Netgear XSM4324FS CLI Manual Software Version 12.x - Page 1005

M4300 Intelligent Edge Series Fully Managed Stackable Switches Priority-Based Flow Control Commands If flow control is enabled on a physical link, it applies to all traffic on the link. If congestion occurs, the hardware sends pause frames that temporarily suspend the traffic flow. Pausing traffic helps to 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. You can configure an interface to pause high priority traffic only (that is, loss-sensitive traffic) when necessary to prevent dropped frames, while allowing traffic with greater loss tolerance to continue to flow on the interface. Priorities are differentiated by the priority field in the IEEE 802.1Q VLAN header, which identifies an IEEE 802.1p priority value. These priority values must be mapped to internal class-of-service (CoS) values on the switch. To enable priority-based flow control for a particular CoS value on an interface, do the following: 1. Ensure that VLAN tagging is enabled on the interface so that the 802.1p priority values are carried through the network (see Provisioning (IEEE 802.1p) Commands on page 444). 2. Ensure that 802.1p priority values are mapped to CoS values on the switch (see classofservice dot1p-mapping on page 924). If priority flow control is disabled, the interface defaults to the IEEE 802.3x flow control setting for the interface. If priority based flow control is enabled, the interface does not pause CoS unless at least one no-drop priority is configured. 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. VLAN tagging (trunk or general mode) must be enabled on the interface to carry the dot1p value through the network. Additionally, mapping between dot1p and the queues must be set to one-to-one. If PFC is enabled on an interface, the normal pause control mechanism is operationally disabled. Default Format Mode off priority-flow-control mode {on | off} Datacenter-Bridging Config mode Data Center Commands 1005 CLI Command Reference Manual