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Chapter 1.3 Computer Networks

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Page 1: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Chapter 1.3

Computer Networks

Page 2: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Client-Server systems

• The question :

Within a large organization, what is the optimal localization of

– Processing power

– Data storage

• The possibilities :– In a global computer center

– In local computer centers

– With the user

– Any combination of the three previous solutions

Page 3: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Client-Server systems

• The question :

What is the optimal localization of– Processing power

– Data storage

• The possibilities :– In a global computer center

– In local computer centers

– With the user

– Any combination of the three previous solutions

Page 4: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Centralized Data Processing

Star Network

Mainframe Computer

Dumb Terminals

Page 5: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Benefits :

Professional Data Management

Enforceable Security

Simple Access to Common Data

Well Defined Cost

Full control by EDP people

Page 6: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

But...

Mainframe Computer

Processing power limited by physics !

1 GIPS : 10-9 s/instruction : d < 30 cm

1 TIPS : 10-12 s/instruction : d < 0.3 mm

Page 7: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Technical arguments against

Central ComputersProcessing Power of a single CPU

can not grow indefinitely

Transmission capacity neededbetween

processor and terminalhas become enormous

Page 8: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

But...

Graphic User Interfaces put extreme

stress on communications !

This screen = 892,800 bytes

transmitting it at 56 Kb/s takes 124 s.

Mainframe Computer

Page 9: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Technical arguments against

Central ComputersProcessing Power of a single CPU

can not grow indefinitely

Transmission capacity neededbetween

processor and terminalhas become enormous

Page 10: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Client-Server systems

• The question :

What is the optimal localization of– Processing power

– Data storage

• The possibilities :– In a global computer center

– In local computer centers

– With the user

– Any combination of the three previous solutions

Page 11: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Independent Personal Computers

The Reaction :

Page 12: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

But ...

Access to common data ???

Risk of loss of data !

Cost of some peripheral equipment

Software Maintenance !

Limited processing power

And many other hidden costs !

Page 13: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Client-Server systems

• The question :

What is the optimal localization of– Processing power

– Data storage

• The possibilities :– In a global computer center

– In local computer centers

– With the user

– Any combination of the three previous solutions

Page 14: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Client - Server Systems

Many computers

with characteristics matching

their specific usage

interconnected by means of

a network

Page 15: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Client - Server Systems

Interconnection Network

Page 16: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Networked Computers Benefits

Sharing of disk space(= access to common data & programs)

(= centralized disk back-up facilities)

Sharing of processing power

Sharing of expensive peripherals(Spooling required)

Page 17: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Client Server Systems

Minimal integration:

“Terminal Emulation”Very User Unfriendly

Full Integration:

“Virtual Mainframe”The user has the feeling all resources

of all networked computers are

part of her/his personal computer

Page 18: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Terminal Emulation

= sub-minimal Client-server system

• The personal workstations are used

– as stand alone computers

– as terminals connected to other computers

• The user has to mentally switch between widely

different user interfaces and operating systems.

• Transferring data between local and remote

applications is far from trivial

• Terminal emulation is very user unfriendly !!!

Page 19: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Client Server Systems

Minimal integration:

“Terminal Emulation”Very User Unfriendly

Full Integration:

“Virtual Mainframe”The user has the feeling all resources

of all networked computers are

part of her/his personal computer

Page 20: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Virtual Mainframe= true Client-Server

system• The users interface of all applications runs on the

personal workstations.

• For some applications, the workstation requests help from specialized servers. The user remains unaware of such requests.

• Servers can be optimized for specific tasks

• Virtual Mainframes can be

– Very user friendly

– cost effective

Page 21: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Network Technology

Local Area NetworksIn a room, a building, a campus

High throughput, low delays, low cost

VUBNET:

10-100 Mbit/s in buildings

Twisted pairs / coaxial cables

1 Gbit/s between buildings

Optical Fibers

Page 22: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Network Technology

Wide Area NetworksAll over the world

Low throughput, high delays, high cost

Leased lines:

From Brussels to

64 Kb/s2 Mb/s

Antwerp

4005 000

Paris

1.60020.000

New York

2.50030.000

(Indicative prices in Euro per month)

Page 23: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Network TechnologyData Transmission over the

Public Switched Telephone Network

PSTN<=

30Kb/s

Page 24: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Network TechnologyData Transmission over the

Integrated Services Digital Network

ISDN=

64Kb/s

Page 25: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Network TechnologyInternet Service Provider Access

over an Hybrid Network

ISDN=

64Kb/s

56Kb/s

ISP ISP

Page 26: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Network TechnologyData Transmission over Data Networks

PrivateAccessPublic

Access

PSTN

Private Data Network(Banksys,...)

Page 27: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

The Early ARPANET (1976)

Hawaii

London

Satellite link

56 Kbps terrestrial link

Page 28: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

The INTERNETCooperative interconnection of

local area networks

BELNET

RESULBVUBNET

RUGNET KULNET

Page 29: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Internet Cost Structure

RARE

- Backbone infrastructure and neutral interconnects paid by interconnected networks, proportional to their access bandwidth.- Cost of direct interconnects shared by partners.- Not ACTUAL but POTENTIAL traffic is charged.

USA

Surfnet

Planet

Uunet

NLBelnet

eunet

SkynetPlanet

Uunet

BE

Page 30: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Private Internet Access• Via Internet Service Provider

• Main problem : local access line– Via PSTN or ISDN• Low throughput• time based charges• conflicting with phone and fax

– Via ADSL or Cable TV• High throughput• Volume based charges• No Conflict with phone, fax or TV

– Via Wireless link• GSM : slow & expensive• GPRS : much better but not yet widely used• UMTS : the wireless paradise ???

Page 31: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

A D S Lfor residential Internet

access

ROUTER

ADSL ADSL

SW

Subscriber's line

600 Kb/s6 Mb/s

Analog Voice

Co-locatedequipment

Page 32: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Data over Cable TV

frequency

VTM RTBF BRTN RTLReturn

7-8 MHz

Data

Cablemodem

Cablemodem

ROUTER

SW

Co-locatedequipment

TVCablehead

Page 33: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Internet Usage

Electronic Mail

Remote Login (TELNET)

File transfers (FTP)

Access to distributed multimedia databases (World Wide Web)

Internet Real-time Chat

Network File System

Internet Telephony

Page 34: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

World Wide Web

• Uniform hypertext based users friendly interface for distributed databases.

• Inexpensive, high quality, browsers available for almost all computers.

• Sophisticated and application specific users interactivity possible by downloading programs to be executed on client’s workstation (Java).

• Already over 200,000,000 pages available worldwide, mainly for public relations, publicity and, to some extent, electronic commerce.

• Electronic commerce still restrained by security concerns.

Page 35: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

HTMLHyperText Markup

Language • Hypertext

– Multimedia document

» Normal text

» Graphics and images (stored in separate files)

» Sound (stored in separate files)

» Executable programs (Java Applets)

– References of other hypertext documents (“Anchors”)

» “clickable” normal text or image (icon)

» address (URL) where the corresponding document can be found

Page 36: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Search Engines

• Finding information becomes more and more

difficult due to the amount of information.

• Automated indexing services, searching all

available databases on the Internet and setting up

keyword databases are very popular.

• Good ranking of keywords can be purchased from

indexing services.

• Many sites use tricks to be favorably presented by

search engines

Page 37: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Internet Domains(= internet distributed

directory)

uk

Root

be brtn

be

ac

ulb

lvhamme

vub

mtv ieee

com orgedu

[email protected]

info

tiberghien

Page 38: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

email

a@m1 d@m4c@m4b@m2

m4

d@m4

INTERNET

m4 is a “pop server”, with a mailbox for each registered user.

Connection between pop server and users can be temporary

Page 39: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

IRC

Internet

Page 40: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Telnet

User of X

Application X

m4

Remote terminal user

m2

INTERNET

User of X

Local terminal user

Telnet

Page 41: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

File Transfer Protocol

m4m2

Internet

Direct FTP userThird party FTP user

Page 42: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Internet Telephony

Internet

+ Access through local PSTN- Quality dependant from network load

LocalPSTN

LocalPSTN

Internet TelephoneGateways

Low costPOTS

emulation

Page 43: Chapter 1.3 Computer Networks. Client-Server systems The question : Within a large organization, what is the optimal localization of –Processing power

Network File System

Intranet

Sharedfilesystem