default) 4 queues 2 queues
1 (lowest) 2% 10% 90%
2 3%
0 (normal) 30% 70%
3 10%
4 10% 10% 10%
5 10%
6 15% 10%
7 (highest) 20%

For more information on queue configuration and the associated default minimum bandwidth settings, see the "Quality of Service (QoS): managing bandwidth more effectively" in the advanced traffic management guide for your switch.