Switching Commands
207
ProSafe Managed Switch
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 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 to 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:
•
Ensure that VLAN tagging is enabled on the interface so that the 802.1p priority values
are carried through the network.
•
Ensure that 802.1p priority values are mapped to IEEE 802.1Q CoS values.
•
Use the datacenter-bridging priority-flow-control mode on command to enable
priority-based flow control on the interface.
•
Use the datacenter-bridging priority-flow-control priority command to specify the CoS
values that should be paused ("no-drop") due to greater loss sensitivity. Unless
configured as "no-drop," all CoS priorities are considered nonpausable ("drop") when
priority-based flow control is enabled.
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.
datacenter-bridging
Use this command to go into datacenter-bridging mode.
Format
datacenter-bridging
Mode
priority-flow-control mode
Use this command to enable or disable priority-based flow control on an interface.
Format
priority-flow-control mode [on | off]
Mode
Default
Interface Config
Datacenter-Bridging Config
Disabled
