Users Guide

The packets come in with packet-dot1p 2 alone are assign to PG6 on ingress.
The packets come in with packet-dot1p 2 alone use Q2 (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.
Table 17. Queue Assignments
Internal-
priority
0 1 2 3 4 5 6 7
Queue 0 0 0 1 2 3 3 3
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.
SNMP Support for PFC and Buer Statistics Tracking
Buer Statistics Tracking (BST) feature provides a mechanism to aid in Resource Monitoring and Tuning of Buer Allocation. The Max Use
Count mode provides the maximum value of the counters accumulated over a period of time.
Priority Flow Control (PFC) provides a link level ow control mechanism, which is controlled independently for each frame priority. The goal
of this mechanism is to ensure zero loss under congestion in DCB networks.
Dell Networking OS provides SNMP support for monitoring PFC and BST counters, and statistics. The enhancement is made on DELL-
NETWORKING-FPSTATS-MIB with additional tables to display the PFC and BST counters and statistics.
The following tables are available in DELL-NETWORKING-FPSTATS-MIB:
Data Center Bridging (DCB)
235