Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 481)

congestion control because the set of priorities mapped to the Priority Group is not known, which leads
into the DCB Priority Table.
The DCB Priority Table defines each CoS mapping to Priority Group, and completes PFC configuration.
The table below shows an example of mapping in the DCB Priority Table.
Example of mapping DCB priority table values TABLE 80
CoS PGID
0 15.6
1 15.7
2 15.5
3 15.4
4 15.3
5 15.2
6 15.1
7 15.0
Brocade VCS Fabric QoS
Brocade VCS Fabric QoS requires very little user configuration. The only options to modify are the
fabric priority and the lossless priority.
Brocade VCS Fabric reserves a mapping priority and fabric priority of seven (7). Any traffic that enters
the Brocade VCS Fabric cluster from upstream that is using the reserved priority value is automatically
remapped to a lower priority.
Changing the mapping or fabric priority is not required. By default the values are set to zero (0) for both
of the remapped priorities.
In Brocade VCS Fabric mode:
• All incoming priority 7 tagged packets are redefined to the default or user-defined value.
• Untagged control frames are counted in queue 7 (TC7).
All switches in the Brocade VCS Fabric cluster must have matching remapping priority values and the
same priority-group-table values.
Restrictions for Layer 3 features in VCS mode
When the switch is in VCS mode, the lossless priority for carrying FCoE traffic and the fabric priority for
carrying fabric traffic must be isolated from any Layer 3 QoS markings and classification. Therefore,
specific restrictions apply to some Layer 3 DSCP QoS features when the switch is working in VCS
mode:
The following are restrictions for using applicable Layer 3 DSCP-Traffic-Class map, DSCP-CoS map,
and DSCP Trust features in VCS mode. Note that DSCP mutation maps and the egress RED feature
are not affected in VCS mode.
Brocade VCS Fabric QoS
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