Advanced Computer Networks Course Objectives

Introduction

Computer Networks: Introduction

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Network Definitions and Classification • Preliminary definitions and network terminology • Sample application paradigms • Classifying networks by transmission technology • Classifying networks by size (or scale) • Classifying networks by topology Computer Networks: Introduction

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Preliminary Definitions computer network :: [Tanenbaum] a collection of “autonomous” computers interconnected by a single technology. [LG&W] communications network ::a set of equipment and facilities that provide a service. [PD] {low level definition} A network can consist of two or more computers directly connected by some physical medium such as coaxial cable or an optical fiber. Wireless connectivity needs to be included in this definition. Computer Networks: Introduction

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Network Building Blocks • Nodes and Hosts: computers, routers, switches • Links: coaxial cable, optical fiber, wireless communication – point-to-point – multiple access

(a)

(b)

P&D slide Computer Networks: Introduction

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Preliminary Definitions In a distributed system the collection of independent computers appears to its users as a single coherent system. Namely, the distinctions lie in the transparency in assigning tasks to computers.

Computer Networks: Introduction

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Switched Networks

Figure 1.3 P&D slide Computer Networks: Introduction

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internet

Figure 1.4 Interconnection of networks P&D slide Computer Networks: Introduction

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Network P&D recursive definition:: i. two or more nodes connected by a link.

or ii. two or more networks connected by a node {an internet}. Computer Networks: Introduction

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W1 T

X

Z W2

W

Y Host L

Host M

W3

AP

Host A

2

4

1

Host B

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nodes

16

14

11 Host C

Host J

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12

15

6

13

10 Host D

W4

3

Host H

7 9 Host E

8 Host G Host F Computer Networks: Introduction

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Sample Application Paradigms

Computer Networks: Introduction

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Client-Server Applications

Figure 1.1 A network with two clients and one server.

Tanenbaum slide

Computer Networks: Introduction

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Client-Server Model

Figure 1-2. The client-server model involves requests and replies. Tanenbaum slide Computer Networks: Introduction

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Peer-to-Peer Applications

Figure 1.3 In a peer-to-peer system there are no fixed clients and servers.

Tanenbaum slide

Computer Networks: Introduction

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Mobile Network Users

Figure 1-5. Combinations of wireless networks and mobile computing. Tanenbaum slide Computer Networks: Introduction

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Classifying Networks by Transmission Technology broadcast :: a single communications channel shared by all machines (addresses) on the network. Broadcast can be either a logical or a physical concept (e.g. Media Access Control (MAC) sublayer ) . multicast :: communications to a specified group. This requires a group address (e.g. – multimedia multicast). point-to-point :: connections are made via links between pairs of nodes. Computer Networks: Introduction

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Network Classification by Size

Figure 1-6. Classification of interconnected processors by scale. Tanenbaum slide Computer Networks: Introduction

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Network Classification by Size • LANs {Local Area Networks} – Wired LANs: typically physically broadcast at the MAC layer (e.g., Ethernet, Token Ring) – Wireless LANs

• MANs {Metropolitan Area Networks} – campus networks connecting LANs logically or physically. – often have a backbone (e.g., FDDI and ATM) Computer Networks: Introduction

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Wired LANs transceivers

z z z

Ethernet bus

Copyright ©2000 The McGraw Hill Companies

z z

z

Ethernet hub

Leon-Garcia & Widjaja: Communication Networks

Figure 1.17

Tanenbaum slide Computer Networks: Introduction

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Wireless LANs

Figure 1-35. (a) Wireless networking with a base station. (b) Ad hoc networking. Tanenbaum slide Computer Networks: Introduction

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Metropolitan Area Networks

Figure 1-8. A metropolitan area network based on cable TV. Tanenbaum slide Computer Networks: Introduction

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MAN 1*

a 2

b 4

3

A

c

Metropolitan network A consists of access subnetworks a, b, c, d.

d

Hierarchical Network Topology A

α β

γ

Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks

Computer Networks: Introduction

National network consists of regional subnetworks α, β, γ. Metropolitan network A is part of regional subnetwork α. Figure 1.8

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Network Classification by Size • WANs {Wide Area Networks} – – – –

also referred to as “point-to-point” networks. ARPANET Æ Internet usually hierarchical with a backbone. Enterprise Networks, Autonomous Systems (ASs) – VPNs (Virtual Private Networks).

Computer Networks: Introduction

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AMES

UTAH

McCLELLAN

BOULDER

GWC

CASE

RADC ILL CARN

LINC USC

AMES

MIT MITRE

UCSB STAN

SCD ETAC

UCLA

RAND

TINKER

BBN

HARV

NBS

ARPAnet circa 1972 a point-to-point network Copyright ©2000 The McGraw Hill Companies

Leon-Garcia & Widjaja: Communication Networks

Computer Networks: Introduction

Figure 1.16

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Wide Area Networks (WANs)

Figure 1-10.A stream of packets from sender to receiver. Tanenbaum slide Computer Networks: Introduction

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net 3 G net 1 G G = gateway

G net 2

Copyright ©2000 The McGraw Hill Companies

G net 5

G

net 4

G

internet - a network of networks Leon-Garcia & Widjaja: Communication Networks

Computer Networks: Introduction

Figure 1.18

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Network Classification by Topology Bus flow of data

Bidirectional flow assumes baseband cable

Repeater

Computer Networks: Introduction

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Network Classification by Topology Ring

Repeater

Repeater

Note - a ring implies unidirectional flow

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Network Classification by Topology Tree

Headend

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Network Classification by Topology Star hub, switch or repeater

Computer Networks: Introduction

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Network Classification by Topology Star W1

W2

AP W3

W4

Wireless Infrastructure Computer Networks: Introduction

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