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Introduction

Chapter 1


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Uses of Computer Networks

Business Applications

Home Applications


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Business Applications of Networks

Client server model

In this model the data are stored on powerful computers called

server.

Users have simple machines called clients, with which they access

remote data.


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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 (3)

Some forms of e-commerce.


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Transmission technology

Two types

Broadcast links Point-to-point links


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Broadcast links

Have a single communication channel shared by all the machines on

the network


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Broadcast Networks (2)

Classification of interconnected processors by scale.


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Personal Area Network

APANis a network that is used for communicating amongcomputers and computer devices (including telephones)in close proximity of around a few meters within a room

PANs can be wired with a computer bus .

PANs can also be wireless through the use ofbluetooth


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A LAN is a networkthatis usedforcommunicating among

computerdevices, usuallywithin an officebuildingor

home (a few hundred meters).

LANs enable the sharing of resourcessuch as files or

hardware devices that may be needed by multiple users

Is fast, with speeds from 10 Mbps to 10 Gbps

Requires little wiring, typically a single cable connecting

to each device

Has lower cost compared to MANs orWANs

Local Area Network


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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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Network Software

Protocol Hierarchies

Design Issues for the Layers

Connection-Oriented and Connectionless Services

Service Primitives

The Relationship of Services to Protocols


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Network SoftwareProtocol Hierarchies

Layers, protocols, and interfaces.


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Protocol Hierarchies (3)

Example information flow supporting virtual communication in layer 5.


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Design Issues for the Layers

Addressing

Error Control

Flow Control Multiplexing

Routing


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Connection-Oriented and Connectionless

Services

Six different types ofservice.


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Service Primitives

Five service primitives for implementing a simple connection-

oriented service.


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Fundamental Parts of a Network

Network - A network is computers connected together in a waythat allows information to be exchanged between the computers.

Node - A node is anything that is connected to the network.

Segment - A segment is any portion of a network that is

separated, by a switch, bridge or router, from other parts of thenetwork.

Topology - Topology is the way that each node is physicallyconnected to the network. Common topologies include:


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Set of nodes is connected via a shared communication line called

backbone.

Information sent from a node travels along the backbone until it

reaches its destination node

Bus Topology


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The ring network is like a bus network, but the end of the network is

connected to the first node

Nodes in the network use tokens to communicate with each other

A token is attached to the message by the sender to identify which

node should receive the message. as the message moves around the

ring.

Backbone

Ring Topology


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Each node is connected to a device in the center of the network

called a hub

The hub simply passes the signal arriving from any node to the

other nodes in the network

Hub

Star Topology


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Star Bus Topology

S

tar bus - Star bus combines elements of the star and bus topologies .Nodes in particular areas are connected to hubs (creating stars),and the hubs are connected together along the network backbone(like a bus network).


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Reference Models

The OSI Reference Model

The TCP/IPReference Model

A Comparison of OSI and TCP/IP A Critique of the OSI Model and Protocols

A Critique of the TCP/IPReference Model


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Reference Models

The OSI

reference

model.


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Reference Models (2)

The TCP/IP reference model.


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Reference Models (3)

Protocols and networks in the TCP/IP model initially.


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Comparing OSI and TCP/IPModels

Concepts central to the OSI model

Service

s

Interfaces

Protocols


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A Critique of the OSI Model and Protocols

Why OSI did not take over the world

Bad timing

Bad technology Bad implementations

Bad politics


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Bad Timing

The apocalypse of the two elephants.


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A Critique of the TCP/IPReference Model

Problems:

Service, interface, and protocol not distinguished

Not a general model

Host-to-network layer not really a layer No mention of physical and data link layers

Minor protocols deeply entrenched, hard to replace


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Hybrid Model

The hybrid reference model to be used in this book.


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The ARPANET

(a) Structure of the telephone system.

(b) Barans proposed distributed switching system.


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The ARPANET (2)

The original ARPANET design.


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The ARPANET (3)

Growth of the ARPANET (a) December 1969. (b) July 1970.

(c) March 1971. (d) April 1972. (e) September 1972.


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NSFNET

The NSFNET backbone in 1988.


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Internet Usage

Traditional applications (1970 1990)

E-mail

News

Remote login

File transfer


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ATM Virtual Circuits

A virtual circuit.


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ATM Virtual Circuits (2)

An ATM cell.


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The ATMReference Model

The ATM reference model.


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The ATMReference Model (2)

The ATM layers and sublayers and their functions.


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Ethernet

Architecture of the original Ethernet.


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WirelessLANs

(a) Wireless networking with a base station.

(b) Ad hoc networking.


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WirelessLANs (2)

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


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WirelessLANs (3)

A multicell 802.11 network.


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Network Standardization

WhosWho in the TelecommunicationsWorld

WhosWho in the International StandardsWorld

Who

sW

ho in the Internet StandardsW

orld


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ITU

Main sectors Radiocommunications

Telecommunications Standardization

Development Classes ofMembers

National governments

Sector member

s

Associate members

Regulatory agencies

IEEE 802 St d d


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IEEE 802 Standards

The 802 working groups. The important ones are

marked with *. The ones marked with are

hibernating. The one marked with gave up.


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Metric Units

The principal metric prefixes.

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