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

Interface AdminMode OperMode Dot1pList Prio Recv

Send Inpps Outpps

--------------------------------------------------------------------------------

-------------------

HGE1/0/1 Enabled Enabled 0 5

5 3 3

Table 1 Command output

Field	Description
Interface	Abbreviated name of the interface.
AdminMode	Administrative PFC status: · Disabled—PFC is disabled for the interface. · Auto—The interface is configured to autonegotiate the PFC status with the remote end. · Enabled—PFC is enabled for the interface.
OperMode	Operative PFC status: · Disabled—PFC is disabled. · Enabled—PFC is enabled.
Dot1pList	802.1p priorities that are enabled with PFC. 802.1p priority values 0 through 7 are available.
Prio	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.
Send	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.

‌

NOTE:

This command is supported only on the S9855 switch series.

‌

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 the slot number of the device, which is fixed at 1.

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

HGE1/0/1 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.

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 HundredGigE 1/0/1.

<Sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] 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.

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.

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 enters the PFC deadlock state, you can use this command to configure the device to drop or forward received data packets during the delay timer period for PFC deadlock detection automatic recovery.

If you specify the forwarding keyword, the following rules apply:

· If the priority-flow-control no-drop dot1p command is executed, packets with the specified 802.1p priority are rate-limited when congestion occurs.

· If the priority-flow-control no-drop dot1p command is not executed, packets are not rate-limited.

If you specify the discard keyword, the following rules apply:

· If the priority-flow-control no-drop dot1p command is executed, packets with all 802.1p priorities are rate-limited when congestion occurs.

· If the priority-flow-control no-drop dot1p command is not executed, packets are not rate-limited.

During the PFC deadlock recovery process, you cannot execute this command to modify the action to take on packets.

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.

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-time: Specifies the delay timer for PFC deadlock detection automatic recovery. The value range for the delay timer is 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 determined by this command and the PFC deadlock detection timer precision.

This command takes effect only in automatic recovery mode.

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.

Syntax

priority-flow-control deadlock cos cos-value interval interval

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.

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 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.

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.

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.

Examples

# Enable PFC deadlock detection on HundredGigE 1/0/1.

<Sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] 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.

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.

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-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.

Syntax

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

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.

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.

Examples

# Set the manual recovery mode for PFC deadlock detection on HundredGigE 1/0/1.

<Sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] priority-flow-control deadlock recover-mode auto

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.

Syntax

priority-flow-control deadlock threshold cos cos-value period period count count

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 seconds. The value range for this parameter is 1 to 60.

count count: Specifies the upper threshold for PFC deadlock times within the specified period. The value range for this parameter is 1 to 500.

Usage guidelines

With this command configured, when the PFC deadlock times within the specified period exceed the upper threshold on an interface, the device disables PFC for the corresponding 802.1p priority on the interface. To recover the PFC feature on the interface in this case, execute the undo priority-flow-control deadlock threshold command.

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.

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 no-drop dot1p

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.

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. The value range is 0 to 257862.

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 and use the priority-flow-control enable command to enable PFC on the specified interface.

If you execute this command or the priority-flow-control no-drop dot1p (Ethernet interface view) command multiple times for the same 802.1p priority, the headroom-number argument in the most recent command 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.

Examples

# Set the headroom buffer threshold to 1000 for 802.1p priority 1.

<sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] priority-flow-control dot1p 1 headroom 1000

Related commands

priority-flow-control (Ethernet interface view)

priority-flow-control (System view)

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.

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 0 to 100.

Usage guidelines

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

Examples

# Set the dynamic back pressure frame triggering threshold to 30 for 802.1p priority 1.

<sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] priority-flow-control dot1p 1 ingress-buffer dynamic 30

Related commands

priority-flow-control (Ethernet interface view)

priority-flow-control (System view)

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.

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. The value range is 48 to 257862.

Usage guidelines

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.

<sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] priority-flow-control dot1p 1 ingress-buffer static 1000

Related commands

priority-flow-control (Ethernet interface view)

priority-flow-control (System view)

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.

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. The value range is 0 to 257862.

Usage guidelines

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

Examples

# Set the offset between the back pressure frame stopping threshold and triggering threshold to 1000 for 802.1p priority 1.

<sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] priority-flow-control dot1p 1 ingress-threshold-offset 1000

Related commands

priority-flow-control (Ethernet interface view)

priority-flow-control (System view)

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.

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. The value range is 0 to 257862.

Usage guidelines

If you execute this command or the priority-flow-control no-drop dot1p (Ethernet interface view) command multiple times for the same 802.1p priority, the reserved-number argument in the most recent command takes effect.

Examples

# Set the PFC reserved threshold to 1000 for 802.1p priority 1.

<sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] priority-flow-control dot1p 1 reserved-buffer 1000

Related commands

priority-flow-control (Ethernet interface view)

priority-flow-control (System view)

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.

You cannot assign an interface with this feature enabled to an aggregation group or enable this feature on an aggregation group member port.

For the S9855 series switches, you can configure up to two DSCP mappings with different original DSCP values on an interface.

For the S9825 series switches, the following restrictions apply:

· Each interface can be configured with only one DSCP mapping.

· The device supports a maximum of 63 groups of DSCP mappings. When different interfaces have the same source DSCP values, Dot1p priorities, and mapped DSCP values, they are considered as one group. Also, when equivalent routes are configured, the outgoing ports must belong to the same group.

· Enabling deadlock prevention will reduce routing specifications, which might lead to abnormal traffic forwarding. Deleting the deadlock prevention configuration can restore normal function.

Examples

# On HundredGigE 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 hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] 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.

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 HundredGigE 1/0/1.

<Sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] 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.

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 HundredGigE 1/0/1.

<Sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] 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 and configure PFC thresholds for 802.1p priorities on an Ethernet interface.

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

Syntax

priority-flow-control no-drop dot1p dot1p-list [ pause-threshold { threshold-value | ratio threshold-ratio } [ headroom headroom-value | pause-threshold-offset offset-value | reserved-buffer reserved-value ] * ]

undo priority-flow-control no-drop dot1p [ dot1p dot1p-list ]

Default

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

Views

Ethernet interface view

Predefined user roles

network-admin

Parameters

pause-threshold: Specifies the back pressure frame triggering threshold. If you do not specify this keyword, all PFC thresholds use their defaults.

threshold-value: Specifies the back pressure frame triggering threshold in absolute value in the range of 48 to 257862.

ratio threshold-ratio: Specifies the back pressure frame triggering threshold in percentage in the range of 1 to 100.

headroom headroom-value: Specifies the maximum number of cell resources that can be used in the headroom storage space for queues, in the range of 0 to 257862.

pause-threshold-offset offset-value: Specifies the offset between the back pressure frame stopping threshold and triggering threshold in the range of 0 to 1000.

reserved-buffer reserved-value: Specifies the PFC reserved threshold for queues, in the range of 0 to 257862.

Usage guidelines

CAUTION:

· After PFC for 802.1p priorities is enabled, each PFC threshold mentioned above uses a default value. As a practice, do not change the default value.

· The offset between the back pressure frame stopping threshold and triggering threshold cannot be greater than the back pressure frame triggering threshold.

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Setting PFC thresholds enables flexible control over PFC and can make good use of the storage spaces. The device supports the following PFC thresholds:

· Headroom buffer threshold—Maximum cell resources that can be used by packets with the specified 802.1p priority values in a headroom storage space. An interface drops received packets once this threshold is reached.

· Back pressure frame triggering threshold—Maximum cell resources that can be used by packets with the specified 802.1p priority values in a shared storage space. PFC is triggered once this threshold is reached. The back pressure frame triggering threshold can be configured in the following methods:

¡ Absolute value—Maximum cell resources set in absolute value (static back pressure frame triggering threshold).

¡ Percentage—Maximum cell resources set in percentage (dynamic back pressure frame triggering threshold).

· Offset between the back pressure frame stopping threshold and triggering threshold—When the number of cell resources used by packets with a specific 802.1p priority value decreases by this offset after PFC is triggered, PFC will be stopped.

· PFC reserved threshold—Number of cell resources reserved for packets with the specified 802.1p priority values in a guaranteed storage space.

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
100-GE	491	5	12	16
200-GE	750	5	12	16
400-GE	1000	5	12	16

The sum of the effective headroom buffer threshold for all ports cannot exceed the global headroom space.

On the S9825 Switch Series, if you configure inbound PFC thresholds on ports in different buffers, the configuration does not affect the traffic proportions of these ports in the outbound direction when the ports are congested.

During the PFC deadlock recovery process, you cannot execute the priority-flow-control no-drop dot1p command to configure PFC and PFC thresholds for the specified 802.1p priorities.

When default settings are used, the PFC function does not take effect for unknown unicast packets.

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

Examples

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

<Sysname> system-view

[Sysname] interface hundredgige 1/0/1

[Sysname-HundredGigE1/0/1] priority-flow-control auto

[Sysname-HundredGigE1/0/1] priority-flow-control no-drop dot1p 5

Related commands

display priority-flow-control

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.

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 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.

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 1 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 resources that can be used in the headroom storage space for a service pool.

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

Syntax

priority-flow-control poolid service-pool-id headroom headroom-number

undo priority-flow-control [ poolid service-pool-id ] headroom

Default

On the S9855 Switch Series, the maximum number of resources that can be used in the headroom storage space for a service pool is 3994.

On the S9825 Switch Series, the maximum number of resources that can be used in the headroom storage space for a service pool is 5000.

Views

System view

Predefined user roles

network-admin

Parameters

poolid service-pool-id: Specifies a service pool by its ID. The value is fixed at 0. If you do not specify this option in the undo form, this command applies to all service pools.

headroom-number: Specifies the maximum number of resources that can be used in the headroom storage space, in cells or bytes. The value range is 0 to 257862.

Usage guidelines

The headroom is a storage space on the forwarding chip of an interface. It contains smaller storage units called cells, which are used to buffer packets received on the interface. Use this command to specify the maximum number of cell resources (or bytes) that can be used in the specified service pool. When the number of used cell resources (or bytes) in the service pool reaches the configured value, the interface will drop received packets.

Typically, you do not need to execute this command, and use the default settings. If you need to execute this command, do that at the guidance of professional engineers.

The S9825 series switches support two Ingress Traffic Managers (ITMs), where ports belonging to the same ITM share the inbound buffer resources. On the S9825-64D or S9825-128B switch, ports numbered 1-32 share one ITM, and ports numbered 33-64 share another ITM. With global Headroom configured on the S9825 series switches, commands are distributed across all ITMs. For example, the priority-flow-control poolid 0 headroom 500 command configures 500 headrooms for each ITM, resulting in a total effective global headrooms of 1000.

When you configure the global headroom space, the shared cell resources in the buffer will be reduced. Total cell resources = Headroom + Shared + Reserved. Among these resources:

· The headroom resources are controlled by using the priority-flow-control poolid headroom command.

· The shared resources can be viewed by using the display buffer usage command.

· The reserved resources are controlled by using the priority-flow-control no-drop dot1p command.

Examples

# Set the maximum number of cell resources that can be used in the service pool 0 to 10000.

<Sysname> system-view

[Sysname] priority-flow-control poolid 0 headroom 10000

Related commands

priority-flow-control

display priority-flow-control

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

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

05-Layer 2—LAN Switching Command Reference

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

priority-flow-control poolid headroom

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