OS10 Enterprise Edition User Guide Release 10.4.0E(R3)

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Priority flow control

In a converged data-center network, to ensure that no frames are lost due to congestion, use priority flow control (PFC). PFC uses the 802.1p priority in the Ethernet header to pause priority-specific traffic sent from a transmitting device. The 802.1p priority is also known as the class of service (CoS) or dot1p priority value.

When PFC detects congestion of a dot1p traffic class, it sends a pause frame for the priority traffic to the transmitting device. In this way, PFC ensures that specified priority traffic is not dropped by the switch.

PFC enhances the existing 802.3x pause capability to enable flow control based on 802.1p priorities. Instead of stopping all traffic on a link, as performed by the 802.3x pause mechanism, PFC pauses traffic for 802.1p traffic types. For example, when LAN traffic congestion occurs on an interface, PFC ensures lossless flows of storage and server traffic while allowing for lossy best-effort transmission of other traffic.

PFC handles traffic congestion by pausing prioritized dot1p traffic on an ingress interface and allowing other dot1p traffic best-effort, lossy data transmission.

Priority flow control


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