Computer networking

Why people need it? Who and how is using computer networks?

Uses of Computer Networks

• Business Applications• Home Applications• Mobile Users• Social Issues

Business Applications• Business – for information and resources– many companies have a substantial number of

computers – to monitor production, keep track of inventories, and do the payroll

– initially, these computers worked in isolation from the others, but at some point a need to be connected arose to be able to extract and correlate information about the entire company

– resource sharing – for example - networked printer is often cheaper, faster, and easier to maintain than a large collection of individual printers

Business Applications• Business– companies are vitally dependent on computerized

information– A failure of the computers may block completely the

functioning of a company– In big companies – computers and employees –

scattered over a number of offices (and for some – in many countries)

– Data is stored on servers (powerful computers), most employees use more common machines - clients

Client-server model

Client-server model

• The client-server model involves requests and replies

Client-server model• In the client/server architecture, clients request

services (client’s process) and servers provide those services (server process) - widely used architecture/mode that forms the basis of much network usage

• Servers may be Web servers, mail servers, FTP servers, etc., server can be on-site or remote

• client/server architecture - example of a centralized architecture, where the whole network depends on central points, namely servers, to provide services

Business Applications

• A computer network can provide a powerful communication medium among employees– E-mail– Sharing and working at the same time on common

documents, sheets, data, shared virtual blackboard, etc.

– ICQ, Skype, etc.– Video conferencing

Business Applications

• Faster, more efficient and convenient business – Companies can carry out business electronically with

other companies, suppliers and customers – for ex. orders can be placed electronically, in real time, thus reducing the need for large inventories and making the process more efficient

– Airlines, bookstores, music vendors were the first to discover that many customers like the convenience of shopping from home

– Today almost all companies provide catalogs of their goods and services online and most are capable to take orders on-line

Business Applications• On-line support– In the past, a problem with an application (for example

accounting program, program forming salaries, store/available goods, invoice issuing program, etc) running on your computer might take 2-3 days to solve – until the engineer comes to your site and solves/repairs the problem

– Nowadays a customer can grant access to his/her systems to a remote site/user and the problem can be solved in a matter of one or few hours

– Update of your server or application can also be performed on-line, saving a lot of time and efforts

Home Network Applications

• Access to remote information• Person-to-person

communication• Interactive entertainment• Electronic commerce

Home Network Applications

• Access to remote information - interaction between a person and a remote database of information – surfing the World Wide Web for information

(arts, business, cooking, government, health) or for fun (too many ways to mention..)

– Newspapers/news sites, on-line digital libraries, Wikipedia, etc.

Home Network Applications

• Person-to-person communication– the 21st century's answer to the 19th century's telephone – E-mail - on a daily basis, used almost universally - contains

audio, video as well as text and pictures – Instant messaging - derived from the UNIX talk program in

use since around 1970, now with applications like Skype, ICQ, Instant messenger, etc.

– Worldwide newsgroups/forums - discussions on every conceivable topic

Peer-to-peer communication

• Another type of person-to-person communication is the peer-to-peer communication

• Different from the client-server model • Individuals who form a loose group can

communicate with others in the group• Every person (or its computer) can, in principle,

communicate with one or more other people (computers) - there is no fixed division into clients and servers

Peer-to-peer communication

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

No fixed clients and servers in peer-to-peer systems

Peer-to-peer communication• Peer-to-peer communication - big hit around 2000

with a service called Napster - over 50 million music fans swapping music!

• Members registered the music they had on their hard disks in a central database maintained on the Napster server

• When a member wanted a song - checked the database to see who had it and directly get it Napster did not keeping any music on its machines, so it was not infringing anyone's copyright. The courts did not agree and shut it down

Peer-to-peer communication• New generation peer-to-peer systems eliminates the

central database by having each user maintain his own database locally, as well as providing a list of other nearby people who are members of the system

• A new user can go to any existing member to see what he has and get a list of other members to inspect for more video or music

• The lookup process can be repeated indefinitely to build up a large local database of what is out there

• Torrents for movies, music, books, etc are the popular peer-to-peer type of communication today

Home Network Applications

• Other communication-oriented applications include – telephone calls– video phone– Internet radio– telelearning – one can attend 9 A.M. class without

the inconvenience of getting out of bed (not the present case)

Home Network Applications

• Interactive entertainment– video on demand - select any movie or television

program, in any country, and have it displayed on your screen instantly

– game playing - multiperson real-time simulation games - such with goggles and three-dimensional real-time, photographic-quality moving images form a worldwide shared virtual reality

Home Network Applications• Electronic commerce– Home shopping – users can seek in on-line

catalogs of thousands of companies – Companies also provide on-line technical support– Banking - many people pay their bills, manage

their bank accounts, and handle their investments electronically

– Trading (person-to-person) – advertising personal goods for sale (instead going to the flea market)

Home Network Applications

• Forms of e-commerce

Home Network Applications• Computer networks are getting hugely important, changing

the need people to live at a big city (where are more opportunities for work), for many types of business - with the proper quality internet access, one can perform the same job at a village or in another country!

• Telelearning may affect education - universities may go national or international

• Telemedicine is likely to become ever more important - remote patient monitoring, even remote surgeries!

• Smart homes are also at the development – one can use a webcam to see if the coffee is ready, or sensors connected to the home network can inform you on events in rooms/places which need your immediate attention and response

Mobile Users• Mobile computers - notebook computers,

tablets, smart phones, personal digital assistants (PDAs), are one of the fastest-growing segments of the computer and communication industry

• Wired connection is impossible at a lot of places - in cars, trains, ship, airplanes, some remote villages, so there is a lot and growing interest in wireless networks

Mobile Users• People on the road or at place different from their home or

office want to use their portable electronic equipment to send and receive telephone calls, faxes, and electronic mail, surf the Web, access remote files, and log on to remote machines - regardless if they are on land, sea or air

• At conferences and meetings, the organizers often set up a wireless network in the conference area and participants turn their computers on and connect to the Internet

• Universities have installed wireless networks on campus so students can sit in the open and consult the library's card catalog or read their e-mail

Mobile Users• Wireless networks are of great value to those,

whose work is mobile - trucks, taxis, delivery vehicles, and repair persons – both for business and keeping in touch with home

• Wireless networks are also important to the military – they can’t rely on the local networking infrastructure but have to set their own

Mobile Users• Wireless networking and mobile computing are often

related but they are not identical• There are fixed wireless (at a university campus, at a

hotel) and mobile wireless• On the other hand – a notebook computer can be

wired - if a traveler plugs a notebook computer into the telephone jack in a hotel room, he has mobility without a wireless network (usually for higher speed network)

• There are mobile, wireless applications – for example checking whether you have paid your parking fee is done by PDA (pers dig assistant)

Mobile Users

• Wireless networks and mobile computing

Mobile Users• Food, drink, and other vending machines can issue a

wireless report once a day announcing their current inventories

• Electricity, gas, water, and other meters in people's homes can report usage over a wireless network – eliminates the need of employees of those companies to go on-site

• Wireless PDAs can be used for banking and shopping - kind of electronic wallet, authorizing payments in stores, replacement for cash and credit cards

Mobile Users

• A lot of mobile services appear - for example, it may be possible to ask for a nearby bookstore or Chinese restaurant

• Mobile maps are widely used nowadays, and so is local weather forecast

• Other used mobile applications include tracking inventory, packages, birds, mammals, dolphins, sharks, whales…

Social Issues • The widespread introduction of networking

has introduced a whole new world of social, ethical, and political problems

• Social networking – in forums, bulleting boards, Facebook, Twitter, etc., where people can exchange messages, photos, materials and other information with like-minded individuals or representatives of organizations can bring offense to other users

Social Issues

• Views posted on topics like politics, religion, or sex may be deeply offensive to some people

• Certain materials (on particular countries, or on religions, pornography, etc.) may be unacceptable in either moral or judicial aspect as different countries have different and conflicting laws in this area

Social Issues

• Another issue is the employee rights versus employer rights

• Many people read and write e-mail at work but some employers claim the right to read and possibly censor employee messages - not all employees agree with this

• Some employers restrict the use and access to certain programs/sites at the workplace

Social Issues• It is not only the employee versus the employer issue

but also governments versus people• The FBI has installed a system at many Internet

service providers to snoop on all incoming and outgoing e-mail for nuggets of interest to it - its goal is to spy on millions of people in the hope of finding information about illegal activities

• China has denied access to Google and on other instances has blocked sites like Twitter, Facebook, Youtube, other examples for similar actions are Iran, Egypt, Pakistan that limit the access to sites/programs. Russia has also passed an “Internet blacklist law”

Social Issues• Computer networks offer the potential for sending

anonymous messages – in some cases this may be desirable. For example, it provides a way for students, soldiers, employees, and citizens to blow the whistle on illegal behavior on the part of professors, officers, superiors, and politicians without fear of reprisals

• On the other hand – in USA anonymous accusations cannot be used as evidence

• Anonymous accusations can be also a form of unsupported blackmailing harming individuals or organizations

Social Issues• The world wide network allows ordinary citizens to

express their views in different ways and to different audiences on a number of unsolved social, political, and moral issues

• At the same time a lot of the information available on Internet is ill-informed, misleading, or downright wrong

• Computer networks have also introduced new kinds of antisocial and criminal behavior - E-mail messages or some sites may contain active content (basically programs or macros that execute on the receiver's machine) with viruses

Social Issues

• Identity theft is becoming a big problem - thieves collect information about a victim and can obtain credit cards details and other private data on the victim (political and religious view, medical records, etc)

• Massive copyright violations is also carried out – music and video are digitally transmitted and companies have problems of enforcing their copyrights

Social Issues

• Having widespread use of electronic payments, banking and business the need of secured networks is becoming more and more vital

• The technology of encryption and authentication is well established but is constantly developing with the new features and challenges of networking

Social Issues• With the development of the computer and

computer networking industry the World has become a Digital World in the 21st century bringing with that not only advantages but serious problems

• New legislations and approaches to almost all areas of human life are needed – just like the introduction of cars a century ago required new skills, rules and legislation but today – this is needed in a larger scale!