DELL S50V User Manual

|

Quality of Service

www.dell.com | support.dell.com

You can assign strict-priority to one unicast queue, 1-7, using the command 

 from 

CONFIGURATION mode. Strict-priority means that FTOS dequeues all packets from the assigned queue 
before servicing any other queues. 

•

The 

 supersedes 

 an 

 percentage configurations.

•

A queue with strict-priority can starve other queues in the same port-pipe.

•

On the E-Series, this configuration is applied to the queue on both ingress and egress.

Weighted Random Early Detection

 is supported only on platform 

e

Weighted Random Early Detection (WRED) congestion avoidance mechanism that drops packets to 
prevent buffering resources from being consumed.

Traffic is a mixture of various kinds of packets. The rate at which some types of packets arrive might be 
greater than others. In this case, the space on the BTM (ingress or egress) can be consumed by only one or 
a few types of traffic, leaving no space for other types. A WRED profile can be applied to a policy-map so 
that specified traffic can be prevented from consuming too much of the BTM resources.

WRED uses a profile to specify minimum and maximum threshold values. The minimum threshold is the 
allotted buffer space for specified traffic, for example 1000KB on egress. If the 1000KB is consumed, 
packets will be dropped randomly at an exponential rate until the maximum threshold is reached 
(

example—is reached, then all incoming packets are dropped until less than 2000KB of buffer space is 
consumed by the specified traffic.

Min

Max

0KB

Buffer Space

P

ack

et Dr

op R

a

te

0 Pckts

All Pckts

Total Buffer Space

Allott

ed Spac

e

Early W

a

rning

No P

a

ck
ets Buff

er

ed

fnC0045mp