The It Department In An Organization

Published Date: 02 Nov 2017

Name : Menaka d/o Krishian

IC : 890124-07-5686

Index No : PP102189

Batch No : 1101

CAMPUS : PENANG

WORD COUNT : 3680

Question

You are working in the IT Department in an Organization and responsible to design a network system for the organization. Do a research on the types of network topology available and identify the network topology that you would recommend to the management. Give the reasons to support your recommendation.

The transmission media that are used to convey information can be classified as guided or unguided. Guide media provide a physical path along which signal propagated; unguided media employ an antenna for transmitting through air, vacuum, or water. Discuss the both transmission media in detail with examples.

Table of Contents

Number

Content

Pages

1

Introduction

4

2

Question 1

5-11

3

Question 2

12-25

4

Conclusion

26

5

References

27-28

6

Apendix

29

Introduction

Today computer is available in many offices and homes and therefore there is a need to share data and programs among various computers. With the advancementof data communication facilities the communication between computers hasincreased and thus it has extended the power of computer beyond the computerroom. Now a user sitting at one place can communicate with computers of any remote site through communication channel. First question is assume that we are working in the IT Department in an Organization and responsible to design a network system for the organization. I briefly explained types of network topology available and identify the network topology that would recommend to the management.

Second question is about the transmission media that are used to convey information can be classified as guided or unguided. Explain Guide media provide a physical path along which signal propagated; unguided media employ an antenna for transmitting through air, vacuum, or water.

Question 1: You are working in the IT Department in an Organization and responsible to design a network system for the organization. Do a research on the types of network topology available and identify the network topology that you would recommend to the management. Give the reasons to support your recommendation.

What is Network Topology

A network topology describes the arrangement of systems on a computer network. It defines how the computers, or nodes, within the network are arranged and connected to each other. Some common network topologies include bus, ring, bus, and mesh configurations.

It is helpful for a network administrator to know the pros and cons of different network topologies when putting together a network. By weighing the benefits of each type, the administrator can choose the configuration that is most efficient for the network's intended purpose.

Types of Network Topologies

1.1 Bus Topology

Busnetworks use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.

Ethernet bus topologies are relatively easy to install and never require much cabling compared to the alternatives. 10Base-2 ("ThinNet") and 10Base-5 ("ThickNet") both were popular Ethernet cabling options many years ago for bus topologies. However, bus networks work best with a limited number of devices. If more than a few dozen computers are added to a network bus, performance problems will likely result. In addition, if the backbone cable fails, the entire network effectively becomes unusable.

http://www.lahitech.com/images/lin_bus.gif

Figure 1.1: Bus Topology

1.2 Ring Topology

In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). A failure in any cable or device breaks the loop and can take down the entire network.To implement a ring network, one typically uses FDDI, SONET, or Token Ring technology. Ring topologies are found in some office buildings or school campuses.http://2.bp.blogspot.com/-lypvJVM-E_0/UNBN0P8ZazI/AAAAAAAAAH8/GKnLfAm_-Hk/s1600/ring-topology2.png

Figure 1.2:Ring Topology

1.3 Star topology

Many home networks use the star topology. A star network features a central connection point called a "hub node" that may be a network hub, switch or router. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet.Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer's network access and not the entire LAN. (If the hub fails, however, the entire network also fails.)

http://fcit.usf.edu/network/chap5/pics/star.gif

Figure 1.3: Star Topology

1.4: Mesh Topology

Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination. (Recall that even in a ring, although two cable paths exist, messages can only travel in one direction.) Some WANs, most notably the Internet, employ mesh routing.

A mesh network in which every device connects to every other is called a full mesh. As shown in the illustration below, partial mesh networks also exist in which some devices connect only indirectly to others.

http://techighost.com/wp-content/uploads/2012/11/mesh-topology1.jpg

Figure 1.4: Mesh Topology

Network topology that I would recommend to my organization.

I am working in a Sapura network & communication and I was given a job to design a network system to IT department in my company. I do many research of the main toplogy in market currently. And I was suggest and recommend star topology is the best topology for my organization and I give some examples to support my suggestion.

Many home networks use the star topology. A star network features a central connection point called a "hub" that may be a hub, switch or router. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet.

Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer's network access and not the entire LAN. (If the hub fails, however, the entire network also fails.)

A star topology is one in which a central unit provides a link through which a group of smaller computers and devices is connected. The central computer is commonly called a host computer. A host computer is usually a large computer such as a minicomputer or a mainframe. A file server is a large storage device that provides volumes of data and programs to the other units in the network.

In the star network, all interactions between different computers in the network travel through the host computer. The central unit will poll each to decide whether a unit has a message to send. If so, the central computer will carry the message to the receiving computer.

Star networks represent a very popular form of configuration for time-sharing systems in which a central computer makes available resources and databases for several "client" computers to share. As such, the star network is appropriate for systems that demand centralized control. The disadvantage of the star network is that a processing problem in the central computer can be paralyzing to the entire system.

In a star network, the central unit may be a host computer or a file server. The host computer is a large centralized computer, usually a minicomputer or a mainframe. In contrast, the file server is a large-capacity hard-disk storage device. It stores data and programs files shared by the users on the network. Also, called a network server.

A star configuration is simple: Each of several devices has its own cable that connects to a central hub, or sometimes a switch, multipoint repeater, or even a Multistation Access Unit (MAU). Data passes through the hub to reach other devices on the network. Ethernet over unshielded twisted pair (UTP), whether it is 10BaseT, 100BaseT, or Gigabit, all use a star topology.

Star networks are one of the most common computer network topologies. In its simplest form, a star network consists of one central switch, hub or computer which acts as a router to transmit messages. If the central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.

The star topology reduces the chance of network failure by connecting all of the systems to a central node. When applied to a bus-based network, this central hub rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, sometimes including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others, but the rest of the systems will be unaffected.

You will find that a star topology is most common in networks. This is mainly because of the ease of configuring and troubleshooting it. If a wire or a single port on the hub or switch goes bad, only one network node goes down, which prevents a huge impact on productivity overall (unless the entire hub or switch fails-in which case, the whole LAN goes down). However, because a star topology involves a central hub or switch as well as a lot more cabling, it costs more to implement.

Advantages of Star Network

Easy to Install: Each device on network simply requires a cable run between it and the concentrator device.

Flexible: Devices can be added or removed without affecting the other devices on the network.

A single device or cable failure will not bring down the network

Easy to set up and to expand.as each device on the network simply requires a cable run between it and the concentrator device

Any non-centralised failure will have very little effect on the network, whereas on a ring network it would all fail with one fault.

Data Packets are sent quickly as they do not have to travel through any unnecessary nodes.

Performance is greater with speeds capable of 10mbps to 100mbps or more

The ability to isolate individual devices in troubleshooting An intelligent central hub or switch that can help diagnose and manage the network Adjusting traffic levels so that computers that place heavy loads on the network are moved to separate hubs

Diagram of the star topology for the organization

http://4.bp.blogspot.com/-Us3XQcWT91M/TiDTPNCZE1I/AAAAAAAACcI/a0fkepJSXPM/s1600/star%2Btopology.jpg

Figure 1.5: Star Topology

Question 2: The transmission media that are used to convey information can be classified as guided or unguided. Guide media provide a physical path along which signal propagated; unguided media employ an antenna for transmitting through air, vacuum, or water. Discuss the both transmission media in detail with examples.

What is Transmission Media

The transmission media that are used to convey information can be classified as guided or unguided. Guided media provide a physical path along which the signals are propagated; these include twisted pair, coaxial cable, and optical fiber. Transmission media is a pathway through which data are transmitted in  Communication Networks. We use different types of cables or waves to transmit data. Bound transmission media are the cables that are tangible or have physical existence and are limited by the physical geography. Popular bound transmission media in use are twisted pair cable, co-axial cable and fiber optical cable.

Bounded media are the physical links through which signals are confined to narrow path. These are also called guide media. Bounded media are made up o a external conductor (Usually Copper) bounded by jacket material. Bounded media are great for LABS because they offer high speed, good security and low cast. However, some time they cannot be used due distance communication. Three common types of bounded media are used of the data transmission. These are

Coaxial Cable

Twisted Pairs Cable

Fiber Optics Cable

COAXIAL CABLE:

Coaxial cable is very common & widely used commutation media. For example TV wire is usually coaxial. Coaxial cable gets its name because it contains two conductors that are parallel to each other. The center conductor in the cable is usually copper. The copper can be either a solid wire or stranded martial. Outside this central Conductor is a non-conductive material. It is usually white, plastic material used to separate the inner Conductor form the outer Conductor. The other Conductor is a fine mesh made from Copper. It is used to help shield the cable form EMI.

Outside the copper mesh is the final protective cover. The actual data travels through the center conductor in the cable. EMI interference is caught by outer copper mesh. There are different types of coaxial cable vary by gauge & impedance. Gauge is the measure of the cable thickness. It is measured by the Radio grade measurement, or RG number. The high the RG number, the thinner the central conductor core, the lower the number the thicker the core.

Here the most common coaxial standards.

50-Ohm RG-7 or RG-11 : used with thick Ethernet.

50-Ohm RG-58 : used with thin Ethernet

75-Ohm RG-59 : used with cable television

93-Ohm RG-62 : used with ARCNET.

CHARACTERISTICS OF COAXIAL CABLE

Low cost

Easy to install

Up to 10Mbps capacity

Medium immunity form EMI

Medium of attenuation

ADVANTAGES COAXIAL CABLE

Inexpensive

Easy to wire

Easy to expand

Moderate level of EMI immunity

DISADVANTAGE COAXIAL CABLE

Single cable failure can take down an entire network.

http://upload.wikimedia.org/wikipedia/commons/thumb/f/f4/Coaxial_cable_cutaway.svg/300px-Coaxial_cable_cutaway.svg.png

Figure 2.0: Coaxial Cable

Twisted Pair Cable

Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. A cable made by intertwining two separate insulated wires together. There are two twisted pair types: shielded and unshielded. Shielded Twisted Pair (STP) has a fine wire mesh surrounding the wires to protect the transmission; Unshielded Twisted Pair (UTP) does not. Shielded cable is used in older telephone networks, network, and data communications to reduce outside interference. The most popular network cabling is Twisted pair. It is light weight, easy to install, inexpensive and support many different types of network. It also supports the speed of 100 mps. Twisted pair cabling is made of pairs of solid or stranded copper twisted along each other. The twists are done to reduce vulnerably to EMI and cross talk. The number of pairs in the cable depends on the type. The copper core is usually 22-AWG or 24-AWG, as measured on the American wire gauge standard.

Unshielded Twisted Pair

Unshielded twisted pair (UTP) is ordinary telephone wire. Office buildings, by universal practice, are prewired with excess unshielded twisted pair, more than is needed for simple telephone support. This is the least expensive of all the transmission media commonly used for local area networks and is easy to work with and easy to install.

UTP is more common. It can be either voice grade or data grade depending on the condition. UTP cable normally has an impedance of 100 ohm. UTP cost less than STP and easily available due to its many use. There are five levels of data cabling

Category 1

These are used in telephone lines and low speed data cable.

Category 2

These cables can support up to 4 mps implementation.

Category 3

These cable supports up to 16 mps and are mostly used in 10 mps.

Category 4

These are used for large distance and high speed. It can support 20mps.

Category 5

This is the highest rating for UTP cable and can support up to 100mps.

UTP cables consist of 2 or 4 pairs of twisted cable. Cable with 2 pair use RJ-11 connector and 4 pair cable use RJ-45 connector.

Characteristics of UTP

low cost

easy to install

High speed capacity

High attenuation

Effective to EMI

100 meter limit

Advantages of UTP

Easy installation

Capable of high speed for LAN

Low cost

Disadvantages of UTP

Short distance due to attenuation

UTP

Figure 2.1: Unshielded Twisted pair

Shielded Twisted Pair

It is similar to UTP but has a mesh shielding that’s protects it from EMI which allows for higher transmission rate.

Characteristics of STP

Medium cost

Easy to install

Higher capacity than UTP

Higher attenuation, but same as UTP

Medium immunity from EMI

100 meter limit

Advantages of STP:

Shielded

Faster than UTP and coaxial

Disadvantages of STP:

More expensive than UTP and coaxial

More difficult installation

High attenuation rate

STP

Figure 2.2: Shielded Twisted Pair

Fiber Optics

Fiber optic cable uses electrical signals to transmit data. It uses light. In fiber optic cable light only moves in one direction for two way communication to take place a second connection must be made between the two devices. It is actually two stands of cable. Each stand is responsible for one direction of communication. A laser at one device sends pulse of light through this cable to other device. These pulses translated into "1’s" and "0’s" at the other end.

In the center of fiber cable is a glass stand or core. The light from the laser moves through this glass to the other device around the internal core is a reflective material known as CLADDING. No light escapes the glass core because of this reflective cladding.

Fiber optic cable has bandwidth more than 2 gbps (Gigabytes per Second)

Characteristics OfFiber Optic Cable:

Expensive

Very hard to install

Capable of extremely high speed

Extremely low attenuation

No EMI interference

Advantages Of Fiber Optic Cable:

Fast

Low attenuation

No EMI interference

Disadvantages Fiber Optics:

Very costly

Hard to install

UNBOUNDED MEDIA

Unbounded or wireless media doesn't use any physical connectors between the two devices communicating. Usually the transmission is send through the atmosphere but sometime it can be just across the rule. Wireless media is used when a physical obstruction or distance blocks are used with normal cable media. The three types of wireless media are:

RADIO WAVES

MICRO WAVES

INFRARED WAVES

1. RADIO WAVES:-

This is a connection via a chain of transmitters and receivers. There are radio links for both analogue and digital transfer. Analogue radio systems can be used to transfer pulse modulated signals while digital systems are purely design for digital transmission. Each radio link connection requires two radio channels, one in each direction. The transmission frequency and the receiving frequency are separated by a few MHz. This is a very small difference, bearing in mind the frequency band use.

It has frequency between 10 K Hz to 1 G Hz. Radio waves has the following types.

Short waves

VHF (Very High Frequency)

UHF (Ultra High Frequency)

SHORT WAVES:-

There are different types of antennas used for radio waves. Radio waves transmission can be divided into following categories.

LOW POWER, SINGLE FREQUENCY.

HIGH POWER, SINGLE FREQUENCY

LOW POWER , SINGLE FREQUENCY:-

As the name shows this system transmits from one frequency and has low power out. The normal operating ranges on these devices are 20 to 25 meter.

CHARACTERISTICS LOW POWER , SINGLE FREQUENCY:-

Low cost

Simple installation with pre-configured

1 M bps to 10 M bps capacity

High attenuation

Low immunity to EMI

2. HIGH POWER, SINGLE FREQUENCY:-

This is similar to low power single frequency. These devices can communicate over greater distances.

CHARACTERISTICS HIGH POWER, SINGLE FREQUENCY:-

Moderate cost

Easier to install than low power single frequency

1 Mbps to 10 Mbps of capacity

Low attenuation for long distances

Low immunity to EMI

MICRO WAVES

Micro waves travels at high frequency than radio waves and provide through put as a wireless network media. Micro wave transmission requires the sender to be inside of the receiver.

Following are the types of Micro waves.

· Terrestrial Micro waves

· Satellite Micro waves

1. Terrestrial Micro waves:-

Terrestrial Micro waves are used are used to transmit wireless signals across a few miles. Terrestrial system requires that direct parabolic antennas can be pointed to each other. These systems operate in a low Giga Hertz range.

CHARACTERISTICS of Terrestrial Micro waves:-

Moderate to high cost.

Moderately difficult installation

1 M bps to 10 M bps capacity

Variable attenuation

Low immunity to EMI

Satellite Micro waves

The main problem with aero wave communication is the curvature of the earth, mountains & other structure often block the line of side. Due to this reason, many repeats are required for long distance which increases the cost of data transmission between the two points. This problem is recommended by using satellites.

Satellite micro wave transmission is used to transmit signals through out the world. These system use satellites in orbit about 50,000 Km above the earth. Satellite dishes are used to send the signals to the satellite where it is again send back down to the receiver satellite. These transmissions also use directional parabolic antenna’ with in line of side.

In satellite communication micro wave signals at 6 GHz is transmitted from a transmitter on the earth through the satellite position in space. By the time signal reaches the satellites becomes weaker due to 50,000 Km distance. The satellite amplifies week signals and transmits it back to the earth at the frequency less than 6 GHz.

Characteristics Satellite Micro waves:

High cost

Extremely difficult and hare installation.

Variable attenuation.

Low immunity to EMI

High security needed because a signal send to satellite is broadcasts through all receivers with in satellite.

Infrared

Infrared frequencies are just below visible light. These high frequencies allow high sped data transmission. This technology is similar to the use of a remote control for a TV. Infrared transmission can be affected by objects obstructing sender or receiver. These transmissions fall into two categories.

Point to point

Broadcast

(i) Point to Point: - Point to point infrared transmission signal directly between two systems. Many lap top system use point to pint transmission. These systems require direct alignment between many devices.

Characteristics of Point to point:-

Wide range of cost

Moderately easy installation.

100 k bps to 16 Mb of capacity.

Variable attenuation.

High immunity to EMI

(i) Broad Cast: - These infrared transmission use sprayed signal, one broad cast in all directions instead of direct beam. This help to reduce the problems of proper alignment and abstraction. It also allows multiple receiver of signal

Characteristics of Broad Cast:-

In expensive.

Single installation.

1M bps capacity.

Variable attenuation.

Satellite Systems

Satellite transmission is similar in principle to the ordinary radio link. Instead of having

all the stations earthbound, we send some up into the space. Communications Satellite rotate at almost exactly the same rate as the earth rotate. Compared to the radio link, the satellite has a considerable large range. They are used for both in the national network and in the international network. There are only a few problems in the transmission characteristics of the satellite link. Due to the long distance that the signals have to travel, resulted in a delay (echo) which have to be counteracted by the echo suppressors. It has to be recognized that this is a communication between two floating bodies in space thus there is always a relative

movement between the earth and the satellite which can cause errors in digital transmissions.

However, this may be compensated for by intermediate storage of the information in buffer

memories. The capacity of the telephone channels increase as time goes on as compared to the time when the satellite was first launch into space. The Intelsat which was first launch

in 1965 have 75 duplex telephone channel but today the basic version of the new

Intelsat VI satellite can handle 80 000 telephone channel

Conclusion

Computer communication, it seems, will become a much more useful networking tool when large numbers of people with similar interests acquire access to the technology. Though it can expedite the formation of new interpersonal networks by overcoming the space and time barriers faced by traditional networking techniques, it still requires a great deal of concentrated effort and resources to get the people to use it. This problem should become increasingly minimized over the coming years as the technological innovations become more diffused throughout society. Topologies are categorized into different virtual shapes or structures with the basic types being Mesh, Bus, Ring, and Star. "More complex networks can be built as hybrids of two or more of the above basic topologies." These basic topologies are structured in to networks as Ethernet, Token Ring, FDDI, and wireless networking. Any business or individual making a decision of which type of topology is best used for a specific environment or network should know and understand the advantages and disadvantages of each type of topology. guide media is that where we use any path for communcation like cables(coaxial,fibre optic,twisted pair) . unguided media is also called wireless where not any phyisical path is used for transmission.

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