Users Guide

You can choose to reset the peak buffer utilization value and determine a new peak buffer utilization value. Use the clear qos
statistics type buffer-statistics-tracking command to clear the tracked value and to refresh this counter.
BST tracks peak buffer utilization over a period of time. At any given point in time, the peak buffer usage from the past is
displayed.
For example, if you enable BST at time T0 and use the show command to view the peak buffer utilization value at time T1, the
peak usage between T0 and T1 is displayed. If you view the peak buffer utilization again at time T2, the peak usage between T0
and T2 is displayed. However, if you clear the counter using the clear qos statistics type buffer-statistics-
tracking command at time T3 and view the peak buffer utilization at time T4, the peak usage between T3 and T4 is displayed.
NOTE: When BST is enabled, if you make any configuration changes that affect the priority group or priority mapping
configuration, such as removal of class map, addition of class map to policy map (nqos), and so on, be sure to clear the
buffer statistics using the clear qos statistics type buffer-statistics-tracking command to view the
actual peak buffer utilization for the current configuration.
Advantages of BST include:
● Detecting microburst congestions
● Monitoring buffer utilization and historical trends
● Determining optimal sizes and thresholds for the ingress or egress shared buffers and headroom on a given port or queue
based on real-time data
NOTE: BST is not supported on the S4248F-ON platforms.
After you disable BST, be sure to clear the counter using the clear qos statistics type buffer-statistics-
tracking command.
Port to port-pipe and MMU mapping
A port pipe handles network traffic to and from a set of front-end I/O ports. On the Z9100–ON, Z9264F–ON, and MX9116n
platforms, interfaces are shared across port pipes and port pipes are shared across Memory Management Units (MMUs).
As interfaces span across port pipes, Dell EMC Networking recommends spreading ingress and egress interfaces across
different port pipes for optimal performance. To find the port to port-pipe and MMU mapping, use the show qos port-map
details command.
Z9100–ON output example:
OS10# show qos port-map details
---------------------------------------------------------------------------
Interface Port Pipe Ingress MMU Egress MMU Oper Status
---------------------------------------------------------------------------
Eth 1/1/1 1 2, 3 0, 2 up
Eth 1/1/2 1 2, 3 0, 2 up
Eth 1/1/3 1 2, 3 0, 2 up
Eth 1/1/4 1 2, 3 0, 2 up
Eth 1/1/5 2 2, 3 1, 3 up
Eth 1/1/6 2 2, 3 1, 3 up
Eth 1/1/7 2 2, 3 1, 3 up
Eth 1/1/8 2 2, 3 1, 3 up
Eth 1/1/9 1 2, 3 0, 2 up
Eth 1/1/10 1 2, 3 0, 2 up
Eth 1/1/11 1 2, 3 0, 2 up
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