Shared Buffer Queuing On The F3 Series Module - Cisco Nexus 7000 Series Configuration Manual

Shared Buffer Queuing on the F3 Series Module

You use the priority command to specify that a class of traffic has low latency requirements with respect to
other classes. You can configure the priority level to a traffic queue as high or low. Use the priority command
to define multiple levels of a strict priority service model. For more information about the priority command,
see the Cisco Nexus 7000 Series NX-OS Quality of Service Command Reference.
The shaper can be configured with a percentage value and it can be enabled on any queue. You use the shape
command to specify that a class of traffic has a maximum rate imposed on it and the outgoing traffic has a
smooth output rate. To achieve a smooth output rate, the excess packets are retained in the queue and then
scheduled for transmission later. For more information about the shape command, see the Cisco Nexus 7000
Series NX-OS Quality of Service Command Reference.
Note A shaper delays excess traffic that does not conform to the profile by queuing it in a buffer to shape the flow.
Shared Buffer Queuing on the F3 Series Module
Note This feature is available only on the F3 Series modules. If you attempt to configure shared buffer queuing on
other modules, the switch returns an error.
Beginning with Cisco NX-OS Release 6.2(10) you can split QoS buffers into dedicated and shared buffers.
With only dedicated buffers based on the CoS value, one queue may have very high traffic even though
memory associated with some of the other queues may be lying idle. The shared buffer pools address this
problem. The shared buffer is between ports in a port group.
The default is disabled for shared buffer queuing.
When you enable this feature, you enable it for each specific module. After you have enabled shared buffer
queuing, the queue is, by default, divided equally into dedicated and shared buffer pools, 50:50 for the specified
module. The dedicated buffer pools continue to function as they always did.
Then, if you want a different ratio, you modify the ratio per port group on the specified module, using the
Command Line Interface (CLI). First you specify the port group for the given module and then you can modify
the default queue limit ratio for that port group. If you want to change the default queue limit ration for other
port groups on that module, you must enter the command for each port group separately.
Finally, you can apply a custom queuing policy to the specified port group.
Note If global level shared buffer queuing is disabled, then shared buffer for all port-groups in that VDC are disabled.
If the global level is enabled, all port groups in the VDC are enabled.
Shared buffer queuing is applicable only to port groups of physical interfaces. Shared buffer queuing on port
groups is independent of membership in port channels. Thus, members of a port channel may have different
shared buffer queuing configurations.
The command is applicable only to the ports in the VDC in which you are working. When you move any of
the port groups from this VDC, the shared buffer queuing feature returns to the default disabled state. When
you move a port group into the VDC, the port group assumes the global shared buffer configuration of that
VDC (for example, if shared buffering is enabled in the VDC, it will also be enabled for the newly moved
Cisco Nexus 7000 Series NX-OS Quality of Service Configuration Guide
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Configuring Queuing and Scheduling on F-Series I/O Modules