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Introduction

Network

Source Destination

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Computer Network?

o interconnected collection of autonomous

computers

o What is the Internet?

network of networks

collection of networks interconnected by routers

a communication medium used by millions

Email, chat, Web surfing, streaming mediao Internet Web

o Distributed system

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The Big Picture of Networks

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Why network?

Before networks:

One large computer (mainframe) used for all

processing in businesses, universities, etc.

Smaller, cheaper computers

Personal computers or workstations on desktops

Interconnecting many smaller computers is

advantageous! Why?

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Why network?Resource sharing!

Hardware: printers, disks, terminals, etc.

Software: text processors, compilers, etc.

Data.

Robustness

Fault tolerance through redundancy

Load balancing

Processing and data can be distributed over the network

Location independence Users can access their files, etc. from anywhere in the

network

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Problems?

Security!

Its much easier to protect centralized resources than

when they are distributed.

Network itself as the target..

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Applications

o WWW

o Instant Messaging (Internet chat, text messaging

on cellular phones)

o Peer-to-Peero Internet Phone

o Video-on-demand

o Distributed Games

o Remote Login (SSH client, Telnet)

o File Transfer

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Applications

Business Applications

Home Applications

Mobile Users Social Issues

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Business Applications of Networks

A network with two clients and one server.

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Business Applications of Networks (2)

The client-server model involves requests and replies.

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Home Network Applications

Access to remote information

Person-to-person communication

Interactive entertainment Electronic commerce

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Home Network Applications (2)

In peer-to-peer system there are no fixed clients and servers.

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Home Network Applications (3)

Some forms of e-commerce.

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Mobile Network Users

Combinations of wireless networks and mobile computing.

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Major Trends in Computing

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The Wider Agenda

year

log

(peopleperc

omputer)

Streaming

Informationto/from PhysicalWorld

Number CrunchingData Storage

ProductivityInteractive

Mainframe

Minicomputer

Workstation

PC

Laptop

PDA

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Various Rates of Improvement

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Networking Scenario: Present

Networks today

Routers

Web servers

Clients

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Routers

Web servers

Clients

Sensors

Mobile users

Audio Video

DevicesWireless

Networking Scenario: Future

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Computers of the Future

Computers are integrated

small, cheap, portable, embedded

Technology is in the background

computer are aware of their environment and adapt (location awareness)

computer recognize the location of the user and react appropriately (e.g., call

forwarding, fax forwarding, context awareness)

Advances in technology

more computing power in smaller devices

flat, lightweight displays with low power consumption

new user interfaces due to small dimensions

more bandwidth

multiple wireless interfaces: wireless LANs, wireless WANs, regional wireless

telecommunication networks etc. (overlay networks)

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Broadcast Networks

Types of transmission technology

Broadcast links Point-to-point links

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Broadcast Networks (2)

Classification of interconnected processors by scale.

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Local Area Networks

Two broadcast networks

(a) Bus

(b) Ring

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Metropolitan Area Networks

A metropolitan area network based on cable TV.

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Wide Area Networks

Relation between hosts on LANs and the subnet.

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Wide Area Networks (2)

A stream of packets from sender to receiver.

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Wireless Networks

Categories of wireless networks:

System interconnection

Wireless LANs

Wireless WANs

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Wireless Networks (2)

(a) Bluetooth configuration

(b) Wireless LAN

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Wireless Networks (3)

(a) Individual mobile computers

(b) A flying LAN

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Home Network Categories

Computers (desktop PC, PDA, shared peripherals

Entertainment (TV, DVD, VCR, camera, stereo, MP3)

Telecomm (telephone, cell phone, intercom, fax)

Appliances (microwave, fridge, clock, furnace, airco) Telemetry (utility meter, burglar alarm, babycam).

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Architecture of the Internet

Overview of the Internet.

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Ethernet

Architecture of the original Ethernet.

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Wireless LANs

(a) Wireless networking with a base station.

(b) Ad hoc networking.

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Wireless LANs (2)

The range of a single radio may not cover the entire system.

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Wireless LANs (3)

A multicell 802.11 network.

IEEE 802 Standards

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IEEE 802 Standards

The 802 working groups. The important ones are

marked with *. The ones marked with are

hib ti Th k d ith