• Priority-based flow control
• Enhanced transmission selection
• Data center bridging exchange protocol
• FCoE initialization protocol (FIP) snooping
DCB processes virtual local area network (VLAN)-tagged packets and dot1p priority values. Untagged
packets are treated with a dot1p priority of 0.
For DCB to operate effectively, you can classify ingress traffic according to its dot1p priority so that it
maps to different data queues. The dot1p-queue assignments used are shown in the following table.
On the MXL Switch, by default, DCB is enabled and MMU buffers are reserved to achieve no-drop traffic
handling for PFC. Disabling DCB does not release the buffers reserved by default. To utilize reserved
buffers for non-DCB applications, you have to explicitly release the buffers (Refer to Configuring the PFC
Buffer in a Switch Stack).
To disable or re-enable DCB on a switch, enter the following commands.
1. Disable DCB.
CONFIGURATION mode
no dcb enable
2. Re-enable DCB.
CONFIGURATION mode
dcb enable
NOTE: Dell Networking OS Behavior: DCB is not supported if you enable link-level flow control on
one or more interfaces.
After you disable DCB, if link-level flow control is not automatically enabled on an interface, to enable
flow control, manually shut down the interface (the shutdown command) and re-enable it (the no
shutdown command).
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 (refer to Honoring dot1p
Values on Ingress Packets).
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 (refer to Policy-Based QoS
Configurations).
1050
FC Flex IO Modules
