Lesson 4

Network Applications

OverviewThis unit provides an overview of the networks. We begin with an introduction to

networks, and then introduce the organizations that play a key role in the development of

network standards. We will look at the network connectors, network categories and the

methods to connect each network. We will also learn the advantages and disadvantages of

networks.

Lessons

1. Understanding networks

2. Network standards and Standards Organization

3. Understand network connectors

4. Advantages and disadvantages of networks

Lesson 1 – Understanding Networks

Objectives:

At the end of this lesson you will be able to:

Describe networks and data communication

The Internet referred to as a collection of networks. A network is created when two or

more computers are connected to each other. A computer can become part of a network

by connecting to a nearby computer or to the Internet. A network allows computers to

share resources, such as printers or programs.

What is data communication?

Data communication is the exchange of data between two devices via some form of

transmission medium.

Data Communication System

Figure 4.1: Data Communication System

Message (data to be communicated)

Sender (computer, telephone, video camera...)

Receiver (computer, telephone, VCR, PDA…)

Medium (cable, radio waves…)

Protocol (set of rules)

Networks

A network is simply a collection of computers or other hardware devices that are

connected together, either physically or logically, using special hardware and software, to

allow them to exchange information and cooperate. Networking is the term that describes

the processes involved in designing, implementing, upgrading, managing and otherwise

working with networks and network technologies.

Figure 4-2: Data Communication Network Criteria

Lesson 2 –Networks Standards and Organizations

Objectives:

At the end of this lesson you will be able to:

Describe the network standards and list down the organizations involved

in creating network standards

Networks Standards

All networking technologies have standards associated with them. These are usually

highly technical documents, and often presume that the reader has a fair bit of knowledge

about networking. If you aren't an expert, you will probably have some difficulty

understanding networking standards. In fact, many technologies have quite a number of

standards associated with them. A networking technology may have more than one

standard for any or all of the following reasons:

The original standard has been revised or updated;

The technology is sufficiently complex that it needs to be described in

more than one document;

The technology borrows from or builds on documents used in related

technologies;

More than one organization has been involved in developing the technology.

Standards documents created in the United States are usually developed in English, but

are also routinely translated into other languages. European standards are often published

simultaneously in English, French and German, and perhaps other languages as well.

Networking standards can be classified as proprietary, open or de facto. Proprietary

standards are owned by one particular organization. If that organization has sufficient

market clout and the industry lacks alternatives to its standard, it may be adopted by the

whole industry, becoming a de facto standard. Usually, however, differing proprietary

standards compete with each other, resulting in a fragmented market. In contrast, open

standards are not owned by anyone—they are created by neutral organizations to ensure

that compatible products can be designed and developed by many different companies.

This makes life easier for the customer as well as promoting the market as a whole.

Today, virtually all networking standards are “open” standards, administered by a

standards organization or industry group. Open standards are more popular than

proprietary ones in the computer industry, and that's particularly so when it comes to

networking. In fact, the few technologies where there is no universally-accepted open

standard have been losing ground to those with open standards, particularly in the areas

of wireless LANs and home networking—pretty much proving how important an open

process really is.

Proprietary Standards

In the early days of computing, many people didn't quite understand just how important

universal standards were. Most companies were run by skilled inventors, who came up

with great ideas for new technologies and weren't particularly interested in sharing them.

It wasn't considered a “smart business move” to share information about new inventions

with other companies—the competition! Every company believed that standards were

important, but they thought it was even more important that they be the ones to control

those standards.

Let’s imagine that it's 1985, and I have just come up with a great networking technology,

which I have incorporated into a fancy new local area networking product called

“SuperGoodNet”. SuperGoodNet is my product. I have patents on the technology, I

control its design and manufacture, and I sure as heck don't tell anyone else how it works

—if I did, they would copy me, right?

Now, I could sell interface cards, cables and accessories for SuperGoodNet, and a

company that wanted to use it could install the cards in all of their PCs and be assured

that they would be able to talk to each other. This solves the interoperability problem for

this company by creating a “SuperGoodNet standard”. This would be an example of a

proprietary standard—it's owned by one company or person.

The problem with proprietary standards is that other companies are excluded from the

standard development process, and therefore have little incentive to cooperate with the

standard owner. In fact, just the opposite: they have a strong motivation to develop a

competing proprietary standard, even if it doesn't improve on the existing one.

So when my competitor sees what I am doing, he is not going to also create network

interface cards that can work with SuperGoodNet, which would require paying me a

royalty. Instead, he's going to develop a new line of networking hardware called

MegaAwesomeNet, which is very similar to SuperGoodNet in operation but uses

different connectors and cable and logic. He too will try to sell bunches of cards and

cables—to my customers, if possible!

You can see what the problem is here: the market ends up with different companies using

different products that can't interoperate. If you install SuperGoodNet, you have to come

to me for any upgrades or changes—you have no choices. Worse, what happens if Acme

Manufacturing, which has 50 PCs running SuperGoodNet, merges with Emca

Manufacturing, which has 40 PCs running MegaAwesomeNet? Well, the IT people have

a problem, that's what. Sure, there would be ways to solve it, but wouldn't everyone be

better off to just avoid these difficulties in the first place? And how could you create

something like the Internet if everyone's networks used different “standards”?

Open Standards

Eventually, companies learned that they would be better off to have standards that

everyone agreed with, instead of constantly fighting with each other. This is particularly

true of networking, where devices need to talk to each other. If many companies get

together and agree to cooperate, they can create an open standard instead of a bunch of

proprietary ones. The name is rather self-explanatory; rather than being the closely-

guarded secret of one organization, and open standard is available to any who are

interested in using it.

One key to the success of an open standard is a steering organization to promote it.

Usually, a neutral, non-profit trade association or working group is established to develop

and promote the standard, and the various for-profit hardware and software companies

join this group and support it financially. These groups also work with standards approval

bodies like the ITU and ISO to gain acceptance for their standards.

Of course, the companies aren't doing this just to be nice to their customers. In creating

open standards, they split the “market share pie” between them, but they make the pie

grow much larger by attracting more customers. Customers like open standards more

than proprietary ones, because they give them more choices, and increase their ability to

interact with other companies, troubleshoot problems, hire skilled workers, and expand in

the future. As for the companies, they still compete in their specific offerings, so it's not

like they all end up making the same products. For all of these reasons, open standards

are now far more common than proprietary ones.

However, the process involved in creating these standards is often a difficult one. In some

cases the standards organization will draft the standard from the ground up, but in others

it may select one technology as the basis for the standard from several that are submitted

in what is commonly called a “technology bake-off”. Thus, many different companies

may come to the table with different approaches, each of them vying for selection as the

standard for use by the group. Politics can cause groups to get bogged down for years

fighting over various options, or even to split into multiple groups. Good examples are

what occurred in the conflict between supporters of 100VG-AnyLAN and Fast Ethernet,

and the problems with standards politics that have plagued the world of power line

networking.

Furthermore, there are still some companies that believe strongly in proprietary

standards, because they really want to control and direct the market. One of the most

famous/infamous in this regard is Sony, a company that makes excellent hardware but

frequently refuses to accept established standards. For this reason, some people avoid

their products, even though they are good; because they want to stick to industry

standards.

De Facto Standards

“De facto” is Latin for “in fact”, so a de facto standard is one that is used as a universal

standard just because over time it became widely used, and not because the standard was

developed and approved by a standards committee. A good example of a de facto

standard is the “AT” command set used by modems; virtually all modems use it, but this

resulted not from an industry group agreeing to adopt and deploy it. Rather, it was

developed unilaterally by Hayes, the pioneering modem company, and then adopted by

virtually every other modem maker until it became a standard.

One reason why proprietary standards are still sometimes seen is that some companies

want to produce a standard that will become so universally used that it becomes the de

facto standard, thus giving them a leadership position in that market. Again, in my

estimation Sony falls into this category—they often want to do things “their way” and

create proprietary standards that they try to promote using their powerful market

presence.

Sometimes this succeeds but often it does not, resulting a fragmented market of

incompatible products. An excellent example is when Sony created a new format for

digital camera flash memory (the “memory stick”) rather than using the CompactFlash

format used by other camera manufacturers. The result of this was not everyone using

memory sticks as Sony had hoped, but two incompatible standards that increase

confusion and yield no real benefit to the customer.

Standards Organizations

The rise of open standards not owned by any one company has been a great boon to

customers of computer and networking products, as well as the manufacturers that sell to

them. In order to facilitate the development of open standards, however, organizations are

needed that will coordinate the creation and publishing of these documents. Generally,

these are non-profit organizations that specifically take a neutral stance regarding

technologies and work for the betterment of the industry as a whole

There are a number of well-known international organizations that play an important role

in the development of open networking standards. Some of the most important of these

are ISO, ITU-T, IEEE, ANSI, ITIC, EIA/TIA and ETSI. These are oversight

organizations, responsible for overall management of the standards development process,

rather than for the particulars of creating individual standards.

International Standards Organization (ISO)

Probably the biggest standards organization in the world, the ISO is really a federation of

standards organizations from dozens of nations. In the networking world, the ISO is best

known for its OSI Reference Model. Each organization is dedicated to worldwide

agreement on international standards in a variety of fields for example the Open System

Interconnection (OSI) model for network communications.

International Telecommunication Union - Telecommunication Standardization Sector

(ITU-T)

ITU-T is another large international body that develops standards for the

telecommunications industry. The ITU-T was formerly named the International

Telephone and Telegraph Consultative Committee or CCITT (the abbreviation was of the

French version of the organization's name, Comité consultatif international téléphonique

et télégraphique.)

Institute of Electric and Electronic Engineers (IEEE)

The IEEE (pronounced “eye-triple-ee”) is a well-known professional engineering society

involved in developing standards for electrical or electronics fields, including computers

and networking. IEEE's main claim to fame in the networking industry is the IEEE 802

Project, which encompasses many popular networking technologies including Ethernet.

American National Standards Institute (ANSI):

ANSI is the main organization responsible for coordinating and publishing computer and

information technology standards in the United States. While they are commonly thought

of as developing and maintaining standards, they do neither. Instead, they oversee and

accredit the organizations that actually create the standards, qualifying them as Standards

Developing Organizations or SDOs. ANSI also publishes the standards documents

created by the SDOs, and serves as the United States' representative to the ISO.

Information Technology Industry Council (ITIC)

ITIC is a group of several dozen companies in the information technology (computer)

industry. ITIC is the SDO approved by ANSI to develop and process standards related to

many computer-related topics. It was formerly known as the Computer and Business

Equipment Manufacturers Association (CBEMA).

Electronic Industries Alliance (EIA)

The EIA is an international industry association that is best known for publishing

electrical wiring and transmission standards.

Telecommunications Industry Association (TIA)

The TIA is the communications sector of the EIA, and is responsible for developing

communications standards. Since communications, wiring and transmission are all

related, and since the TIA and EIA organizations are also related, standards produced by

the EIA or TIA are often labelled with the combined prefixes “EIA/TIA” or “TIA/EIA”.

European Telecommunications Standards Institute (ETSI)

An organization with members from dozens of countries both within and outside Europe

that is dedicated to developing telecommunications standards for the European market

(and elsewhere). ETSI is known for, among other things, regulating the use of radio

bandwidth in Europe and developing standards such as HiperLAN.

Lesson 3 – Understanding Network Connectors

Objectives:

At the end of this lesson you will be able to:

Describe different types of network connectors and list down the

categories of network

Describe the methods of connecting a network to another network

Networks are connected in a variety of ways, depending on the available technology.

Network connection creates communication circuits through which data can travel. You

can connect computers using old-fashioned twisted pair cables, more powerful coaxial

cables, or ultramodern fiber-optic cables. Alternatively you can dispense with cables

altogether and use a wireless network.

Types of network connectors

Twisted-Pair Cable

The oldest cable type is twisted-pair cable, which consists of two or more insulated

copper wires twisted around each other and enclosed in a layer of plastic insulation. The

wires are twisted to reduce interference from any current-carrying wires located nearby.

A twisted-pair cable is much less expensive than other cable types. Telephone companies

have used one type of twisted-pair transmits cable, called Category 1 cable, for years to

wire residences and businesses. Category 1 cable transmits information more slowly than

other cable types, but it is also much less expensive. Newer types of twisted-pair cables

called Category 5 cable and Category 5e cable are used in computer networks.

Coaxial Cable

Coaxial cable is an insulated copper wire encased in a metal shield that is enclosed with

plastic insulation. The signal-carrying wire is completely shielded, so it resists electrical

interference better than twisted-pair cable. Coaxial cable carries signals about 20 times

faster than Category 1 twisted-pair cable however it is considerably more expansive.

Category 5 and 5e cable transmit information 10 to 100 times faster than coaxial cable.

Additionally, coaxial cable is considerably more expensive than Category 1, 5 or 5e

cable. Most cable television connections use coaxial cable. Since coaxial cable is thicker

and less flexible than twisted-pair it is harder for installation workers to handle and thus

is more expensive to install.

Fiber-Optic Cable

Fiber-optic cable transmits information by pulsing beams of light through very thin

strands of glass. It does not use an electrical signal. Fiber-optic cable transmits signals

much faster than coaxial cable and because it does not use electricity, it is completely

immune to electrical interference. Fiber-optic cable is lighter and more durable than

coaxial cable, but it’s more difficult to work with and much more expensive. Because of

these drawbacks, in general, only large computer networks that transmit huge volumes of

data use fiber-optic cable.

Wireless Networks

Wireless Networks use technologies such as radio frequency (RF) and infrared (IR)

systems to link computers. These types of networks are becoming more common as the

cost of the wireless transmitters and receives that plug into NICs continues to drop.

Wireless LANs are will suited to organizations that occupy old buildings that were built

before electricity and telephones were widely available or offices in which cables are

difficult to install. Today, wireless connections are especially popular with companies

whose employees use laptop computers and take them from meeting to meeting. A

wireless network can really help workers be more effective and productive in flexible

team environments. The cost of wireless networks is dropping, and many people are even

installing them in their homes.

Networks Categories

Networks can be categorized by size, ownership, coverage area and physical architecture.

Three primary categories are:

Client/Server Local Area Network

A local area network (LAN) consists of a group of computers connected through

NICs. This network is described as “local” because the direct connection from

one computer to another through NICs works only over relatively short distances

(no more than a few thousand feet). Figure 3-1 shows how a typical client/server

LAN could be set up in an office environment.

The server runs software that coordinates the information flow among other

computes, which are called clients. The software that runs on the server computer

is called a network operating system. Connecting computers this way in which

one server computer shares its resources with multiple client computers, is called

a client/server network.

Single Building LAN

Multiple Building LAN

Metropolitan Area

Network (MAN)

MAN may be wholly

owned and operated by a private company or may be a service provided by a

public company. MANs, are large computer networks usually spanning a city.

They typically use wireless infrastructure or Optical fiber connections to link their

sites.

Wide Area Network

WAN is a computer network that covers a broad area (i.e., any network whose

communications links cross metropolitan, regional, or national boundaries). Or, less

formally, a network that uses routers and public communications links. Contrast with

personal area networks (PANs), local area networks (LANs), campus area networks

(CANs), or metropolitan area networks (MANs) which are usually limited to a room,

building, campus or specific metropolitan area (e.g., a city) respectively. The largest and

most well-known example of a WAN is the Internet.

WANs are used to connect LANs and other types of networks together, so that users and

computers in one location can communicate with users and computers in other locations.

Many WANs are built for one particular organization and are private. Others, built by

Internet service providers, provide connections from an organization's LAN to the

Internet. WANs are often built using leased lines. At each end of the leased line, a router

connects to the LAN on one side and a hub within the WAN on the other. Leased lines

can be very expensive. Instead of using leased lines, WANs can also be built using less

costly circuit switching or packet switching methods. Network protocols including

TCP/IP deliver transport and addressing functions. Protocols including Packet over

SONET/SDH, MPLS, ATM and Frame relay are often used by service providers to

deliver the links that are used in WANs. X.25 was an important early WAN protocol, and

is often considered to be the "grandfather" of Frame Relay as many of the underlying

protocols and functions of X.25 are still in use today (with upgrades) by Frame Relay.

Internetwork

When two or more networks are connected they become an internetwork or internet.

Methods of Connecting a Network to another Network

They are four main methods of connecting a network (or an independently connected

computer) to another network are:

Modem connection

A modem converts digital data into an analogue form that can be transmitted over

a standard telephone line.

ISDN connection

An ISDN (integrated services digital network) connection uses the public

telephone service and differs from a modem connection in that it sends data in a

digital form.

Gateway

A gateway connects one type of network to another type.

Bridge or router

Bridges and routers normally connect one type of network to one of the same

type. At the moment, gateways are normally routers.

Lesson 4 – Advantages and disadvantages of networks

Objectives:

At the end of this lesson you will be able to:

Understand the advantages and disadvantages of networks.

Advantages of Networks

Networks allow the orderly flow of information between connected notes. Their main

advantages are that:

1. It is easier to set up new users and equipment.

2. It allows the sharing of resources.

3. It is easier to administer users.

4. It is easier to administer software licenses.

5. It allows electronic mail to be sent between users.

6. It allows simple electronic access to remote computers and sites.

7. It allows the connection of different types of computers which can communicate with

each other.

Sharing the information

A major advantage of LANs is their ability to share information over a network.

Normally, it is easier to store application programs at a single location and make them

available to users than having copies individually installed on each computer (unless the

application program requires special configurations or there are special licensing

agreements). This saves on expensive disk space and increases the availability of

common data and configurations. The disadvantage of this is that it increases the traffic

on a network.

Sharing disk resources (network file servers)

Many computer systems require access to a great deal of information and to run many

application programs such as word processors, spreadsheets, compilers, presentation

packages, computer-aided design (CAD) packages, and so on. Most local hard-disks

could not store all the required data and application programs, thus a network allows

users to access files and application programs or remote disks.

Some distributed multi-tasking operating systems such as UNIX and VMS allow all the

hard disks on a network to be electronically linked as a single file system. Most PCs

normally are networked to file servers, which provide networked file systems. A network

file server thus allows users to access a central file system (for PCs) or a distributed file

system (for Unix/VMS).

Sharing resources

Computers not connected to a network may require extra peripherals such as printers, fax

machines, modems, plotters and so on. This may be resource inefficient as other users

cannot get access to them unless they are physically disconnected and connected to their

own computer. Normally, it is more efficient to share resources over a network.

Access to networked peripherals is also likely to be simpler as the system manager can

standardize configurations. Peripherals that are relatively difficult to set up such as

plotters, fax machines and modems can be set up once and their configuration stored. The

network manager can also bar certain users from using certain peripherals.

There is normally a trade-off between the usage of a peripheral and the number required.

For example a single laser printer in a busy office may not be able to cope with the

demand. A good network copes with this by segmentation, so that printers are assigned to

different area or users. The network may also allow for re-direction of printer data if a

printer was to fail or become busy.

Electronic Mail

Electronic mail (e-mail) is one use of the Internet which according to most businesses

improves productivity. Traditional methods of sending mail within an office environment

are inefficient, as it normally requires an individual requesting a secretary to type the

letter. This must then be proofread and sent through the internal mail system, which is

relatively slow and can be open to security breaches.

A faster method and more secure method of sending information is to use electronic mail,

where messages are sent almost in an instant. For example, a memo with 100 words can

be sent within a fraction of a second. It is also simple to send to specific groups, various

individuals, company-wide and so on. Other types of data can also be sent with the mail

message such as images, sound, and so on. It may also be possible to determine if a user

has read the mail. The main advantages can be summarized as:

It is normally much cheaper than using the telephone (although as time equates to

money for most companies this relates any savings or costs to a user’s typing

speed.

Many different types of data can be transmitted such as images, documents,

speech and so on.

It is much faster than the postal service.

Users can filter incoming e-mail easier than incoming telephone calls.

It normally cuts out the need for work to be typed, edited and printed by a

secretary.

It reduces the burden on the mailroom.

It is normally more secure than traditional methods.

It is relatively easy to send to groups of people (traditionally, either a circulation

list was required or a copy to everyone in the group was required.

It is usually possible to determine whether the recipient has actually read the

message (the electronic mail system sends back an acknowledgement).

The main disadvantages of e-mail are:

1. It stops people using the telephone.

2. It cannot be used as a legal document.

3. Electronic mail messages can be sent impulsively and may be later regretted (sending

by traditional methods normally allows for a rethink). In extreme cases messages can

be sent to the wrong person (typically when replying to an e-mail message, where a

message is sent to the entire mailing list [Reply to All] rather than the originator).

4. It may be difficult to send to some remote sites. Some organizations have either no

electronic mail or merely an intranet. Large companies are particularly wary of

Internet connections and limit the amount of external traffic.

5. Not everyone reads his or her electronic mail on a regular basis (although this is

changing as more organizations adopt e-mail as the standard communications

medium).

Peer-to-peer communication

A major problem with computers is to make them communicate with a different

computer type or with another that possibly uses a different operating system. A local

network allows different types of computers running different operating systems to share

information over the network. This is named peer-to-peer exchange.

Remote login

A major advantage of networks is that they allow users to remotely log into other

computers. The computer being logged into must be running a multi-tasking operating

system such as Unix. This method allows many less powerful computers to be linked to a

few powerful machines.

Protecting Information

Most computers have information which must be not be read or modified by certain

users. It is difficult to protect information on a stand-alone computer, as typically all that

is required is to wait until the user is not using the computer. On a network each user can

be granted certain rights and privileges to stored information which can be protected by

password.

Centralized storage and backup of information

A particular problem with stand-alone computers is that when they crash the user can lose

a lot of information, especially of they have not taken regular backups. As file sizes have

increased it has also become more difficult for users to perform these backups as it

normally involves spanning several floppy disks. Thus a better solution is to have a

networked central storage and backup device. The network manager can then schedule

backups at regular intervals (typically each day). If a network crash occurs on the central

storage the manager can recover the previous backup, thus only losing a small amount of

newly created data.

Disadvantages of Networks

The main disadvantages of networks are:

1. If a network file server develops a fault then users may not be able to run application

programs.

2. A fault on the network can cause users to lose data (especially if they have not saved

the files they have recently been working with).

3. If the network stops operating then it may not be possible to access various resources.

4. Users’ work-throughput becomes dependent upon network and the skill of the system

manager.

5. It is difficult to make the system secure from hackers, novices or industrial espionage

(again this depends on the skill of the system manager).

6. Decisions on resource planning tend to become centralized for example what word

processor is used, what printers are brought and so on.

7. Networks that have grown with little thought can be inefficient in the long term.

8. As traffic increases on a network the performance degrades unless it is designed

properly.

9. Resources may be located too far away from some users.

10. The larger the network becomes the more difficult it is to manage.

References:

1. Westnet Learning Technologies (2002).Internet Technologies. Singapore: Thomson Course Technology

2. Gary P.Schneider and Jessica Evans (2002). The Internet (3rd Ed) United States: Thomson Course Technology.

3. Gary B.Shelly, Thomas J.Cashman & Misty E.Vermaat (2007) Discovering Computers 2007: A Gateway to Information, Web Enhanced Complete. USA: Thomson Course Technology

4. William Buchanan (2002). Distributed Systems and Network. Singapore: McGraw-Hill Higher Education