How Does The Bus Topology Works Information Technology Essay

The bus topology is a series of nodes which are all connected to a backbone. Bus networks typically work well for smaller networks and use Ethernet cables for networking. It is easy to maintain and troubleshoot in a bus network.

How does the BUS topology works :

The bus topology connects each computer on the network into something called the segment trunk. A bus is usually referred to a cable that connects end to end and this is used to transmit the signals from one end to the other end. At every end a terminator is placed so that it understands in which direction the data is traveling and also the terminator is used to absorb the signals

Figure 1 : BUS topology

ii. Star topology :

A star topology is based on a central node which acts as a hub. A star topology is common in homes networks where all the computers connect to the single central computer using it as a hub.

How does the Star topology works :

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.

Figure 2 : Star topology

iii. Ring topology :

A ring network is circular in shape and every node will have one node on either side of it. The ring topology is rare to come across because of its limitations. If there is damaged cable or breakdown in any one of the nodes then the entire network stops functioning.

How does the Ring topology works :

A ring network is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node – a ring. Data travels from node to node, with each node along the way handling every packet. Because a ring topology provides only one pathway between any two nodes, ring networks may be disrupted by the failure of a single link.

Figure 3 : Ring topology

iv. Mesh topology :

Mesh topology is a group of nodes which are all connected to each other and many types of connections are possible in a mesh topology

How does the Mesh topology works :

In a Mesh Network every node is connected to other nodes on the network through hops. Some are connected through single hops and some may be connected with more than one hope. While the data is traveling on the Mesh Network it is automatically configured to reach the destination by taking the shortest route which means the least number of hops.

Figure 4 : Mesh topology

v. Tree topology:

The tree topology is a group of star networks put together. The only difference is that the tree topology follows a hierarchy in structure and the entire tree is dependent on this hierarchy.

How does the Tree topology works :

Among all the Network Topologies we can derive that the Tree Topology is a combination of the bus and the Star Topology. The tree like structure allows you to have many servers on the network and you can branch out the network in many ways.

Figure 5 : Tree topology

Task -1 (b)

The advantages and disadvantages for each medium of network topology.

Some of medium are cat5, cat6, fiber optic, coaxial cable etc.

Cat5 : Category 5 cable is a twisted pair high signal integrity cable type often referred to as Cat5 or Cat-5. Most cables are unshielded, relying on the twisted pair design for noise rejection, and some are shielded.

Figure 6 : Cat5 Cable

This category of UTP cable is the most commonly used cable in present day networks. It consists of four twisted pairs and is used in those Ethernet networks that run at the speed of 100 Mbps. Category 5 cable can also provide a higher speed of up to 1000 Mbps.

Cat6 : Category 6 cable, commonly referred to as Cat-6, is a cable standard for Gigabit Ethernet and other network protocols that are backward compatible with the Category 5/5e and Category 3 cable standards. Compared with Cat-5 and Cat-5e, Cat-6 features more stringent specifications for crosstalk and system noise.

Figure 7 : Cat6

Advantages :

Cat 6 will be very effective in the residential market to support higher Internet access speeds.

The better balance of cat6 will make it easier to meet the residential EMC requirements compared to cat 5e cabling.

The growth of streaming media applications to the home will increase the need for higher data rates which are supported more easily and efficiently by category 6 cabling.

Disadvantages :

It transfer data in Gigabytes per seconds.

It is costly.

Fiber optic cable : Fiber optic cables are made up of glass, and they transmit data in the form of light, unlike the copper wire that uses electrical signals. A reflective coating that allows light beams to travel without outer interference covers the glass cable.

Figure 8 : Fiber optic cables

The advantages of Fiber optic cables are that signals can be sent at a much higher speed and to very long distances without the risk of outer interference.

There are more advantages of fiber optic cables are :

System Performance

Greatly increased bandwidth and capacity

Lower signal attenuation (loss)

Immunity to Electrical Noise

No crosstalk

Lower bit error rates

Signal Security

Difficult to tap

Overall System Economy

Low per-channel cost

Lower installation cost

Disadvantages of fiber optic cable :

One problems with optical fibers is that the electrical information signals must be converted (modulated) to light at the transmitter and then down converted (demodulated) from light back to electrical signals at the receiver. The main disadvantage of fiber optics is that the cables are expensive to install and are more fragile than metal wire and are more difficult to split.

Coaxial cable : Coaxial cable, or coax, is an electrical cable with an inner conductor surrounded by a tubular insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer called the shield, and finally covered with a thin insulating layer on the outside.

Figure 9 : Coaxial cable

Advantages of coaxial cables are :

Coax has a sufficient frequency range to support multiple channels, which allows for much greater throughput.

Compared to twisted-pair, coax provides greater bandwidth systemwide, and it also offers greater bandwidth for each channel. Because it has greater bandwidth per channel, it supports a mixed range of services. Voice, data, and even video and multimedia can benefit from the enhanced capacity.

Disadvantages of coaxial cables are :

More expensive than twisted pairs and is not supported for some network standards (eg token ring), its also very bulky and also has high attenuation so would have the need to implement repeaters etc.

Task 1 (c)

From our above investigation and determination that BUSS topology is too much vulnerable. Ring topology creates too much redundant link. MASS topology is more expensive and difficult to install. So Star topology will be the best solution for the network of the headquarter of police department in Townsville.

Because, according to our investigation here are the key points.

Good performance;

Reliable (if one connection fails, it doesn’t affect others);

Easy to replace, install or remove hosts or other devices.

There are several medium we have found but we have decided to use ‘Cat6’ cable as medium for this network.

TASK – 2

Task – 2 (a)

After investigate I have many internet service in my country.

The Internet Services are :

Broadband Internet Service, Fiber Optic Internet Services, Radio Link Internet Services, WiFi etc.

Broadband Internet Service : Broadband Internet access, often shortened to just broadband, is a high data rate Internet access-.

Fiber Optic Internet Service : An optical fiber is a glass or plastic fiber that carries light along its length. fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers.

Radio Link Internet Service : Radio Link Protocol (RLP) is an automatic repeat request (ARQ) fragmentation protocol used over a wireless (typically cellular) air interface

WiFi Technology : Wi-Fi works with no physical wired connection between sender and receiver by using radio frequency (RF) technology, a frequency within the electromagnetic spectrum associated with radio wave propagation. When an RF current is supplied to an antenna, an electromagnetic field is created that then is able to propagate through space. The cornerstone of any wireless network is an access point (AP).

But I think it will be best to use Fiber Optic Internet Services for the police department of Townsville. Because, it has so many advantages and this may be the best way for the police department of Townsville.

Task – 2 (b)

The police department in Townsville needs an own server to maintain their all information that are so confidential. If they use other server then that confidential data may be lost.

Server needs to high configured PC with high speed Internet speed, cooling system (because, all time the server will be opened), a big storages and finally it requires the best and secure operating system such as Linux or Windows 200 Server.

There are different people in the headquarter house who needs different type of internet connection based on their designation and responsibility. Here is a comparison list of each person to show what internet connection is required for whom.

The Chief Constable – The Chief Constable, who is responsible for the policing of that area, needs more powerful configuration than others. He needs 2 MBPS internet speed.

The assistant Chief Constable – The assistant Chief Constable assist to the Chief Constable and he needs higher configuration than others but lower than the Chief Constable a little bit. It needs 1 MBPS internet speed.

District Commander – The policing in each district is the responsibility of a district command. They need 512KBPS internet speed.

Deputy District Commander – The deputy district command assist to the district commander. They need 512 KBPS internet speed.

For sergeants and constables – Each district has three sergeants and twenty four constables allocated to it. And they need also 512 KBPS internet speed.

The police officers – Each district has five police car to patrolling the area and responding the incidents. The police officer also patrols the local area on foot. The police officer needs 512 KBPS for it.

A large office – Each district has its own large office within the headquarters building and requires a workstation for each district commander and for each deputy district commander. They need 512KBPS for their job.

Detective Chief Inspector – They need 1 MBPS internet speeds also. Because, they need to search, make a report, send and get any information easily and quickly.

Detective Inspector – The detective inspector assist to the Detective Chief Inspector. So they also heed 1 MPBS internet speeds.

The civilian staff – The police department also has twenty civilian staff, responsible for general administration work including operating the telephone system and general administration duties. They need 512 KBPS internet speed.

Task – 2 (c)

There are so many Internet Service Provider (ISP) in Bangladesh. Such as : : – it has the best package that name ‘Corporate High-Speed Internet’.

Bangladesh Online :

Bijoy Online Limited :

Grameen Cyber Net Limited :

Dhaka Com :

Task – 2 (d)

I recommend to use ‘’ for Internet Service Providers (ISP). Because, they have more facilities with low price.


Task-3 (a)

Characteristics of Private Mobile Radio (PMR) :

Provides, for example, taxi firms with local radio communications on a single channel.

Communications are half duplex, so this requires strict operating procedures to control conversation (for example use of key words such as ‘over and out’).

Requires a license from the appropriate government department.

Bandwidth and channel availability is limited.

Coverage area is limited.

Disadvantages of PMR :

Lack of privacy as all communications take place on a single channel that anyone with a suitable radio receiver can listen to.

Coverage limitations (25 km radius max). Generally, PRM services have only one base station covering the area of operation of the company. If a mobile unit exceeds these boundaries communications are lost.

Public Trunked Mobile Radio (PTMR) :

PTMR was originally designed for voice communications but it can also support data. It communication area half duplex.

Characteristics of PTMR :

The prime application suited to PTMR is vehicle fleet communications.

Half duplex voice communication is provided, using over and out etc. to control conversation flow.

Some PTMR radio sets have a data port, usually RS-232. Data is transmitted at 1.2 Kbit/s.

Task-3 (b)

Legal requirements are :

Requirements of frequencies –

For omni directional and point to multi-point system –

Sl Symbol

Frequency Range

(Lower Limit Exclusive, Upper

Limit Inclusive)

1 VLF 3~30 KHz 200.00

2 LF 30~300 KHz 200.00

3 MF 300~3000KHz 200.00

4 HF 3~30 MHz 300.00

5 VHF 30~300 MHz 100.00

6 UHF1 300~1000 MHz 50.00

7 UHF2 1000~3000 MHz 30.00

8 SHF 3~16 GHz 20.00

9 SHF2 & EHF1 16~65 GHz 10.00

10 EHF2 65~300 GHz 1.00

1 VLF 3~30 KHz 200.00

2 LF 30~300 KHz 200.00

3 MF 300~3000KHz 200.00

4 HF 3~30 MHz 300.00

5 VHF 30~300 MHz 100.00

6 UHF1 300~1000 MHz 50.00

7 UHF2 1000~3000 MHz 30.00

8 SHF 3~16 GHz 20.00

9 SHF2 & EHF1 16~65 GHz 10.00

10 EHF2 65~300 GHz 1.00

1 VLF 3~30 KHz 200.00

2 LF 30~300 KHz 200.00

3 MF 300~3000KHz 200.00

4 HF 3~30 MHz 300.00

5 VHF 30~300 MHz 100.00

6 UHF1 300~1000 MHz 50.00

7 UHF2 1000~3000 MHz 30.00

8 SHF 3~16 GHz 20.00

9 SHF2 & EHF1 16~65 GHz 10.00

10 EHF2 65~300 GHz 1.00

1 VLF 3~30 KHz 200.00

2 LF 30~300 KHz 200.00

3 MF 300~3000KHz 200.00

4 HF 3~30 MHz 300.00

For UHF, M/W, EHF point to point links per year basis –


Frequency Range (Lower Limit Exclusive, Upper Limit Inclusive)


UHF 1 ~3 GHz


M/W 3 GHz ~16 GHz


M/W 16 GHz ~65 GHz


M/W 65 GHz ~100 GHz


Above 100 GHz

Requirements of license –


Category of Licence




International Gateway (IGW) Services


including BTCL


Interconnection Exchange (ICX) Services


including BTCL


International Internet Gateway (IIG) Services


including BTCL


Broadband Wireless Access (BWA)



Cellular Mobile Telecom Operator


including Taletalk


Public Switched Telephone Network (PSTN) Operator


including BTCL


Nationwide Telecommunication Transmission Network (NTTN) Services Provider



Nationwide Optical Fibre Telecommunication Transmission Network



Pre-Paid Card Service Operator



Vehicle Tracking Services



Internet Protocol Telephony Service Provider – Nationwide



Internet Protocol Telephony Service Provider – Central Zone



Internet Protocol Telephony Service Provider – Zonal



Internet Service Provider – Nationwide



Internet Service Provider – Central Zone



Internet Service Provider – Zonal



Internet Service Provider – Category A



Internet Service Provider – Category B



Internet Service Provider – Category C






VSAT Provider



VSAT Provider with HUB



Call Centre



Hosted Call Centre



Hosted Call Centre Service Provider



International Call Centre


Total Number of Present Licenses


Task-3 (c)

Requirements of some equipment are :






Transmitter etc.

The estimation cost for everything to setup this system –

Frequency cost – 200 taka or more for per Khz in per year.

Equipment cost – around 1000000 taka.

So, total estimating cost around 10,000000 or above.

Task-3 (d)

Limitation of PMR :

Lack of privacy;

Coverage limitations (25 km radium max);

Congestion, as many users are assigned to a single channel.

Limitation of PTMR :

It has time limitation, if large amounts of data have to be transmitted.

Task-3 (e)

I recommend using Private Mobile Radio (PMR) to set up voice communication. Because, it has not noise, cost efficiency, frequency rate good, international standard, Confidentiality etc.

TASK – 4

Task – 4 (a)

The main equipment that would be installed are :

Telephone instruments.

Private Branch Exchanges (PBXs).

Key Telephone Systems (KTSs).

Automatic Call Distribution (ACD) systems.

Voice Processing Systems.

Telephone Answering Machines.

Telephone Call Information Loggers (CIL).

Facsimile Machines.


Local Area Network (LAN) Bridges.

Local Area Network (LAN) Routers.


Task – 4 (b)

The available features for this systems are :


A private branch exchange (PBX) is a telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public.

PBXs are also referred to as:

* PABX – private automatic branch exchange

* EPABX – electronic private automatic branch exchange

Figure 10 How PBX works

Features of PBXs :

Account Code: Account code for dialing calls

Alternate Number Ring: Assign a different number to same line that rings with a different cadence

Attendant: Main Operator extension

Autodialer: Support multiple autodialing techniques

Automatic Attendant

PBX Automatic Line Selection

Automatic Hold

PBX Automatic Redial

Automated directory: Automatically connect to an extension by name

Automatic Call Distribution: ACD

Barge-In: Allow an extension to break into a call at another extension

Billed Calls Only: Outgoing calls must be collect or 3rd-party billed

Boss-secretary functions: The boss’es phone and the secretary’s phone are linked togheter

PBX Busy Ring

Call Back

Call Center: Organizations using PBX technology

Call Forwarding: Redirects all incoming calls towards other extension

Call Monitoring

Call Recording

Call Return: ??

Call Through: Service for savings on local interconnect charges

Call Transfer: Hand a call off to another extension

Call Trace: mark a call in system logs as requiring tracing or special attention

Call Park: Place a call on hold and allow anyone to dial an extension and take the call

Call Pickup: Take a parked call off hold


A key system or key telephone system is a multiline telephone system typically used in small office environments. Key was a Bell System term of art for a manually operated switch, such as the line-buttons on the phones associated with such systems. A key system was originally distinguished from a private branch exchange (PBX) in that it allowed the station user to see and control the calls directly, manually, using lighted line buttons.

Key systems are noted for their expandability and having individual line selection buttons for each connected phone line, however some features of a private branch exchange such as dialable intercoms may also commonly be present.

Key systems can be built using three principal architectures:

* Electromechanical shared-control

* Electronic shared-control

* Independent keysets

The features of KTSs :


allows you to record a greeting (20 second maximum) that the incoming caller will hear after one ring. The caller may then select one of the options offered in the recording which will ring the extension of the desired party. A typical business recording might be “Thank you for calling


when utilizing the AUTOMATED ATTENDANT, the system will recognize an incoming fax, and will automatically route to the fax machines’ extension. This feature saves you money by freeing up “dedicated” fax lines for voice or other uses.


allows extensions with a key phone to receive internal intercom calls directly through their speaker phone without having to pickup the handset.


allows private communication between system users. IPS Key Telephones can dial another internal extension by simply pressing the button or “key” associated with the other extension .


when utilizing the AUTOMATED ATTENDANT, the incoming caller may, upon hearing the recorded greeting, connect to any desired extension by dialing the three digit extension number (100 to 107 on the IPS308, 100 to 115 on the IPS416)


one of the most significant features of the IPS is the ability to program its features utilizing the IPS programming software. The software’s graphics, help menus, and cue cards make programming simple from start to finish.


(requires caller id option and an IPS Key Telephone) – displays incoming caller name and number on all Key Telephones with display.


a micro-mini input port on the IPS may be connected to any external music source (tape, CD, radio, or continuous play advertising message) to provide background sound for incoming callers while transferring to a desired extension or while remaining on hold.


allows an extension to preset a specified time for a reminder ring or wake-up call.

Task – 4 (c)

The cost of equipment and installation :

There are user who will use these equipments –

The Chief Constable

The assistant Chief Constable

District Commander

Deputy District Commander

Sergeants and constables

The police officers

Detective Chief Inspector

Detective Inspector

The civilian staff


Users with quantity


Price (tk)

Telephone instruments

The Chief Constable – 5

The assistant Chief Constable – 3

District Commander – 3

Deputy District Commander – 3

Sergeants and constables – 3

The police officers – 2

Detective Chief Inspector – 4

Detective Inspector – 3

The civilian staff – 2



Private Branch Exchanges (PBXs)

The Chief Constable – 1

Detective Chief Inspector – 1



Key Telephone Systems (KTSs)

The Chief Constable – 1

The assistant Chief Constable – 1

District Commander – 1

Deputy District Commander – 1

Sergeants and constables – 1

The police officers – 1

Detective Chief Inspector – 1

Detective Inspector – 1

The civilian staff – 1



Automatic Call Distribution (ACD) systems

The Chief Constable – 1

The assistant Chief Constable – 1

Chief Inspector – 1

Detective Inspector – 1



Voice Processing Systems

The Chief Constable – 1

The assistant Chief Constable – 1

District Commander – 1

Deputy District Commander – 1

Detective Chief Inspector – 1

Detective Inspector – 1



Telephone Answering Machines

The Chief Constable – 1

The assistant Chief Constable – 1

District Commander – 1

Deputy District Commander – 1

Detective Chief Inspector – 1



Telephone Call Information Loggers (CIL)

The Chief Constable – 1

The assistant Chief Constable – 1

District Commander – 1

The police officers – 1

Detective Chief Inspector – 1



Facsimile Machines

The Chief Constable – 1

Detective Chief Inspector – 1




The Chief Constable – 1

The assistant Chief Constable – 1

District Commander – 1

Deputy District Commander – 1

Sergeants and constables – 1

The police officers – 1

Detective Chief Inspector – 1

Detective Inspector – 1

The civilian staff – 1



Local Area Network (LAN) Bridges

Just two bridges can be supported for all.



Local Area Network (LAN) Routers

Just two routers can be supported for all.






Total Cost :


Task – 4 (d)

The cost of operating the system :

Actually this system will be so much benefited. It needs so much high configuration system. The estimated cost for this system about 7,54,784.00 taka or more.

Task – 4 (e)

I described both of two systems. But I will recommend to use PBXs. Because, it has so many advantages.

The advantages of PBX are :

1. It is much easier to install and configure than a normal home line. Anyone that can handle a computer and is familiar with Windows features can install it. If you are familiar with networking computers is in good shape. You don’t have to have someone come out to your location and install and hook things up. It is in your hands and not in someone else’s.

2. It is easier to manage. IP PBX can be managed in a web based configuration interface or a GUI. This allows you to fine tune and maintain you phone system. Once again, if you are dealing with a regular home line you have to rely on a technician.

3. Significant cost savings when you use voip service providers. This is a big deal right now as we are all trying to cut back and save money. You can easily connect phone systems between branches and make free phone calls.

4. You can eliminate phone wiring. This is something that can bring a comfort to a business owner. Software phones can be installed directly onto the computer. You can now have much more control over adding and moving of extensions in your office. In new offices you can eliminate the extra ports completely.

5. Eliminate vendor lock in. This is exciting because you are now taking your phone services into your own hands and you don’t have to make decisions based on one company. You can mix and match in order to gain the best savings.

Task 5

Police Department Automation


Police Department Headquarter


To develop a new automation system for Townsville Police Department I have investigate to find the best network topology among many topologies and recommend one topology that suits best for police department.

Summary: In the above investigation I have tried to find the most convenient system for police department. Here are the key points that I found:

Among various topologies Star Topology will be the best solution to setup the network for the police department.

Investigating the best network medium for the network.

Investigating for best internet connection and connection that may require operating the system smoothly.

Investigating in details the methods of operating two-way voice communication, the legal requirements to setup two-way voice communication, costs, limitation of each system etc.

The main equipment for the telephone system that would be installed, each systems features, cost of equipment installation and operating it.

Strength of this report:

The strengths of the report are:

There are many networks type I have shown, we can easily determine which one is best for this type network

Details breakdown

Well organized and readable and understandable by non-technical people.

Costs break-down of the system setup.

Weekness of this report:

There some weakness in my report and investigation. To collect data I have faced many difficulties. Also there is no system in my country that run this or similar type network. I could do well if could get some more time.



Some network equipments etc.


When I was doing this assignment, I got many difficulties which I got solved from discussion with others and from my teacher help. I have tried to gather as much as detailed information.

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