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 Forwarding Service

In traditional IP networks, packets are treated equally. That is, the FIFO (first in first out) policy is adopted for packet processing. Network resources required for packet forwarding is determined by the order in which packets arrive. All the packets share the resources of the network. Network resources available to the packets completely depend on the time they arrive. This service policy is known as Best-effort, which delivers the packets to their destination with the best effort, with no assurance and guarantee for delivery delay, jitter, packet loss ratio, reliability, and so on.

The traditional Best-Effort service policy is only suitable for applications insensitive to bandwidth and delay, such as WWW, FTP and E-mail.

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, FTP, and E-mail, 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 switch over a high-speed link and are forwarded out over a low-speed link.

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

If the outbound traffic exceeds the line rate, the traffic encounters 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.

Chapter 2 Traffic Classification, TP, and LR Configuration

When configuring traffic classification, TP, and LR, go to these section for information you are interested in:

l Traffic Classification Overview

l TP and LR Overview

l Traffic Evaluation and Token Bucket

l LR Configuration

l Displaying and Maintaining LR

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 last two bits (bit 6 and bit 7) are reserved bits.

Table 2-1 Description on IP Precedence

IP Precedence (decimal)	IP Precedence (binary)	Description
0	000	Routine
1	001	priority
2	010	immediate
3	011	flash
4	100	flash-override
5	101	critical
6	110	internet
7	111	network

In a network providing differentiated services, traffics are grouped into the following four classes, and packets are processed according to their DSCP values.

l Expedited Forwarding (EF) class: In this class, packets can be forwarded regardless of link share of other traffic. The class is suitable for preferential services with low delay, low packet loss ratio, low jitter, and assured bandwidth (such as virtual leased line);

l Assured forwarding (AF) class: This class is further divided into four subclasses (AF1/2/3/4) and a subclass is further divided into three drop priorities, so the AF service level can be segmented. The QoS rank of the AF class is lower than that of the EF class;

l Class selector (CS) class: This class comes from the IP ToS field and includes eight subclasses;

l Best Effort (BE) class: This class is a special class without any assurance in the CS class. The AF class can be degraded to the BE class if it exceeds the limit. Current IP network traffic belongs to this class by default.

Table 2-2 Description on DSCP precedence values

DSCP value (decimal)	DSCP value (binary)	Description
46	101110	ef
10	001010	af11
12	001100	af12
14	001110	af13
18	010010	af21
20	010100	af22
22	010110	af23
26	011010	af31
28	011100	af32
30	011110	af33
34	100010	af41
36	100100	af42
38	100110	af43
8	001000	cs1
16	010000	cs2
24	011000	cs3
32	100000	cs4
40	101000	cs5
48	110000	cs6
56	111000	cs7
0	000000	be (default)

2) 802.1p precedence

802.1p precedence 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, 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 precedence in the range of 0 to 7. In the figure above, the priority field (three bits in length) in TCI is 802.1p precedence (also known as CoS precedence), which ranges from 0 to 7.

Table 2-3 Description on 802.1p precedence

802.1p precedence (decimal)	802.1p precedence (binary)	Description
0	000	best-effort
1	001	background
2	010	spare
3	011	excellent-effort
4	100	controlled-load
5	101	video
6	110	voice
7	111	network-management

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

2.2 TP and LR 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 is traffic control policies for limiting traffic and resource usage by supervising the traffic. The prerequisite for TP 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 Token Bucket

2.3.1 Token Bucket

A token bucket can be considered as a container with a certain capacity to hold tokens. The system puts tokens into the bucket at a pre-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 traffic with a token bucket

2.3.2 Evaluating Traffic with a 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 Forwarding conforming packets or non-conforming packets.

l Dropping conforming or non-conforming packets.

l Marking a conforming packet with a new 802.1p precedence value and forwarding the packet.

l Marking a conforming packet with a new IP precedence value and forwarding the packet.

l Marking a conforming packet or a non-conforming packet with a new DSCP precedence value and forwarding the packet.

2.3.5 LR

Port rate limiting refers to limiting the total rate of inbound or outbound packets on a port.

Port rate limiting can be implemented through token buckets. That is, if you perform port rate limiting configuration for a port, the token bucket determines the way to process the packets to be sent by this port or packets reaching the port. Packets can be sent or received if there are enough tokens in the token bucket; otherwise, they will be dropped.

Compared to TP, port rate limiting applies to all the packets passing a port. It is a simpler solution if you want to limit the rate of all the packets passing a port.

2.4 LR Configuration

2.4.1 LR Configuration Procedure

Follow these steps to configure LR:

To do…		Use the command…	Remarks
Enter system view		system-view	—
Enter interface view or port group view	Enter port view	interface interface-type interface-number	Enter either view. For Ethernet interface view, the following configuration takes effect only on the current interface. For entering port group view, the following configuration takes effect on all the ports.
Enter interface view or port group view	Enter port group view	port-group { manual port-group-name \| aggregation agg-id }
Configure LR		qos lr outbound cir committed-information-rate [ cbs committed-burst-size ]	Required

2.4.2 LR Configuration Examples

Limit the outbound rate of GigabitEthernet 1/0/1 to 640 kbps.

# Enter system view

<Sysname> system-view

# Enter interface view

[Sysname] interface GigabitEthernet 1/0/1

# Configure LR parameter and limit the outbound rate to 640 kbps

[Sysname-GigabitEthernet1/0/1] qos lr outbound cir 640

2.5 Displaying and Maintaining LR

To do…	Use the command…	Remarks
Display the LR configuration of an interface	display qos lr interface [ interface-type interface-number ]	Available in any view

Chapter 3 QoS Policy Configuration

When configuring QoS policy, go to these sections for information that you are interested in:

l Overview

l Configuring QoS Policy

l Displaying and Maintaining QoS Policy

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/port group view.

3.2.1 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.

3.2.2 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

Follow these steps to 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 3-1 describes the available forms of this argument.

Table 3-1 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 4999. In a class configured with the operator and, the logical relationship between rules defined in the referenced IPv4 ACL is or.
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. In a class configured with the operator and, the logical relationship between rules defined in the referenced IPv6 ACL is or.
any	Specifies to match all packets.
customer-dot1p 8021p-list	Specifies to match packets by 802.1p precedence of the customer network. The 8021p-list 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.
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, in the form of vlan-id to vlan-id or multiple discontinuous VLAN IDs (separated by space). You can specify up to eight VLAN IDs for this argument at a time. VLAN ID is in the range 1 to 4094. In a class configured with the operator and, the logical relationship between the customer VLAN IDs specified for the customer-vlan-id keyword is or.
destination-mac mac-address	Specifies to match the packets with a specified destination MAC address.
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 or IPv6.
service-dot1p 8021p-list	Specifies to match packets by 802.1p precedence of the service provider network. The 8021p-list 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. In a class configured with the operator and, the logical relationship between the service VLAN IDs specified for the service-vlan-id keyword is or.
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, in the form of vlan-id to vlan-id or multiple discontinuous VLAN IDs (separated by space). You can specify up to eight VLAN IDs for this argument at a time. 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.

& Note:

Suppose the logical relationship between classification rules is and. Note the following when using the if-match command to define matching rules.

l If multiple matching rules with the acl or acl ipv6 keyword specified are defined in a class, the actual logical relationship between these rules is or when the policy is applied.

l If multiple matching rules with the customer-vlan-id or service-vlan-id keyword specified are defined in a class, the actual logical relationship between these rules is or.

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

3.2.3 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.

I. Configuration procedure

Follow these steps to define a 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 ] [ green action ] [ red action ] [ yellow action ]
Configure traffic filtering behavior	filter { deny \| permit }
Configure traffic mirroring action	mirror-to { cpu \| interface interface-type interface-number }
Configure nested VLAN tag action	nest top-most vlan-id vlan-id
Configure traffic redirect action	redirect { cpu \| interface interface-type interface-number \| link-aggregation group agg-id \| next-hop { ipv4-add [ ipv4-add ] \| ipv6-add [ interface-type interface-number ] [ ipv6-add [ interface-type interface-number ] ] } }
Remark the customer network VLAN ID for packets	remark customer-vlan-id vlan-id-value
Remark DSCP value for packets	remark dscp dscp-value
Remark 802.1p precedence 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 the service provider network VLAN ID for packets	remark service-vlan-id vlan-id-value

II. Configuration example

1) Network requirements

Create a traffic behavior named test, configuring TP action for it, with the CAR being 640 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 640

3.2.4 Defining a Policy

A policy associates a class with a traffic behavior. Each traffic behavior is comprised of a group of QoS actions. A device executes these QoS actions in the order they are defined.

Follow these steps to 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

3.2.5 Applying a Policy

I. Configuration procedure

Follow these steps to 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 view or port group view	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 GigabitEthernet 1/0/1 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 GigabitEthernet 1/0/1

[Sysname-GigabitEthernet1/0/1]

# Apply the policy to the port.

[Sysname-GigabitEthernet1/0/1] qos apply policy test inbound

3.3 Displaying and Maintaining 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 ] ]	Available 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

When configuring congestion management, go to these section for information that you are interested in:

l Overview

l Congestion Management Policy

l Configuring an SP Queue

l Configuring a WRR Queue

l Configuring SP+WRR Queues

l Displaying and Maintaining 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

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 eight output queues on the port and the preferential queue classifies the eight output queues on the port into eight classes, which are queue7, queue6, queue5, queue4, queue3, queue2, queue1, and queue0. Their priorities decrease in order.

In queue scheduling, SP sends packets in the queue with higher priority strictly following the priority order from high to low. When the queue with higher priority is empty, packets in the queue with lower priority are sent. You can put critical service packets into the queues with higher priority and put non-critical service (such as e-mail) packets into the queues with lower priority. In this case, critical service packets are sent preferentially and non-critical service packets are sent when critical service groups are not sent.

The disadvantage of SP queue is that: if there are packets in the queues with higher priority for a long time in congestion, the packets in the queues with lower priority will be “starved” because they are not served.

2) WRR queue-scheduling algorithm

Figure 4-2 Diagram for WRR queuing

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 output 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 S5500-SI 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

4.3.1 Configuration Procedure

Follow these steps to 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 view or port group view	Enter port group view	port-group { manual port-group-name \| aggregation agg-id }
Configure SP queue scheduling algorithm		qos sp	Required By default, all the ports adopt the WRR queue scheduling algorithm, with the weight values assigned to queue 0 through queue 7 being 1, 2, 3, 4, 5, 9, 13, and 15.

4.3.2 Configuration Examples

I. Network requirements

Configure GigabitEthernet1/0/1 to adopt SP queue scheduling algorithm.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Configure an SP queue for GigabitEthernet1/0/1 port.

[Sysname] interface GigabitEthernet 1/0/1

[Sysname-GigabitEthernet1/0/1] qos sp

4.4 Configuring a WRR Queue

By default, SP queue scheduling algorithm is adopted on all the ports. You can adopt WRR queue scheduling algorithm as required.

4.4.1 Configuration Procedure

Follow these steps to 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 view or port group view	Enter port group view	port-group { manual port-group-name \| aggregation agg-id }
Configure WRR queue scheduling		qos wrr queue-id group group-id weight queue-weight	Required By default, all the ports adopt the WRR queue scheduling algorithm, with the weight values assigned to queue 0 through queue 7 being 1, 2, 3, 4, 5, 9, 13, and 15.

4.4.2 Configuration Examples

I. Network requirements

Configure WRR queue scheduling algorithm on GigabitEthernet1/0/1, and assign weight 1, 2, 4, 6, 8, 10, 12, and 14 to queue 0 through queue 7.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Configure the WRR queues on GigabitEthernet1/0/1 port.

[Sysname] interface GigabitEthernet 1/0/1

[Sysname-GigabitEthernet1/0/1] qos wrr 0 group 1 weight 1

[Sysname-GigabitEthernet1/0/1] qos wrr 1 group 1 weight 2

[Sysname-GigabitEthernet1/0/1] qos wrr 2 group 1 weight 4

[Sysname-GigabitEthernet1/0/1] qos wrr 3 group 1 weight 6

[Sysname-GigabitEthernet1/0/1] qos wrr 4 group 1 weight 8

[Sysname-GigabitEthernet1/0/1] qos wrr 5 group 1 weight 10

[Sysname-GigabitEthernet1/0/1] qos wrr 6 group 1 weight 12

[Sysname-GigabitEthernet1/0/1] qos wrr 7 group 1 weight 14

4.5 Configuring SP+WRR Queues

As required, you can configure part of the queues on the port to adopt the SP queue-scheduling algorithm and parts of queues to adopt the WRR queue-scheduling algorithm. Through adding the queues on a port to the SP scheduling group and WRR scheduling group (namely, group 1), the SP+WRR queue scheduling is implemented. During the queue scheduling process, the queues in the SP scheduling group is scheduled preferentially. When no packet is to be sent in the queues in the SP scheduling group, the queues in the WRR scheduling group are scheduled. The queues in the SP scheduling group are scheduled according to the strict priority of each queue, while the queues in the WRR queue scheduling group are scheduled according the weight value of each queue.

4.5.1 Configuration Procedure

Follow these steps to 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 view or port group view	Enter port group view	port-group { manual port-group-name \| aggregation agg-id }
Configure SP queue scheduling		qos wrr queue-id group sp	Required By default, all the ports adopt the WRR queue scheduling algorithm, with the weight values assigned to queue 0 through queue 7 being 1, 2, 3, 4, 5, 9, 13, and 15.
Configure WRR queue scheduling		qos wrr queue-id group group-id weight queue-weight	Required

4.5.2 Configuration Examples

I. Network requirements

l Configure to adopt SP+WRR queue scheduling algorithm on GigabitEthernet1/0/1.

l Configure queue 0, queue 1, queue 2 and queue 3 on GigabitEthernet1/0/1 to be in SP queue scheduling group.

l Configure queue 4, queue 5, queue 6 and queue 7 on GigabitEthernet1/0/1 to be in WRR queue scheduling group, with the weight being 2, 4, 6 and 8 respectively.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Enable the SP+WRR queue scheduling algorithm on GigabitEthernet1/0/1.

[Sysname] interface GigabitEthernet 1/0/1

[Sysname-GigabitEthernet1/0/1] qos wrr 0 group sp

[Sysname-GigabitEthernet1/0/1] qos wrr 1 group sp

[Sysname-GigabitEthernet1/0/1] qos wrr 2 group sp

[Sysname-GigabitEthernet1/0/1] qos wrr 3 group sp

[Sysname-GigabitEthernet1/0/1] qos wrr 4 group 1 weight 2

[Sysname-GigabitEthernet1/0/1] qos wrr 5 group 1 weight 4

[Sysname-GigabitEthernet1/0/1] qos wrr 6 group 1 weight 6

[Sysname-GigabitEthernet1/0/1] qos wrr 7 group 1 weight 8

4.6 Displaying and Maintaining Congestion Management

To do…	Use the command…	Remarks
Display WRR queue configuration information	display qos wrr interface [ interface-type interface-number ]	Available in any view
Display SP queue configuration information	display qos sp interface [ interface-type interface-number ]	Available in any view

Chapter 5 Priority Mapping

When configuring priority mapping, go to these sections for information you are interested in:

l Priority Mapping Overview

l Configuring a Priority Mapping Table

l Configuring the Port Priority

l Configuring Port Priority Trust Mode

l Displaying and Maintaining 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 precedence, 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. The higher the drop precedence, the more likely a packet is dropped.

S5500-SI series Ethernet switches provide the following two priority trust modes:

l Trusting the DSCP precedence of received packets. In this mode, the switch searches the dscp-dot1p/dp/dscp mapping table based on the DSCP precedence of the received packet for the 802.1p precedence/drop precedence/DSCP precedence to be used to mark the packet. Then the switch searches the dot1p-lp mapping table based on the marked 802.1p precedence for the corresponding local precedence and marks the received packet with the local precedence.

l Trusting the 802.1p precedence of received packets. In this mode, if a packet is received without an 802.1q tag, the switch takes the priority of the receiving port as the 802.1p precedence of the packet and then based on the priority searches the dot1p-dp/lp mapping table for the local/drop precedence for the packet. If packet is received with an 802.1q tag, the switch searches the dot1p-dp/lp mapping table based on the 802.1p precedence in the tag for local/drop precedence for the packet.

The default dot1p-lp/dp mapping and dscp-dot1p/dp/dscp mapping provided by S5500-SI series Ethernet switches are shown in the following two tables.

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 precedence (dot1p)	Local precedence (lp)	Drop precedence (dp)
0	2	0
1	0	0
2	1	0
3	3	0
4	4	0
5	5	0
6	6	0
7	7	0

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

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

& Note:

You cannot configure to map any DSCP value to drop precedence 1.

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

Follow these steps to 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-dp \| dot1p-lp \| dscp-dot1p \| dscp-dp \| 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.

5.2.3 Configuration Examples

I. Network requirements

Modify the dot1p-lp mapping table as those listed in Table 5-3.

Table 5-3 The specified dot1p-lp mapping

802.1p precedence	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

By default, if a port receives packets without 802.1q tags, the switch takes the priority of the receiving port as the 802.1p precedence of the received packets, searches the dot1p-lp/dp mapping table for the corresponding local precedence and drop precedence according to the 802.1p precedence of the received packets, and then marks the received packets with the corresponding local precedence and drop precedence.

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

Follow these steps to 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 view or port group view	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 Examples

I. Network requirements

Configure the port priority to 7.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Configure port priority of GigabitEthernet1/0/1.

[Sysname] interface GigabitEthernet 1/0/1

[Sysname-GigabitEthernet1/0/1] qos priority 7

5.4 Configuring Port Priority Trust Mode

You can configure the switch to trust the DSCP precedence of the received packets. In this case, the switch searches the dscp-dot1p/dp/dscp mapping table for the corresponding precedence according to the DSCP precedence of the packets and marks the received packets with the precedence.

5.4.1 Configuration Prerequisites

It is determined to trust the DSCP precedence of received packets.

5.4.2 Configuration Procedure

Follow these steps to 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 view or port group view	Enter port group view	port-group { manual port-group-name \| aggregation agg-id }
Configure to trust the DSCP precedence of the received packets		qos trust dscp	Required By default, the 802.1p precedence of the received packets is trusted.

5.4.3 Configuration Examples

I. Network requirements

Configure to trust the DSCP precedence of the received packets.

II. Configuration procedure

# Enter system view.

<Sysname> system-view

# Enter port view.

[Sysname] interface GigabitEthernet 1/0/1

[Sysname-GigabitEthernet1/0/1]

# Configure to trust the DSCP precedence of the received packets.

[Sysname-GigabitEthernet1/0/1] qos trust dscp

5.5 Displaying and Maintaining Priority Mapping

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

Chapter 6 Applying a QoS Policy to VLANs

When applying a QoS policy to VLANs, go to these sections for information that you are interested in:

l Overview

l Applying a QoS Policy to VLANs

l Displaying and Maintaining QoS Policies Applied to VLANs

l Configuration Examples

6.1 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.

A QoS policy is not effective on dynamic VLANs, for example, VLANs created by GVRP.

6.2 Applying a QoS Policy to VLANs

6.2.1 Configuration Prerequisites

l The QoS policy to be applied is defined. Refer to Configuring QoS Policy for policy defining.

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

6.2.2 Configuration Procedure

Follow these steps to apply a QoS policy to VLANs:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Apply the QoS policy to the specified VLAN(s)	qos vlan-policy policy-name vlan vlan-id-list inbound	Required

6.3 Displaying and Maintaining QoS Policies Applied to VLANs

To do…	Use the command…	Remarks
Display the QoS policies applied to VLANs	display qos vlan-policy { name policy-name \| vlan [ vlan-id ] }	Available in any view
Clear the statistics information about the QoS policies applied to VLANs	reset qos vlan-policy [ vlan vlan-id ]	Available in user view

6.4 Configuration Examples

6.4.1 Network Requirements

l The QoS policy test is defined to perform traffic policing for the packets matching basic IPv4 ACL 2000, with CIR as 64 kbps. The exceeding packets are dropped.

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.

6.4.2 Configuration Procedure

# Enter system view.

<Sysname> system-view

# Create a class and enter class view.

[Sysname] traffic classifier cl1

# Define a classification rule.

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

[Sysname-classifier-cl1] quit

# Create a traffic behavior and enter traffic behavior view.

[Sysname] traffic behavior be1

# Configure the traffic behavior.

[Sysname-behavior-be1] car cir 64

[Sysname-behavior-be1] quit

# Create a QoS policy and enter QoS policy view.

[Sysname] qos policy test

# Associate a class with a traffic behavior.

[Sysname-qospolicy-test] classifier cl1 behavior be1

[Sysname-qospolicy-test] quit

# Apply the policy to specific VLANs.

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

Chapter 7 Traffic Mirroring Configuration

When configuring traffic mirroring, go to these sections for information that you are interested in:

l Overview

l Configuring Traffic Mirroring

l Displaying and Maintaining Traffic Mirroring

l Traffic Mirroring Configuration Examples

7.1 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.

& Note:

On S5500-SI series Ethernet switches, traffic can only be mirrored to ports and to CPU.

7.2 Configuring Traffic Mirroring

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

Follow these steps to 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 traffic mirroring action in the traffic behavior	mirror-to { cpu \| interface interface-type interface-number }	Required

7.3 Displaying and Maintaining 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	Available in any view
Display the configuration information about the user-defined policy	display qos policy user-defined policy-name	Available in any view

7.4 Traffic Mirroring Configuration Examples

7.4.1 Network Requirements

The user's network is as described below:

l Host A (with the IP address 192.168.0.1) and Host B are connected to GigabitEthernet1/0/1 of the switch.

l The data monitoring device is connected to GigabitEthernet1/0/2 of the switch.

It is required to monitor and analyze packets sent by Host A on the data monitoring device.

Figure 7-1 Network diagram for configuring traffic mirroring to a port

7.4.2 Configuration Procedure

Configure Switch:

# Enter system view.

<Sysname> system-view

# Configure basic IPv4 ACL 2000 to match packets with the source IP address 192.168.0.1.

[Sysname] acl number 2000

[Sysname-acl-basic-2000] rule permit source 192.168.0.1 0

[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 GigabitEthernet1/0/2 in the traffic behavior.

[Sysname] traffic behavior 1

[Sysname-behavior-1] mirror-to interface GigabitEthernet 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 GigabitEthernet1/0/1.

[Sysname] interface GigabitEthernet 1/0/1

[Sysname-GigabitEthernet1/0/1] qos apply policy 1 inbound

After the configurations, you can monitor all packets sent from Host A on the data monitoring device.

H3C S5500-SI Series Ethernet Switches Operation Manual(V1.01)

Chapter 1 QoS Overview

2.5 Displaying and Maintaining LR

I. Class

II. Traffic behavior

III. Policy

I. Configuration procedure

II. Configuration example

I. Configuration procedure

II. Configuration example

I. Configuration procedure

II. Configuration example

I. Network requirements

II. Configuration procedure

4.4 Configuring a WRR Queue

I. Network requirements

II. Configuration procedure

I. Network requirements

II. Configuration procedure

I. Network requirements

II. Configuration procedure

I. Network requirements

II. Configuration procedure

I. Network requirements

II. Configuration procedure

Chapter 6 Applying a QoS Policy to VLANs

6.2 Applying a QoS Policy to VLANs

6.3 Displaying and Maintaining QoS Policies Applied to VLANs

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