IEEE Standards for DCB

Data Center Bridging (DCB) is designed to enhance Ethernet networks by providing mechanisms for bandwidth allocation across links, aiming to minimize data loss. While DCB can be configured to support lossless environments, it also offers traffic shaping capabilities.

The features of DCB are applicable to any high performance Ethernet environment and have significant benefits for both LAN and RDMA traffic.

DCB includes the following components:

• PFC: IEEE 802.1Qbb — Defines eight different traffic priorities that can be paused independently.
• Enhanced Transmission Selection (ETS): IEEE 802.1Qaz — Maps priorities to Traffic Classes and assigns minimum guaranteed bandwidth percentages to those traffic classes.
• Congestion Notification: IEEE 802.1Qau — End-to-end congestion management, further avoiding frame loss.
• Data Center Bridging Capabilities Exchange Protocol (DCBX): IEEE 802.1az (same standard as ETS) — Discover and exchange DCB capabilities between link neighbors. Based on functionality provided by Link Layer Discovery Protocol (LLDP) (IEEE 802.1AB).
• Differentiated Services Code Point (DSCP): RFC 2474 — Defines the IP header field called Differentiated Services (DS), which can be used instead of the Priority Code Point field of the VLAN header to identify the priority of a packet for mapping to a Traffic Class. In the E800 series, the 64 DSCP values are mapped down to the standard 8 priorities and then to the appropriate Traffic Class. Note:VLAN mode (default) and DSCP mode are mutually exclusive.