Table of Contents

Chapter 1 QoS Overview.. 1-1

1.1 Introduction. 1-1

1.2 Traditional Packet Delivery Service. 1-1

1.3 New Requirements Brought forth by New Services. 1-1

1.4 Occurrence and Influence of Congestion and the Countermeasures. 1-2

1.4.1 Occurrence of Congestion. 1-2

1.4.2 Influence of Congestion. 1-3

1.4.3 Countermeasures. 1-3

1.5 Major Traffic Management Techniques. 1-3

Chapter 2 Traffic Classification, TP, and TS Configuration. 2-1

2.1 Traffic Classification Overview. 2-1

2.1.1 Traffic Classification. 2-1

2.1.2 Priority. 2-1

2.2 TP and TS Overview. 2-3

2.3 Traffic Evaluation and the Token Bucket 2-3

2.3.1 Token bucket 2-3

2.3.2 Evaluating the traffic with the token bucket 2-4

2.3.3 Complicated evaluation. 2-4

2.3.4 TP. 2-4

2.3.5 TS. 2-5

2.4 Configure TP and TS. 2-6

2.4.1 Configuring TP. 2-6

2.4.2 Configuring TS. 2-7

2.5 Displaying TP&TS. 2-8

Chapter 3 QoS Policy Configuration. 3-1

3.1 Overview. 3-1

3.2 Configuring QoS Policy. 3-1

3.3 Introduction to QoS Policies. 3-2

3.4 Configuring a QoS Policy. 3-2

3.4.1 Configuration Prerequisites. 3-2

3.4.2 Defining a Class. 3-2

3.4.3 Defining a Traffic Behavior 3-5

3.4.4 Defining a Policy. 3-7

3.4.5 Applying a Policy. 3-8

3.5 Displaying QoS Policy. 3-9

Chapter 4 Congestion Management 4-1

4.1 Overview. 4-1

4.2 Congestion Management Policy. 4-1

4.3 Configuring an SP Queue. 4-2

4.3.1 Configuration Procedure. 4-3

4.3.2 Configuration Example. 4-3

4.4 Configuring a WRR Queue. 4-4

4.4.1 Configuration Procedure. 4-4

4.4.2 Configuration Example. 4-5

4.5 Configuring SP+WRR Queues. 4-5

4.5.1 Configuration Procedure. 4-6

4.5.2 Configuration Example. 4-6

Chapter 5 Priority Mapping. 5-1

5.1 Priority Mapping Overview. 5-1

5.2 Configuring a Priority Mapping Table. 5-3

5.2.1 Configuration Prerequisites. 5-3

5.2.2 Configuration Procedure. 5-3

5.2.3 Configuration Example. 5-4

5.3 Configuring the Port Priority. 5-5

5.3.1 Configuration Prerequisites. 5-5

5.3.2 Configuration Procedure. 5-5

5.3.3 Configuration Example. 5-5

5.4 Configuring Port Priority Trust Mode. 5-5

5.4.1 Configuration Prerequisites. 5-6

5.4.2 Configuration Procedure. 5-6

5.4.3 Configuration Example. 5-6

5.5 Displaying Priority Mapping. 5-7

Chapter 6 Congestion Avoidance. 6-1

6.1 Overview. 6-1

6.2 Configuring WRED. 6-2

6.2.1 Configuration Prerequisites. 6-2

6.2.2 Configuration Procedure. 6-2

6.2.3 Configuration Example. 6-3

6.3 Displaying WRED. 6-3

Chapter 7 Aggregation CAR Configuration. 7-1

7.1 Aggregation CAR Overview. 7-1

7.2 Applying Aggregation CAR on Ports. 7-1

7.2.1 Configuration Prerequisites. 7-1

7.2.2 Configuration Procedure. 7-1

7.2.3 Configuration Example. 7-2

7.3 Referencing Aggregation CAR in Traffic Behaviors. 7-2

7.3.1 Configuration Prerequisites. 7-2

7.3.2 Configuration Procedure. 7-3

7.3.3 Configuration Example. 7-3

7.4 Displaying the Statistics Information of Aggregation CAR. 7-3

Chapter 8 VLAN Policy Configuration. 8-1

8.1 Overview. 8-1

8.2 Applying VLAN Policy. 8-1

8.2.1 Configuration Prerequisites. 8-1

8.2.2 Configuration Procedure. 8-2

8.3 Displaying and Maintaining VLAN Policy. 8-2

8.4 VLAN Policy Configuration Example. 8-2

8.4.1 Network Requirements. 8-2

8.4.2 Configuration Procedure. 8-2

Chapter 9 Traffic Mirroring Configuration. 9-1

9.1 Overview. 9-1

9.2 Configuring Traffic Mirroring to a Port 9-1

9.3 Displaying Traffic Mirroring. 9-2

9.4 Traffic Mirroring Configuration Example. 9-2

9.4.1 Network Requirements. 9-2

9.4.2 Configuration Procedure. 9-3

 

Chapter 1  QoS Overview

1.1  Introduction

Quality of Service (QoS) is a concept generally existing in occasions where service supply-demand relations exist. QoS measures the ability to meet the service needs of customers. Generally, the evaluation is not to give precise grading. The purpose of the evaluation is to analyze the conditions where the services are good and the conditions where the services still need to be improved, so that specific improvements can be implemented.

In Internet, QoS measures the ability of the network to deliver packets. The evaluation on QoS can be based on different aspects because the network provides diversified services. Generally speaking, QoS is the evaluation on the service ability to support the critical indexes such as delay, delay jitter and packet loss rate in packet delivery.

1.2  Traditional Packet Delivery Service

The traditional IP network treats all the packets equally. The switch adopts the first in first out (FIFO) policy in packet processing and assigns resources necessary for packet forwarding according to the arrival time of the packet. All the packets share the network and router resources. The resources that the packet can get depend completely on the chance at packets arrival.

This service policy is called Best-Effort. The switch makes its best effort to deliver the packets to the destination but it cannot provide any guarantee for delay, delay jitter, packet loss rate, and reliability in packet delivery.

The traditional Best-Effort service policy is only applicable to services such as WWW, FTP, and E-mail, which are not sensitive to the bandwidth and the delay performance.

1.3  New Requirements Brought forth by New Services

With the fast development of computer networks, more and more networks are connected into Internet. Internet extends very quickly in scale, coverage and the number of users. More and more users use the Internet as a platform for data transmission and develop various applications on it.

Besides traditional applications such as WWW, E-mail, and FTP, Internet users also try to develop new services on Internet, such as tele-education, tele-medicine, video phones, video conferencing, and video on demand (VOD). Enterprise users also hope to connect their branch offices in different locations through the VPN technology to develop some transaction applications, such as to access to the database of the company or to manage remote switches through Telnet.

The new services have one thing in common: they all have special requirements for delivery performances such as bandwidth, delay, and delay jitter. For example, video conferencing and VOD require the guarantee of high bandwidth, low delay and low delay jitter. Some key services such as the transaction handling and the Telnet do not necessarily require high bandwidth but they are highly dependent on low delay and need to be processed preferentially in case of congestion.

The emergence of new services brings forward higher requirements for the service capability of the IP network. In the delivery process, users hope to get better services, such as dedicated bandwidth for users, reduced packet loss rate, management and avoidance of network congestion, control of network traffic, provision of packet priority, and so on, instead of just having packets delivered to the destination. To meet these requirements, the network service capability need to be further improved.

1.4  Occurrence and Influence of Congestion and the Countermeasures

QoS issues that traditional networks face are mainly caused by congestion. Congestion means reduced service rate and extra delay introduced because of relatively insufficient resource provisioned.

1.4.1  Occurrence of Congestion

Congestion is very common in a complicated environment of packet switching on Internet. The diagram below gives two examples:

Figure 1-1 Traffic congestion

1)         Packets enter a router over a high-speed link and are forwarded out over a low-speed link.

2)         Packets enter a router through multiple interfaces of the same rate at the same time and are forwarded out on an interface of the same rate.

If the traffic arrives at the wire speed, the traffic will encounter the bottleneck of resources and congestion occurs.

Besides bandwidth bottleneck, any insufficiency of resources for packet forwarding, such as insufficiency of assignable processor time, buffer size, and memory resources can cause congestion. In addition, congestion will also occur if the traffic that arrives within a certain period of time is improperly controlled and the traffic goes beyond the assignable network resources.

1.4.2  Influence of Congestion

Congestion may cause a series of negative influences:

l           Congestion increases delay and delay jitter in packet delivery.

l           Excessively high delay will cause retransmission of packets.

l           Congestion decreases the effective throughput of the network and the utilization of the network resources.

l           Aggravated congestion will consume a large amount of network resources (especially memory resources), and unreasonable resource assignment will even lead to system resource deadlock and cause the system breakdown.

It is obvious that congestion is the root of service performance declination because congestion makes traffic unable to get resources timely. However, congestion is common in a complicated environment where packet switching and multi-user services coexist. Therefore, congestion must be treated carefully.

1.4.3  Countermeasures

Increasing network bandwidth is a direct way to solve the problem of resource insufficiency, but it cannot solve all the problems that cause network congestion.

A more effective way to solve network congestion problems is to enhance the function of the network layer in traffic control and resource assignment, to provide differentiated services for different requirements, and to assign and utilize resources correctly. In the process of resource assignment and traffic control, the direct or indirect factors that may cause network congestion must be properly controlled so as to reduce the probability of congestion. When congestion occurs, the resource assignment should be balanced according to the features and requirements of all the services to minimize the influence of congestion on QoS.

1.5  Major Traffic Management Techniques

Traffic classification, traffic policing (TP), traffic shaping (TS), congestion management, and congestion avoidance are the foundation for providing differentiated services. Their main functions are as follows:

l           Traffic classification: Identifies packets according to certain match rules. Traffic classification is the prerequisite of providing differentiated services.

l           TP: Monitors and controls the specifications of specific traffic entering the device. When the traffic exceeds the threshold, restrictive or punitive measures can be taken to protect the business interests and network resources of the operator from being damaged.

l           Congestion management: Congestion management is necessary for solving resource competition. Congestion management is generally to cache packets in the queues and arrange the forwarding sequence of the packets based on a certain scheduling algorithm.

l           Congestion avoidance: Excessive congestion will impair the network resources. Congestion avoidance is to supervise the network resource usage. When it is found that congestion is likely to become worse, the congestion avoidance mechanism will drop packets and regulate traffic to solve the overload of the network.

l           TS: TS is a traffic control measure to regulate the output rate of the traffic actively. TS regulates the traffic to match the network resources that can be provided by the downstream devices so as to avoid unnecessary packet loss and congestion.

Among the traffic management techniques, traffic classification is the basis because it identifies packets according to certain match rules, which is the prerequisite of providing differentiated services. TP, TS, congestion management, and congestion avoidance control network traffic and assigned resources from different approaches, and are the concrete ways of providing differentiated services.

H3C S3610 and S5510 Series Ethernet Switches support the following functions:

l           Traffic classification

l           Access control

l           TP and TS

l           Congestion management

l           Congestion avoidance

 

Chapter 2  Traffic Classification, TP, and TS Configuration

2.1  Traffic Classification Overview

2.1.1  Traffic Classification

Traffic classification is to identify packets conforming to certain characters according to certain rules. It is the basis and prerequisite for proving differentiated services.

A traffic classification rule can use the precedence bits in the type of service (ToS) field of the IP packet header to identify traffic with different precedence characteristics. A traffic classification rule can also classify traffic according to the traffic classification policy set by the network administrator, such as the combination of source addresses, destination addresses, MAC addresses, IP protocol or the port numbers of the applications. Traffic classification is generally based on the information in the packet header and rarely based on the content of the packet. The classification result is unlimited in range. They can be a small range specified by a quintuplet (source address, source port number, protocol number, destination address, and destination port number), or all the packets to a certain network segment.

Generally, the precedence of bits in the ToS field of the packet header is set when packets are classified on the network border. Thus, IP precedence can be used directly as the classification criterion inside the network. Queue techniques can also process packets differently according to IP precedence. The downstream network can either accept the classification results of the upstream network or re-classify the packets according to its own criterion.

The purpose of traffic classification is to provide differentiated services, so traffic classification is significant only when it is associated with a certain traffic control or resource assignment action. The specific traffic control action to be adopted depends on the phase and the current load status. For example, when the packets enter the network, TP is performed on the packets according to CIR; before the packets flow out of the node, TS is performed on the packets; when congestion occurs, queue scheduling is performed on the packets; when congestion get worse, congestion avoidance is performed on the packets.

2.1.2  Priority

The following describes several types of precedence:

1)         IP precedence, ToS precedence, and DSCP precedence

Figure 2-1 DS field and TOS field

The ToS field in an IP header contains eight bits, which are described as follows:

l           The first three bits indicate IP precedence in the range of 0 to 7.

l           Bit 3 to bit 6 indicate ToS precedence in the range of 0 to 15.

l           RFC2474 re-defines the ToS field in the IP packet header, which is called the DS field. The first six (bit 0 to bit 5) bits of the DS field indicate DSCP precedence in the range of 0 to 63. The first three bits in DSCP precedence are class selector codepoints, bit 4 and bit 5 indicate drop precedence, and bit 6 is zero indicating that the device sets the service class with the DS model. The last two bits (bit 6 and bit 7) are reserved bits.

2)         802.1p priority

802.1p priority lies in Layer 2 packet headers and is applicable to occasions where the Layer 3 packet header does not need analysis but QoS must be assured at Layer 2.

Figure 2-2 An Ethernet frame with an 802.1Q tag header

As shown in the figure above, each host supporting 802.1Q protocol adds a 4-byte 802.1Q tag header after the source address of the former Ethernet frame header when sending packets.

The 4-byte 802.1Q tag header contains a 2-byte Tag Protocol Identifier (TPID) whose value is 8100 and a 2-byte Tag Control Information (TCI). TPID is a new class defined by IEEE to indicate a packet with an 802.1Q tag. Figure 2-3 describes the detailed contents of an 802.1Q tag header.

Figure 2-3 802.1Q tag headers

In the figure above, the 3-bit priority field in TCI is 802.1p priority in the range of 0 to 7. These three bits specify the precedence of the frame. Eight classes of precedence are used to determine which packet is sent preferentially when congestion occurs.

The precedence is called 802.1p priority because the related applications of this precedence are defined in detail in the 802.1p specifications.

2.2  TP and TS Overview

If the traffic from users is not limited, a large amount of continuous burst packets will result in worse network congestion. The traffic of users must be limited in order to make better use of the limited network resources and provide better service for more users. For example, if a traffic flow obtains only the resources committed to it within a certain period of time, network congestion due to excessive burst traffic can be avoided.

TP and TS are traffic control policies for limiting traffic and resource usage by supervising the traffic. The prerequisite for TP or TS is to determine whether or not the traffic exceeds the set threshold. Traffic control policies are adopted only when the traffic exceeds the set threshold. Generally, token bucket is used for evaluating traffic.

2.3  Traffic Evaluation and the Token Bucket

2.3.1  Token bucket

The token bucket can be considered as a container with a certain capacity to hold tokens. The system puts tokens into the bucket at the set rate. When the token bucket is full, the extra tokens will overflow and the number of tokens in the bucket stops increasing.

Figure 2-4 Evaluate the traffic with the token bucket

2.3.2  Evaluating the traffic with the token bucket

The evaluation for the traffic specification is based on whether the number of tokens in the bucket can meet the need of packet forwarding. If the number of tokens in the bucket is enough to forward the packets, the traffic is conforming to the specification; otherwise, the traffic is nonconforming or excess.

When the token bucket evaluates the traffic, its parameter configurations include:

l           Average rate: The rate at which tokens are put into the bucket, namely, the permitted average rate of the traffic. It is generally set to committed information rate (CIR).

l           Burst size: The capacity of the token bucket, namely, the maximum traffic size that is permitted in each burst. It is generally set to committed burst size (CBS). The set burst size must be greater than the maximum packet length.

An evaluation is performed on the arrival of each packet. In each evaluation, if the bucket has enough tokens for use, the traffic is controlled within the specification and a number of tokens equivalent to the packet forwarding authority must be taken out; otherwise, this means too many tokens have been used — the traffic is in excess of the specification.

2.3.3  Complicated evaluation

You can set two token buckets in order to evaluate more complicated conditions and implement more flexible regulation policies. For example, TP uses four parameters:

l           CIR

l           CBS

l           Peak information rate (PIR)

l           Excess burst size (EBS)

Two token buckets are used in this evaluation. Their rates of putting tokens into the buckets are CIR and PIR respectively, and their sizes are CBS and EBS respectively (the two buckets are called C bucket and E bucket respectively for short), representing different permitted burst levels. In each evaluation, you can implement different regulation policies in different conditions, including “enough tokens in C bucket”, “insufficient tokens in C bucket but enough tokens in E bucket” and “insufficient tokens in both C bucket and E bucket”.

2.3.4  TP

The typical application of TP is to supervise the specification of certain traffic into the network and limit it within a reasonable range, or to "discipline" the extra traffic. In this way, the network resources and the interests of the operators are protected. For example, you can limit HTTP packets to be within 50% of the network bandwidth. If the traffic of a certain connection is excess, TP can choose to drop the packets or to reset the priority of the packets.

TP is widely used in policing the traffic into the network of internet service providers (ISPs). TP can classify the policed traffic and perform pre-defined policing actions based on different evaluation results. These actions include:

l           Forward: Forward the packets although the evaluation result is “incompliant”.

l           Drop: Drop the packets whose evaluation result is “incompliant”.

2.3.5  TS

TS is a policy used to adjust the rate of outbound traffic actively. A typical TS implementation is to control outbound traffic according to the traffic control settings of the downstream network nodes.

The difference between TP and TS lies in that when traffic exceeds the set threshold, TP drops packets and TS caches packets or add packets to queues, as shown inFigure 2-5. Cached packets are sent at a even rate only when there are enough tokens in the token bucket. Another difference between the two is, TS results in additional delay and TP seldom does.

Figure 2-5 Diagram for TS

For example, assume that Switch A sends packets to Switch B. Switch B performs TP for packets from Switch A. Packets exceeding the set threshold are simply dropped.

To decrease the number of the packets dropped, you can employ TS on the port of Switch A through which the packets are sent to Switch B. So, packets are cached on Switch A when the traffic sent to Switch B exceeds the TS threshold. When the next batch of packets can be sent, the cached packets are sent to Switch B. Such scheme ensures that the traffic sent to Switch B conforms to the traffic limit of Switch B.

2.4  Configure TP and TS

Operation	Description	Related section
Configure ACL-based TP	Configure ACL	Configure ACL-based TP
	Apply TP policies to ports
Configure queue-based TS	Configure TS on ports	Configure queue-based TS
Configure TS for all traffic	Configure TS on ports	Configure TS for all traffic

 

2.4.1  Configuring TP

TP configuration includes the following two tasks: the first task is to define the characteristics of the packets to be policed; the second task is to define policing policies for the matched packets.

I. Configure ACL-based TP

Configure ACL-based TP

To do…		Use the command…	Remarks
Enter system view		system-view	—
Create ACL rules		Refer to the ACL module	Required
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in port view applies to the current port only. Configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Apply TP policies		qos car inbound acl [ ipv6 ] acl-number cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ pir peak-information-rate ] [ red action ]	Required CBS defaults to 100,000 bytes. EBS defaults to 100,000 bytes. PIR defaults to 0. The red action keyword is discard by default.

 

II. TP configuration example

Configure TP on Ethernet1/0/1 to control the packets received by Ethernet1/0/1 port and matching ACL 2000. Packets are dropped if the traffic rate exceeds 1 Mbps.

# Enter system view.

<Sysname> system-view

# Enter port view.

[Sysname] interface Ethernet 1/0/1

# Configure TP parameters.

[Sysname-Ethernet1/0/1] qos car inbound acl 2000 cir 1000 red discard

2.4.2  Configuring TS

TS can be implemented in the following ways.

l           Queue-based TS, where TS is applied to the packets of a specific queue.

l           TS applied to all traffic.

I. Configure queue-based TS

Configure queue-based TS

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in Ethernet port view applies to the current port only. The configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure TS for the ports		qos gts queue queue-number cir committed-information-rate	Required CIR must be a multiple of 650.

 

II. Configure TS for all traffic

Configure TS for all traffic

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in Ethernet port view applies to the current port only. The configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure TS for the ports		qos gts any cir committed-information-rate	Required CIR must be a multiple of 650.

 

III. TS configuration example

Configure TS for Ethernet1/0/1 port. Cache the packets when the traffic rate exceeds 1,300 kbps.

# Enter system view.

<Sysname> system-view

# Enter port view.

[Sysname] interface Ethernet 1/0/1

# Configure TS parameters.

[Sysname-Ethernet1/0/1] qos gts any cir 1300

2.5  Displaying TP&TS

After the above configuration, you can execute the display command to view the running status of TP&TS and verify the configuration.

Table 2-1 Display TP&TS

To do…	Use the command…	Remarks
Display the configuration and statistics about TP on a port	display qos car interface [ interface-type interface-number ]	You can execute the display command in any view.
Display the configuration and statistics about TS on a port	display qos gts interface [ interface-type interface-number ]

 

Chapter 3  QoS Policy Configuration

3.1  Overview

QoS policy includes the following three elements: class, traffic behavior and policy. You can bind the specified class to the specified traffic behavior through QoS policies to facilitate the QoS configuration.

I. Class

Class is used for identifying traffic.

The elements of a class include the class name and classification rules.

You can use commands to define a series of rules to classify packets. Additionally, you can use commands to define the relationship among classification rules: “and” and “or”.

l           and: The devices considers a packet to be of a specific class when the packet matches all the specified classification rules.

l           or: The device considers a packet be of a specific class when the packet matches one of the specified classification rules.

II. Traffic behavior

Traffic behavior is used to define all the QoS actions performed on packets.

The elements of a QoS behavior include traffic behavior name and actions defined in traffic behavior.

You can use commands to define multiple actions in a traffic behavior.

III. Policy

Policy is used to bind the specified class to the specified traffic behavior.

The elements of a policy include the policy name and the name of the classification-to-behavior binding.

3.2  Configuring QoS Policy

The procedure for configuring QoS policy is as follows:

1)         Define a class and define a group of traffic classification rules in class view.

2)         Define a traffic behavior and define a group of QoS actions in traffic behavior view.

3)         Define a policy and specify a traffic behavior corresponding to the class in policy view.

4)         Apply the QoS policy in Ethernet port view.

3.3  Introduction to QoS Policies

Table 3-1 QoS policies

Policy name	Corresponding class	Related command
Accounting	Use the if-match match-criteria command to define the class as required for the policy to be associated with.	accounting
TP	Use the if-match match-criteria command to define the class as required for the policy to be associated with.	car
Traffic filtering	Use the if-match match-criteria command to define the class as required for the policy to be associated with .	filter
Traffic mirroring	Use the if-match match-criteria command to define the class as required for the policy to be associated with.	mirror-to
Nested VLAN tag	Use the if-match match-criteria command to define the class as required for the policy to be associated with.	nest
Priority mapping	Use the if-match match-criteria command to define the class as required for the policy to be associated with.	primap
Traffic redirect	Use the if-match match-criteria command to define the class as required for the policy to be associated with.	redirect
Priority marking	Use the if-match match-criteria command to define the class as required for the policy to be associated with.	remark

 

3.4  Configuring a QoS Policy

3.4.1  Configuration Prerequisites

l           The name and the rules of the class to which the policy is to be bound to are determined.

l           The traffic behavior name and actions in the traffic behavior in the policy are determined.

l           The policy name is determined.

l           Apply the QoS policy in Ethernet port view/port group view.

3.4.2  Defining a Class

To define a class, you need to create a class and then define rules in the corresponding class view.

I. Configuration procedure

Table 3-2 Define a class

To do…	Use the command…	Remarks
Enter system view	system-view	—
Create a class and enter the corresponding class view	traffic classifier classifier-name [ operator { and | or } ]	Required By default, the and keyword is specified. That is, the relation between the rules in the class view is logic AND. This operation leads you to class view.
Define a rule used to match packets	if-match match-criteria	Required

 

match-criteria: Matching rules to be defined for a class. Table 3-3 describes the available forms of this argument.

Table 3-3 The form of the match-criteria argument

Form	Description
acl access-list-number	Specifies an ACL to match packets. The access-list-number argument is in the range 2000 to 5999.
acl ipv6 access-list-number	Specifies an IPv6 ACL to match IPv6 packets. The access-list-number argument is in the range 2000 to 3999.
any	Specifies to match all packets.
customer-vlan-id vlan-id-list	Specifies to match the packets of specified VLANs of user networks. The vlan-id-list argument specifies a list of VLAN IDs. You can provide up to eight space-separated VLAN IDs for this argument. VLAN ID is in the range 1 to 4094.
destination-mac mac-address	Specifies to match the packets with a specified destination MAC address.
dot1p 8021p	Specifies to match packets by 802.1p priority. The 8021p argument is a list of COS values. You can provide up to eight space-separated COS values for this argument. COS is in the range 0 to 7.
dscp dscp-list	Specifies to match packets by DSCP precedence. The dscp-list argument is a list of DSCP values. You can provide up to eight space-separated DSCP values for this argument. DSCP is in the range of 0 to 63.
ip-precedence ip-precedence-list	Specifies to match packets by IP precedence. The ip-precedence-list argument is a list of IP precedence values. You can provide up to eight space-separated IP precedence values for this argument. IP precedence is in the range 0 to 7.
protocol protocol-name	Specifies to match the packets of a specified protocol. The protocol-name argument can be IP, IPv6 or Bittorrent. The S3610&5510 series Ethernet switches do not support the Bittorrent protocol currently.
service-vlan-id vlan-id-list	Specifies to match the packets of the VLANs of the operator’s network. The vlan-id-list argument is a list of VLAN IDs. You can provide up to eight space-separated VLAN IDs for this argument. VLAN ID is in the range of 1 to 4094.
source-mac mac-address	Specifies to match the packets with a specified source MAC address.

 

 

II. Configuration example

1)         Network requirements

Configure a class named test to match the packets with their IP precedence being 6.

2)         Configuration procedure

# Enter system view.

<Sysname> system-view

# Create the class. (This operation leads you to class view.)

[Sysname] traffic classifier test

# Define the classification rule.

[Sysname-classifier-test] if-match ip-precedence 6

3.4.3  Defining a Traffic Behavior

To define a traffic behavior, you need to create a traffic behavior and then configure attributes for it in traffic behavior view.

If you want to define a primap behavior, you need to define a priority mapping table as required. Refer to Chapter 5  “Priority Mapping” for more information.

I. Configuration procedure

Table 3-4 Define traffic behavior

To do…	Use the command…	Remarks
Enter system view	system-view	—
Create a traffic behavior and enter the corresponding traffic behavior view	traffic behavior behavior-name	Required behavior-name: Behavior name. This operation leads you to traffic behavior view
Configure accounting action	accounting	Required You can configure the traffic behavior as required.
Configure TP action	car { cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ pir peak-information-rate ] [ red { discard | pass } ] | name global-car-name }
Configure traffic filtering behavior	filter { deny | permit }
Configure traffic mirroring action	mirror-to interface-type interface-number
Configure nested VLAN tag action	nest top-most vlan-id vlan-id
Configure traffic redirect action	redirect { interface interface-type interface-number | next-hop { ipv4-add [ ipv4-add ] | ipv6-add [ interface-type interface-number ] [ ipv6-add [ interface-type interface-number ] ] } }
Remark DSCP value for packets	remark dscp dscp-value
Remark 802.1p priority for packets	remark dot1p 8021p
Remark drop precedence for packets	remark drop-precedence drop-precedence-value
Remark IP precedence for packets	remark ip-precedence ip-precedence-value
Remark local precedence for packets	remark local-precedence local-precedence
Remark VLAN IDs for packets	remark service-vlan-id vlan-id-value
Configure to get other precedence’s for packets through the corresponding priority mapping table	primap pre-defined { dscp-lp | dscp-dp | dscp-dot1p | dscp-dscp }

 

 

The red action keyword for configuring the CAR action specifies the action to be performed on packets when the traffic exceeds the rate specified by CAR. The action argument can be:

l           discard, which drops the packets.

l           pass, which forwards the packets.

For a traffic behaviors with both the priority mapping action and the DSCP precedence remarking action configured, the QoS policy related to it can be applied to a switch successfully. In this case, the switch uses the DSCP precedence defined for packets in the DSCP precedence remarking action to get other precedence for packets by looking up the priority mapping table.

For a traffic behavior with both the priority mapping action and any priority remarking actions (except the DSCP precedence remarking action) configured, the QoS policy related to it cannot be applied to a switch successfully.

II. Configuration example

1)         Network requirements

Create a traffic behavior named test, configuring TP action for it, with the CAR being 100 kbps.

2)         Configuration procedure

# Enter system view.

<Sysname> system-view

# Create the traffic behavior (This operation leads you to traffic behavior view).

[Sysname] traffic behavior test

# Configure TP action for the traffic behavior.

[Sysname-behavior-test] car cir 100

3.4.4  Defining a Policy

A policy associates a class with a traffic behavior. Each traffic behavior is comprised of a group of QoS actions.

Table 3-5 Associate a traffic behavior with a class

To do…	Use the command…	Remarks
Enter system view	system-view	—
Create a policy (This operation leads you to policy view)	qos policy policy-name	—
Specify the traffic behavior for a class	classifier classifier-name behavior behavior-name	Required classifier-name: Class name. It must be the name of a existing class. behavior-name: Name of a traffic behavior. It must be the name of a existing behavior.

 

3.4.5  Applying a Policy

I. Configuration procedure

Use the qos apply policy command to apply a policy to a specific port. A policy can be applied to multiple ports or port groups.

Table 3-6 Apply a policy on a port

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in Ethernet port view applies to the current port only. The configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Apply an associated policy		qos apply policy policy-name inbound	Required

 

II. Configuration example

1)         Network requirements

Configure a policy named test to associate the traffic behavior named test_behavior with the class named test_class. Apply the policy to the inbound direction of Ethernet1/0/1 port.

2)         Configuration procedure

# Enter system view.

<Sysname> system-view

# Create a policy (This operation leads you to policy view).

[Sysname]qos policy test

[Sysname-qospolicy-test]

# Associate the traffic behavior named test_behavior with the class named test_class.

[Sysname-qospolicy-test] classifier test_class behavior test_behavior

[Sysname-qospolicy-test] quit

# Enter port view.

[Sysname] interface Ethernet 1/0/1

[Sysname-Ethernet1/0/1]

# Apply the policy to the port.

[Sysname-Ethernet1/0/1] qos apply policy test inbound

3.5  Displaying QoS Policy

After the about-mentioned configuration, you can exec the display command in any view to view the running information about QoS policy, so as to verify the configuration.

Table 3-7 Display QoS policy

To do…	Use the command…	Remarks
Display the information about a class and the corresponding actions associated by a policy	display qos policy user-defined [ policy-name [ classifier classifier-name ] ]	You can execute the display command in any view.
Display the information about the policies applied on a port	display qos policy interface [ interface-type interface-number ] [ inbound ]
Display the information about a traffic behavior	display traffic behavior user-defined [ behavior-name ]
Display the information about a class	display traffic classifier user-defined [ classifier-name ]

 

Chapter 4  Congestion Management

4.1  Overview

When the rate at which the packets arrive is higher than the rate at which the packets are transmitted on an interface, congestion occurs on this interface. If there is not enough storage space to store these packets, parts of them will be lost. Packet loss may cause the transmitting device to retransmit the packets because the lost packets time out, which causes a malicious cycle.

The core of congestion management is how to schedule the resources and determine the sequence of forwarding packets when congestion occurs.

4.2  Congestion Management Policy

Queuing technology is generally adopted to solve the congestion problem. The queuing technology is to classify the traffic according to a specified queue-scheduling algorithm and then use the specified priority algorithm to forward the traffic. Each queuing algorithm is used to solve specific network traffic problems and affects the parameters such as bandwidth allocation, delay and delay jitter.

The following paragraphs describe strict-priority (SP) queue-scheduling algorithm, and weighted round robin (WRR) queue-scheduling algorithm.

1)         SP queue-scheduling algorithm

Figure 4-1 Diagram for SP queuing

The SP queue-scheduling algorithm is specially designed for critical service applications. An important feature of critical services is that they demand preferential service in congestion in order to reduce the response delay. Assume that there are four output queues on the port and the four output queues on the port are classified into four classes, which are high queue, middle queue, normal queue and bottom queue (namely, queue 3, queue 2, queue 1 and queue 0). Their priority levels decrease in order.

During queue scheduling, the SP algorithm sends packets in higher-priority queues strictly following the high-to-low priority order. When the queues with higher priority levels are empty, packets in the queues with lower priority levels are sent. You can put packets of critical service into the queues with higher priority levels and put packets of non-critical services (such as E-mail) into the queues with lower priority levels, so that packets of critical services are sent in priority and packets of non-critical services are sent when packets of critical services are not sent.

SP queue-scheduling algorithm does have its disadvantage: if packets exist for a long time in the queues with higher priority levels during congestion, the packets in the queues with lower priority levels will be “starved to death” because they are not served.

2)         WRR queue-scheduling algorithm

A port of the switch supports eight outbound queues. The WRR queue-scheduling algorithm schedules all the queues in turn to ensure that every queue can be assigned a certain service time. Assume there are eight priority queues on the port. The eight weight values (namely, w 7, w 6, w 5, w 4, w 3, w 2, w 1, and w 0) indicating the proportion of assigned resources are assigned to the eight queues respectively. On a 100M port, you can configure the weight values of WRR queue-scheduling algorithm to 50, 30, 10, 10, 50, 30, 10, and 10 (corresponding to w7, w6, w5, w4, w3, w2, w1, and w0 respectively). In this way, the queue with the lowest priority can be assured of 5 Mbps of bandwidth at least, thus avoiding the disadvantage of SP queue-scheduling algorithm that packets in low-priority queues are possibly not to be served for a long time. Another advantage of WRR queue-scheduling algorithm is that though the queues are scheduled in turn, the service time for each queue is not fixed, that is to say, if a queue is empty, the next queue will be scheduled immediately. In this way, the bandwidth resources are fully utilized.

H3C S3610 and S5510 Series Ethernet Switches support the following three queue scheduling algorithms:

l           All the queues are scheduled through the SP algorithm.

l           All the queues are scheduled through the WRR algorithm.

l           Some queues are scheduled through the SP algorithm, while other queues are scheduled through the WRR algorithm.

4.3  Configuring an SP Queue

An SP queue contain multiple queues, each of which has different precedence. Queues in an SP queue are scheduled according to precedence in the descending order.

 

 

4.3.1  Configuration Procedure

Table 4-1 Configure SP queues

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in Ethernet port view applies to the current port only. The configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure an SP Queue		qos wrr queue-id group sp	Required

 

4.3.2  Configuration Example

I. Network requirements

Configure Ethernet1/0/1 to adopt SP queue scheduling algorithm.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Configure an SP queue for Ethernet1/0/1 port.

[Sysname] interface Ethernet 1/0/1

[Sysname-Ethernet1/0/1] qos wrr 0 group sp

4.4  Configuring a WRR Queue

You can divide the outbound queues into WRR precedence queue group 1 and WRR precedence queue group 2. The SP scheduling algorithm is adopted for WRR groups. For example, queue 0, queue 1, queue 2, and queue 3 are in WRR group 1, and queue 4, queue 5, queue 6, and queue 7 are in group 2. Round robin is performed in WRR group 2 firstly. If no packet is to be sent in WRR group 2, round robin is performed in WRR group 1.

 

 

4.4.1  Configuration Procedure

Table 4-2 Configure WRR queues

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in Ethernet port view applies to the current port only. The configuration performed in port group view applies to all the ports in the port group
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure WRR queues		qos wrr queue-id group group-id weight schedule-value	Required The group-id argument can be 1 or 2.
Display the configuration information of WRR queues on the port		display qos wrr interface [ interface-type interface-number ]	Optional The display command can be executed in any view.

 

4.4.2  Configuration Example

I. Network requirements

l           Configure queues on the port as WRR queues.

l           Configure queue 0, queue 1, queue 2, and queue 3 to be in WRR group 1, with the weight being 10, 20, 50, and 70 respectively.

l           Configure queue 4, queue 5, queue 6, and queue 7 to be in WRR group 2, with the weight being 20, 50, 70, and 100 respectively.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Configure the WRR queues on Ethernet1/0/1 port.

[Sysname] interface Ethernet 1/0/1

[Sysname-Ethernet1/0/1] qos wrr 0 group 1 weight 10

[Sysname-Ethernet1/0/1] qos wrr 1 group 1 weight 20

[Sysname-Ethernet1/0/1] qos wrr 2 group 1 weight 50

[Sysname-Ethernet1/0/1] qos wrr 3 group 1 weight 70

[Sysname-Ethernet1/0/1] qos wrr 4 group 1 weight 20

[Sysname-Ethernet1/0/1] qos wrr 5 group 2 weight 50

[Sysname-Ethernet1/0/1] qos wrr 6 group 2 weight 70

[Sysname-Ethernet1/0/1] qos wrr 7 group 2 weight 100

4.5  Configuring SP+WRR Queues

As required, you can adopt SP queue scheduling algorithm for a part of the queues on a port, and meanwhile adopt WRR queue scheduling algorithm for another part of the queues on this port. In this way, the SP+WRR queue scheduling is enabled through adding queues on a port to SP queue scheduling groups and WRR queue scheduling groups respectively. SP queue scheduling algorithm is adopted between each group.

For example, queue 0 and queue 1 are in the SP queue scheduling group, and queue 2, queue 3, and queue 4 are in the WRR queue scheduling group 1, queue 5, queue 6, and queue 7 are in WRR queue scheduling group 2. Round robin is performed in WRR group 2 firstly. If no packet is to be sent in WRR group 2, round robin is performed in WRR group 1. At last, packets in the SP queue scheduling group are processed.

4.5.1  Configuration Procedure

Table 4-3 Configure SP+WRR queues

To do…		Use the command…	Remarks
Enter system view		system-view	-
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in Ethernet port view applies to the current port only. The configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Enable WRR queues on a port		qos wrr	Required
Configure SP queues		qos wrr queue-id group sp	Required
Configure WRR queues		qos wrr queue-id group group-id weight queue-weight	Required

 

4.5.2  Configuration Example

I. Network requirements

l           Configure to adopt SP+WRR queue scheduling algorithm on Ethernet1/0/1.

l           Configure queue 0 and queue 1 on Ethernet1/0/1 to be in SP queue scheduling group.

l           Configure queue 2, queue 3, and queue 4 on Ethernet 1/0/1 to be in WRR queue scheduling group 1, with the weight being 20, 70, and 100 respectively.

l           Configure queue 5, queue 6, and queue 7 on Ethernet1/0/1 to be in WRR queue scheduling group 2, with the weight being 10, 50, and 80 respectively.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Enable the SP+WRR queue scheduling algorithm on Ethernet1/0/1.

[Sysname] interface Ethernet 1/0/1

[Sysname-Ethernet1/0/1] qos wrr 0 group sp

[Sysname-Ethernet1/0/1] qos wrr 1 group sp

[Sysname-Ethernet1/0/1] qos wrr 2 group 1 weight 20

[Sysname-Ethernet1/0/1] qos wrr 3 group 1 weight 70

[Sysname-Ethernet1/0/1] qos wrr 4 group 1 weight 100

[Sysname-Ethernet1/0/1] qos wrr 5 group 2 weight 10

[Sysname-Ethernet1/0/1] qos wrr 6 group 2 weight 50

[Sysname-Ethernet1/0/1] qos wrr 7 group 2 weight 80

 

Chapter 5  Priority Mapping

5.1  Priority Mapping Overview

When a packet reaches a switch, the switch assigns the packet parameters according to it configuration, such as 802.1p priority, DSCP precedence, IP precedence, local precedence, and drop precedence.

The local precedence and drop precedence are described as follows.

l           Local precedence is the precedence that the switch assigns to a packet and it is corresponding to the number of an outbound queue on the port. Local precedence takes effect only on the local switch.

l           Drop precedence is a parameter that is referred to when dropping packets.

A switch provides two port priority trust modes:

l           In the packet priority trust mode, a switch assigns priorities to packets by looking up the priority mapping table based on the packet priority.

l           In the port priority trust mode, a switch assigns local precedence to packets by mapping the port priority of the receiving port.

You can select one port priority trust mode as required. Figure 5-1 shows the process of priority mapping on a switch.

Figure 5-1 Diagram for the process of priority mapping

A switch has multiple priority mapping tables which correspond to specific types of priority. The following are the priority mapping tables and the default priority values.

l           dot1p-lp: 802.1p priority-to-local precedence mapping table

l           dot1p-dp: 802.1p priority-to-drop precedence mapping table.

l           dscp-lp: DSCP-to-local precedence mapping table, which is applicable to IP packets only.

l           dscp-dp: DSCP-to-drop precedence mapping table, which is applicable to IP packets only.

l           dscp-dot1p: DSCP-to-802.1p priority mapping table, which is applicable to IP packets only.

l           dscp-dscp: DSCP-to-DSCP precedence mapping table, which is applicable to IP packets only.

The default values of these priority mapping tables are shown below.

Table 5-1 The default values of dot1p-lp mapping and dot1p-dp mapping

Imported priority value	dot1p-lp mapping	dot1p-dp mapping
802.1p priority (dot1p)	Local precedence (lp)	Drop precedence (dp)
0	2	2
1	0	2
2	1	2
3	3	1
4	4	1
5	5	1
6	6	0
7	7	0

 

Table 5-2 The default values of dscp-lp mapping, dscp-dp mapping, dscp-dot1p mapping, and dscp-dscp mapping

Imported priority value	dscp-lp mapping	dscp-dp mapping	dscp-dot1p mapping	dscp-dscp mapping
DSCP precedence (dscp)	Local precedence (lp)	Drop precedence (dp)	802.1p priority (dot1p)	DSCP precedence (dscp)
0 to 7	0	2	0	0
8 to 15	1	2	1	8
16 to 23	2	2	2	16
24 to 31	3	1	3	24
32 to 39	4	1	4	32
40 to 47	5	1	5	40
48 to 55	6	0	6	48
56 to 63	7	0	7	56

 

Table 5-3 Port-priority-to-local precedence mapping

Port priority	Local precedence
0	0
1	1
2	2
3	3
4	4
5	5
6	6
7	7

 

5.2  Configuring a Priority Mapping Table

You can modify the priority mapping tables in a switch as required.

Follow the two steps to configure priority mapping tables:

l           Enter priority mapping table view;

l           Configure priority mapping parameters.

5.2.1  Configuration Prerequisites

The new priority mapping table is determined.

5.2.2  Configuration Procedure

Table 5-4 Configure a priority mapping table

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter priority mapping table view	qos map-table { dot1p-lp | dot1p-dp | dscp-lp | dscp-dp | dscp-dot1p | dscp-dscp }	Required To configure a priority mapping table, you need to enter the corresponding priority mapping table view.
Configure priority mapping parameters	import import-value-list export export-value	Required The newly configured mapping entries overwrite the corresponding previous entries.

 

The DSCP priority mapping table is associated with the priority mapping action in traffic behavior. The priority mapping table takes effect only when the priority mapping action is configured in the associated traffic behavior specified by a policy. For the detailed information about configuring traffic behavior, refer to section 3.4.3  “Defining a Traffic Behavior”.

The 802.1p priority mapping table is associated with the priority trust mode on a port. The 802.p priority mapping table takes effect only when the 802.1p priorities carried in packets are trusted on ports. For information about configuring port priority trust modes, refer to 5.4  Configuring Port Priority Trust Mode.

5.2.3  Configuration Example

I. Network requirements

Modify the dot1p-lp mapping table as those listed in Table 5-5.

Table 5-5 The specified dot1p-lp mapping

802.1p priority	Local precedence
0	0
1	0
2	1
3	1
4	2
5	2
6	3
7	3

 

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Enter dot1p-lp priority mapping table view.

[Sysname] qos map-table dot1p-lp

# Modify dot1p-lp priority mapping parameters.

[Sysname-maptbl-dot1p-lp] import 0 1 export 0

[Sysname-maptbl-dot1p-lp] import 2 3 export 1

[Sysname-maptbl-dot1p-lp] import 4 5 export 2

[Sysname-maptbl-dot1p-lp] import 6 7 export 3

5.3  Configuring the Port Priority

Port priority is in the range 0 to 7. You can set the port priority as required.

5.3.1  Configuration Prerequisites

The port priority of the port is determined.

5.3.2  Configuration Procedure

Table 5-6 Configure port priority

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in Ethernet port view applies to the current port only. The configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure port priority		qos priority priority-value	Required By default, the port priority is 0.

 

5.3.3  Configuration Example

I. Network requirements

Configure the port priority to 7.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Configure port priority of Ethernet1/0/1.

[Sysname] interface Ethernet 1/0/1

[Sysname-Ethernet1/0/1] qos priority 7

5.4  Configuring Port Priority Trust Mode

You can configure whether to trust packet priority. For H3C S3610 series and S5510 series Ethernet switches, only 802.1p priorities carried in packets can be trusted.

5.4.1  Configuration Prerequisites

The priory mode set on the port is trusted. Packet priority is not trusted.

The priority mapping table corresponding to the trusted priority is determined. For information about priority mapping table, refer to section 5.2  “Configuring a Priority Mapping Table”.

5.4.2  Configuration Procedure

Table 5-7 Configure the port priority trust mode

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in Ethernet port view applies to the current port only. The configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Configure to trust 802.1p priorities carried in the packets		qos trust dot1p	Required

 

5.4.3  Configuration Example

I. Network requirements

Configure to trust 802.1p priorities carried in the packets.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Enter port view.

[Sysname] interface Ethernet 1/0/1

[Sysname-Ethernet1/0/1]

# Configure to trust 802.1p priorities.

[Sysname-Ethernet1/0/1] qos trust dot1p

5.5  Displaying Priority Mapping

After the about-mentioned configuration, you can exec the display command in any view to view the running information about priority mapping, so as to verify the configuration.

Table 5-8 Display priority mapping

To do…	Use the command…	Remarks
Display the information about a specified priority mapping table	display qos map-table [ dot1p-lp | dot1p-dp | dscp-lp | dscp-dp | dscp-dot1p | dscp-dscp ]	You can execute the display command in any view.
Display the priority trust mode configured for a port	display qos trust interface [ interface-type interface-number ]

 

Chapter 6  Congestion Avoidance

6.1  Overview

Serious congestion will bring great impact to the network resources, so some measures must be taken to avoid congestion. As a type of flow control mechanism, congestion avoidance monitors the utilization of network resources (such as queues or buffer in the memory), and can drop packets when congestion deteriorates. In this way, the congestion avoidance mechanism adjusts the network traffic so as to solve the overloading problem in the network.

Compared to the port-to-port flow control, congestion avoidance controls more traffic loading in the switch. When the switch drops packets from the source end, it can still cooperate with the flow control actions (such as TCP flow control) on the source end so as to adjust the traffic in the whole network to a reasonable load status. The combination of packet drop policy and flow control mechanism on the source end can maximize throughput and utilization rate of the network and minimize packet loss and delay.

I. Traditional packet drop policy

Tail drop is adopted in the traditional packet drop policy. When a queue length reaches the maximum value, all the new packets are dropped.

This packet drop policy will result in global TCP synchronization. If the queue drops packets from multiple TCP connections simultaneously, these TCP connections will go into the state of congestion avoidance and slow startup to reduce and adjust traffic and then reach traffic peak in a certain future time. Such changes will cause the network traffic jitter repeatedly.

II. RED and WRED

When congestion is too serious, the switch can adopt the random early detection (RED) or weighted RED (WRED) algorithm to solve the problem of excessive congestion and avoid global TCP synchronization caused by the tail-drop algorithm.

In the RED algorithm, an upper limit and a lower limit are set for each queue, and it is stipulated that:

l           When the queue length is smaller than the lower limit, packets are not dropped.

l           When the queue length is bigger than the upper limit, all inbound packets all dropped.

l           When the queue length is in the range of the upper limit and the lower limit, the inbound packets are dropped at random. In this case, a number is assigned to each inbound packet and then compared with the drop probability of the current queue. If the number is bigger than the drop probability, the inbound packet is dropped. The longer a queue is, the higher the drop probability is. However, there is a top drop probability.

Compared with the RED algorithm, the WRED algorithm generates precedence-based random numbers. It adopts IP precedence in determining drop policy and takes the benefits of high-precedence packets into consideration, so the drop probability is comparatively low.

In the RED and WRED algorithm, packets are dropped at random so that global TCP synchronization is avoided. When packets in a TCP connection are dropped and sent at a low rate, packets in other TCP connections are still sent at a high rate. In this way, packets in a part of connections are sent at a high rate in any case. Thus, the utilization rate of bandwidth is improved.

 

 

6.2  Configuring WRED

6.2.1  Configuration Prerequisites

Prepare a network environment where congestion may occur.

6.2.2  Configuration Procedure

Table 6-1 Configure WRED

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in port view applies to the current port only. Configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Enable WRED		qos wred	Required

 

6.2.3  Configuration Example

I. Network requirements

Enable WRED on Ethernet1/0/1.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Enter port view.

[Sysname] interface Ethernet 1/0/1

# Enable WRED.

[Sysname-Ethernet1/0/1] qos wred

6.3  Displaying WRED

After the above-mentioned configuration, you can execute the display command in any view to view the running information about WRED, so as to verify the configuration.

Table 6-2 Display WRED

To do…	Use the command…	Remarks
Display the configuration information and statistics information about WRED on the port	display qos wred interface [ interface-type interface-number ]	You can execute the display command in any view.

 

Chapter 7  Aggregation CAR Configuration

7.1  Aggregation CAR Overview

Aggregation CAR enables traffic policing on multiple ports using the same CAR. If an aggregation CAR is applied to multiple ports, the total traffic on these ports must be within the traffic policing range specified in the aggregation CAR.

 

 

7.2  Applying Aggregation CAR on Ports

7.2.1  Configuration Prerequisites

l           Parameter values of the aggregation CAR are determined.

l           Ports where aggregation CAR is applied are determined.

l           Matching rules for traffic are determined on the ports. ACLs must be defined if ACL-based matching rules are used.

l           Refer to the ACL module for details on ACL defining.

7.2.2  Configuration Procedure

Table 7-1 Configure aggregation CAR

To do…		Use the command…	Remarks
Enter system view		system-view	—
Configure parameters for CAR		qos car global-car-name aggregative cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ pir peak-information-rate ] [ red action ]	Required CBS is 100,000 bytes by default. EBS is 100,000 bytes by default. PIR is 0 by default. The default action for red packets is discard.
Enter port view or port group view	Enter port view	interface interface-type interface-number	Perform either of the two operations. The configuration performed in port view applies to the current port only. Configuration performed in port group view applies to all the ports in the port group.
	Enter port group view	port-group { manual port-group-name | aggregation agg-id }
Apply aggregation CAR		qos car inbound acl [ ipv6 ] acl-number name global-car-name	Required

 

7.2.3  Configuration Example

Specify the aggregation CAR named aggcar-1 to adopt the following parameters for CAR: CIR is 200, CBS is 2,000, and red packets are dropped.

Apply the aggregation CAR named aggcar-1 to the packets matching ACL 2001 in the inbound direction of Ethernet1/0/1.

The configuration procedure is as follows:

<Sysname> system-view

[Sysname] qos car aggcar-1 aggregative cir 200 cbs 2000 red discard

[Sysname] interface Ethernet 1/0/1

[Sysname-Ethernet1/0/1] qos car inbound acl 2001 name aggcar-1

7.3  Referencing Aggregation CAR in Traffic Behaviors

7.3.1  Configuration Prerequisites

l           Parameter values of the aggregation CAR are determined.

l           Traffic behaviors where aggregation CAR is referenced are determined.

7.3.2  Configuration Procedure

Table 7-2 Reference aggregation CAR in traffic behaviors

To do…	Use the command…	Remarks
Enter system view	system-view	—
Configure parameters for CAR	qos car global-car-name aggregative cir committed-information-rate [ cbs committed-burst-size [ ebs excess-burst-size ] ] [ pir peak-information-rate ] [ red action ]	Required CBS is half of CIR in a unit time by default. EBS is 0 by default. PIR is 0 by default. The default action for red packets is discard.
Enter traffic behavior view	traffic behavior behavior-name	Required
Reference aggregation CAR in the traffic behavior	car name global-car-name	Required

 

7.3.3  Configuration Example

Specify the aggregation CAR named aggcar-1 to adopt the following parameters for CAR: CIR is 200, CBS is 2,000, and red packets are dropped.

Reference aggregation CAR named aggcar-1 in traffic behavior named be1.

The configuration procedure is as follows:

<Sysname> system-view

[Sysname] qos car aggcar-1 aggregative cir 200 cbs 2000 red discard

[Sysname] traffic behavior be1

[Sysname-behavior-be1] car name aggcar-1

7.4  Displaying the Statistics Information of Aggregation CAR

After the above-mentioned configuration, you can execute the display command in any view to view the running information about aggregation CAR, so as to verify the configuration.

You can execute the reset command in user view to clear the statistics information about aggregation CAR.

Table 7-3 Display the statistics information of aggregation CAR

To do…	Use the command…	Remarks
Clear the statistics information of the specified aggregation CAR	reset qos car name [ global-car-name ]	The reset command must be executed in user view.
Display the configuration information and statistics information about the specified aggregation CAR	display qos car name global-car-name	You can execute the display command in any view.

 

Chapter 8  VLAN Policy Configuration

8.1  Overview

QoS polices support the following application modes:

l           Port-based application: QoS policies are effective for inbound packets on a port.

l           VLAN-based application: QoS policies are effective for inbound traffic on a VLAN.

VLAN-based QoS policies are also known as VLAN policies for short. VLAN policies can facilitate the application and management of QoS policies on the switch.

VLAN policies are not effective on dynamic VLANs. VLAN policies will not be applied to dynamic VLANs. For example, the device may create VLANs dynamically when GVRP protocol is running. In this case, the corresponding VLAN policies are not effective on dynamic VLANs.

 

 

8.2  Applying VLAN Policy

8.2.1  Configuration Prerequisites

l           The VLAN policy to be applied is defined. Refer to section 3.4  “Configuring a QoS Policy” for policy defining.

l           VLANs where the VLAN policy is to be applied are determined.

8.2.2  Configuration Procedure

Table 8-1 Apply VLAN policies

To do…	Use the command…	Remarks
Enter system view	system-view	—
Apply the VLAN policy to the specified VLAN(s)	qos vlan-policy policy-name vlan vlan-id-list inbound	Required vlan-id-list: List of VLAN IDs, presented in the form of vlan-id to vlan-id or discontinuous VLAN IDs. Up to eight VLAN IDs can be specified at a time.

 

8.3  Displaying and Maintaining VLAN Policy

After the above-mentioned configuration, you can use the display command in any view to view the running information about VLAN policy, so as to verify the configuration.

You can execute the reset command in user view to clear the statistics information about VLAN policy.

Table 8-2 Display and maintain VLAN policy

To do…	Use the command…	Remarks
Display the VLAN policy	display qos vlan-policy { name policy-name | vlan [ vlan-id ] }	The reset command must be executed in user view.
Clear the statistics information about the VLAN policy	reset qos vlan-policy [ vlan vlan-id ]	You can execute the display command in any view.

 

8.4  VLAN Policy Configuration Example

8.4.1  Network Requirements

l           The VLAN policy named test is defined to perform traffic policing for the packets matching ACL 2000, with CIR as 8.

l           Apply the VLAN policy test to the inbound direction of VLAN 200, VLAN 300, VLAN 400, VLAN 500, VLAN 600, VLAN 700, VLAN 800, and VLAN 900.

8.4.2  Configuration Procedure

<Sysname> system-view

[Sysname] traffic classifier cl1 operator or

[Sysname-classifier-cl1] if-match acl 2000

[Sysname-classifier-cl1] quit

[Sysname] traffic behavior be1

[Sysname-behavior-be1] car cir 8

[Sysname-behavior-be1] quit

[Sysname] qos policy test

[Sysname-qospolicy-test] classifier cl1 behavior be1

[Sysname-qospolicy-test] quit

[Sysname] qos vlan-policy test vlan 200 300 400 500 600 700 800 900 inbound

 

Chapter 9  Traffic Mirroring Configuration

9.1  Overview

Traffic mirroring is to replicate the specified packets to the specified destination. It is generally used for testing and troubleshooting the network. .

Depending on different types of mirroring destinations, there are three types of traffic mirroring:

l           Mirroring to port: The desired traffic on a mirrored port is replicated and sent to a destination port (that is, a mirroring port).

l           Mirroring to CPU: The desired traffic on a mirrored port is replicated and sent to the CPU on the board of the port for further analysis.

l           Mirroring to VLAN: The desired traffic on a mirrored port is replicated and sent to a VLAN, where the traffic is broadcast and all the ports (if available) in the VLAN will receive the traffic. If the destination VLAN does not exist, you can still configure the function, and the function will automatically take effect after the VLAN is created and a port is added to it.

 

 

9.2  Configuring Traffic Mirroring to a Port

To configure traffic mirroring, you must enter the view of an existing traffic behavior.

Table 9-1 Configure traffic mirroring to a port

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter traffic behavior view	traffic behavior behavior-name	Required
Configure a destination port for the traffic mirroring action in the traffic behavior	mirror-to interface interface-type interface-number	Required

 

 

9.3  Displaying Traffic Mirroring

After the above-mentioned configuration, you can execute the display command in any view to view the running information about traffic mirroring, so as to verify the configuration.

Table 9-2 Display traffic mirroring

To do…	Use the command…	Remarks
Display the configuration information about the user-defined traffic behavior	display traffic behavior user-defined behavior-name	You can execute the display command in any view.
Display the configuration information about the user-defined policy	display qos policy user-defined policy-name

 

9.4  Traffic Mirroring Configuration Example

9.4.1  Network Requirements

The user's network is as described below:

l           PC A is accessed to Switch A through Ethernet1/0/1.

l           Server is connected to Ethernet1/0/2 of Switch A.

The requirement is that the server analyze and monitor all the packets that PC A sends. Network Diagram

Figure 9-1 Network diagram for configuring traffic mirroring to a port

9.4.2  Configuration Procedure

Configure Switch A:

# Enter system view.

<Sysname> system-view

# Configure ACL 2000 to permit all packets.

[Sysname] acl number 2000

[Sysname-acl-basic-2000] rule 1 permit

[Sysname-acl-basic-2000] quit

# Configure a traffic classification rule to use ACL 2000 for traffic classification.

[Sysname] traffic classfier 1

[Sysname-classifier-1] if-match acl 2000

[Sysname-classifier-1] quit

# Configure a traffic behavior and define the action of mirroring traffic to Ethernet1/0/2 in the traffic behavior.

[Sysname] traffic behavior 1

[Sysname-behavior-1] mirror-to interface Ethernet 1/0/2

[Sysname-behavior-1] quit

# Configure a QoS policy and associate traffic behavior 1 with classification rule 1.

[Sysname] qos policy 1

[Sysname-policy-1] classifier 1 behavior 1

[Sysname-policy-1] quit

# Apply the policy in the inbound direction of Ethernet1/0/1.

[Sysname] interface Ethernet 1/0/1

[Sysname-Ethernet1/0/1] qos apply policy 1 inbound

After the above configuration, you can analyze and monitor all the packets that PC A sends on the Server.