Intel® Ethernet 700/800 Series
Windows Performance Tuning Guide
Flow Control
The Flow Control feature enables adapters to more effectively regulate traffic. Adapters generate Flow Control frames when their receive queues reach a predefined limit. Generating Flow Control frames signals the transmitter to slow transmission. Adapters respond to Flow Control frames by pausing packet transmission for the time specified in the Flow Control frame.
By enabling adapters to adjust packet transmission, Flow Control helps prevent dropped packets. You can improve RDMA performance by enabling Flow Control on all nodes, on the switch to which they are connected.
- For adapters to benefit from this feature, link partners must support Flow Control frames.
- On systems running a Microsoft Windows Server operating system, enabling *QoS/Priority Flow Control disables link level Flow Control.
- Some devices support Auto Negotiation. Selecting this will cause the device to advertise the value stored in its NVM (usually "Disabled").
Layer 2 Flow Control can impact TCP performance considerably, and is disabled by default on the driver. This is the recommended setting for most workloads. A potential exception to this recommendation is where very bursty traffic (bursts not long in duration) can result is packet drops.
To manage Flow Control: