Huawei AR1200-S Series Configuration manual

Huawei AR2200 Series Enterprise Routers

V200R002C01

Configuration Guide - QoS

Issue 01

Date 2012-04-20

HUAWEI TECHNOLOGIES CO., LTD.

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and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.

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Huawei Technologies Co., Ltd.

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About This Document

Intended Audience

This document describes the concepts and configuration procedures of QoS features on the

AR2200, and provides the configuration examples.

This document provides guidance for configuring QoS features.

This document is intended for:

l Data configuration engineers

l Commissioning engineers

l Network monitoring engineers

l System maintenance engineers

Symbol Conventions

The symbols that may be found in this document are defined as follows.

Symbol

Description

DANGER

Indicates a hazard with a high level of risk, which if not

avoided, will result in death or serious injury.

WARNING

Indicates a hazard with a medium or low level of risk, which

if not avoided, could result in minor or moderate injury.

CAUTION

Indicates a potentially hazardous situation, which if not

avoided, could result in equipment damage, data loss,

performance degradation, or unexpected results.

TIP

Indicates a tip that may help you solve a problem or save

time.

NOTE

Provides additional information to emphasize or supplement

important points of the main text.

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Command Conventions

The command conventions that may be found in this document are defined as follows.

Convention Description

Boldface The keywords of a command line are in boldface.

Italic Command arguments are in italics.

[ ] Items (keywords or arguments) in brackets [ ] are optional.

{ x | y | ... } Optional items are grouped in braces and separated by

vertical bars. One item is selected.

[ x | y | ... ] Optional items are grouped in brackets and separated by

vertical bars. One item is selected or no item is selected.

{ x | y | ... }

Optional items are grouped in braces and separated by

vertical bars. A minimum of one item or a maximum of all

items can be selected.

[ x | y | ... ]

Optional items are grouped in brackets and separated by

vertical bars. Several items or no item can be selected.

&<1-n> The parameter before the & sign can be repeated 1 to n times.

# A line starting with the # sign is comments.

Interface Numbering Conventions

Interface numbers used in this manual are examples. In device configuration, use the existing

interface numbers on devices.

Change History

Updates between document issues are cumulative. Therefore, the latest document issue contains

all updates made in previous issues.

Changes in Issue 01 (2012-04-20)

Initial commercial release.

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iii

Contents

About This Document.....................................................................................................................ii

1 QoS Configuration........................................................................................................................1

1.1 QoS Overview....................................................................................................................................................3

1.2 QoS Features Supported by the AR2200............................................................................................................3

1.3 Configuring Priority Mapping..........................................................................................................................12

1.3.1 Establishing the Configuration Task.......................................................................................................12

1.3.2 Configuring the Packet Priority Trusted by an Interface.........................................................................13

1.3.3 Setting the Default 802.1p Priority of an Interface..................................................................................14

1.3.4 Configuring a Priority Mapping Table....................................................................................................15

1.3.5 Checking the Configuration.....................................................................................................................16

1.4 Configuring Traffic Policing............................................................................................................................16

1.4.1 Establishing the Configuration Task.......................................................................................................16

1.4.2 Configuring Traffic Policing on an Interface..........................................................................................17

1.4.3 Configuring Flow-based Traffic Policing................................................................................................18

1.4.4 Checking the Configuration.....................................................................................................................19

1.5 Configuring Traffic Shaping............................................................................................................................20

1.5.1 Establishing the Configuration Task.......................................................................................................20

1.5.2 Configuring Interface-based Traffic Shaping..........................................................................................22

1.5.3 Configuring Interface-based Adaptive Traffic Shaping..........................................................................23

1.5.4 Configuring Queue-based Traffic Shaping..............................................................................................25

1.5.5 Configuring Flow-based Traffic Shaping................................................................................................26

1.5.6 Configuring Flow-based Adaptive Traffic Shaping................................................................................26

1.5.7 Checking the Configuration.....................................................................................................................28

1.6 Configuring Congestion Management..............................................................................................................29

1.6.1 Establishing the Configuration Task.......................................................................................................29

1.6.2 Configuring Queue-based Congestion Management...............................................................................30

1.6.3 Configuring Class-based Congestion Management................................................................................32

1.6.4 Checking the Configuration.....................................................................................................................33

1.7 Configuring Congestion Avoidance.................................................................................................................34

1.7.1 Establishing the Configuration Task.......................................................................................................34

1.7.2 Configuring Queue-based WRED...........................................................................................................35

1.7.3 Configuring Flow-based WRED.............................................................................................................37

1.7.4 Checking the Configuration.....................................................................................................................38

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1.8 Configuring HQoS............................................................................................................................................39

1.8.1 Establishing the Configuration Task.......................................................................................................39

1.8.2 Configuring a Traffic Policy....................................................................................................................41

1.8.2.1 Configuring a Sub Traffic Policy...................................................................................................41

1.8.2.2 Configuring a Traffic Policy...........................................................................................................41

1.8.2.3 Applying the Traffic Policy to an Interface....................................................................................43

1.8.3 (Optional) Configuring Traffic Policing on an Interface.........................................................................43

1.8.4 (Optional) Configuring Traffic Shaping on an Interface.........................................................................43

1.8.5 Checking the Configuration.....................................................................................................................44

1.9 Maintaining QoS...............................................................................................................................................45

1.9.1 Displaying the Queue-based Traffic Statistics........................................................................................45

1.9.2 Clearing the Queue-based Traffic Statistics............................................................................................45

1.10 Configuration Examples.................................................................................................................................45

1.10.1 Example for Configuring Priority Mapping..........................................................................................46

1.10.2 Example for Configuring Traffic Policing............................................................................................49

1.10.3 Example for Configuring Traffic Shaping.............................................................................................54

1.10.4 Example for Configuring Adaptive Traffic Shaping.............................................................................58

1.10.5 Example for Configuring Congestion Avoidance and Congestion Management.................................61

1.10.6 Example for Configuring HQoS............................................................................................................68

2 Traffic Policy Configuration.....................................................................................................78

2.1 Traffic Policy Overview...................................................................................................................................79

2.2 Traffic Policy Features Supported by the AR2200..........................................................................................79

2.3 Configuring a Traffic Classifier.......................................................................................................................82

2.3.1 Establishing the Configuration Task.......................................................................................................83

2.3.2 (Optional) Configuring SAC...................................................................................................................84

2.3.2.1 Configuring a Signature File..........................................................................................................84

2.3.2.2 Configuring an SAC Group............................................................................................................84

2.3.2.3 Configuring the SAC Statistics Function.......................................................................................85

2.3.2.4 Checking the Configuration............................................................................................................86

2.3.3 Configuring a Traffic Classifier..............................................................................................................86

2.3.4 Checking the Configuration.....................................................................................................................88

2.4 Configuring a Traffic Behavior........................................................................................................................89

2.4.1 Establishing the Configuration Task.......................................................................................................89

2.4.2 Configuring a Permit or Deny Action.....................................................................................................90

2.4.3 Configuring Redirection..........................................................................................................................91

2.4.4 Configuring Re-marking..........................................................................................................................91

2.4.5 Configuring Traffic Policing...................................................................................................................92

2.4.6 Configuring Traffic Shaping...................................................................................................................93

2.4.7 Configuring Adaptive Traffic Shaping....................................................................................................94

2.4.8 Configuring Congestion Management.....................................................................................................94

2.4.9 Configuring Congestion Avoidance........................................................................................................97

2.4.10 Binding a Sub Traffic Policy.................................................................................................................97

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2.4.11 Configuring Traffic Statistics................................................................................................................99

2.4.12 Checking the Configuration...................................................................................................................99

2.5 Configuring a Traffic Policy...........................................................................................................................100

2.6 Maintaining a Traffic Policy...........................................................................................................................101

2.6.1 Displaying the Flow-based Traffic Statistics.........................................................................................101

2.6.2 Clearing the Flow-based Traffic Statistics............................................................................................101

2.7 Configuration Examples.................................................................................................................................102

2.7.1 Example for Configuring Re-marking...................................................................................................102

2.7.2 Example for Configuring Traffic Statistics...........................................................................................106

2.7.3 Example for Configuring Association Between NQA and Redirection................................................110

2.7.4 Example for Preventing BT Download.................................................................................................114

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1 QoS Configuration

About This Chapter

This chapter describes common QoS functions on interfaces of the AR2200: priority mapping,

traffic policing, traffic shaping, congestion management, congestion avoidance, and

Hierarchical Quality of Service (HQoS). It also provides configuration methods and examples.

1.1 QoS Overview

QoS is designed to provide differentiated services based on networking requirements.

1.2 QoS Features Supported by the AR2200

This section describes QoS features supported by the AR2200.

1.3 Configuring Priority Mapping

After priority mapping is configured, the AR2200 determines the queues and output priorities

of the received packets based on packet priorities or the default 802.1p priority of the interface.

By doing this, the AR2200 provides differentiated services.

1.4 Configuring Traffic Policing

The AR2200 supports interface-based traffic policing and flow-based traffic policing.

1.5 Configuring Traffic Shaping

Traffic shaping enables outgoing traffic to be sent out at an even rate and reduces the number

of discarded packets whose rate exceeds the rate limit.

1.6 Configuring Congestion Management

If congestion occurs on a network after congestion management is configured, the AR2200

determines the sequence at which packets are forwarded according to the defined scheduling

policy.

1.7 Configuring Congestion Avoidance

After congestion avoidance is complete, the AR2200 discards the packets whose rate exceeds

the rate limit based on the WRED configuration.

1.8 Configuring HQoS

To provide differentiated QoS services, configure HQoS on the AR2200.

1.9 Maintaining QoS

This section describes how to maintain QoS.

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1.10 Configuration Examples

This section provides several configuration examples of traffic policing, traffic shaping,

congestion avoidance, and congestion management.

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1.1 QoS Overview

QoS is designed to provide differentiated services based on networking requirements.

QoS evaluates the capabilities of the service supplied to meet customer requirements. On the

Internet, QoS is used to evaluate capabilities of a network to transmit packets. The network

provides various services, and QoS evaluates services from different aspects. Generally, QoS

evaluates core items, including the delay, jitter, and packet loss ratio during packet transmission.

QoS uses the following models:

l Best-Effort (BE) model: The BE model is a service model that handles all packets equally.

In the BE model, a network attempts to send packets, but cannot ensure performance such

as delay and reliability. The BE model can be applied to various network applications, such

as FTP and email. The BE model can be implemented using the First in First out (FIFO)

queue.

l IntServ model: The IntServ model is an integrated service model. A device must submit a

request to a network before sending packets. Combined with multicast, the IntServ model

can be used in real-time multimedia applications that require high bandwidth and low delay,

such as video conference and video on demand (VoD).

l DiffServ model: The DiffServ model is a multi-service model and can meet different QoS

requirements, which ensures that applications are provided with differentiated QoS levels.

QoS can be specified based on various information, such as the IP precedence, source

address, and destination address of packets. Network devices perform traffic classification,

traffic shaping, traffic policing, and queue scheduling based on the information.

1.2 QoS Features Supported by the AR2200

This section describes QoS features supported by the AR2200.

The AR2200 supports the following functions:

l Priority Mapping

l Traffic Policing

l Traffic Shaping

l Congestion Avoidance

l Congestion Management

l HQoS

Table 1-1 Implementation of QoS features

Feature

Implementation

Priority Mapping Priority mapping can be applied to inbound

and outbound interfaces.

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Feature Implementation

Traffic policing Interface-based traffic policing can be

applied to inbound and outbound WAN-side

interfaces, but can only be applied to inbound

LAN-side interfaces.

Flow-based traffic policing can be applied to

inbound and outbound interfaces.

Traffic shaping

Interface-based traffic shaping can only be

applied to outbound interfaces.

Interface-based adaptive traffic shaping can

only be applied to outbound interfaces.

Queue-based traffic shaping can only be

applied to outbound interfaces.

Flow-based traffic shaping can only be

applied to outbound WAN-side interfaces.

Flow-based adaptive traffic shaping can only

be applied to outbound WAN-side interfaces.

Congestion avoidance

Queue-based congestion avoidance can only

be applied to outbound WAN-side interfaces.

Flow-based congestion avoidance can only

be applied to outbound WAN-side interfaces.

Congestion management Queue-based congestion management can

only be applied to outbound interfaces.

Class-based congestion management can

only be applied to outbound WAN-side

interfaces.

HQoS Flow-based hierarchical QoS (HQoS) can

only be applied to outbound WAN-side

interfaces.

Priority Mapping

Different packets carry different precedence fields. For example, VLAN packets carry the 802.1p

field, IP packets carry the DSCP field, and MPLS packets carry the EXP field. The mappings

between priority fields must be configured on gateways to retain priorities of packets when the

packets traverse different networks.

To ensure QoS for different packets, the AR2200 determines the queues that received packets

enter based on 802.1p priorities or DSCP priorities in packets or the default 802.1p priority of

an interface. The AR2200 can re-mark packet priorities so that the connected device can provide

differentiated QoS based on precedence fields of the packets.

The AR2200 sends packets to different interface queues based on local priority, and performs

traffic shaping, congestion avoidance, and queue scheduling for the queues. Table 1-2 lists the

mappings between local priorities and queues.

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Table 1-2 Mappings between local priorities and queues

Local Priority Queue Index

0 0

1 1

2 2

3 3

4 4

5 5

6 6

7 7

Traffic Policing

Traffic policing limits the traffic and resource usage by monitoring the rate limit.

Traffic policing discards the excess traffic to limit traffic within a proper range and to protect

network resources.

Traffic policing limits the traffic entering the Internet Service Provider (ISP).

l Token bucket and traffic measurement

The AR2200 needs to determine whether the traffic rate exceeds the rate limit before

performing traffic policing. Token buckets are usually used to measure traffic.

With a certain capacity, a token bucket stores tokens. The system places tokens into a token

bucket at the configured rate (one token occupies one bit). If the token bucket is full, excess

tokens overflow and no token is added.

When measuring traffic, a token bucket forwards packets based on the number of tokens

in the token bucket. If there are enough tokens in the token bucket for forwarding packets,

the traffic rate is within the rate limit. Otherwise, the traffic rate is not within the rate limit.

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Figure 1-1 Measuring traffic using token buckets

Packets sent by the

interface

Continue to send

packets

Token

bucket

Put tokens into the bucket at the

specified rate

Classification

Drop

Packets that

need to be

policed

Packets that do

not need to be

policed

The AR2200 supports dual token bucket technology:

The dual token bucket technology uses the following parameters:

– Committed Burst Size (CBS): capacity of bucket C, that is, the maximum volume of

burst traffic (in bytes) allowed by bucket C each time.

– Committed Information Rate (CIR): rate at which tokens are put into bucket C, that is,

the average rate of traffic (in kbit/s) allowed by bucket C.

– Peak Burst Size (PBS): capacity of bucket P, that is, the maximum volume of burst

traffic (in bytes) allowed by bucket P each time.

– Peak Information Rate (PIR): rate at which tokens are put into bucket P, that is, the

average rate of traffic (in kbit/s) allowed by bucket P.

When dual token buckets are used, the packets whose rate is less than the CIR value are

colored green, the packets whose rate is greater than the PIR value are colored red, and the

packets whose rate is greater than the CIR value, but less than the PIR value are colored

yellow.

Traffic policing actions include permit, deny, and forward after a priority change. By

default, green packets and yellow packets are allowed to pass through, and red packets are

discarded.

l Traffic policing features supported by the AR2200

The AR2200 supports the following traffic policing features:

– Interface-based traffic policing limits the incoming or outgoing service traffic on an

interface.

NOTE

You can use interface-based traffic policing to:

l Limit all the service traffic on an interface.

l Limit the service traffic matching a specified ACL rule.

l Limit the service traffic whose source and destination IP addresses within a specified range.

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– Flow-based traffic policing limits incoming or outgoing service traffic matching traffic

classification rules.

Traffic Shaping

Traffic shaping also limits traffic and resource usage by monitoring the rate limit. It also uses

the token bucket technology to measure traffic.

Traffic shaping adjusts the speed of outgoing traffic so that the downstream device has

capabilities to process traffic.

l Differences between traffic shaping and traffic policing

Traffic policing directly discards the excess packets. Traffic shaping buffers the packets

whose rate is greater than the traffic shaping rate in queues; therefore, traffic shaping

reduces the number of discarded packets. As shown in Figure 1-2, when there are sufficient

tokens in the token bucket, the buffered packets are forwarded at an even rate. If the tokens

are insufficient, packets are buffered continuously. If the number of packets to be buffered

is greater than the queue length, excess packets are discarded.

Figure 1-2 Traffic shaping

Packets sent by the

interface

Flows

Token

bucket

Put tokens into

token bucket at

specified rate

Simple traffic

classification

Packets

within the

rate limit

Packets not

within the rate

limit

Token

Buffer

packets in

queues

Discarded

packets when

the token bucket

is full

Packets that do

not need to be

shaped

Packets that

need to be

shaped

Traffic shaping increases the delay because it buffers packets in queues, whereas traffic

policing does not.

l Traffic shaping features supported by the AR2200

The AR2200 supports the following traffic shaping features:

– Traffic shaping on an interface or a sub-interface

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Shapes all the packets that pass through an interface or a sub-interface.

– Adaptive traffic shaping on an interface or a sub-interface

Shapes all the packets that pass through an interface or a sub-interface.

You can enable NQA between an upstream device and a downstream device so that

adaptive traffic shaping can dynamically adjust traffic shaping parameters based on the

NQA result.

– Queue-based traffic shaping

Shapes packets in a specified queue on an interface so that packets are shaped based on

priorities.

– Flow-based traffic shaping

Shapes packets of a specified type that pass through an interface so that packets

matching traffic classification rules can be shaped.

– Flow-based adaptive traffic shaping

Shapes packets of a specified type that pass through an interface. That is, packets

matching traffic classification rules are shaped.

You can enable NQA between an upstream device and a downstream device so that

adaptive traffic shaping can dynamically adjust traffic shaping parameters based on the

NQA result.

Congestion Avoidance

Congestion avoidance is a flow control mechanism. A system configured with congestion

avoidance monitors network resources such as queues and memory buffers. When congestion

occurs or aggravates, the system discards packets.

Congestion avoidance policies include tail drop, Random Early Detection (RED), and Weighted

Random Early Detection (WRED):

l Tail drop

The traditional packet loss policy uses the tail drop method. This method processes all

packets equally without classifying the packets into different types. When congestion

occurs, packets at the end of a queue are discarded until the congestion problem is solved.

This policy leads to global TCP synchronization. When packets of multiple TCP

connections are discarded simultaneously, these TCP connections enter the congestion

avoidance and slow start state. After a while, the peak of these TCP connections occurs.

The volume of traffic varies greatly, affecting link usage.

l RED

The RED technique randomly discards packets to prevent the transmission speed of

multiple TCP connections from being reduced simultaneously.

As specified by the RED algorithm, the upper drop threshold and lower drop threshold are

set. RED processes packets as follows:

– When the queue length is shorter than the lower drop threshold, no packet is discarded.

– When the queue length is longer than the upper drop threshold, all packets are discarded.

– When the queue length is between the lower drop threshold and the upper drop threshold,

incoming packets are discarded randomly. RED generates a random number for each

incoming packet and compares it with the drop probability of the current queue. If the

random number is greater than the drop probability, the packet is discarded. A longer

queue indicates a higher drop probability.

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l WRED

WRED also discards packets randomly to prevent global TCP synchronization. WRED,

however, generates random numbers of packets based on packet priorities. WRED discards

packets based on packet priorities, so the drop probability of packets with higher priorities

is low.

By default, the AR2200 uses tail drop. The AR2200 supports queue-based WRED and flow-

based RED.

Congestion Management

If a network transmitting both delay-sensitive and delay-insensitive services is congested

intermittently, congestion management is required. However, if a network is always congested,

bandwidth needs to be increased.

Generally, the AR2200 uses the following queue scheduling mechanisms:

l PQ scheduling

l WRR scheduling

l DRR scheduling

l WFQ scheduling

l PQ+WRR/PQ+DRR/PQ+WFQ scheduling

l CBQ scheduling

l PQ scheduling

Priority queuing (PQ) schedules packets in descending order of priorities. Queues with

lower priories are processed only after all the queues with higher priorities have been

processed.

By using PQ scheduling, the AR2200 puts packets of delay-sensitive services into queues

with higher priorities and packets of other services into queues with lower priorities. In this

manner, packets of key services can be transmitted first.

PQ scheduling has a disadvantage. If a lot of packets exist in queues with higher priorities

when congestion occurs, packets in queues with lower priorities cannot be transmitted for

a long time.

l WRR scheduling

Weighted Round Robin (WRR) scheduling ensures that packets in all the queues are

scheduled in turn.

For example, eight queues are configured on an interface. Each queue is configured with

a weight: w7, w6, w5, w4, w3, w2, w1, and w0. The weight value represents the percentage

of obtaining resources. The following scenario assumes that the weights of queues on the

100M interface are 50, 50, 30, 30, 10, 10, 10, and 10, which match w7, w6, w5, w4, w3,

w2, w1, and w0. Therefore, the queue with the lowest priority can obtain at least 5 Mbit/s

bandwidth. This ensures that packets in all the queues can be scheduled.

In addition, WRR can dynamically change the time of scheduling packets in queues. For

example, if a queue is empty, WRR ignores this queue and starts to schedule the next queue.

This ensures efficient use of bandwidth.

WRR scheduling has two disadvantages:

– WRR schedules packets based on the number of packets. When the average packet

length in each queue is the same or known, you can obtain the required bandwidth by

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setting WRR weight values. When the average packet length in each queue is variable,

you cannot obtain the required bandwidth by setting WRR weight values.

– Delay-sensitive services, such as voice services, cannot be scheduled in a timely

manner.

l DRR scheduling

Implementation of Deficit Round Robin (DRR) is similar to that of WRR.

The difference between DRR and WRR is as follows: WRR schedules packets based on

the number of packets, whereas DRR schedules packets based on the packet length. If the

packet length is too long, DRR allows the negative weight value so that long packets can

be scheduled. In the next round, the queue with the negative weight value is not scheduled

until its weight value becomes positive.

DRR offsets the disadvantages of PQ scheduling and WRR scheduling. That is, in PQ

scheduling, packets in queues with lower priorities cannot be scheduled for a long time; in

WRR scheduling, bandwidth is allocated improperly when the packet length of each queue

is different or variable.

DRR cannot schedule delay-sensitive services such as voice services in time.

l WFQ scheduling

Fair Queue (FQ) ensures that network resources are allocated evenly to optimize the delay

and jitter of all flows. Weighted FQ (WFQ) schedules packets based on priorities, and

schedules more packets with higher priorities than packets with lower priorities.

WFQ can automatically classify flows based on the session information, including the

protocol type, source and destination TCP or UDP port numbers, source and destination IP

addresses, and precedence field in the ToS field. In addition, WFQ provides a large number

of queues and evenly puts flows into queues to smooth out the delay. When flows leave

queues, WFQ allocates the bandwidth on the outbound interface for each flow based on

the precedence of each flow. Flows with the lowest priorities obtain the least bandwidth.

l PQ+WRR/PQ+DRR/PQ+WFQ scheduling

PQ, WRR, DRR, and WFQ have their own advantages and disadvantages. If only PQ

scheduling is used, packets in queues with lower priorities cannot obtain bandwidth. If only

WRR, DRR, or WFQ scheduling is used, delay-sensitive services cannot be scheduled in

time. PQ+WRR, PQ+DRR, or PQ+WFQ scheduling integrates the advantages of PQ

scheduling and WRR or DWRR scheduling and offsets their disadvantages.

By using PQ+WRR, PQ+DRR, or PQ+WFQ scheduling, the AR2200 puts important

packets, such as protocol packets and packets of delay-sensitive services to the PQ queue,

and allocates bandwidth to the PQ queue. Then the AR2200 can put other packets into

WRR, DRR, or WFQ queues based on the packet priority. Packets in WRR, DRR, or WFQ

queues can be scheduled in turn.

l CBQ scheduling

Class-based queueing (CBQ) is an extension of WFQ and matches packets with traffic

classifiers. CBQ classifies packets based on the IP precedence or DSCP priority, inbound

interface, or 5-tuple (protocol type, source IP address and mask, destination IP address and

mask, source port range, and destination port range). Then CBQ puts packets into different

queues. If packets do not match any configured traffic classifiers, CBQ matches packets

with the default traffic classifier.

CBQ provides the following types of queues:

– Expedited Forwarding (EF) queues are applied to short-delay services.

An EF queue has the highest priority. You can put one or more types of packets into EF

queues and set different bandwidth for different types of packets. During scheduling, if

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EF queues have packets, packets in EF queues are sent first. Packets in other queues are

sent only after EF queues are empty or the maximum reservable bandwidth of EF queues

is exceeded.

UDP packets of VoIP services often exist in EF queues; therefore, use the tail drop

method but not WRED.

– Assured Forwarding (AF) queues are applied to key data services that require assured

bandwidth.

Each AF queue corresponds to one type of packets. You can set bandwidth for each

type of packets. During scheduling, the system sends packets based on the configured

bandwidth. AF implements fair scheduling. If an interface has remaining bandwidth,

packets in AF queues obtain the remaining bandwidth based on weights. When

congestion occurs, each type of packets can obtain the minimum bandwidth.

If the length of an AF queue reaches the maximum value, the tail drop method is used

by default. You can choose to use WRED.

– Best-Effort (BE) queues are applied to best-effort services that require no strict QoS

assurance.

If packets do not match any configured traffic classifiers, packets match the default

traffic classifier defined by the system. You are allowed to configure AF queues and

bandwidth for the default traffic classifier, whereas BE queues are configured in most

situations. BE uses WFQ scheduling so that the system schedules packets matching the

default traffic classifier based on flows.

If the length of a BE queue reaches the maximum value, the tail drop method is used

by default. You can choose to use WRED.

HQoS

The traditional QoS technology schedules packets based on interfaces. An interface, however,

can identify only priorities of different services but cannot identify services of different users.

Packets of the same priority are placed into the same queue on an interface, and compete for the

same queue resource. Therefore, the traditional QoS technology is unable to provide

differentiated services based on types of traffic and users.

As the number of users increases continuously and services develop, users require differentiated

services to have better QoS and gain more profits. Hierarchical QoS (HQoS) implements

hierarchical scheduling based on queues and differentiates services and users. It provides QoS

guarantee and saves network operation and maintenance costs.

l Queues supported by HQoS

The AR2200 supports three levels of queues, that is, level-3 flow queue (FQ), level-2

subscriber queue (SQ), and level-1 port queue (PQ). The HQoS hierarchy is a tree structure.

The flow queue is taken as the leaf node and the port queue is taken as the root node. When

packets pass through an interface using HQoS, the packets are classified so that they

traverse the branches of the tree. Packets arrive at the top of the tree and are classified on

one of the leaves. Packets then traverse down the tree until they are transmitted out the

interface at the root.

l HQoS implementation

HQoS is implemented by traffic policy nesting supported by the AR2200.

A traffic policy can be nested into another traffic policy. That is, the traffic behavior or

action in a traffic policy is a sub traffic policy. When a sub traffic policy is bound to a traffic

policy, the traffic behavior in the traffic policy is taken for packets matching the traffic

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classifier associated with the traffic behavior. Then the packets are classified by the sub

traffic policy and the traffic behavior in the sub traffic policy is taken for the classified

packets.

A traffic classifier in the traffic policy differentiates users. That is, the packets that match

the traffic classifier in the traffic policy enter the same subscriber queue.

The traffic classifier in a sub traffic policy differentiates services. That is, the packets that

match the traffic classifier in the sub traffic policy enter the same flow queue.

l HQoS scheduling

HQoS implements hierarchical scheduling and provides good service support. Scheduler

levels are relevant to the topology.

The AR2200 provides three levels of schedulers, that is, flow queue scheduler, subscriber

queue scheduler, and port queue scheduler. The flow queue scheduler and subscriber queue

scheduler support PQ scheduling, WFQ scheduling, and PQ+WFQ scheduling. The port

queue scheduler uses RR scheduling.

HQoS deployment for enterprise users is used as an example. Enterprise users have VoIP

services, video conference (VC) services, and data services. Each subscriber queue

corresponds to one enterprise user and each flow queue corresponds to a type of services.

By deploying HQoS, the AR2200 implements the following functions:

– Controlling traffic scheduling among the three types of services of a single enterprise

user

– Controlling total bandwidth of the three types of services of a single enterprise user

– Controlling bandwidth allocation between multiple enterprise users

– Controlling total bandwidth of multiple enterprise users

1.3 Configuring Priority Mapping

After priority mapping is configured, the AR2200 determines the queues and output priorities

of the received packets based on packet priorities or the default 802.1p priority of the interface.

By doing this, the AR2200 provides differentiated services.

1.3.1 Establishing the Configuration Task

Before configuring priority mapping, familiarize yourself with the applicable environment,

complete the pre-configuration tasks, and obtain the data required for the configuration. This

will help you complete the configuration task quickly and accurately.

Applicable Environment

The AR2200 can determine the queues that packets enter based on packet priorities (802.1p/

DSCP priorities) or the priority of an interface. The AR2200 can re-mark packet priorities so

that the connected device can provide differentiated QoS based on precedence fields of the

packets.

l When the AR2200 is configured to trust packet priorities (802.1p priorities, DSCP

priorities), it maps packet priorities to local priorities, determines the queues that packets

enter, and can re-mark packet priorities.

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l When the AR2200 is configured to use the priority of an interface, it maps the priority of

the interface to the local priority based on priority mapping, determines the queues that

packets enter, and can re-mark packet priorities.

Pre-configuration Tasks

Before configuring priority mapping, complete the following tasks:

l Configuring link layer attributes of interfaces to ensure that these interfaces work properly

l Configuring IP addresses and routing protocols for interfaces to ensure connectivity

Data Preparation

To configure priority mapping, you need the following data.

No. Data

1 Types and numbers of interfaces

2 Priority of an interface

3 Packet priority trusted by an interface

4 Input priority and output priority

1.3.2 Configuring the Packet Priority Trusted by an Interface

After an interface is configured to trust the priority of packets, the AR2200 performs mapping

based on the specified priority.

Context

The AR2200 trusts the following priorities:

l 802.1p priority

– The AR2200 maps 802.1p priorities in tagged packets to local priorities, determines the

queues that the tagged packets enter, and can modify packet priorities based on the

priority mapping table.

– The AR2200 adds the default 802.1p priority of the interface to untagged packets, and

maps the default 802.1p priority to the local priority, determines the queues that the

untagged packets enter, and can modify packet priorities based on the priority mapping

table.

l DSCP priority

The AR2200 maps DSCP priorities of packets to local priorities, determines the queues

that packets enter, and can modify packet priorities based on the priority mapping table.

l Priority of an interface

The AR2200 maps the interface priority of packets to local priorities, determines the queues

that packets enter, and can modify packet priorities based on the priority mapping table.

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Huawei AR1200-S Series, AR2200 Series Configuration manual

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