Reference Guide

276 | Data Center Bridging (DCB)
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Table 15-1. Default dot1p Priority-Queue Assignment on Switch
Configuring Priority-Based Flow Control
.Priority-based flow control provides a flow control mechanism based on the 802.1p priorities in
converged Ethernet traffic received on an interface and is enabled by default. As an enhancement to the
existing Ethernet pause mechanism, PFC stops traffic transmission for specified priorities (CoS values)
without impacting other priority classes. Different traffic types are assigned to different priority classes.
When traffic congestion occurs, PFC sends a pause frame to a peer device with the CoS priority values of
the traffic that needs to be stopped. DCBX provides the link-level exchange of PFC parameters between
peer devices. PFC allows network administrators to create zero-loss links for SAN traffic that requires
no-drop service, while at the same time retaining packet-drop congestion management for LAN traffic.
To ensure complete no-drop service, you must apply the same DCB input policy with the same pause time
and dot1p priorities on all PFC-enabled peer interfaces.
To configure PFC and apply a PFC input policy to an interface, follow these steps:
dot1p Value in Incoming Frame Egress Queue Assignment
02
10
21
33
44
55
66
77
Step Task Command Command Mode
1 Create a DCB input policy to apply pause or
flow control for specified priorities using a
configured delay
time.
Maximum: 32 alphanumeric characters.
dcb-input policy-name CONFIGURATION
2 Configure the link delay used to pause
specified priority traffic.One quantum is equal
to a 512-bit transmission.
Valid values (in quanta): 712-65535.
Default: 45556 quantum in link delay.
pfc link-delay value DCB INPUT POLICY