846 Configuring Data Center Bridging FeaturesDCB Capability ExchangeThe Data Center Bridging Exchange Protocol (DCBx) is used by DCBdevices to exchange configuration information with directly connected peers.DCBx uses type-length-value (TLV) information elements over LLDP toexchange information, so LLDP must be enabled on the port to enable theinformation exchange. By default, LLDP is enabled on all ports. For moreinformation, see "Discovering Network Devices" on page 659.The main objective of DCBx is to perform the following operations:• Discovery of DCB capability in a peer: DCBx is used to learn about thecapabilities of the peer device. It is a means to determine if the peer devicesupports a particular feature such as PFC.• DCB feature misconfiguration detection: DCBx can be used to detectmisconfiguration of a feature between the peers on a link.Misconfiguration detection is feature-specific because some features mayallow asymmetric configuration.• Peer configuration of DCB features: DCBx can be used by a device toperform configuration of DCB features in its peer device if the peer deviceis willing to accept configuration.DCBx is expected to be deployed in Fibre Channel over Ethernet (FCoE)topologies in support of lossless operation for FCoE traffic. In these scenarios,all network elements are DCBx-enabled. In other words, DCBx is enabledend-to-end. For discussion and examples of configuring iSCSI with DCBX,refer to "Configuring iSCSI Optimization" on page 409.The DCBx protocol supports the propagation of configuration informationfor the following features:• Enhanced Transmission Selection (ETS)• Priority-based Flow Control (PFC)• Application PrioritiesThese features use DCBx to send and receive device configuration andcapability information to the peer DCBx device.The Application Priorities information is simply captured from the peer andpotentially propagated to other peers by the DCBx component, as well asbeing configured when iSCSI is enabled on an operationally active PFC port.
