PFC Watchdog
Overview
In an AI lossless Ethernet fabric, priority-based flow control (PFC) pause frames instruct the link partner to halt packet transmission. These frames can propagate through the network, causing traffic on the PFC streams to stop in what is known as a PFC pause storm. Use the PFC watchdog to detect and to resolve PFC pause storms.
The PFC watchdog monitors PFC-enabled ports for PFC pause storms. The PFC watchdog intervenes when a PFC-enabled port receives PFC pause frames for an extended period of time and is unable to schedule any of the data packets on PFC-enabled queues. The PFC watchdog mitigates the situation by disabling the queue where the PFC pause storm was detected for a set length of time. This length of time, called the recovery time, is configurable. After the recovery time passes, the PFC watchdog reenables the affected queue.
The PFC watchdog plays a critical role with its three key functions: detection, mitigation, and restoration.
Benefits
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Quickly detect and resolve PFC pause storms.
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Maintain lossless traffic links.
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Improve link quality.
Platform Support
See Feature Explorer for platform and release support. Starting in Junos OS Evolved Release 23.4R2, this feature is supported on these platforms:
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QFX5230-64CD
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QFX5240-64OD
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QFX5240-64QD
Configuration Statements
set class-of-service congestion-notification-profile cnp-name pfc-watchdog set class-of-service congestion-notification-profile cnp-name pfc-watchdog watchdog-action <drop/forward> set class-of-service congestion-notification-profile cnp-name pfc-watchdog watchdog-interval <1/10/100> set class-of-service congestion-notification-profile cnp-name pfc-watchdog detection polling-interval set class-of-service congestion-notification-profile cnp-name pfc-watchdog recovery time in milliseconds
Implementation Notes
The watchdog recovery is a global setting, so it requires the same action on all ports to function. When you configure the PFC watchdog on multiple ports, make sure all ports are configured with the same type of action (drop or forward). By default, all ports use the drop action.
You can enable the PFC watchdog on all PFC-enabled queues.
The device logs PFC watchdog detection and recovery events in the system log with a timestamp.
Verification and Troubleshooting
show class-of-service congestion-notification-profile cnp-name show interfaces extensive interface-name