Priority-Based Flow Control Commands - D-Link 5000 Series Cli Reference Manual

5000 Series Layer 2/3 Managed Data Center Switch CLI Reference Guide
Display Parameters
Global Mode
FCoE VLAN List
FCFs
ENodes
Sessions
Max VLANs
Max FCFs in VLAN
Max ENodes
Max Sessions

Priority-Based Flow Control Commands

Typically, when a physical link is enabled with flow control, the flow control is applied to all of the traffic on
the link. In the event of congestion, the hardware then sends pause frames that halt the traffic flow
temporarily, which helps to prevent buffer overflow and the dropping of frames.
Priority-based flow control (PFC) provides a means by which to determine, based on the priority of the
traffic, which traffic on a physical link will be paused when congestion occurs. It is possible to configure an
interface to pause only high priority (that is, loss-sensitive) traffic as necessary to prevent dropped frames,
while still allowing traffic with greater loss tolerance to continue flowing over the interface.
The priority field of the IEEE 802.1Q VLAN header differentiates among priorities, with the field identifying
the given IEEE 802.1 p priority value. In D-LINK OS, it is required that these priority value be mapped to
internal class-of-service (CoS) values.
The following steps should be taken to enable priority-based flow control for a specific CoS value on a
given interface:
1. Ensure that VLAN tagging has been enabled on the interface to make sure that the 802.1p
priority values are transmittied through the network.
2. Ensure that the 802.1p priority values are then mapped to the relevant D-LINK OS CoS value.
The interface defaults to the IEEE 802.3x flow control setting for the interface when priority-flow-control is
disabled. When, in contrast, priority-based flow control has been enabled, the interface will not cause any
CoS to be paused unless at least one no-drop priority is present.
6-25 priority-flow-control mode
The priority-flow-control mode command is used in the Datacenter-Bridging Config mode in order to
enable Priority-Flow-Control (PFC) on a specific interface.
In order to carry the dot1p value through the network, VLAN tagging (whether trunk or general mode) has
to be enabled on the interface. Additionally, the setting for dot1mapping to class-of-service must be one-
to-one.
The normal PAUSE control mechanism is operationally disabled when PFC is enabled on an interface.
The no command is used to reset the PFC mode to the default mode (off).
FIP snooping configuration status on the switch. It displays Enable
when FIP snooping is enabled on the switch and Disable when FIP
snooping is disabled on the switch.
List of VLAN IDs on which FIP snooping is enabled.
Number of FCFs discovered on the switch.
Number of ENodes discovered on the switch.
Total virtual sessions on the switch.
Maximum number of VLANs that can be enabled for FlP snooping on
the switch.
Maximum number of FCFs supported in a VLAN.
Maximum number of ENodes supported in the switch.
Maximum number of Sessions supported in the switch.
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