Congestion Point Queue

The settings for a subset of parameters associated with a congestion point queue can be modified. Congestion point indexes are assigned to congestion point queues which have one or more CNPVs mapped to them on a given port. These congestion queues can be configured using the assigned congestion point index. The congestion point index is one greater than the lowest CNPV which is mapped to the congestion notification queue. For example: if CNPVs 4 and 7 are configured for a transmit queue, the congestion point index is 5. A queue profile which supports the configuring of a minimum sample option can also be associated with the congestion point configuration.

Congestion point queues are configured with the set dcb congestion-point command. You can configure the following:

• Set point – A target value for the number of octets in the congestion point queue. CNM PDUs are transmitted to the sources of frames queued in this congestion point's queue in order to keep the total number of octets stored in the queue at the set point value.
• Weight – An integer value used for calculating W. W is the weight to be given to the change in queue length when calculating a measure of transmit queue congestion known as quantitized feedback (Fb) as defined in the IEEE 802.1Q-2011 standard.

  The weight option is an integer value from which W is derived. W is equal to two to the power of the weight value specified here. Thus, if weight equals a -1, W = 1/2. W can be between the values specified by Min Weight and Max Weight for this device as displayed by the show dcb cn q-profile command. See the IEEE 802.1Q-2011 standard for a detailed discussion for W, weight, and Fb.

A maximum of two congestion notification queue profiles can be associated with a congestion point queue configuration. The default queue profile on the S- and 7100-Series has an identifier of 0.1 and can be displayed using the show dcb cn q-profile command. This default queue profile can not be modified. A second queue profile, 1.1, can be configured. The queue profile is configured using the set dcb cn q-profile command. See Congestion Notification Queue Profile for a congestion notification queue profile discussion.

Use the show dcb cn congestion-point command to display congestion point queue information.