Configuring Priority Flow Control; Finding Feature Information; Information About Priority Flow Control - Cisco Nexus 7000 Series Configuration Manual

Configuring Priority Flow Control

This chapter describes how to configure priority flow control (PFC) on the Cisco NX-OS device.
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Finding Feature Information

Your software release might not support all the features documented in this module. For the latest caveats
and feature information, see the Bug Search Tool at
for your software release. To find information about the features documented in this module, and to see a list
of the releases in which each feature is supported, see the "New and Changed Information"chapter or the
Feature History table in this chapter.

Information About Priority Flow Control

Priority flow control (PFC; IEEE 802.1bb), which is also referred to as Class-based Flow Control (CBFC) or
Per Priority Pause (PPP), is a mechanism that prevents frame loss that is due to congestion. PFC is similar to
802.3x Flow Control (pause frames) or link-level flow control (LFC). However, PFC functions on a per
class-of-service (CoS) basis.
When a buffer threshold is exceeded due to congestion, LFC sends a pause frame to its peer to pause all data
transmission on the link for a specified period of time. When the congestion is mitigated (traffic comes under
the configured threshold), a resume frame is generated to restart data transmission on the link.
In contrast, during congestion, PFC sends a pause frame that indicates which CoS value needs to be paused.
A PFC pause frame contains a 2-octet timer value for each CoS that indicates the length of time that the traffic
needs to be paused. The unit of time for the timer is specified in pause quanta. A quanta is the time that is
Finding Feature Information, on page 147
Information About Priority Flow Control, on page 147
Licensing Requirements, on page 148
Prerequisites for Priority Flow Control, on page 148
Guidelines and Limitations, on page 148
Default Settings for Priority Flow Control, on page 149
Configuring Priority Flow Control, on page 149
Verifying the Priority Flow Control Configuration, on page 150
Configuration Examples for Priority Flow Control, on page 150
Feature History for Priority Flow Control, on page 150
C H A P T E R
https://tools.cisco.com/bugsearch/
Cisco Nexus 7000 Series NX-OS Quality of Service Configuration Guide
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and the release notes
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