Users Guide

The packets come in with packet-dot1p 2 alone use Q1 (as per dot1p to Queue classication – Table 2) on the egress port.
• When Peer sends a PFC message for Priority 2, based on above PRIO2COS table (TABLE 2), Queue 1 is halted.
• Queue 1 starts buering the packets with Dot1p 2. This causes PG6 buer counter to increase on the ingress, since P-dot1p 2 is
mapped to PG6.
• As the PG6 watermark threshold is reached, PFC generats for dot1p 2.
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.
NOTE
: Although, each port on the S4810, S4820T, and S5000 devices support 8 QoS queues, you can congure only 4
QoS queues (0-3)to manage data trac. The remaining 4 queues (4-7) are reserved for control trac.
Table 17. Queue Assignments
Internal-
priority
0 1 2 3 4 5 6 7
Queue 0 0 0 1 2 3 3 3
3 Dot1p->Queue Mapping Conguration is retained at the default value.
Default dot1p-queue mapping is,
Dell#show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 0 0 0 1 2 3 3 3
Default dot1p-queue mapping is,
Dell#show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 2 0 1 3 4 5 6 7
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.
Dell(conf-if-te-1/1)#pfc priority 1,2
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
Data Center Bridging (DCB)
243