Service Manual

QoS dot1p Traffic Classification and Queue
Assignment
The following section describes QoS dot1P traffic classification and assignments.
DCB supports PFC, ETS, and DCBx to handle converged Ethernet traffic that is assigned to an egress queue according to the
following QoS methods:
Honor dot1p You can honor dot1p priorities in ingress traffic at the port or global switch level (refer to Default dot1p to
Queue Mapping) using the service-class dynamic dot1p command in INTERFACE configuration
mode.
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.
NOTE: Dell EMC Networking does not recommend mapping all ingress traffic to a single queue when using PFC and ETS.
However, Dell EMC Networking does recommend using Ingress traffic classification using the service-class dynamic
dot1p command (honor dot1p) 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 the following table and the maximum number of
two lossless queues supported on a port (refer to Configuring Lossless Queues).
Although Dell EMC Networking OS allows you to change the default dot1p priority-queue assignments (refer to Setting
dot1p Priorities for Incoming Traffic), DCB policies applied to an interface may become invalid if you reconfigure dot1p-
queue mapping. If the configured DCB policy remains valid, the change in the dot1p-queue assignment is allowed.
Configuring the Dynamic Buffer Method
Priority-based flow control using dynamic buffer spaces is supported on the switch.
To configure the dynamic buffer capability, perform the following steps:
1. Enable the DCB application. By default, DCB is enabled and link-level flow control is disabled on all interfaces.
CONFIGURATION mode
dcb enable
2. Configure the shared PFC buffer size and the total buffer size. A maximum of 4 lossless queues are supported.
CONFIGURATION mode
dcb pfc-shared-buffer-size value
dcb pfc-total-buffer-size value
The buffer size range is from 0 to 3399. Default is 3088.
3. Configure the number of PFC queues.
CONFIGURATION mode
dcb enable pfc-queues pfc-queues
The number of ports supported based on lossless queues configured depends on the buffer. The default number of PFC
queues in the system is two.
For each priority, you can specify the shared buffer threshold limit, the ingress buffer size, buffer limit for pausing the
acceptance of packets, and the buffer offset limit for resuming the acceptance of received packets.
4. Configure the profile name for the DCB buffer threshold
CONFIGURATION mode
dcb-buffer-threshold dcb-buffer-threshold
5.
DCB-BUFFER-THRESHOLD mode
priority 0 buffer-size 52 pause-threshold 16 resume-offset 10 shared-threshold-weight 7
6. Assign the DCB policy to the DCB buffer threshold profile on stack ports.
CONFIGURATION mode
Data Center Bridging (DCB)
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