Default Parameters for 1q4t rx
Jul 08,2008 00:00 by admin
Default Parameters for 1q4t rx
Switch1 (enable) show qos info config 1q4t rx

QoS setting in NVRAM for 1q4t receive:

QoS is enabled

Queue and Threshold Mapping for 1q4t (rx):

Queue Threshold CoS

----- --------- ---------------

1     1         0 1

1     2         2 3

1     3         4 5

1     4         6 7

Rx drop thresholds:

Queue #  Thresholds - percentage

-------  -------------------------------------

50% 60% 80% 100%

Rx WRED thresholds:

WRED feature is not supported for this port type.

Rx queue size ratio:

Rx queue size-ratio feature is not supported for this port type.


The 1p1q4t has an extra queue called the strict priority queue, which is associated with CoS value of 5. The strict priority queue, queue 2, takes precedence over the standard queue, queue 1. Traffic in the strict priority queue is always serviced first. Typically critical user traffic is marked with CoS 5 at Layer 2 and the equivalent of DSCP value of 40 at Layer 3. The reason user traffic is not marked with higher CoS values such as CoS 6 or 7 is that these values are generally associated with control traffic. The bulletins outline the two queues and their associated drop threshold levels:

  • CoS 0 and 1 are mapped to threshold 1/standard queue (set at 50 percent)

  • CoS 2 and 3 are mapped to threshold 2/standard queue (set at 60 percent)

  • CoS 4 is mapped to threshold 3/standard queue (set at 80 percent)

  • CoS 5 is mapped to priority queue (set at 100 percent)

  • CoS 6 and 7 are mapped to threshold 4/standard queue (set at 100 percent)

Both the queue and threshold settings can be changed, if necessary. For example, using the set qos map command, the CoS 4 has now been mapped to drop threshold level 2:




Switch1 (enable) set qos map 1p1q4t rx 1 2 cos 4

QoS rx priority queue and threshold mapped to cos successfully.


The switch, however, will not allow for the priority queue to be associated with any threshold other than its own threshold. The following configuration attempted to link threshold 4 with CoS value of 6 with priority 2 queue. This example would have worked if the threshold had been set at 1:




Switch1 (enable) set qos map 1p1q4t rx 2 4 cos 6

Incompatible queue/threshold number with port-type specified.


The following changes the drop threshold for threshold 1 from 50 percent to 60 percent:




Switch1 (enable) set qos drop-threshold 1q4t rx queue 1 60 60 80 100

Receive drop thresholds for queue 1 set at 60% 60% 80% 100%