Dell Force10 MXL Blade MXL 10/40GbE Switch IO Module Configuration Guide - Page 119
Data Center Bridging Exchange Protocol (DCBX), Data Center Bridging in a Traffic Flow
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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 Link Layer Discovery Protocol (LLDP) chapter. 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 8-3 shows how DCB handles a traffic flow on an interface. Figure 8-3. DCB PFC and ETS Traffic Handling Ingress Traffic Apply QoS traffic classification using dot1p priority and map to queue Apply PFC no-drop handling for lossless queues of ingress priority traffic Switching Egress Traffic Map priority traffic to ETS priority groups Apply ETS bandwidth allocation and scheduling to priority-group traffic Transmit ETS-handled priority traffic on egress queue Data Center Bridging (DCB) | 117
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