Administrator Guide

QoS dot1p Trac Classication and Queue
Assignment
The following section describes QoS dot1P trac classication and assignments.
DCB supports PFC, ETS, and DCBx to handle converged Ethernet trac that is assigned to an egress queue according to the following
QoS methods:
Honor dot1p You can honor dot1p priorities in ingress trac at the port or global switch level (refer to Default dot1p to Queue
Mapping) using the service-class dynamic dot1p command in INTERFACE conguration mode.
Layer 2 class maps You can use dot1p priorities to classify trac in a class map and apply a service policy to an ingress port to map
trac to egress queues.
NOTE: Dell Networking does not recommend mapping all ingress trac to a single queue when using PFC and ETS. However,
Dell Networking does recommend using Ingress trac classication using the service-class dynamic dot1p command
(honor dot1p) on all DCB-enabled interfaces. If you use L2 class maps to map dot1p priority trac to egress queues, take into
account the default dot1p-queue assignments in the following table and the maximum number of two lossless queues supported
on a port (refer to Conguring Lossless Queues).
Although Dell Networking OS allows you to change the default dot1p priority-queue assignments (refer to Setting dot1p Priorities for
Incoming Trac), DCB policies applied to an interface may become invalid if you recongure dot1p-queue mapping. If the congured
DCB policy remains valid, the change in the dot1p-queue assignment is allowed.
For DCB to operate eectively, you can classify ingress trac according to its dot1p priority so that it maps to dierent data queues. The
dot1p-queue assignments used are shown in the following table.
dot1p Value in
the Incoming
Frame
Egress Queue Assignment
0 1
1 0
2 2
3 3
4 4
5 5
6 6
7 7
Dell#show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 1 0 2 3 4 5 6 7
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. Max Use
Count mode in Buer Statistics is supported. 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.
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Data Center Bridging (DCB)