Priority-Flow-Control Mode; Priority-Based Flow Control Commands - NETGEAR M6100 Series Reference Manual

Priority-Based Flow Control Commands

Ordinarily, when flow control is enabled on a physical link, it applies to all traffic on the link.
When congestion occurs, the hardware sends pause frames that temporarily suspend traffic
flow. Pausing traffic helps prevent buffer overflow and dropped frames.
Priority-based flow control (PFC) provides a way to distinguish which traffic on physical link is
paused when congestion occurs, based on the priority of the traffic. An interface can be
configured to pause only high priority (i.e., loss-sensitive) traffic when necessary prevent
dropped frames, while allowing traffic that has greater loss tolerance to continue to flow on
the interface.
Priorities are differentiated by the priority field of the IEEE 802.1Q VLAN header, which
identifies an IEEE 802.1p priority value. In NETGEAR Managed Switch, these priority values
must be mapped to internal class-of-service (CoS) values.
To enable priority-based flow control for a particular CoS value on an interface:
1. Ensure that VLAN tagging is enabled on the interface so that the 802.1p priority values
are carried through the network (see
page 383).
2. Ensure that 802.1p priority values are mapped to NETGEAR Managed Switch CoS values
(see classofservice dot1p-mapping
When priority-flow-control is disabled, the interface defaults to the IEEE 802.3x flow control
setting for the interface. When priority-based flow control is enabled, the interface will not
pause any CoS unless there is at least one no-drop priority.

priority-flow-control mode

Use the priority-flow-control mode on command in Datacenter-Bridging Config
mode to enable Priority-Flow-Control (PFC) on the given interface.
PFC must be enabled before FIP snooping can operate over the interface. Use the no form
of the command to return the mode to the default (off). VLAN tagging (trunk or general mode)
must be enabled on the interface in order to carry the dot1p value through the network.
Additionally, the dot1mapping to class-of-service must be set to one-to-one.
When PFC is enabled on an interface, the normal PAUSE control mechanism is operationally
disabled.
Default Priority-flow-control mode is off (disabled) by default.
Format
priority-flow-control mode {on | off}
Mode Datacenter-Bridging Config mode
Parameter Description
on Enable PFC on the interface.
off Disable PFC on the interface.
M6100 Series Switches
Provisioning (IEEE 802.1p) Commands
on page 995).
Data Center Commands
616
on