The following have been adopted as IEEE standards: Priority-based Flow Control (PFC): IEEE 802.1Qbb provides a link-level flow control mechanism that can be controlled independently for each frame priority. The goal of this mechanism is to ensure zero loss under congestion in DCB networks. Enhanced Transmission Selection (ETS): IEEE 802.1Qaz provides a common management framework for assignment of bandwidth to frame priorities. Congestion Notification: IEEE 802.1Qau provides end-to-end congestion management for protocols that are capable of transmission rate limiting to avoid frame loss. It is expected to benefit protocols such as TCP that do have native congestion management because it reacts to congestion in a timely manner. Data Center Bridging Capabilities Exchange Protocol (DCBX): A discovery and capability exchange protocol that is used for conveying capabilities and configuration of the preceding features between neighbors to ensure consistent configuration across the network. This protocol leverages functionality provided by IEEE 802.1AB (LLDP). It is actually included in the 802.1az standard.
Priority-based Flow Control: IEEE 802.1Qbb Link sharing is critical to I/O consolidation. For link sharing to succeed, large bursts from one traffic type must not affect other traffic types, large queues of traffic from one traffic type must not starve other traffic types’ resources, and optimization for one traffic type must not create large latency for small messages of other traffic types. The Ethernet pause mechanism can be used to control the effects of one traffic type on another. Priority-based Flow Control (PFC), shown in Figure 23-43, is an enhancement to the pause mechanism.