1Prof. Younghee Lee1

Computer Networks Lecture 1: Introduction

Prof. Younghee Lee

Some part of this teaching materials are prepared referencing the lecture note made by F. Kurose and Keith W. Ross

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Computer Networks Overview

o It introduces the concepts clearly first. o It examines network applications

o client-server model, socket API, DNS, e-mail file transfer, Web browsing.

o Finally, the explanation of how the underlying communication component works, fundamental of packet switching, basic principles of various Internet protocols including Protocols such as IP, TCP, ICMP, ARP etc.

o The course involves lecture, reading/discussion and homework. http://cnlab.icu.ac.kr/~yhlee, Room 635, 866-6112, yhlee@icu.ac.kro Office hour: 13:30-14:30 (M) &15:00-16:30 (W) Or by appointment

Text o Computer Networking: A Top-down Approach Featuring the Internet Third edition by Jim Kurose and Keith Ross, A

ddison Wesley, 2005 TA

o Tung, Tao: Room 617: 866-6251

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Computer Networks?

Computer Networks: Interconnected Collection of Autonomous Computers– Bus, LAN, MAN, WAN

(The Internet, The TCP/IP Internet): The set of subnetwork that are interconnected through TCP/IP

– interconnection of many networks:an internetwork => an internet

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The Internet?

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What’s the Internet: “nuts and bolts” view

protocols: control sending, receiving of msgs– e.g., TCP, IP, HTTP, FTP, PP

P Internet: “network of network

s”– loosely hierarchical– public Internet versus private i

ntranet Internet standards

– RFC: Request for comments– IETF: Internet Engineering Tas

k Force

local ISP

companynetwork

regional ISP

router workstation

servermobile

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Computer Networks?

0.1 m Circuit board Data flow machine 1m System Multiprocessor

10m Room100m Building Local Network1km Campus10km City Metropolitan Area100km Country (Wide Area) Network1,000km Continent10,000km Planet The Internet

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Computer Networks: Bandwidth-Distance Characteristics

Data Rate MPS(BPS) Local Area Network

WAN

MPS : Multi-Processor System

108

107

106

105

104

103

10-1 100 101 102 103 104 105 106 107

Distance, meters

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Applications of computer networks Access to Remote Programs

– Simulation, Computer Aided Ed.,, Medical Diagnosis Access to Remote Data Bases

– Reservations For Hotels, Airplanes, Home Banking– Automated Newspaper, Automated Library– Access to Information System: (e.g. World Wide Web)

Communication Medium– Electronic Funds Transfer System, Electronic Mail, Teleconferencing– Worldwide Newsgroups, International Contacts by Humans

Entertainment Industry– Video On Demand, Multiperson real-time simulation games– Selecting any movie/TV program ever made– Live TV may becomes interactive with audience

Pervasive computing– Context-aware networking– Resource Management for Application-Aware Networks– Autoconfiguration, Registration, Mobility management– Service discovery for wireless ad hoc network

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Lecture Contents

Introduction, Protocols and layering Applications: Client- server, Socket, DNS, e-mail, Web,

SNMP, Security TCP, UDP Internetworking: Concepts, Architecture, and Protocols Routing Principle, Internet Routing IP, ARP, ICMP, Mobile networks LAN, Hub, Wireless Link, PPP, WAN, ATM Performance Modeling and Estimation Multimedia Networking, Stream Protocols Security in computer network Network management

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Evaluation

Evaluation– Assignment 20%– Midterm exam 30%– Final exam 30%– Quiz 15%– Class participation 5%

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A brief Computer Networks History

Centralized: Communication within a single system Decentralized: Communications between geographically

separated component of system Distributed: Network communications between systems Transparent: Networking without explicit network related

commands(acces, Location, Control, Execution(process migration, load balancing))– Definition of System: a self-contained entity capable

of autonomous operation

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Internet History

1961: Kleinrock - queueing theory shows effectiveness of packet-switching

1964: Baran - packet-switching in military nets

1967: ARPAnet conceived by Advanced Research Projects Agency

1969: first ARPAnet node operational

1972: – ARPAnet demonstrate

d publicly– NCP (Network Control

Protocol) first host-host protocol

– first e-mail program– ARPAnet has 15 node

s

1961-1972: Early packet-switching principles

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Internet History

1970: ALOHAnet satellite network in Hawaii

1973: Metcalfe’s PhD thesis proposes Ethernet

1974: Cerf and Kahn - architecture for interconnecting networks

late70’s: proprietary architectures: DECnet, SNA, XNA

late 70’s: switching fixed length packets (ATM precursor)

1979: ARPAnet has 200 nodes

Cerf and Kahn’s internetworking principles:– minimalism, autonomy - no

internal changes required to interconnect networks

– best effort service model– stateless routers– decentralized control

define today’s Internet architecture

1972-1980: Internetworking, new and proprietary nets

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Internet History

1983: deployment of TCP/IP

1982: smtp e-mail protocol defined

1983: DNS defined for name-to-IP-address translation

1985: ftp protocol defined 1988: TCP congestion co

ntrol

new national networks: Csnet, BITnet, NSFnet, Minitel

100,000 hosts connected to confederation of networks

ITU Packet switch protocols: X.25…– Expected to be more pop

ular

1980-1990: new protocols, a proliferation of networks

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Internet History

Early 1990’s: ARPAnet decomissioned

1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)

early 1990s: WWW– hypertext [Bush 1945, Nels

on 1960’s]– HTML, http: Berners-Lee– 1994: Mosaic, later Netscap

e– late 1990’s: commercializati

on of the WWW

Late 1990’s: est. 50 million computers on

Internet est. 100 million+ users backbone links runnning at 1

Gbps

1990’s: commercialization, the WWW

ITU Packet switch protocols: X.25…– Expected to be more popular – TCP/IP win!:

– Web protocols are available first on the top of TCP/IP

– X. protocol products were introduced to market too late and expensive.

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The need for Speed and Quality of service The emergence of High Speed LANs (Amdahl's rule)

Multimedia applications– Video Conference– VoD– Live broadcasting

Mobility Embedded Network Network support for Pervasive computing

– Service discovery, autoconfiguration

CPU memory I/O, network

performance 1 Instruction 1 byte 1 bps

Modern computer 1 Gips 1 Gbyte 1 Gbps