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Cairo University

Faculty of Engineering

Electronics &Communication dpt.

4th year

Linux-based Implementation Of a

Router

(B.Sc Graduation project)2002

Supervisor:

Prof. Dr. Khaled Foad El-Sayed.

Submitted by:Ashraf Kamal Rahoma

Hazem Mohamed Sobhi Hassanein

Hossam El-Sayed Abd Allah

Tarek Amr Abdallah

Zein El-Abidin Mohamed WALI

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Introduction to QoS:

Motivation:

QoS Terminology and Parameters:

Internet Protocol (IP).was designed to provide best-effort service.• VoIP• FTP

QOS: Quality of Service (QoS) implies the ability to differentiate traffic streams and to define a level of performance for those traffic streams across a network. When heavily utilized networks are carrying various types of traffic for different users, QoS is a mean of offering better service

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Parameters

1. Latencythe delay a flow experiences when passing through a device

2. Jitter the latency variations

3. loss probabilitybandwidth distribution and availability (throughput or goodput)

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IntServ vs. DiffServ IntServ overview

Data path: Per-flow

classification Per-flow

buffer management.

Per-flow scheduling

Control path: Install and

maintain per-flow state for data and control planes.

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RSVP Protocol

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RSVP Protocol

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RSVP Protocol

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RSVP Protocol

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IntServ vs. DiffServ

Each has its won points of strengthAnd weakness

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DiffServ Architecture

DiffServ Architectural Model

Differentiated Services Domain

DS Boundary Nodes and Interior Nodes:DS Ingress Node and Egress Node:Differentiated Services Region:Traffic Classification and Conditioning:

Classifiers:Traffic Profiles:Traffic Conditioners:

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Meters:Markers:Shapers:Droppers:

Location of Traffic Conditioners and MF Classifiers:Within the Source Domain:At the Boundary of a DS Domain:In non-DS-Capable Domains:In Interior DS Nodes:

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ToS VS DSCP

Introduction

Type of service byte definition

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Type of service byte definition

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Table 2.1: IP precedence bits

Bits (0-2) IP-precedence definition 111 Network control 110 Internetwork control 101 CRITIC/ECP 100 Flash override 011 Flash 101 Immediate 001 Priority 000 routine

Table 2.2: ToS field values

Bits (3-6) ToS field definition

1000 Minimize delay 0100 Maximize throughput 0010 Maximize reliability 0001 Minimize monetary cost 0000 Normal service

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Disadvantages of ToS •The IP-precedence scheme allows only specification of relative priority of a packet. it has no provisions to specify different drop precedence for packets of a certain priority.

•The 3 bits restrict the number of possible priority classes to 8

•The ToS mechanism is not powerful enough to allow an application to quantify the level of service it desires.

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Differentiated services field definition

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Per Hop Behavior PHB

A per-hop behavior (PHB) is a description of the externally observable forwarding behavior of a DS node applied to a particular DS behavior aggregate (BA).

Different PHB’s

Currently there are 4 standard different per hop behaviors PHB’s:

Default PHBClass-Selector PHB.Assured Forwarding (AFny) PHB.Expedited Forwarding (EF) PHB.

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Name DSCP (Hex) Description

Default PHB 000000 0x0h Best Effort (BE)

111000 0x38h Network Control

110000 0x30h Inter-netwrok Control

101000 0x28h CRITIC/ECP

100000 0x20h Flash override

011000 0x18h Flash

101000 0x28h Immediate

Class-selector PHBs ’xxx000’

001000 0x8h Priority

Expedited Forwarding EF

101110 0xB8h Low-loss, low-latency, low-jitter and assured bandwidth

010 0x28h Low dP

100 0x30h medium dP AF1y 001 110 0x38h high dP

010 0x48h low dP

100 0x50h medium dP AF2y 010

110 0x58h high dP

010 0x68h low dP

100 0x70h medium dP AF3y 011

110 0x78h high dP

010 0x88h low dP

100 0x90h medium dP

Assured Forwarding AF

AF4y 100

110 0x98h high dP

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DiffServ Support under Linux

Linux Traffic Control Overview

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Linux Traffic ControllerSyntax:

tc [OPTIONS] OBJECT {COMMAND | help}

Where OBJECT: = {qdisc | class | filter}

OPTIONS: = {-s [tatistics] | -d [etails] | -r [aw]}

Queueing disciplines 1. DSMARK 2. CBQ 3. TBF 4. p/bFIFO 5. PRIO 6. RED 7. GRED 8. Ingress

Classes 1. DSMARK 2. CBQ

filters (or classifier) 1. U32 2. TCINDEX 3. ROUTE 4. FIREWALL

Police

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Implementation and Code

TC Implementation

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Note: In this drawing only one AF class is shown for the simplicity of the drawing, the other ones are just the same. DSMARK CBQ pFIFO:

Low queuing delay (latency). Well defined minimum departure rate, i.e. independent of the other traffic at the node. No burst. (policing).

4 CBQ: Four AF classes with different fractions of the bandwidth allocated for each. In each one we have three dropping precedence’s (RED)Bandwidth assurance,RED:

No bandwidth guarantee. No quality of service: No policing filters, no shaping.

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Traffic Classes

Variables:

Setting Functions:

Constructor.DestructorSet DeviceSet NetworkSet RatesSet PHB’sSet Police Set ToS

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Infra-structure Functions: t_start( ) t_reset( )

Make_phb( )

make_EF( )

make_AF( )

make_BE( )

make_Subfilter ( )

make_marker ( )

Filtering Functions:

Make FilterGet Command

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Software implementation

Architecture Overview.

Graphical User Interface (GUI).

System programming.

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using C++ Classes

Architecture Overview

To ensure encapsulation & independence

To control the communication & error tracing

To give the ability to change or update any specific parts.

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using C++ Classes

Architecture Overview

DiffServ Configuration tool

System Programming GUI

DiffServ.h Traffic.h

Traffic.cpp DiffServ.cpp

Interface.ui

Interface.h

Interface.cpp

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Detailed view DiffServ Configuration

tool

System Programming GUI

DiffServ.h Traffic.h

Traffic.cpp DiffServ.cpp

Interface.ui

Interface.h

Interface.cpp

Setting Fn’s

Set_device()

Set_network()

Set_rates()

Set_phb()

Set_policing()

GUI manipulation

System interface

Apply_PHB()

Apply_advanced()

Apply_Filter()

Private Fn’s

Filtering

Make_Filter()

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Communication between Classes

T r a f f i c

C l a s s

A p p l y _ p h b ( ) S e t _ d e v i c e ( ) S e t _ n e t w o r k ( ) S e t _ R a t e s ( )

A p p l y _ a d v a n c e d ( ) S e t _ p h b ( ) S e t _ p o l i c i n g ( ) S e t _ t o s ( )

A p p l y _ f i l t e r ( ) m a k e _ f i l t e r ( )

D i f f S e r v

C l a s s

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GUI tabs PHB configuration tab

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Advanced PHB

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Filter Setup Tab

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Summary view Tab

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TC Experts Tab

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4.4 Testing:

Description PC1 DiffServ Router PC2

Platform Linux Linux Windows XP Speed PIII –1000 MHZ PIII – 850 MHZ PIII –600 MHZ Running s/w Traffic Generator

( TG) DiffServ S/W

Traffic Monitoring (CommView)

eth0 Ethernet cards eth0

eth1 eth0

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4.5 Testing procedure

We have performed testing on 3 basic levels:1. Marking: Testing if packets were marked

according to specified classification.

2. ToS: Testing if the classification according to ToS and monitoring packets flow were mapped to the required PHB

3. PHB’s Implementation: Monitoring different rates assigned to each class

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Than You !