interface-type: Specifies an interface type. If you do not specify an interface type, the command displays the PFC information for all Ethernet interfaces.

interface-number: Specifies an interface number. If you do not specify an interface number, the command displays the PFC information for all Ethernet interfaces of the specified type.

Examples

# Display the PFC information for all Ethernet interfaces.

<Sysname> display priority-flow-control interface

Conf -- Configured mode Ne -- Negotiated mode P -- Priority

Interface Conf Ne Dot1pList P Recv Sent Inpps Outpps

WGE1/0/1 Auto On 0,2-3,5-6 0 178 43 12 15

Table 1 Command output

Field	Description
Conf -- Configured mode	Locally configured PFC status.
Ne -- Negotiated mode	Negotiated PFC status.
P -- Priority	802.1p priority value for which PFC is enabled.
Interface	Abbreviated name of the interface.
Conf	Locally configured PFC status: · Auto—The interface is configured to autonegotiate the PFC status with the remote end. · Off—PFC is disabled for the interface. · On—PFC is enabled for the interface.
Ne	Negotiated PFC status: · Off—PFC is disabled. · On—PFC is enabled.
Dot1pList	802.1p priorities that are enabled with PFC. 802.1p priority values 0 through 7 are available.
P	An 802.1p priority is displayed only when the 802.1p priority is enabled with PFC and the interface has received or sent packets with the 802.1p priority.
Recv	Number of received PFC pause frames.
Sent	Number of sent PFC pause frames.
Inpps	Incoming PFC frame rate in pps for the 802.1p priority.
Outpps	Outgoing PFC frame rate in pps for the 802.1p priority.

‌

Related commands

priority-flow-control

priority-flow-control no-drop dot1p

display priority-flow-control dscp-mapping statistics

Use display priority-flow-control dscp-mapping statistics to display DSCP mapping statistics.

Syntax

display priority-flow-control dscp-mapping statistics [ slot slot-number ]

Views

Any view

Predefined user roles

network-admin

network-operator

Parameters

slot slot-number: Specifies an IRF member device by its member ID. If you do not specify a member device, this command displays the DSCP mapping statistics for the master device.

Examples

# Display DSCP mapping statistics.

<Sysname> display priority-flow-control dscp-mapping statistics

O/N: Original/New

slot 1:

OutInterface Priority(O/N) DSCP(O/N) Count LastMappingTime

WGE1/0/1 1/2 11/12 2001 2021-08-10 08:18:01

Related commands

priority-flow-control dscp-mapping

priority-flow-control (Ethernet interface view)

Use priority-flow-control to enable PFC on an Ethernet interface.

Use undo priority-flow-control to disable PFC.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control { auto | enable [ receive | send ] }

undo priority-flow-control

Default

PFC is disabled on Ethernet interfaces.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

auto: Specifies PFC in auto mode. In this mode, the local end automatically negotiates the PFC status with the remote end.

enable: Forcibly enables PFC.

receive: Enables Rx PFC.

send: Enables Tx PFC.

Usage guidelines

The local device notifies the remote end to stop sending packets carrying the specified 802.1p priority if all of the following conditions exist:

· Both the local end and the remote end have PFC enabled.

· Both the local end and the remote end have the priority-flow-control no-drop dot1p dot1p-list command configured.

· The specified 802.1p priority is in the 802.1p priority list specified by the dot1p-list argument.

· The local end receives packets carrying the specified 802.1p priority, and the received packets cause congestion.

When congestion is eliminated, the local end notifies the remote end to continue to send packets carrying the specified 802.1p priority. In this way, the local device can forward packets carrying 802.1p priorities in the specified 802.1p priority list without packet drops.

When you enable Rx PFC, the device can receive but cannot send PFC pause frames. When you enable Tx PFC, the device can send but cannot receive PFC pause frames. If neither receive nor send is specified, this command enables both Rx PFC and Tx PFC.

If you execute this command in system view and Ethernet interface view multiple times, the most recent configuration takes effect.

Examples

# Enable PFC on Twenty-FiveGigE 1/0/1.

<Sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control enable

Related commands

display priority-flow-control

priority-flow-control (system view)

priority-flow-control no-drop dot1p

priority-flow-control (system view)

Use priority-flow-control to enable PFC on all Ethernet interfaces.

Use undo priority-flow-control to disable PFC on all Ethernet interfaces.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control { auto | enable [ receive | send ] }

undo priority-flow-control

Default

PFC is disabled on Ethernet interfaces.

Views

System view

Predefined user roles

network-admin

Parameters

auto: Specifies PFC in auto mode. In this mode, the local end automatically negotiates the PFC status with the remote end.

enable: Forcibly enables PFC.

receive: Enables Rx PFC.

send: Enables Tx PFC.

Usage guidelines

The local device notifies the remote end to stop sending packets carrying the specified 802.1p priority if all of the following conditions exist:

· Both the local end and the remote end have PFC enabled.

· Both the local end and the remote end have the priority-flow-control no-drop dot1p command configured.

· The specified 802.1p priority is in the 802.1p priority list specified by the dot1p-list argument.

· The local end receives packets carrying the specified 802.1p priority, and the received packets cause congestion.

If you execute this command in system view and Ethernet interface view multiple times, the most recent configuration takes effect.

Examples

# Enable PFC on all Ethernet interfaces.

<Sysname> system-view

[Sysname] priority-flow-control enable

Related commands

display priority-flow-control

priority-flow-control (Ethernet interface view)

priority-flow-control no-drop dot1p

priority-flow-control deadlock auto-recover action

Use priority-flow-control deadlock auto-recover action to configure the action to take on packets during the delay timer period for PFC deadlock detection automatic recovery.

Use undo priority-flow-control deadlock auto-recover action to restore the default.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control deadlock auto-recover action { discard | forwarding }

undo priority-flow-control deadlock auto-recover action

Default

The device forwards the received data packets during the delay timer period for PFC deadlock detection automatic recovery.

Views

System view

Predefined user roles

network-admin

Parameters

discard: Drops the received data packets.

forwarding: Forwards the received data packets.

Usage guidelines

When the device is in the PFC deadlock state, you cannot execute this command.

Examples

# Configure the device to drop received data packets during the delay timer period for PFC deadlock detection automatic recovery.

<Sysname> system-view

[Sysname] priority-flow-control deadlock auto-recover action discard

Related commands

priority-flow-control deadlock cos

priority-flow-control deadlock enable

priority-flow-control deadlock auto-recover cos

Use priority-flow-control deadlock auto-recover cos to configure the delay timer for PFC deadlock detection automatic recovery.

Use undo priority-flow-control deadlock auto-recover cos to delete the delay timer for PFC deadlock detection automatic recovery.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control deadlock auto-recover cos cos-value delay delay-interval

undo priority-flow-control deadlock auto-recover cos [ cos-value ]

Default

The delay timer for PFC deadlock detection automatic recovery is not configured.

Views

System view

Predefined user roles

network-admin

Parameters

cos cos-value: Specifies the CoS value of packets, in the range of 0 to 7. Different CoS values correspond to different 802.1p priority values. To see the CoS-to-802.1p mapping, execute the display qos map-table dot1p-lp command.

delay delay-interval: Specifies the delay timer for PFC deadlock detection automatic recovery, in the range of 1 to 15.

Usage guidelines

PFC deadlock detection periodically detects whether deadlock occurs to packets carrying the specified CoS value. If the device enters the PFC deadlock state and PFC deadlock detection is recovered in automatic mode, the device automatically recovers PFC deadlock detection after the delay timer expires. The delay timer is 100 ms + delay-interval * 100 ms.

This command takes effect only in automatic recovery mode. When the device is in the PFC deadlock state, you cannot execute this command.

The specified CoS value must be within the 802.1p priority values configured by using the priority-flow-control no-drop dot1p command.

You can set the same delay timer for different CoS values.

If you execute this command multiple times for the same CoS value, the most recent configuration takes effect.

Examples

# Set the delay timer for PFC deadlock detection automatic recovery to 5 for packets carrying CoS value 7.

<Sysname> system-view

[Sysname] priority-flow-control deadlock auto-recover cos 7 delay 5

Related commands

display qos map-table dot1p-lp (ACL and QoS Command Reference)

priority-flow-control deadlock precision

priority-flow-control no-drop dot1p

priority-flow-control deadlock cos

Use priority-flow-control deadlock cos to set the PFC deadlock detection interval for the specified CoS value.

Use undo priority-flow-control deadlock cos to delete the PFC deadlock detection interval for the specified CoS value or all CoS values.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control deadlock cos cos-value interval interval [ pause-recover ]

undo priority-flow-control deadlock cos [ cos-value ]

Default

The PFC deadlock detection interval for a CoS value is not set.

Views

System view

Predefined user roles

network-admin

Parameters

cos cos-value: Specifies the CoS value of packets, in the range of 0 to 7.

interval interval: Specifies the PFC deadlock detection interval in the range of 1 to 15.

pause-recover: Automatically recovers the PFC feature and PFC deadlock detection feature based on whether an interface receives PFC pause frames.

· If an interface is in PFC deadlock state and can still receive PFC pause frames when the detection interval expires, the interface is considered as not recovered and stays in PFC deadlock state.

· If an interface is in PFC deadlock state and receives no PFC pause frames when the detection interval expires, the interface is considered as recovered, and the PFC feature and PFC deadlock detection feature will be automatically recovered on the interface.

If you do not specify this keyword, the PFC feature and PFC deadlock detection feature are automatically recovered on an interface when the detection interval expires, no matter whether the interface receives PFC pause frames.

Usage guidelines

The PFC deadlock detection feature periodically detects whether deadlock occurs to packets that carry the specified CoS value. To obtain the length of time for the detection interval, multiply the detection interval by the precision of the PFC deadlock detection timer.

The PFC deadlock detection interval for a CoS value is the product of the interval argument configured by using the priority-flow-control deadlock cos interval command and the precision configured by using the priority-flow-control deadlock precision command. For example, if you execute the priority-flow-control deadlock cos 5 interval 10 command to set the interval argument to 10 for CoS priority 5 and execute the priority-flow-control deadlock precision command to set the precision to high (which represents 10 milliseconds) for CoS priority 5, the PFC deadlock detection interval for CoS priority 5 is 10*10 =100 milliseconds.

The specified CoS value must be within the 802.1p priority list specified by using the priority-flow-control no-drop dot1p command. To view the 802.1p priority for each CoS value, execute the display qos map-table dot1p-lp command.

You can set the same detection interval for different CoS values.

If you execute this command for the same CoS value multiple times, the most recent configuration takes effect.

You cannot execute this command when the device is in PFC deadlock state.

Examples

# Set the PFC deadlock detection interval to 5 for packets carrying CoS value 7.

<Sysname> system-view

[Sysname] priority-flow-control deadlock cos 7 interval 5

Related commands

display qos map-table dot1p-lp (ACL and QoS Command Reference)

priority-flow-control deadlock precision

priority-flow-control no-drop dot1p

priority-flow-control deadlock enable

Use priority-flow-control deadlock enable to enable PFC deadlock detection on an interface.

Use undo priority-flow-control deadlock enable to disable PFC deadlock detection on an interface.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control deadlock enable

undo priority-flow-control deadlock enable

Default

PFC deadlock detection is disabled on an interface.

Views

Ethernet interface view

Predefined user roles

network-admin

Usage guidelines

The device enters the PFC deadlock state if the following conditions exist on an interface:

· PFC for 802.1p priorities is enabled by using the priority-flow-control and priority-flow-control no-drop dot1p commands.

· Packets carrying the specified 802.1p priority are transmitted in a loop.

· No packets in the data buffer can be forwarded.

This command enables periodically detecting whether the device is in PFC deadlock state.

When the device is in the PFC deadlock state, you cannot execute this command.

Examples

# Enable PFC deadlock detection on Twenty-FiveGigE 1/0/1.

<Sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control deadlock enable

Related commands

priority-flow-control

priority-flow-control deadlock cos

priority-flow-control no-drop dot1p

priority-flow-control deadlock precision

Use priority-flow-control deadlock precision to set the precision for the PFC deadlock detection timer.

Use undo priority-flow-control deadlock precision to restore the default.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control deadlock precision { high | normal }

undo priority-flow-control deadlock precision

Default

The PFC deadlock detection timer uses normal precision.

Views

System view

Predefined user roles

network-admin

Parameters

high: Specifies the high precision for the PFC deadlock detection timer.

normal: Specifies the normal precision for the PFC deadlock detection timer.

Usage guidelines

Use this command to adjust the precision for the PFC deadlock detection timer and change the PFC deadlock detection interval. On this switch series, the high precision means 10 ms, and the normal precision means 100 ms.

When the device is in the PFC deadlock state, you cannot execute this command.

If you execute this command multiple times, the most recent configuration takes effect.

Examples

# Set the high precision for the PFC deadlock detection timer.

<Sysname> system-view

[Sysname] priority-flow-control deadlock precision high

priority-flow-control deadlock recover

Use priority-flow-control deadlock recover to recover PFC deadlock detection on an interface.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control deadlock recover

Views

Ethernet interface view

Predefined user roles

network-admin

Usage guidelines

Before executing this command, first use the priority-flow-control deadlock recover-mode command to configure the recovery mode for PFC deadlock detection.

The device can automatically release the deadlock state, but both the PFC deadlock detection and PFC features are disabled on the interface at the same time. To manually recover PFC deadlock detection on the interface, execute this command after setting the manual recovery mode for PFC deadlock detection on the interface. The PFC feature is also enabled again when you execute this command.

When the device is in the PFC deadlock state, you cannot execute this command.

Examples

# Recover PFC deadlock detection on Twenty-FiveGigE 1/0/1.

<Sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control deadlock recover

Related commands

priority-flow-control deadlock recover-mode

Use priority-flow-control deadlock recover-mode to set the recovery mode for PFC deadlock detection on an interface.

Use undo priority-flow-control deadlock recover-mode to restore the default.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control deadlock recover-mode { auto | manual }

undo priority-flow-control deadlock recover-mode

Default

PFC deadlock detection recovers in automatic mode on an interface.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

auto: Specifies the automatic recovery mode.

manual: Specifies the manual recovery mode.

Usage guidelines

When the PFC deadlock state is detected and PFC deadlock detection is recovered in automatic mode, the device automatically releases the deadlock state and recovers PFC and PFC deadlock detection after the delay timer expires. Within the delay timer period, the device disables PFC and PFC deadlock detection on the interface, so that packets can be forwarded properly. PFC deadlock detection can be recovered in automatic or manual mode on the interface. Recovering this feature enables the PFC feature again at the same time. Use the automatic recovery mode when no serious failures occur.

When a packet loop cannot be resolved and the device enters the PFC deadlock state frequently, manually recover PFC deadlock detection on the interface as follows:

1. Perform troubleshooting and set the manual recovery mode for PFC deadlock detection.

2. Execute the priority-flow-control deadlock recover command to recover the PFC deadlock detection and PFC features.

When the device is in the PFC deadlock state, you cannot execute this command.

Examples

# Set the manual recovery mode for PFC deadlock detection on Twenty-FiveGigE 1/0/1.

<Sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control deadlock recover-mode manual

Related commands

priority-flow-control deadlock recover

priority-flow-control deadlock threshold

Use priority-flow-control deadlock threshold to configure the upper threshold for PFC deadlock times within the specified period.

Use undo priority-flow-control deadlock threshold to restore the default.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control deadlock threshold cos cos-value period period count count [ error-down ]

undo priority-flow-control deadlock threshold cos [ cos-value ]

Default

The upper threshold for PFC deadlock times within the specified period is not configured.

Views

System view

Predefined user roles

network-admin

Parameters

period period: Specifies the period for detecting PFC deadlock times, in the range of 1 to 60 seconds.

count count: Specifies the upper threshold for PFC deadlock times within the specified period, in the range of 1 to 500.

error-down: Shuts down an interface when the number of PFC deadlock times within the detection period reaches the upper threshold. If you do not specify this keyword, PFC will be disabled for the corresponding 802.1p priority when the number of PFC deadlock times within the detection period reaches the upper threshold.

Usage guidelines

After this command is executed, when the PFC deadlock times within the specified period exceed the upper threshold on an interface, how the device reacts depends on the command settings:

· If the error-down keyword is not specified, the device disables PFC for the corresponding 802.1p priority on the interface. To recover PFC on the interface in this case, first execute the undo priority-flow-control enable command and then execute the priority-flow-control enable command.

Alternatively, you can execute the undo priority-flow-control deadlock threshold command to recover PFC on an interface. However, this command might affect the PFC state on multiple interfaces. Use this command as needed.

· If the error-down keyword is specified, the device will shut down the interface. To bring up the interface and recover PFC on the interface, execute the undo shutdown command on the interface.

When the PFC deadlock times within the specified period exceed the upper threshold on an interface, how the device reacts depends on the configuration in system view and interface view.

· If the priority-flow-control deadlock threshold action command is not executed on the interface, the priority-flow-control deadlock threshold command in system view takes effect. If the priority-flow-control deadlock threshold action command is executed on the interface, this command takes effect.

· If the priority-flow-control deadlock threshold command is not executed in system view, the priority-flow-control deadlock threshold action command on the interface does not take effect.

The detection period specified in this command must be longer than the PFC deadlock detection interval configured by using the priority-flow-control deadlock cos command, so that you can determine whether the device frequently enters the PFC deadlock state.

You cannot execute this command when the device is in PFC deadlock state.

The specified CoS value must be within the 802.1p priority values configured by using the priority-flow-control no-drop dot1p command.

You can set the same detection period for different CoS values.

If you execute this command multiple times for the same CoS value, the most recent configuration takes effect.

Examples

# Set the upper threshold for PFC deadlock times to 100 within the period of 5 seconds.

<Sysname> system-view

[Sysname] priority-flow-control deadlock threshold cos 7 period 5 count 100

Related commands

priority-flow-control deadlock cos

priority-flow-control deadlock threshold action

priority-flow-control no-drop dot1p

priority-flow-control deadlock threshold action

Use priority-flow-control deadlock threshold action to configure the action to take on an interface when the number of PFC deadlock times within the specified detection period exceeds the upper threshold.

Use undo priority-flow-control deadlock threshold action to restore the default.

Syntax

priority-flow-control deadlock threshold action { error-down | turn-off }

undo priority-flow-control deadlock threshold action

Default

The action specified by the priority-flow-control deadlock threshold command in system view takes effect.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

error-down: Shuts down an interface when the number of PFC deadlock times within the specified detection period reaches the upper threshold and stops traffic forwarding on the interface.

turn-off: Disables PFC for the corresponding 802.1p priority when the number of PFC deadlock times within the specified detection period reaches the upper threshold.

Usage guidelines

The threshold for PFC deadlock times and the detection period are configured by using the priority-flow-control deadlock threshold command in system view. If the priority-flow-control deadlock threshold action command is not executed on the interface, the priority-flow-control deadlock threshold command in system view takes effect. If the priority-flow-control deadlock threshold action command is executed on the interface, this command takes effect.

If the priority-flow-control deadlock threshold command is not executed in system view, the priority-flow-control deadlock threshold action command on the interface does not take effect.

If the turn-off keyword is specified, the device disables PFC for the corresponding 802.1p priority on the interface when the number of PFC deadlock times within the specified detection period exceeds the upper threshold. To recover PFC on the interface in this case, first execute the undo priority-flow-control enable command and then execute the priority-flow-control enable command. Alternatively, you can execute the undo priority-flow-control deadlock threshold command to recover PFC on an interface. However, this command might affect the PFC state on multiple interfaces. Use this command as needed.

If the error-down keyword is specified, the device shuts down the interface when the number of PFC deadlock times within the specified detection period exceeds the upper threshold on the interface. To bring up the interface and recover PFC on the interface in this case, execute the undo shutdown command on the interface.

Examples

# Configure PFC to shut down the interface when the PFC deadlock times within the specified period reaches the upper threshold.

<Sysname> system-view

[Sysname] interface gigabitethernet 1/0/1

[Sysname-GigabitEthernet1/0/1] priority-flow-control deadlock threshold action error-down

Related commands

priority-flow-control deadlock threshold

priority-flow-control dot1p headroom

Use priority-flow-control dot1p headroom to set the headroom buffer threshold.

Use undo priority-flow-control dot1p headroom to restore the default.

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

Syntax

priority-flow-control dot1p dot1p headroom headroom-number

undo priority-flow-control dot1p dot1p headroom

Default

See Table 2.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

dot1p: Specifies an 802.1p priority in the range of 0 to 7.

headroom-number: Specifies the headroom buffer threshold in the range of 1 to 131072 on the S6850&S9850 switch series and 1 to 19968 on the S6805 and S6825 switch series.

Usage guidelines

Before executing this command, you must use the priority-flow-control no-drop dot1p command to enable PFC for the specified 802.1p priority.

If you execute this command multiple times for the same 802.1p priority, the most recent configuration takes effect.

When two directly connected interfaces transmit data, the buffers of interfaces are used for buffering received data. A longer transmission distances needs a large buffer size. You can use this command to set the headroom buffer threshold to implement zero packet loss.

· For a 100-GE interface:

¡ When the transmission distance is 300 meters, you only need to execute the priority-flow-control no-drop dot1p command on the interface. This command automatically sets the default headroom buffer threshold, which is adequate for implementing zero packet loss for the transmission distance.

¡ When the transmission distance is 10000 meters, you must use the priority-flow-control dot1p headroom command on the interface to set the headroom buffer threshold. As a best practice, set the headroom buffer threshold to 9984. You can adjust the threshold as needed to ensure zero packet loss for the transmission distance.

¡ When the transmission distance is longer than 10000 meters, the device series does not support transceiver modules with the transmission distance in the current software version.

· For a non-100-GE interface:

¡ When the transmission distance is 300, 10000, or 20000 meters, you only need to execute the priority-flow-control no-drop dot1p command on the interface. This command automatically sets the default headroom buffer threshold, which is adequate for implementing zero packet loss for the transmission distance.

¡ When the transmission distance is 40000 meters, you must use the priority-flow-control dot1p headroom command on the interface to set the headroom buffer threshold. As a best practice, set the headroom buffer threshold to 9984. You can adjust the threshold as needed to ensure zero packet loss for the transmission distance.

If you set the headroom buffer threshold when packets are being forwarded, traffic will be interrupted and packets will be lost transiently.

Examples

# Set the headroom buffer threshold to 1000 for 802.1p priority 1 on Twenty-FiveGigE 1/0/1.

<sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control dot1p 1 headroom 1000

Related commands

priority-flow-control no-drop dot1p

priority-flow-control dot1p ingress-buffer dynamic

Use priority-flow-control dot1p ingress-buffer dynamic to set the dynamic back pressure frame triggering threshold.

Use undo priority-flow-control dot1p ingress-buffer to restore the default.

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

Syntax

priority-flow-control dot1p dot1p ingress-buffer dynamic ratio

undo priority-flow-control dot1p dot1p ingress-buffer

Default

See Table 2.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

dot1p: Specifies an 802.1p priority in the range of 0 to 7.

ratio: Specifies the dynamic back pressure frame triggering threshold in percentage. The value range for this argument is 1 to 100.

Usage guidelines

Before executing this command, you must use the priority-flow-control no-drop dot1p command to enable PFC for the specified 802.1p priority.

If you execute this command multiple times for the same 802.1p priority, the most recent configuration takes effect.

If you set the dynamic back pressure frame triggering threshold when packets are being forwarded, traffic will be interrupted and packets will be lost transiently.

Examples

# Set the dynamic back pressure frame triggering threshold to 30 for 802.1p priority 1 on Twenty-FiveGigE 1/0/1.

<sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control dot1p 1 ingress-buffer dynamic 30

Related commands

priority-flow-control no-drop dot1p

priority-flow-control dot1p ingress-buffer static

Use priority-flow-control dot1p ingress-buffer static to set the static back pressure frame triggering threshold.

Use undo priority-flow-control dot1p ingress-buffer to restore the default.

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

Syntax

priority-flow-control dot1p dot1p-list ingress-buffer static threshold

undo priority-flow-control dot1p dot1p-list ingress-buffer

Default

The static back pressure frame triggering threshold is not set.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

dot1p: Specifies an 802.1p priority in the range of 0 to 7.

threshold: Specifies the static back pressure frame triggering threshold in the range of 1 to 131072 on the S6850&S9850 switch series and 1 to 19968 on the S6805 and S6825 switch series.

Usage guidelines

Before executing this command, you must use the priority-flow-control no-drop dot1p command to enable PFC for the specified 802.1p priority.

If you set the static back pressure frame triggering threshold when packets are being forwarded, traffic will be interrupted and packets will be lost transiently.

If you execute this command for the same 802.1p priority multiple times, the most recent configuration takes effect.

Examples

# Set the static back pressure frame triggering threshold to 1000 for 802.1p priority 1 on Twenty-FiveGigE 1/0/1.

<sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control dot1p 1 ingress-buffer static 1000

Related commands

priority-flow-control no-drop dot1p

priority-flow-control dot1p ingress-threshold-offset

Use priority-flow-control dot1p ingress-threshold-offset to set the offset between the back pressure frame stopping threshold and triggering threshold.

Use undo priority-flow-control dot1p ingress-threshold-offset to restore the default.

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

Syntax

priority-flow-control dot1p dot1p ingress-threshold-offset offset-number

undo priority-flow-control dot1p dot1p ingress-threshold-offset

Default

See Table 2.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

dot1p: Specifies an 802.1p priority in the range of 0 to 7.

offset-number: Specifies the offset between the back pressure frame stopping threshold and triggering threshold in the range of 1 to 131072 on the S6850&S9850 switch series and 1 to 19968 on the S6805 and S6825 switch series.

Usage guidelines

Before executing this command, you must use the priority-flow-control no-drop dot1p command to enable PFC for the specified 802.1p priority.

If you execute this command multiple times, the most recent configuration takes effect.

If you set the offset between the back pressure frame stopping threshold and triggering threshold when packets are being forwarded, traffic will be interrupted and packets will be lost transiently.

Examples

# Set the offset between the back pressure frame stopping threshold and triggering threshold to 1000 for 802.1p priority 1 on Twenty-FiveGigE 1/0/1.

<sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control dot1p 1 ingress-threshold-offset 1000

Related commands

priority-flow-control no-drop dot1p

priority-flow-control dot1p reserved-buffer

Use priority-flow-control dot1p reserved-buffer to set the PFC reserved threshold.

Use undo priority-flow-control dot1p reserved-buffer to restore the default.

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

Syntax

priority-flow-control dot1p dot1p reserved-buffer reserved-number

undo priority-flow-control dot1p dot1p reserved-buffer

Default

See Table 2.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

dot1p: Specifies an 802.1p priority in the range of 0 to 7.

reserved-number: Specifies the PFC reserved threshold in the range of 1 to 131072 on the S6850&S9850 switch series and 1 to 19968 on the S6805 and S6825 switch series.

Usage guidelines

Before executing this command, you must use the priority-flow-control no-drop dot1p command to enable PFC for the specified 802.1p priority.

If you execute this command multiple times for the same 802.1p priority, the most recent configuration takes effect.

If you set the PFC reserved threshold when packets are being forwarded, traffic will be interrupted and packets will be lost transiently.

Examples

# Set the PFC reserved threshold to 1000 for 802.1p priority 1 on Twenty-FiveGigE 1/0/1.

<sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control dot1p 1 reserved-buffer 1000

Related commands

priority-flow-control no-drop dot1p

priority-flow-control dscp-mapping

Use priority-flow-control dscp-mapping to configure DSCP mappings for packets on an interface.

Use undo priority-flow-control dscp-mapping to restore the default.

Syntax

priority-flow-control dscp-mapping { original-dscp original-dscp-value to priority priority dscp dscp-value }&<1-2>

undo priority-flow-control dscp-mapping

Default

No DSCP mappings are configured.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

original-dscp original-dscp-value: Specifies the original DSCP value in the range of 0 to 63.

priority priority: Specifies the 802.1p priority for the packets, in the range of 0 to 7.

dscp dscp-value: Specifies the new DSCP value in the range of 0 to 63.

&<1-2>: Indicates a maximum of two values can be entered.

Usage guidelines

A device assigns an incoming packet to a queue with an 802.1p priority based on the DSCP value of the packet and the DSCP-802.1p priority map. When packets carrying the specified 802.1p priority are transmitted in a loop, each node on the path stops transmitting packets with the specified DSCP values. In this case, a PFC deadlock occurs. To prevent PFC deadlocks, you can modify the DSCP-802.1p mappings for packets. The packets will be forwarded based on the new DSCP value.

This command enables the device to modify the 802.1p priority and DSCP value of packets when forwarding them.

A maximum number of two DSCP mappings can be configured, and the original DSCP values must be different.

The device supports configuring DSCP mappings for only IPv4 packets, and you can configure up to four groups of DSCP mappings. DSCP mappings with the same source DSCP, 802.1p priority value, and target DSCP value are considered as belonging to the same group.

This feature is supported only when the QoS and ACL resource sharing mode is preemption. To switch to the non-preemption mode after this feature is configured, first execute the undo priority-flow-control dscp-mapping command to delete the DSCP mappings for packets. For more information about the QoS and ACL resource sharing mode, see ACL and QoS Command Reference.

An interface configured with DSCP mappings cannot be assigned to an aggregation group. The DSCP mappings configured on aggregation member ports do not take effect.

Examples

# On Twenty-FiveGigE 1/0/1, map DSCP value 2 to DSCP value 4 in packets and assign the packets to the queue with 802.1 priority 3.

<Sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control dscp-mapping original-dscp 2 to priority 3 dscp 4

priority-flow-control early-warning inpps

Use priority-flow-control early-warning inpps to configure the early warning threshold for incoming PFC packets.

Use undo priority-flow-control early-warning inpps to delete the early warning threshold for incoming PFC packets.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control early-warning dot1p dot1p-list inpps pps-value

undo priority-flow-control early-warning [ dot1p dot1p-list ] inpps

Default

No early warning threshold is configured for incoming PFC packets.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

dot1p-list: Specifies an 802.1p priority (or dot1p priority) list to identify flows that are subject to PFC (for example: 1,3-5). A hyphen (-) connects two numeric values, which together indicate a continuous value range. Different values or value ranges are separated with commas (,). You can configure up to 16 characters for this argument.

inpps pps-value: Specifies the number of PFC frames that an interface can receive in pps, in the range of 1 to 159783010.

Usage guidelines

You can configure the early warning threshold for incoming or outgoing PFC packets of an interface as needed. The early warning threshold notifies a situation where the PFC packet transmission rate is still within a normal range but needs attention.

When the rate of PFC packets that an interface sends or receives reaches the early warning threshold, the system generates traps and logs to notify the user. According to the traps and logs, the user can discover some exceptions in the network, for example:

· The NIC of the peer device fails and continuously sends PFC packets at a high speed. In this case, you can set the early warning threshold for incoming PFC packets.

· The device fails and continuously sends PFC frames. In this case, you can set the early warning threshold for outgoing PFC packets.

To monitor bidirectional PFC packets, you can set the early warning thresholds for incoming packets and outgoing packets separately.

The number of PFC pause frames that an interface receives is counted and the early warning threshold configuration takes effect only when PFC is enabled.

If you execute this command multiple times, the most recent configuration takes effect.

Examples

# Set the early warning threshold to 80 pps for incoming PFC packets with 802.1p priority value 7 on Twenty-FiveGigE 1/0/1.

<Sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control early-warning dot1p 7 inpps 80

priority-flow-control early-warning outpps

Use priority-flow-control early-warning outpps to configure the early warning threshold for outgoing PFC packets.

Use undo priority-flow-control early-warning outpps to delete the early warning threshold for outgoing PFC packets.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control early-warning dot1p dot1p-list outpps pps-value

undo priority-flow-control early-warning [ dot1p dot1p-list ] outpps

Default

No early warning threshold is configured for outgoing PFC packets.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

outpps pps-value: Specifies the number of PFC frames that an interface can send in pps, in the range of 1 to 159783010.

Usage guidelines

· The NIC of the peer device fails and continuously sends PFC packets at a high speed. In this case, you can set the early warning threshold for incoming PFC packets.

· The device fails and continuously sends PFC frames. In this case, you can set the early warning threshold for outgoing PFC packets.

To monitor bidirectional PFC packets, you can set the early warning thresholds for incoming packets and outgoing packets separately.

The number of PFC pause frames that an interface sends is counted and the early warning threshold configuration takes effect only when PFC is enabled.

If you execute this command multiple times, the most recent configuration takes effect.

Examples

# Set the early warning threshold to 50 pps for outgoing PFC packets with 802.1p priority value 1 on Twenty-FiveGigE 1/0/1.

<Sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control early-warning dot1p 1 outpps 50

priority-flow-control no-drop dot1p (Ethernet interface view)

Use priority-flow-control no-drop dot1p to enable PFC.

Use undo priority-flow-control no-drop dot1p to disable PFC for 802.1p priorities on an Ethernet interface.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control no-drop dot1p dot1p-list

undo priority-flow-control no-drop dot1p

Default

PFC is disabled for all 802.1p priorities on an Ethernet interface.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

Usage guidelines

If you enable PFC and execute this command on both the local and peer devices, the local device will notify the peer device to stop transmitting packets with the specified 802.1p priority when congestion occurs. When congestion is removed, the local device notifies the peer device to transmitting the packets again. This prevents packet loss for traffic with the specified priority. For more information about 802.1p priority, see QoS configuration in ACL and QoS Configuration Guide.

After PFC is enabled for 802.1p priorities, the PFC thresholds use the default values, which are adequate in typical network environments. As a practice, change the thresholds only when necessary. Table 2 describes the default PFC thresholds.

Table 2 Default PFC thresholds

PFC threshold (right) Interface type (below)	Headroom buffer threshold	Dynamic back pressure frame triggering threshold	Offset between the back pressure frame stopping threshold and triggering threshold	PFC reserved threshold
1-GE/10-GE	100	5	12	17
25-GE	125	5	12	17
40-GE	200	5	12	17
100-GE	491	5	12	17

This command is mutually exclusive with the flow-control or flow-control receive enable command.

If you execute this command multiple times in system view and interface view, the most recent configuration takes effect.

If you enable or disable PFC for the specified 802.1p priority when packets are being forwarded, traffic will be interrupted, and transient packet loss will occur.

Examples

# Enable PFC in auto mode on Twenty-FiveGigE 1/0/1, and enable PFC for 802.1p priority 5.

<Sysname> system-view

[Sysname] interface twenty-fivegige 1/0/1

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control auto

[Sysname-Twenty-FiveGigE1/0/1] priority-flow-control no-drop dot1p 5

Related commands

display priority-flow-control

flow-control (Interface Command Reference)

flow-control receive enable (Interface Command Reference)

priority-flow-control

priority-flow-control no-drop dot1p (system view)

Use priority-flow-control no-drop dot1p to enable PFC for 802.1p priorities on all Ethernet interfaces.

Use undo priority-flow-control no-drop dot1p to disable PFC for 802.1p priorities on all Ethernet interfaces.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control no-drop dot1p dot1p-list

undo priority-flow-control no-drop dot1p

Default

PFC is disabled for all 802.1p priorities on all Ethernet interfaces.

Views

System view

Predefined user roles

network-admin

Parameters

Usage guidelines

The local device notifies the remote end to stop sending packets carrying the specified 802.1p priority if all of the following conditions exist:

· Both the local end and the remote end have PFC enabled.

· Both the local end and the remote end have the priority-flow-control no-drop dot1p command configured.

· The specified 802.1p priority is in the 802.1p priority list specified by the dot1p-list argument.

· The local end receives packets carrying the specified 802.1p priority, and the received packets cause congestion.

If you enable or disable PFC for the specified 802.1p priority when packets are being forwarded, traffic will be interrupted and packets will be lost transiently.

If you execute this command in system view and Ethernet interface view multiple times, the most recent configuration takes effect.

Examples

# Enable PFC for 802.1p priority 5 globally.

<Sysname> system-view

[Sysname] priority-flow-control no-drop dot1p 5

Related commands

priority-flow-control no-drop dot1p (Ethernet interface view)

priority-flow-control pause-time

Use priority-flow-control pause-time to set the pause time in PFC pause frames.

Use undo priority-flow-control pause-time to restore the default.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control pause-time time-vale

undo priority-flow-control pause-time

Default

The pause time in PFC pause frames is 65535.

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

time-vale: Specifies the pause time in PFC pause frames, in the range of 0 to 65535. The unit is the time needed for transmitting 512-bit data on the current interface.

Usage guidelines

This command sets the pause time in PFC pause frames sent by an Ethernet interface. When the peer interface receives the PFC frames, the peer interface reads the pause time in the PFC pause frames and does not forward data traffic within the pause time.

If the peer interface receives PFC pause frames again before the pause time in PFC pause frames expires, the pause time is refreshed according to the newly received PFC pause frames.

After the pause time in PFC pause frames expires, the peer interface resumes forwarding data traffic if it does not receive new PFC pause frames.

Examples

# Set the pause time in PFC pause frames to 200.

<Sysname> system-view

[Sysname] priority-flow-control pause-time 200

Related commands

priority-flow-control deadlock cos

priority-flow-control deadlock enable

priority-flow-control poolID headroom

Use priority-flow-control poolID headroom to set the maximum number of cell resources that can be used in a headroom storage space.

Use undo priority-flow-control poolID headroom to restore the default.

‌

NOTE:

This command is not supported on the two 1-Gbps SFP interfaces on the rear panel of an S9850-4C, S9850-32H, or S6850-56HF switch.

‌

Syntax

priority-flow-control poolID pool-number headroom headroom-number

undo priority-flow-control poolID pool-number headroom

Default

The maximum number of cell resources that can be used in a headroom storage space is 12288.

Views

System view

Predefined user roles

network-admin

Parameters

pool-number: Specifies a headroom storage space by its number in the range of 0 to 3.

headroom-number: Specifies the maximum number of cell resources, in the range of 1 to 131072 on the S6850&S9850 switch series and 1 to 19968 on the S6805 and S6825 switch series.

Examples

# Set the headroom buffer threshold to 1000 for headroom storage space 1.

<sysname> system-view

[Sysname] priority-flow-control poolID 1 headroom 1000

17-Intelligent Lossless Network Command Reference

priority-flow-control no-drop dot1p (Ethernet interface view)

priority-flow-control poolID headroom

Intelligent Terminal Products

Product Support Services

Technical Service Solutions

Resource Center

Policy

Online Help

Become a Partner

Partner Policy & Program

Global Learning

Partner Sales Resources

Service Business

News & Events

Contact Us