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