The Data Center Bridging eXchange (DCBX) protocol is used by DCB (Data Center Bridging) devices to exchange DCB configuration information with directly connected peers. In an ExtremeXOS enabled switch, the switch uses DCBX to advertise its DCB configuration to end stations. The end stations can then configure themselves to use the switch DCB services. If the peers do not support a common configuration for one or more features, the switch generates messages to alert network management. The switch does not accept configuration change requests from end stations.
DCBX version information, so that the peers can negotiate a common version to use.
Enhanced Transmission Selection (ETS) information for QoS (Quality of Service) parameters such as bandwidth allocation per traffic class (802.1p COS), priority for each traffic class, and the algorithm used for servicing traffic classes.
Priority-based Flow Control (PFC) information for managing flow control between peers.
Application priority information for prioritizing traffic for special applications that do not map directly to an established traffic class.
The ExtremeXOS software supports two versions of DCBX standards. The first version is a pre-standard version known as the baseline version, or more specifically as Baseline Version 1.01. The DCBX baseline version is specified in DCB Capability Exchange Protocol Base Specification Rev 1.01 and was developed outside of the IEEE and later submitted to the IEEE for standardization. The IEEE agreed to standardize DCBX as part of IEEE 802.1Qaz Enhanced Transmission Selection for Bandwidth Sharing Between Traffic Classes. While IEEE 802.1Qaz has progressed through the standards process, many companies have released support for the baseline version. IEEE 802.1Qaz is nearing completion, and support is expected to start rolling out during 2011.
After you enable DCBX, the protocol collects most of the information to be advertised from other switch services such as QoS and PFC. The only DCBX feature that needs configuration is the application priority feature.
DCBX uses the LLDP (Link Layer Discovery Protocol) (IEEE 802.1AB) to exchange attributes between two link peers. DCBX attributes are packaged into organizationally specific TLVs, which are different for the Baseline and IEEE 802.1Qaz versions. Information on the TLV support differences is provided in the ExtremeXOS Command Reference under the command description for the command: show lldp {port [all | port_list]} dcbx {ieee|baseline} {detailed}
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