Contents

Configuring data buffers· 1

About data buffers· 1

Data buffer types· 1

Cell resources and packet resources· 1

Fixed area and shared area· 1

Restrictions and guidelines: Data buffer configuration· 2

Enabling the Burst feature· 2

Configuring data buffer alarms· 3

About data buffer alarms· 3

Restrictions and guidelines for data buffer alarm configuration· 3

Configuring queue-level alarm thresholds for the ingress or egress buffer 3

Configuring queue-level alarm thresholds for the Headroom buffer 4

Configuring packet-drop alarms· 5

Displaying and maintaining data buffers· 5

Configuring TCB·· 1

About TCB· 1

Overview· 1

How TCB works· 1

Restrictions and guidelines: TCB configuration· 2

Enabling and configuring TCB· 2

Enabling and configuring TCB in system view· 2

Enabling and configuring TCB in interface view· 3

TCB configuration examples· 4

Example: Configuring TCB on an interface· 4

 

Configuring data buffers

About data buffers

Data buffer types

Data buffers temporarily store packets to avoid packet loss.

The following data buffers are available:

·     Ingress buffer—Stores incoming packets when the CPU is busy.

·     Egress buffer—Stores outgoing packets when network congestion occurs.

·     Headroom buffer—Stores packets when the ingress buffer or egress buffer is used up.

Figure 1 shows the structure of ingress and egress buffers.

Figure 1 Data buffer structure

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Cell resources and packet resources

A buffer uses the following types of resources:

·     Cell resources—Store packets. The buffer uses cell resources based on packet sizes. Suppose a cell resource provides 208 bytes. The buffer allocates one cell resource to a 128-byte packet and two cell resources to a 300-byte packet.

·     Packet resources—Store packet pointers. A packet pointer indicates where the packet is located in cell resources. The buffer uses one packet resource for each incoming or outgoing packet. Packet resources are not supported in the current software version.

Fixed area and shared area

Each type of resources has a fixed area and a shared area.

·     Fixed area—Partitioned into queues, each of which is equally divided by all the interfaces on a card, as shown in Figure 2. When congestion occurs or the CPU is busy, the following rules apply:

a.     An interface first uses the relevant queues of the fixed area to store packets.

b.     When a queue is full, the interface uses the corresponding queue of the shared area.

c.     When the queue in the shared area is also full, the interface discards subsequent packets.

The system allocates the fixed area among queues as specified by the user. Even if a queue is not full, other queues cannot preempt its space. Similarly, the share of a queue for an interface cannot be preempted by other interfaces even if it is not full.

·     Shared area—Partitioned into queues, each of which is not equally divided by the interfaces, as shown in Figure 2. The system determines the actual shared-area space for each queue according to user configuration and the number of packets actually received and sent. If a queue is not full, other queues can preempt its space.

The system puts packets received or sent on all interfaces into a queue in the order they arrive. When the queue is full, subsequent packets are dropped.

Figure 2 Fixed area and shared area

 

Restrictions and guidelines: Data buffer configuration

Inappropriate data buffer changes can cause system problems. Before enabling the Burst feature, make sure you understand its impact on your device. As a best practice, use the burst-mode enable command only if the system requires large buffer spaces.

Enabling the Burst feature

The Burst feature enables the device to automatically allocate buffer resources. It is well suited to the following scenarios:

·     Broadcast or multicast traffic is intensive, resulting in bursts of traffic.

·     Traffic comes in and goes out in one of the following ways:

¡     Enters a device from a high-speed interface and goes out of a low-speed interface.

¡     Enters from multiple same-rate interfaces at the same time and goes out of an interface with the same rate.

Before enabling the Burst feature, make sure all interfaces on cards that support this feature use SP queuing.

A card enabled with the Burst feature supports only WRR queuing. To use other queuing methods, first disable the Burst feature.

To enable the Burst feature:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable the Burst feature.	In standalone mode: burst-mode enable slot slot-number In IRF mode: burst-mode enable chassis chassis-number slot slot-number	By default, the Burst feature is disabled.

 

Configuring data buffer alarms

About data buffer alarms

This feature works with a network management system (such as IMC). Data buffer alarms include threshold-crossing alarms and packet drop alarms. The device reports these alarms to the network management system for displaying the data buffer usage. Threshold-crossing alarms are generated when the usage of a data buffer type exceeds the specified alarm thresholds.

The alarm thresholds are configured on a per-queue basis.

Restrictions and guidelines for data buffer alarm configuration

Only the following modules support this feature:

·     FD interface modules.

·     FE interface modules.

·     SG interface modules: LSUM1CGS20XSH0, LSUM1CGS32XSH0, LSUM1CGS8QSSH0, LSUM1CGS8SH0, LSUM1TGS48RSH0, LSUM1TGS48SH0, LSUM1YGS24CSSH0, LSUM1YGS48XSH0.

·     SH interface modules: LSUM1CQGS12XSG0, LSUM1TGS48XSG0, LSUM2CQGS12SG0, LSUM2QGS12SG0, LSUM2QGS24RSG0, LSUM2TGS48SH0, LSUM2TGS32QSSG0, LSUM2TGS48SG0.

If an interface is not configured with generic flow control or PFC in the inbound direction, alarms for Headroom buffer will not occur. For information about generic flow control or PFC, see Ethernet interface configuration in Interface Configuration Guide.

If you have configured the burst-mode enable, flow-control, or priority-flow-control command before configuring alarm thresholds, you must reconfigure the alarm thresholds. For more information about the flow-control and priority-flow-control commands, see Ethernet interface commands in Interface Command Reference.

Configuring queue-level alarm thresholds for the ingress or egress buffer

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Configure the alarm thresholds.	Configure the global alarm threshold for a queue. In standalone mode: buffer { egress | ingress } usage threshold slot slot-number queue queue-id ratio ratio In IRF mode: buffer { egress | ingress } usage threshold chassis chassis-number slot slot-number queue queue-id ratio ratio	The default setting is 100%.
	Execute the following commands in sequence to configure the alarm threshold for a queue on an interface: ·     interface interface-type interface-number ·     buffer { egress | ingress } usage threshold queue queue-id ratio ratio	By default, an interface uses the global alarm threshold. In this case, the display this [ all ] command does not display the global alarm threshold that the interface uses when it is executed in interface view. For this command to display the alarm threshold that the interface uses, configure the alarm threshold as the default value and or a non-default value in interface view.
3.     Enable threshold-crossing alarms.	buffer threshold alarm { egress | ingress } enable	By default, threshold-crossing alarms are disabled.
4.     (Optional.) Set the interval for sending threshold-crossing alarms.	buffer threshold alarm { egress | ingress } interval interval	The default setting is 5 seconds.

 

Configuring queue-level alarm thresholds for the Headroom buffer

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Configure the alarm thresholds.	Configure the global per-queue alarm threshold. In standalone mode: buffer usage threshold headroom slot slot-number ratio ratio In IRF mode: buffer usage threshold headroom chassis chassis-number slot slot-number ratio ratio	The default setting is 100%.
	Execute the following commands in sequence to configure the alarm threshold for a queue on an interface: ·     interface interface-type interface-number ·     buffer usage threshold headroom queue queue-id ratio ratio	By default, an interface uses the global per-queue alarm threshold. In this case, the display this [ all ] command does not display the global per-queue alarm threshold that the interface uses when it is executed in interface view. For this command to display the per-queue alarm threshold that the interface uses, configure the per-queue alarm threshold as the default value and or a non-default value in interface view.
3.     Enable threshold-crossing alarms.	buffer threshold alarm headroom enable	By default, threshold-crossing alarms are disabled.
4.     (Optional.) Set the interval for sending threshold-crossing alarms.	buffer threshold alarm headroom interval interval	The default setting is 5 seconds.

 

Configuring packet-drop alarms

This feature allows the device to periodically send packet-drop information to the NMS.

This feature does not take effect on the Headroom buffer.

To configure packet-drop alarms:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable packet-drop alarms.	buffer packet-drop alarm enable	By default, packet-drop alarms are disabled.
3.     (Optional.) Set the interval for sending packet-drop alarms.	buffer packet-drop alarm interval interval	The default setting is 5 seconds.

 

Displaying and maintaining data buffers

Execute display commands in any view.

 

Task	Command
(In standalone mode). Display data buffer usage.	display buffer usage [ slot slot-number ]
(In IRF mode.) Display data buffer usage.	display buffer usage [ chassis chassis-number slot slot-number ]

 

 

Configuring TCB

About TCB

Overview

The Transient Capture Buffer (TCB) feature monitors packet drop events on a set of memory management unit (MMU) resources. When a packet is dropped on a queue, the system collects drop time, drop reason, packet metadata, and other information and reports them to an NMS through gRPC.

An MMU manages the allocation of the ingress buffer and egress buffer and flexibly schedules queues to deal with traffic bursts.

Figure 3 MMU

 

How TCB works

The TCB state machine works as follows:

1.     The state machine enters the idle state when TCB is enabled.

2.     When the queue length is greater than start-threshold-value, the state machine transitions from the idle state to the pre-trigger state. The system captures packets by using the pre-sample-rate.

3.     When packet drops occur on the queue, the state machine transitions from the pre-trigger to the post-trigger state.

4.     When the queue length is smaller than stop-threshold-value, the state machine transitions from the post-trigger to the idle state. The system stops capturing packets.

5.     When the queue length is greater than start-threshold-value, step 2 is repeated.

6.     When the number of captured packets reaches the frozen-number or the capture timer expires, the state machine transitions from the post-trigger to the frozen state.

7.     The state machine analyzes the drop reason and dropped packet characteristics and sends the analysis results to the gRPC module, which reports them to an NMS.

8.     The state machine transitions from the frozen to the idle state.

Figure 4 TCB state machine

 

Restrictions and guidelines: TCB configuration

You can configure TCB in system view or interface view, but not in both views at the same time. For example, if you have configured TCB in system view, to configure TCB in interface view, you must first delete the TCB configuration in system view.

The TCB configuration in system view takes effect on all TCB-capable interfaces. The TCB configuration in interface view takes effect only on the specified interface.

The gRPC sampling paths for TCB are tcb/tcbpacketinfoevent and tcb/tcbrawpacketinfoevent. For more information about gRPC, see "Configuring gRPC."

Only SH-series interface modules support TCB.

TCB cannot identify tunnel-encapsulated TCP or UDP packets if local analysis is enabled or an ACL is referenced.

In the inbound direction of interfaces, TCB takes effect only on traffic of the interfaces in the same port group. To identify port group information, execute the debug port mapping command for the specified slot in probe view. Interfaces with the same Unit value belong to the same interface group.

Enabling and configuring TCB

Enabling and configuring TCB in system view

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable the Burst feature.	In standalone mode: buffer transient-capture global [ slot slot-number [ cpu cpu-number ] ] { egress | ingress } enable [ no-local-analysis ] [ acl { ipv4-acl-number | name ipv4-acl-name } ] [ start-threshold start-threshold-value stop-threshold stop-threshold-value ] [ frozen-number frozen-number frozen-timer timer-value ] [ pre-sample-rate pre-sample-rate post-sample-rate post-sample-rate ] [ poll-frequency frequency-value ] In IRF mode: buffer transient-capture global [ chassis chassis-number slot slot-number [ cpu cpu-number ] ] { egress | ingress } enable [ no-local-analysis ] [ acl { ipv4-acl-number | name ipv4-acl-name } ] [ start-threshold start-threshold-value stop-threshold stop-threshold-value ] [ frozen-number frozen-number frozen-timer timer-value ] [ pre-sample-rate pre-sample-rate post-sample-rate post-sample-rate ] [ poll-frequency frequency-value ]	By default, TCB is disabled.

 

Enabling and configuring TCB in interface view

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enter interface view.	interface interface-type interface-number	N/A
3.     Enable the Burst feature.	buffer transient-capture { egress [ queue queue-id ] | ingress } enable [ no-local-analysis ] [ acl { ipv4-acl-number | name ipv4-acl-name } ] [ start-threshold start-threshold-value stop-threshold stop-threshold-value ] [ frozen-number frozen-number frozen-timer timer-value ] [ pre-sample-rate pre-sample-rate post-sample-rate post-sample-rate ] [ poll-frequency frequency-value ]	By default, TCB is disabled.

 

TCB configuration examples

Example: Configuring TCB on an interface

Network configuration

As shown in Figure 5, configure TCB and gRPC on the device to monitor packet drops and report packet drop information to the collector through gRPC.

Figure 5 Network diagram

 

Procedure

1.     Assign IP addresses to the device and the collector and configure routes. Make sure the network connections are available. (Details not shown.)

2.     Configure TCB:

# Create an IPv4 advanced ACL numbered 3001, and configure a rule to match packets with source IP address 192.168.5.2.

<Device> system-view

[Device] acl advanced 3001

[Device-acl-ipv4-adv-3001] rule permit ip source 192.168.5.2 0

[Device-acl-ipv4-adv-3001] quit

# Configure TCB on Ten-GigabitEthernet 1/0/1.

[Device] interface ten-gigabitethernet 1/0/1

[Device-Ten-GigabitEthernet1/0/1] buffer transient-capture egress queue 1 enable no-local-analysis acl 3001 start-threshold 10000 stop-threshold 5000 frozen-number 1000 frozen-timer 500 pre-sample-rate 10 post-sample-rate 10 poll-frequency 600

[Device-Ten-GigabitEthernet1/0/1] quit

3.     Configure gRPC:

# Enable the gRPC service.

[Device] grpc enable

# Create a sensor group named test, and add sensor paths tcb/tcbpacketinfoevent and tcb/tcbrawpacketinfoevent.

[Device] telemetry

[Device-telemetry] sensor-group test

[Device-telemetry-sensor-group-test] sensor path tcb/tcbpacketinfoevent

[Device-telemetry-sensor-group-test] sensor path tcb/tcbrawpacketinfoevent

[Device-telemetry-sensor-group-test] quit

# Create a destination group named collector1. Specify a collector that uses IPv4 address 192.168.2.1 and port number 50050.

[Device-telemetry] destination-group collector1

[Device-telemetry-destination-group-collector1] ipv4-address 192.168.2.1 port 50050

[Device-telemetry-destination-group-collector1] quit

# Configure a subscription named A to bind sensor group test with destination group collector1. Set the sampling interval to 10 seconds.

[Device-telemetry] subscription A

[Device-telemetry-subscription-A] sensor-group test sample-interval 10

[Device-telemetry-subscription-A] destination-group collector1

[Device-telemetry-subscription-A] quit

[Device-telemetry] quit

Verifying the configuration

# Verify that the collector receives packet drop information when packet drops occur on a queue enabled with TCB. (Details not shown.)