Data Center Bridging Exchange Protocol (Dcbx); Data Center Bridging In A Traffic Flow - Dell PowerEdge M IO Aggregator Command Reference Manual

Data Center Bridging Exchange Protocol (DCBX)

The data center bridging exchange (DCBX) protocol is enabled by default on any switch on which PFC or
ETS are enabled. DCBX allows a switch to automatically discover DCB-enabled peers and exchange
configuration information. PFC and ETS use DCBX to exchange and negotiate parameters with peer
devices. DCBX capabilities include:
• Discovery of DCB capabilities on peer-device connections
• Determination of possible mismatch in DCB configuration on a peer link
• Configuration of a peer device over a DCB link
DCBX requires the link layer discovery protocol (LLDP) to provide the path to exchange DCB parameters
with peer devices. Exchanged parameters are sent in organizationally specific type, length, values (TLVs)
in LLDP data units. For more information, refer to the
The following LLDP TLVs are supported for DCB parameter exchange:
• PFC parameters: PFC Configuration TLV and Application Priority Configuration TLV.
• ETS parameters: ETS Configuration TLV and ETS Recommendation TLV.

Data Center Bridging in a Traffic Flow

Figure 6-3 shows how DCB handles a traffic flow on an interface.
Figure 6-3. DCB PFC and ETS Traffic Handling
Ingress Traffic
Apply QoS traffic
classification using
dot1p priority and
map to queue
Egress Traffic
Map priority traffic
to ETS priority
groups
Apply PFC no-drop handling
for lossless queues of
ingress priority traffic
Switching
Apply ETS bandwidth
Transmit ETS-handled
allocation and
scheduling to
priority-group traffic
Link Layer Discovery Protocol (LLDP)
priority traffic
on egress queue
chapter.
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