Service Manual

Dot1p to Queue Mapping Requirement
The dot1p to queue mapping on the system is global and this is used to congure the PRIO2COS table conguration. For DSCP
based PFC feature on untagged packets, this mapping must be the same as the default dot1p to queue mapping and should not be
changed (as in TABLE 1). If a custom dot1p to queue mapping is present it should be recongured to the default dot1p to queue
mapping.
• Currently Dell Networking OS supports matching only the following TCP ags:
– ACK
– FIN
– SYN
– PSH
– RST
– URG
In the existing software, ECE/CWR TCP ag qualiers are not supported.
• Because this functionality forcibly marks all the packets matching the specic match criteria as ‘yellow’, Dell Networking OS does
not support Policer based coloring and this feature concurrently.
• If single rate two color policer is congured along with this feature, then by default all packets less than PIR would be considered
as “Green” But ‘Green’ packets matching the specic match criteria for which ‘color-marking’ is congured will be over-written
and marked as “Yellow”.
• If two rate three color policer is congured along with this feature then,
– x < CIR – will be marked as “Green”
– CIR < x< PIR – will be marked as “Yellow”
– PIR < x – will be marked as “Red”
But ‘Green’ packets matching the specic match criteria for which ‘color-marking’ is congured will be over-written and marked as
“Yellow”.
Create a QoS Policy
There are two types of QoS policies — input and output.
Input QoS policies regulate Layer 3 and Layer 2 ingress trac. The regulation mechanisms for input QoS policies are rate policing and
setting priority values.
• Layer 3 — QoS input policies allow you to rate police and set a DSCP or dot1p value. In addition, you can congure a drop
precedence for incoming packets based on their DSCP value by using a DSCP color map. For more information, see DSCP Color
Maps.
• Layer 2 — QoS input policies allow you to rate police and set a dot1p value.
Output QoS policies regulate egress trac. The regulation mechanisms for output QoS policies are bandwidth percentage, scheduler
strict, rate shaping and WRED.
NOTE: When changing a "service-queue" conguration in a QoS policy map, all QoS rules are deleted and re-added
automatically to ensure that the order of the rules is maintained. As a result, the Matched Packets value shown in the
show qos statistics command is reset.
NOTE: To avoid issues misconguration causes, Dell Networking recommends conguring either DCBX or Egress QoS
features, but not both simultaneously. If you enable both DCBX and Egress QoS at the same time, the DCBX
conguration is applied and unexpected behavior occurs on the Egress QoS.
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Quality of Service (QoS)