Default Priority - Supermicro SSE-X3348S Configuration Manual

Weighted RoundRobin (WRR)
In WRR scheduling, theuser specifies a number to indicate the importance (weight) of thequeue relative
to the other CoS queues. WRR scheduling prevents low-priority queues frombeing completely neglected
during periods of high-priority traffic. The WRR scheduler sends somepackets from each queue in turn.
The number of packets it sends corresponds to the relativeimportance of the queue. By using WRR,low-
priority queues can send packets even when high-priority queues are not empty.
DeficitWRR
Bandwidth allocation can be unfair when the average packet sizes are different between the queues and
their flows. This behavior can result in service degradation for queues with smaller average packet sizes.
Deficit Weighted Round Robin (DWRR) is a modified weighted round-robin scheduling that can handle
packets of variable size.

1.3.3 Default Priority

The Class of Service (CoS) priority field is taken from the VLAN header of a received packet. If the
received packet does not have a VLAN header, the default port priority is used as the CoS value.
Supermicro switches provide an option to configure the default priority.
Figure QoS-4: VLAN Tag and CoS Priority
In the above figures, CoS priority is a 3-bit field in a tagged frame that indicates the frame priority level,
ranging from 0 (best effort) to 7 (highest) with 1 representing the lowest priority. These values can be
used to prioritize different classes of traffic (voice, video, data, etc.).
For IEEE 802.1Q frames with tag information, the priority value from the header frame is used. For
native frames, the default priority of the input port is used. Supermicro switches allow users to
configure the default port priority.
Each ingress port on the switch has a single receive queue buffer for incoming traffic. When an untagged
frame arrives, it is assigned the value of the port as its port default priority. Tagged frames use the
assigned CoS value when it passes through the ingress port.
CoS C
Priority F VLAN ID
I
Supermicro L2/L3 Switches Configuration Guide 9