Users Guide

In ingress, the buers are accounted at per PG basis and would indicate the number of the packets that has ingress this port PG but still
queued up in egress pipeline. However, there is no direct mapping between the PG and Queue.
Packet is assigned an internal priority on the ingress pipeline based on the queue to which it is destined. This Internal-priority to Queue
mapping has been modied and enhanced as follows for the device:
Table 19. Priority to Queue Mapping
Dot1p
Priority
0 1 2 3 4 5 6 7
Queue
1 0 2 3 4 5 6 7
Default dot1p to queue conguration is as follows:
Conguration Example for DSCP and PFC Priorities
Consider a scenario in which the following DSCP and PFC priorities are necessary:
DSCP 0 – 5, 10 - 15 20 – 25, 30 – 35
Expected PFC
Priority
1 2
To congure the aforementioned DSCP and PFC priority values, perform the following tasks:
1 Create class-maps to group the DSCP subsets
class-map match-any dscp-pfc-1
match ip dscp 0-5,10-15
!
class-map match-any dscp-pfc-2
match ip dscp 20-25,30-35
2 Associate above class-maps to Queues Queue assignment as below.
Dell(conf)#do show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 1 0 2 3 4 5 6 7
3 Dot1p->Queue Mapping Conguration is retained at the default value.
4 Interface Congurations on server connected ports.
a Enable DCB globally.
Dell(conf)#dcb enable
b Apply PFC Priority conguration. Congure priorities on which PFC is enabled.
Using PFC to Manage Converged Ethernet Trac
To use PFC for managing converged Ethernet trac, use the following command:
dcb-map stack-unit all dcb-map-name
Generation of PFC for a Priority for Untagged Packets
In order to generate PFC for a particular priority for untagged packets, and conguring PFC for that priority, you should nd the queue
number associated with priority from TABLE 1 and Associate a DCB map to forward the matched DSCP packet to that queue. PFC frames
gets generated with PFC priority associated with the queue when the queue gets congested.
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Data Center Bridging (DCB)