HPE FlexFabric 5940 Switch Series
Intelligent Lossless Network Configuration Guide
Software version: Release 671x and later
Document version: 6W100-20230822
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Contents
Configuring PFC ···························································································· 1
About PFC·························································································································································· 1
Restrictions and guidelines ································································································································ 1
Configuring PFC on interfaces ··························································································································· 2
Configuring PFC on an Ethernet interface ································································································· 2
Setting PFC thresholds ······························································································································ 2
Configuring PFC deadlock detection·················································································································· 4
Verifying and maintaining PFC··························································································································· 5
Document conventions and icons ·································································· 7
Conventions ······················································································································································· 7
Network topology icons ······································································································································ 8
Support and other resources ········································································· 9
Accessing Hewlett Packard Enterprise Support································································································· 9
Accessing updates ············································································································································· 9
Websites ·················································································································································· 10
Customer self repair ································································································································· 10
Remote support ········································································································································ 10
Documentation feedback ························································································································· 10
Index ············································································································ 12
1
Configuring PFC
About PFC
Priority-based flow control (PFC) provides a finer flow control mechanism to implement lossless
packet transmission on Ethernet.
PFC performs flow control for packets based on the 802.1p priorities carried in packets. As shown in
Figure 1, PFC establishes eight virtual channels over an Ethernet link, each corresponding to an
802.1p priority. Any virtual channel can be paused or restarted independent of the other channels.
This mechanism allows multiple types of traffic to coexist on and share an Ethernet link.
Figure 1 How PFC works
When congestion occurs on the local end, the device determines how to process received packets
based on the 802.1p priorities carried in packets as follows:
•
If PFC is enabled for the 802.1p priority carried in a packet, the local end accepts the packet
and sends PFC pause frames to notify the remote end to stop sending packets carrying the
802.1p priority. The remote end stops sending packets carrying the 802.1p priority after
receiving the PFC pause frames. This process is repeated until congestion is eliminated.
•
If PFC is not enabled for the 802.1p priority carried in a packet, the local end drops the packet.
Restrictions and guidelines
You can configure PFC in system view or Ethernet interface view. When you configure PFC in
system view and Ethernet interface view multiple times, the most recent configuration takes effect.
If you do not enable PFC on an interface, the interface can receive but cannot process PFC pause
frames. To make PFC take effect, you must enable PFC on both ends.
To avoid packet loss, apply the same PFC configuration to all interfaces that the packets pass
through.
In an IRF network, follow these restrictions and guidelines:
•
For IRF and other protocols to operate correctly, as a best practice, do not enable PFC for
802.1p priority 0, 6, or 7.
•
To perform PFC on an IRF port, configure PFC on the IRF port and the IRF physical ports that
are bound to the IRF port.
0
3
1
4
5
6
2
7
0
3
1
4
5
6
2
7
STOP PAUSE
Device A Device B
Ethernet Link
Transmission Queue Receiving Queue
2
For information about IRF, see IRF configuration Guide.
For PFC to take effect in an overlay network, execute the qos trust tunnel-dot1p command.
For information about the overlay network, see VXLAN Configuration Guide. For information about
the qos trust tunnel-dot1p command, see ACL and QoS Command Reference.
Configuring PFC on interfaces
Configuring PFC on an Ethernet interface
Restrictions and guidelines
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.
Procedure
1. Enter system view.
system-view
2. Enable PFC on all Ethernet interfaces.
priority-flow-control { auto | enable }
By default, PFC is disabled on all Ethernet interfaces.
3. Enable PFC for 802.1p priorities on all Ethernet interfaces.
priority-flow-control no-drop dot1p dot1p-list
By default, PFC is disabled for all 802.1p priorities on all Ethernet interfaces.
4. Enter Ethernet interface view.
interface interface-type interface-number
5. Enable PFC on the Ethernet interface.
priority-flow-control { auto | enable }
By default, PFC is disabled.
6. Enable PFC for 802.1p priorities.
priority-flow-control no-drop dot1p dot1p-list
By default, PFC is disabled for all 802.1p priorities.
Setting PFC thresholds
About PFC thresholds
The storage spaces for an interface include the following types:
•
Headroom storage space.
•
Shared storage space.
•
Guaranteed storage space.
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 number of cell resources that can be used by packets
with a specific 802.1p priority value in a headroom storage space. An interface drops received
packets once this threshold is reached.
•
Back pressure frame triggering threshold—Maximum number of cell resources that can be
used by packets with a specific 802.1p priority value in a shared storage space. PFC is
3
triggered once this threshold is reached. The back pressure frame triggering threshold includes
the following types:
Dynamic back pressure frame triggering threshold—Maximum cell resources set in
percentage.
Static back pressure frame triggering threshold—Maximum cell resources set in an
absolute value.
•
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 a specific
802.1p priority value in a guaranteed storage space.
Restrictions and guidelines
WARNING!
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.
You must enable PFC for 802.1p priorities before setting the PFC thresholds.
If you cancel PFC threshold settings on an interface, the PFC thresholds are restored to the state
when only the priority-flow-control no-drop dot1p command is executed.
If you execute any of the following commands when packets are being forwarded, traffic will be
interrupted and packets will be lost transiently:
•
priority-flow-control headroom
•
priority-flow-control dot1p ingress-buffer dynamic
•
priority-flow-control dot1p ingress-threshold-offset
•
priority-flow-control dot1p reserved-buffer
This feature does not support preprovisioning. For more information about preprovisioning, see
Fundamentals Configuration Guide.
Procedure
1. Enter system view.
system-view
2. Set the maximum number of cell resources in a headroom storage space.
priority-flow-control headroom headroom-number
By default, the maximum number of cell resources in a headroom storage space is 12288.
3. Enter Ethernet interface view.
interface interface-type interface-number
4. Enable PFC for the specified 802.1p priority values on the Ethernet interface.
priority-flow-control no-drop dot1p dot1p
By default, PFC is disabled for all 802.1p priority values on an interface.
5. Set the headroom buffer threshold.
priority-flow-control dot1p dot1p headroom headroom-number
By default, the headroom buffer threshold is 4000 for 40-GE interfaces and 1000 for 10-GE
interfaces.
6. Set the back pressure frame triggering threshold.
Set the dynamic back pressure frame triggering threshold.
4
priority-flow-control dot1p dot1p ingress-buffer dynamic ratio
By default, no dynamic back pressure frame triggering thresholds are set.
Set the static back pressure frame triggering threshold.
priority-flow-control dot1p dot1p ingress-buffer static threshold
By default, the static back pressure frame triggering threshold is 1000 for 40-GE interfaces
and 250 for 10-GE interfaces.
7. Set the offset between the back pressure frame stopping threshold and triggering threshold.
priority-flow-control dot1p dot1p ingress-threshold-offset
offset-number
By default, the offset between the back pressure frame stopping threshold and triggering
threshold is 204 for 40-GE interfaces and 51 for 10-GE interfaces.
8. Set the PFC reserved threshold.
priority-flow-control dot1p dot1p reserved-buffer reserved-number
By default, the PFC reserved threshold is 15.
Configuring PFC deadlock detection
About this task
When packets carrying the specified 802.1p priority are transmitted in a loop, packets in the data
buffer cannot be forwarded and PFC frames are repeatedly transmitted between devices. As a result,
the cell resources in the buffer for device interfaces always cannot be released. In this case, the
device enters the PFC deadlock state.
This feature periodically detects whether the device is in the PFC deadlock state. If an interface is
always in the PFC XOFF state within the PFC deadlock detection interval, the device enters the PFC
deadlock state. If 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. During the delay timer period, the device disables PFC and PFC deadlock detection on the
interface, so that packets can be forwarded properly.
After the PFC deadlock state is released, the PFC deadlock detection feature can be recovered on
the interface in automatic or manual mode. 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 eliminated and the device enters 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.
Restrictions and guidelines
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.
Prerequisites
Before you configure PFC deadlock detection on an Ethernet interface, complete the following tasks:
•
Enable PFC in auto mode or forcibly on the Ethernet interface.
•
Enable PFC for 802.1p priorities on the Ethernet interface.
Procedure
1. Enter system view.
5
system-view
2. Set the precision for the PFC deadlock detection timer.
priority-flow-control deadlock precision { high | normal | low }
By default, the PFC deadlock detection timer uses normal precision.
3. Set the PFC deadlock detection interval for the specified CoS value.
priority-flow-control deadlock cos cos-value interval interval
By default, the PFC deadlock detection interval is not set.
4. Configure the delay timer for PFC deadlock detection automatic recovery.
priority-flow-control deadlock auto-recover cos cos-value delay
delay-time
By default, the delay timer for PFC deadlock detection automatic recovery is not configured.
5. Configure the action to take on packets during the delay timer period for PFC deadlock
automatic recovery.
priority-flow-control deadlock auto-recover action { discard |
forwarding }
By default, the device forwards received data packets during the delay timer period for PFC
deadlock detection automatic recovery.
6. Configure the upper threshold for PFC deadlock times during the specified period.
priority-flow-control deadlock threshold cos cos-value period period
count count [ error-down ]
By default, the upper threshold for PFC deadlock times during the specified period is not
configured.
7. Enter Ethernet interface view.
interface interface-type interface-number
8. Configure the action to take on the interface when the PFC deadlock times within the specified
detection period reaches the upper threshold.
priority-flow-control deadlock threshold action { error-down |
turn-off }
By default, the action specified by the priority-flow-control deadlock threshold
command in system view takes effect.
9. Set the recovery mode for PFC deadlock detection on the Ethernet interface.
priority-flow-control deadlock recover-mode { auto | manual }
By default, PFC deadlock detection recovers in automatic mode.
10. Enable PFC deadlock detection on the Ethernet interface.
priority-flow-control deadlock enable
By default, PFC deadlock detection is disabled.
11. (Optional.) Recover PFC deadlock detection on the Ethernet interface.
priority-flow-control deadlock recover
You can use only this command to recover PFC deadlock detection if you set the manual
recovery mode for PFC deadlock detection on the Ethernet interface.
Verifying and maintaining PFC
Execute display commands in any view.
6
Task
Command
Display the PFC information of
interfaces. display priority-flow-control interface
[ interface-type [ interface-number ] ]
7
Document conventions and icons
Conventions
This section describes the conventions used in the documentation.
Command conventions
Convention
Description
Boldface Bold text represents commands and keywords that you enter literally as shown.
Italic Italic text represents arguments that you replace with actual values.
[ ] Square brackets enclose syntax choices (keywords or arguments) that are optional.
{ x | y | ... }
Braces enclose a set of required syntax choices separated by vertical bars, from which
you select one.
[ x | y | ... ]
Square brackets enclose a set of optional syntax choices separated by vertical bars,
from which you select one or none.
{ x | y | ... } *
Asterisk marked braces enclose a set of required syntax choices separated by vertical
bars, from which you select at least one.
[ x | y | ... ] *
Asterisk marked square brackets enclose optional syntax choices separated by vertical
bars, from which you select one choice, multiple choices, or none.
&<1-n> The argument or keyword and argument combination before the ampersand (&) sign
can be entered 1 to n times.
# A line that starts with a pound (#) sign is comments.
GUI conventions
Convention
Description
Boldface Window names, button names, field names, and menu items are in Boldface. For
example, the New User window opens; click OK.
> Multi-level menus are separated by angle brackets. For example, File > Create >
Folder.
Symbols
Convention
Description
WARNING! An alert that calls attention to important information that if not understood or followed
can result in personal injury.
CAUTION:
An alert that calls attention to important information that if not understood or followed
can result in data loss, data corruption, or damage to hardware or software.
IMPORTANT:
An alert that calls attention to essential information.
NOTE:
An alert that contains additional or supplementary information.
TIP:
An alert that provides helpful information.
8
Network topology icons
Convention
Description
Represents a generic network device, such as a router, switch, or firewall.
Represents a routing-capable device, such as a router or Layer 3 switch.
Represents a generic switch, such as a Layer 2 or Layer 3 switch, or a router that
supports Layer 2 forwarding and other Layer 2 features.
Represents an access controller, a unified wired-WLAN module, or the access
controller engine on a unified wired-WLAN switch.
Represents an access point.
Represents a wireless terminator unit.
Represents a wireless terminator.
Represents a mesh access point.
Represents omnidirectional signals.
Represents directional signals.
Represents a security product, such as a firewall, UTM, multiservice security
gateway, or load balancing device.
Represents a security module, such as a firewall, load balancing, NetStream, SSL
VPN, IPS, or ACG module.
Examples provided in this document
Examples in this document might use devices that differ from your device in hardware model,
configuration, or software version. It is normal that the port numbers, sample output, screenshots,
and other information in the examples differ from what you have on your device.
T
T
T
T
9
Support and other resources
Accessing Hewlett Packard Enterprise Support
•
For live assistance, go to the Contact Hewlett Packard Enterprise Worldwide website:
www.hpe.com/assistance
•
To access documentation and support services, go to the Hewlett Packard Enterprise Support
Center website:
www.hpe.com/support/hpesc
Information to collect
•
Technical support registration number (if applicable)
•
Product name, model or version, and serial number
•
Operating system name and version
•
Firmware version
•
Error messages
•
Product-specific reports and logs
•
Add-on products or components
•
Third-party products or components
Accessing updates
•
Some software products provide a mechanism for accessing software updates through the
product interface. Review your product documentation to identify the recommended software
update method.
•
To download product updates, go to either of the following:
Hewlett Packard Enterprise Support Center Get connected with updates page:
www.hpe.com/support/e-updates
Software Depot website:
www.hpe.com/support/softwaredepot
•
To view and update your entitlements, and to link your contracts, Care Packs, and warranties
with your profile, go to the Hewlett Packard Enterprise Support Center More Information on
Access to Support Materials page:
www.hpe.com/support/AccessToSupportMaterials
IMPORTANT:
Access to some updates might require product entitlement when accessed through the Hewlett
Packard Enterprise Support Center. You must have an HP Passport set up with relevant
entitlements.
10
Websites
Website
Link
Networking websites
Hewlett Packard Enterprise Information Library for
Networking www.hpe.com/networking/resourcefinder
Hewlett Packard Enterprise Networking website www.hpe.com/info/networking
Hewlett Packard Enterprise My Networking website www.hpe.com/networking/support
Hewlett Packard Enterprise My Networking Portal www.hpe.com/networking/mynetworking
Hewlett Packard Enterprise Networking Warranty www.hpe.com/networking/warranty
General websites
Hewlett Packard Enterprise Information Library www.hpe.com/info/enterprise/docs
Hewlett Packard Enterprise Support Center www.hpe.com/support/hpesc
Hewlett Packard Enterprise Support Services Central ssc.hpe.com/portal/site/ssc/
Contact Hewlett Packard Enterprise Worldwide www.hpe.com/assistance
Subscription Service/Support Alerts www.hpe.com/support/e-updates
Software Depot www.hpe.com/support/softwaredepot
Customer Self Repair (not applicable to all devices) www.hpe.com/support/selfrepair
Insight Remote Support (not applicable to all devices) www.hpe.com/info/insightremotesupport/docs
Customer self repair
Hewlett Packard Enterprise customer self repair (CSR) programs allow you to repair your product. If
a CSR part needs to be replaced, it will be shipped directly to you so that you can install it at your
convenience. Some parts do not qualify for CSR. Your Hewlett Packard Enterprise authorized
service provider will determine whether a repair can be accomplished by CSR.
For more information about CSR, contact your local service provider or go to the CSR website:
www.hpe.com/support/selfrepair
Remote support
Remote support is available with supported devices as part of your warranty, Care Pack Service, or
contractual support agreement. It provides intelligent event diagnosis, and automatic, secure
submission of hardware event notifications to Hewlett Packard Enterprise, which will initiate a fast
and accurate resolution based on your product’s service level. Hewlett Packard Enterprise strongly
recommends that you register your device for remote support.
For more information and device support details, go to the following website:
www.hpe.com/info/insightremotesupport/docs
Documentation feedback
Hewlett Packard Enterprise is committed to providing documentation that meets your needs. To help
us improve the documentation, send any errors, suggestions, or comments to Documentation
Feedback (docsfeedback@hpe.com). When submitting your feedback, include the document title,
11
part number, edition, and publication date located on the front cover of the document. For online help
content, include the product name, product version, help edition, and publication date located on the
legal notices page.
12
Index
C
configuring
Ethernet interface PFC, 2
Ethernet interface PFC deadlock detection, 4
PFC, 1
D
detection
PFC deadlock detection, 4
E
Ethernet interface
PFC configuration, 2
PFC deadlock detection, 4
F
flow control
Ethernet interface PFC, 2
PFC, 1
I
interface
PFC configuration, 1
M
maintaining
PFC, 5
N
network
Ethernet interface PFC deadlock detection, 4
PFC, 1
P
PFC
Ethernet interface PFC deadlock detection, 4
maintain, 5
verify, 5
PFC (Ethernet interface), 2
priority
priority-based flow control. Use PFC
procedure
configuring Ethernet interface PFC, 2
configuring PFC, 1
configuring PFC deadlock detection, 4
maintaining PFC, 5
verifying PFC, 5
R
restrictions and guidelines
PFC configuration, 1
V
verifying
PFC, 5
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