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21 Data Center Bridging
Commands
Fibre Channel was developed as a dedicated fabric that loses little to no packets,
and was not designed to work on an unreliable network. For this reason, a set of
standards termed Data Center Bridging (DCB) have been developed to increase the
reliability of Ethernet-based networks in the data center. DCB consists of four
different technologies: DCB Exchange (DCBX), Priority-based Flow Control (PFC),
Enhanced Transmission Selection (ETS), and Congestion Notification (CN).
Openflow allows the switch to be managed by a centralized controller using multi-
flow tables to provision forwarding behavior. These standards provide an effective
method of speeding traffic through the data center.
Table 108: Data Center Bridging Commands
Command Function
DCB Exchange Provides the mechanism which allows peers to exchange configuration
information via LLDP TLVs about ETS and PFC settings and their
willingness to accept ETS configuration recommendations.
Priority-based Flow
Control
Adds fields to the standard PAUSE frame that allow a device to inhibit the
transmission of frames for certain priorities as opposed to inhibiting all
frame transmissions.
Enhanced Transmission
Selection
Allows the priorities used for services with similar bandwidth
requirements to be combined into a traffic class group, and a minimum
bandwidth set for each group.
Congestion Notification CN is a mechanism to transmit congestion information on an end-to-end
basis per traffic flow back to the edge of the network where the flow that
causes the congestion can be easily isolated and rate limited.
Openflow This feature allows the switch to be managed by a centralized Openflow
controller, giving access to the forwarding plane of a network switch or
router over the network.
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