Reference Guide

Data Center Bridging (DCB) | 283
QoS dot1p Traffic Classification and Queue Assignment
DCB supports PFC, ETS, and DCBx to handle converged Ethernet traffic that is assigned to an egress
queue according to the following quality of service (QoS) methods:
• Honor dot1p: Using the
service-class dynamic dot1p command, you can honor dot1p priorities in ingress
traffic at the port or global switch level (see Default dot1p to Queue Mapping). Honoring dot1p
priorities in ingress traffic is enabled by default.
• Layer 2 class maps: You can use dot1p priorities to classify traffic in a class map and apply a service
policy to an ingress port to map traffic to egress queues (see Policy-based QoS Configurations).
Table 13-1 shows the default queue assignment for each dot1p priority value in incoming Ethernet traffic.
Table 13-1. Default dot1p Priority-Queue Assignment on Switch
Important: of two S5000
Note: Dell does not recommend mapping all ingress traffic to a single queue when using PFC and ETS.
Ingress traffic classification using the service-class dynamic dot1p command (honor dot1p) is
recommended on all DCB-enabled interfaces. If you use L2 class maps to map dot1p priority traffic to
egress queues, take into account the default dot1p-queue assignments in Table 13-1 and the maximum
number of two lossless queues supported on a port (see Configuring Lossless Queues).
Dell Networking OS allows you to change the default dot1p priority-queue assignments (see Setting dot1p
Priorities for Incoming Traffic) only if the change satisfies the following requirements in DCB maps already
applied to S5000 interfaces:
- All 802.1p priorities mapped to the same queue must be in the same priority group.
- A maximum of two PFC-enabled, lossless queues are supported on an interface.
Otherwise the reconfiguration of a default dot1p-queue assignment is rejected.
dot1p Value in Incoming Frame Egress Queue Assignment
00
10
20
31
42
53
63
73