Service Manual

Data Center Bridging in a Trac Flow
The following gure shows how DCB handles a trac ow on an interface.
Figure 28. DCB PFC and ETS Trac Handling
Enabling Data Center Bridging
DCB is automatically congured when you congure FCoE or iSCSI optimization.
Data center bridging supports converged enhanced Ethernet (CEE) in a data center network. DCB is disabled by default. It must be
enabled to support CEE.
• Priority-based ow 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 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.
To enable DCB, enable either the iSCSI optimization conguration or the FCoE conguration.
To enable DCB with PFC buers on a switch, enter the following commands, save the conguration, and reboot the system to allow
the changes to take eect.
1. Enable DCB.
CONFIGURATION mode
dcb enable
2. Set PFC buering on the DCB stack unit.
CONFIGURATION mode
dcb stack-unit all pfc-buffering pfc-ports 64 pfc-queues 2
Data Center Bridging (DCB)
211