# Topology

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#### How the topology operates

Topology is the link between the parts or the connecting together in a computer system using interconnected nodes. So, it is the fully interconnected network structure. Topologies can be divided into two types. They are Bus topology and Peer to Peer topology. Bus topology is mainly one branched but Peer to Peer topology contains Ring topology, Star topology. And Peer to Peer also contains Mesh topology (Grid Topology).

#### LAN topologies

In a local area network system, the computers are connected by the form of networking medium. And this medium provide as the way for the network signal transmitted. For the types of network medium, the layout of the networks is the way it provided. So, the topologies depend upon the layout and its structure. The workstations physically connected to the network are described the topology.

#### Bus topology

In Bus topology, computers are linked through a single set of wires, called a bus. A bus topology connects all networking devices by a cable as a central backbone. Data can pass on a straight-line from one location to another. One computer transmits data to another by broadcasting the receiver address and the data over the bus. But, in practice only one computer can send data at the same time. The others must wait to send their data. In a Bus topology all network communications are broadcast to the entire network. Bust topology is mainly used in LAN topologies. But today, it is more common in Star topology.

#### Ring topology

Ring networks run like bus networks with the exception of a terminal. A ring topology is one in which all nodes of the network are linked to a ring. In Ring topology, transmissions pass from one node to the next in an ordered cycle. When the signals reach the last node, they are returned to the first. In Ring topology, there has no beginning or end point because signal is passed in a circular system, using tokens. In Ring, it can also have an ability to bypass any broken or failed node. But, new nodes can be difficult to add because of the closed ring.

#### Star topology

In Star topology, a LAN network in which each nodes connected to a main device (central) in a star-shaped pattern; mainly, a network consisting of a hub surrounded by workstations (terminals). So, transmissions pass directly from a node to the central computer, which holds any extra routing as to another node. As with the Bus topology with a backbone, the failure of one computer node does not cause a failure in the network. A Star topology is one which the hub includes all of the intelligence of the whole system and passes directly all network signals. In a Bus topology or Ring topology, a fault segment can take down the whole network. In Star topology if an error occurs in a segment, the remaining segments can work properly. Central terminal of star network has external connections, to the other networks, as well as connections to the nodes of computers in the network.

#### Mesh Topology (Grid Topology)

On a mesh network, topology can actually change on the fly. No central device directs a mesh network, and no set route is applied to pass signals back and fore between computers. Instead, each computer includes everything it needs to serve as a relay point for sending information to any other computer on the network. So, if any one computer is malfunctioned or faulty, information is redirected to nodes of other computers. It is so called self-healing process.

#### Network Mediums

Network mediumusedtobroadcast transmissions limits the network speeds, the distance between computers in system, and the networking topology. Network Medium has existed variously for networking, having defined characteristics and suitability for different purposes. Its suitability determined by factors such as bandwidth, cost, east of installation. In generally, it can be divided into two categories-Guided Media and Unguided Media.

#### Guided Media

• At the broadest comprises cables (metallic conductors) and optical fibre.
• Cables subdivide to-
• Coaxial cable
• Twisted pair cables
• Optical fibre subdivides to-
• Multimode fibre
• Single mode fibre

#### Coaxial cable

• Rarely used in LAN networking nowadays.
• Used in cable TV connections and some WAN applications.
• Can support long runs due to efficiently of shielding
• Can support data rates up to 1Gbps

#### Twisted pair Cable

• Comes in several varieties of cable useful for differing applications
• Each pair of wires is twisted together in the manner of DNA strands
• Cable core are normally copper, of varying purity
• Extensively used in both IT networking and telephony

• Well known and easy technology
• Fairly robust
• Good carrying capacity for LAN applications

• Distance limited
• Susceptible to data loss through interference
• Limited in carrying capacity for WAN applications

#### Unguided Media

• In some cases a slight misnomer, as they can be highly directional
• All may be group under the generic term "wireless"
• Uses a single fibre either glass or plastic
• Light sources vary from various colours of LED.

• Secure-almost impossible to tap into fibre optic successfully
• Huge bandwidth-already used in multi-gigabit applications
• Reasonably robust given careful handling

• Fragile if roughly handled
• Highly specialised equipment needed to split and join
• Expensive

#### Recommendations

For the Townsville Police Department, I would like to recommend using star topology. According to the facts that I have been found; star topology is one which the hub includes all of the intelligence of the whole system and passes directly all network signals. Because the Townsville Police Department is divided into four district and it covers an area of 100 square kilometres.

Among the network mediums, I suggest that wireless network is most suitable for the Townsville Police Department. In populated areas, wireless network kills the cable costs for the large distance from the server. Wireless also facilitates office relocations and easier to maintain. It makes available real-time data in broader range of coverage areas. It also more secure than the other mediums. So, wireless is the most suitable network medium for Townsville Police Department.

#### Internet services that may be require

There have many kinds of internet services to access online. They include Dial-up, DSL, Broadband and Wireless Services.

#### Dial-up

Dial-up is the basic way of internet services. Generally, its speed less than 56 Kbps. Dial-up speeds can differ according to the quality of the phone-line and the user configurations. There have many dial-up users who familiar with particularly slow speeds for example 28 Kbps on 56k connections. Usually users need to be assigned a different IP number every time you connect providing some anonymity.

Dial-upistheleastexpensive access way of connection, but it also has the least convenient. When you disconnect, you are truly disconnected unlike the always on high speed tactics like cable which create somewhat of a security risk.

#### DSL

DSL (Digital Subscriber Line) is a high speed telephone line supplying phone-line, television and internet access. A DSL service transmits signals along the same wires that telephony uses, and cable modems that use the same as the cable TV uses. In those cases, the electronic devices that are applied to transmit signals along the wires use different frequencies or channels that do not disturb with other signals on the common wires. So, a DSL Internet service connection can transmit signals along a pair of wires at the same time the wires are being used for a phone line, and cable modems can transmit signals over a cable at the same time the cable is being used to obtain television signals.

DSL is a very distance sensitive medium. DSL providers are only able to offer its facility to locations in its range. The high speed will drop off quite a bit any further from DSL providers. This means that only locations that are close to a DSL hub can even get the top speeds of 3 Mbps to 7 Mbps. Users who live further than the drop-off point will only be able to get the basic DSL plans which offer speeds from 768 Kbps to 1.5 Mbps.

Broadband is one of the higher speed internet transmission facilities. In this service, you can get a high band-width service from satellites. Broadband service allows data to flow from an Internet service provider to a user's computer hundreds of times faster than ordinary dialup modems. Broadband service is ready for all-time as you wish. Its transmissions pass through the satellite connections and it can provide cable television and internet access at the same time. Broadband higher speeds also support the fast downloads. So, it has a high speed internet accessing facilities by using advanced technologies.

Broadband service provides offers a speed at basic of 4mbps to 6 mbps. In an advanced transmissions it can provides at a speed of 16 mbps or higher. Broadband is not only a fast internet access facility but also a maximum security from hackers and internet risks.

#### Recommendation

Townsville Police Department covers an area of 100 square kilometres, so DSL cannot provide that far distance. It cannot provide for the reason that DSL is a very distance sensitive medium. DSL providers are only able to offer its facility to locations in its range. The connection speed will slow down quite a bit any further from DSL providers. Nevertheless, Broadband connection covers that far distance and broadband connection can be set up easily without any further medium such as cable. Moreover, broadband connection has high band width that provides faster connection and downloading speed.

For that reasons, I would like to recommend using broadband connection for renewing all of its computer networks for the new headquarters.

#### Example of internet service providers (ISPs)

Internet service providers (ISPs) provide internet access by each connection types of services. For Townsville Police Department, broadband is most reliable for some reasons. Broadband connections do not have any distance sensitive problems and it can offer a most suitable security for the police department. There are top 10 Broadband Providers in the country, this happens when you Broadband, Internet Services, Prices and Compare Features. The top broadband companies are Media X, Virgin Media, MPT, Ducal, NT Total, Plus Net, and Eclipse, Star Net.

For the above ISPs I suggested to NT total broadband company for Townsville Police Department because it has a fair price and NT total can provide a higher security with limitation accesses and most reliable connections.

#### Frequencies for two way communications

There are many types of frequencies for radio communications but there are only two frequency types for two way communicating system. They are

• Very High Frequency (VHF)
• Ultra High Frequency (UHF)

#### Very High Frequency

Very high frequency (VHF) is the radio frequency between 30 MHz (wavelength 10 m) to 300 MHz (wavelength 1 m). VHF frequencies' broadcast characteristics are perfect for short-distance terrestrial communication. Very high frequency (VHF) is also less involved by atmospheric noise and interference from electrical equipment than low frequencies. It was also easier to construct efficient transmitters, receivers, and antennas for it in the earlier days of radio. In most countries, the VHF spectrum is used for broadcast audio and television, as well as commercial two-way radios (such as that operated by police), marine two-way audio communications, and aircraft radios. Common uses for VHF are FM radio broadcast at 88-108 MHz and television broadcast (together with UHF).

#### Ultra High Frequency (UHF)

Ultra high frequency (UHF) radio frequencies are in the range between 300 MHz and 3.0 GHz, which is higher than those of very high frequency (VHF). UHF and VHF are the most common frequency bands for television. The frequencies of 300-3000 MHz are always at least an order of magnitude above the MUF (Maximum Usable Frequency). The MUF for most of the earth is generally between 25-35 MHz. Higher frequencies also benefit less from ground mode transmission.

#### Full and Half Duplex

Duplex is a method which transmit radio frequency on various channels. There are two types of duplex - Half duplex and full duplex.

Half Duplex - to communicate with half duplex, push to talk switch is necessitate.

Full Duplex - transmit and receive conversation like mobile phones capability. This can transmit signals by two-way simultaneously at the same time.

#### Legal requirements

If a radio broadcasting system, it will need licensing for those transmissions. Other private business radios operate on either VHF or, UHF radio frequencies are identical for some time. For a police department it is necessary to license the frequency for the secure radio conversation and some legal issues. There are benefits of a licensed frequency such as: larger range, less interference from other users.

#### Licensing requirement

If the range of the two-way radio frequency is more than two miles, there would be registration with FCC-Federal Communication Commission. Following are the minimum requirement for the registration.

1. Type of frequency to use
2. Type of equipment to use
• Model No. of the equipment
• Supplying company
1. Transmission Area (Rural Area, Sub Urban Area, Highly Populated Area)

Nevertheless, some of the company already provide registration with Federal Communication Commission before the equipments are set up. Thus, there would be no more further registration for two-way radio communication.

#### Licensing Cost

There are three types of areas for licensing the two-way radio. They include rural area, sub urban area, highly populated area. Licensing Cost for the rural area will vary from &pound;75-80 per year. Licensing Cost for the sub urban area will vary from &pound;100-120 per year. Licensing Cost for the highly populated area will vary from &pound;200-220 per year.

#### Equipment Cost

Equipment cost for the two way radio communication will be vary from the type of two way radios that chosen by the Townsville Police Department. From the scenario, the Townsville police department is divided into four districts. Each district has five police car for patrolling the area and police officer also patrol local area on foot. Townsville police department has a serious crimes squad which has eight cars. These patrolling cars and police officers require two-way voice communication. Thus, the department provide them with two way radios which govern an area of 100 square kilometres.

For all the 20 patrolling cars and 8 serious crime squad cars, the 28 transceiver will be necessitated. Each transceiver will cost around &pound;85, so all the transceiver s for the cars will be around &pound;2380.

For the police officers, two-way radio which can operate 25 miles will be needed. Each of these two-way radios will cost around &pound;40.

#### Limitation of each method

Two way radios communication can be used on both Very high frequency and Ultra high frequency. Both VHF and UHF frequencies are covered around four mile of range. VHF waves are not very strong for penetrating walls, structures and rocky landscape. So range will be reduced for VHF radios in these environments. That may not necessarily be a problem if the range needed is only around a hundred feet. Anything that frustrates a radio wave will weaken a radio signal. UHF lessens that effect. Though it may not go as far, UHF radio waves will penetrate obstacles better than VHF. One advantage of UHF transmission is the physically short wave that is produced by the high frequency. That means the antenna on the radio can be shorter than an equivalent VHF radio.

#### Recommendation

As Townsville is a populated area, VHF can't perform well because as a city there has many complex radio transmissions and broadcastings. VHF cannot penetrate through the buildings and structures and the communicating security cannot get safety. And most VHF radios are half -duplex. For the UHF, the frequencies are extremely high and the penetrating ability is more immense. And, the distance limitations between VHF and UHF are quite different. UHF can go more distant location and can perform effectively for 24 hour. For the above reasons, I suggested Ultra High Frequency (UHF) is more suitable for The Townsville Police department.

As a government organization, Townsville Police Department needs a telecommunication system because of the emergency calls, recommended calls, official calls and communication within the department. There are several types of telecommunication system that provides services for organizations as Townsville Police Department. But, mainly there are two types of telecommunication system set ups which are suitable for a police department. They are Private Branch Exchange (PBX) and Voice over Internet Protocol (VOIP).

#### PBX

Private branch exchange (PBX) is a telecommunication exchange that serves a particular business or office, as opposed to one that a main carrier or telephone company that serves for many organizations or for the general public. PBX provides the communication within the private organization networks and public switched telephone networks.

PBX extension permits the entities which are small or medium in volume to obviously connect their remote office and tele-workers to the community PBX throughout the corporate IP communication infrastructure, which is commonly under-utilized. PBX extension maximizes bandwidth efficiency by connecting with voice and data traffic onto one network.

#### VOIP

Voice over internet protocol (VOIP) is a telecommunication technology that enables voice transmission to be sent over the internet sometimes containing text messages or data. VOIP is location independence and fairly fast system. It is integrated with other services such as data exchange, messaging, video conversation and audio conferencing. With VOIP it can be call from any location where there has a broadband connectivity. VOIP is not only flexible for any local calls but also convenient for any international calls.

VOIP network signal activates and coordinates the different apparatus to complete a call. But, there are some technical and architectural differences in a VOIP network.

#### The main equipment that would be installed

In Townsville Police Department, there have four district departments and the police headquarter. Sergeants in each district will have one work station between and there will be five workstations for use by the constables in each district. So, each police station requires one main phone line. As a police department, telephone lines may busy with variety of phone calls. So, every headquarters need five extensions for at least. For five departments, there would be twenty-five phone handsets and accessories are required. Five phone network hubs and cables are also required to set up the extension networks. Townsville police department also has a serious crime squad which has twenty detectives and each detective has a work station. Thus, another main phone line is required and that phone line should be divided into twenty extensions for twenty work stations.

Therefore, six main phone line and forty five extensions will covered the four districts headquarters and the serious crime squad.

#### PBX

Private branch exchange (PBX) provides the following features and functions:

1. Multi-Location Functionality - PBX system can take full access from more than one location on a central line.
2. One Number Calling-Find-To - if need to call the other extension phone,
3. Voicemail via Email - Digital voicemail file is sent via Email. It is also easy to reply and forward voicemail messages.
4. Advanced Phone System Menus - PBX provide a multi-level menu for a variety of call-routing options. The whole system is set up with scheduling after-hours operation, posting holiday attendant messages, and dealing with special situations. Menus are provided with easy functional interface and secure from unauthorized accesses.
5. Live Receptionist with Backup Menu - PBX supports live receptionist by answering from calls when no one is answer.
6. Caller ID Control - PBX can control the outgoing call by making a call log and call history to redial and checking the call history from unauthorized calls.
7. Incoming Caller ID - PBX manages the incoming calls by identifying and displaying the incoming calls and making memory log for the incoming callers.
8. Call Record - PBX can record the conversation on phone line and sent automatically to the email box after the call ends.
9. Busy status light - If an extension phone is used, a busy status light status light will indicate who is using the phone.
10. Direct Inward Dial - For a normal extension phone line, one of the incoming phone calls is reached to the reception first. Then dial extension number to reach to specific extensions. But in PBX the incoming phone can dial directly to the specific destinations
11. Fax Handling - PBX manage the fax incoming and outgoings through the main line to the extension destinations.

#### VOIP

1. Voice over internet protocol (VOIP) available the following functions and features:
2. Call forward - If an incoming call is accepted, it can forward to the particular extension destination.
3. Voicemail service - If no one is answer the incoming calls, it can transform into voice mail and can replay that conversations.
4. Three-way calling - During the conversation on phone line, the third call that permits for the conversations is allow to convert into three way calling.
5. Caller ID - As in PBX network, VOIP can display the incoming and outgoing calls and can record these calls to redial or look back.
6. Messaging service - Even an email or text message on line is sent into the VOIP system via the internet. It can also send back merely.
7. Database service - VOIP can also transmit data exchange over the internet into the main system. This also provides the update news and advertising listings.
8. Video conferencing - Using PCs, VOIP also provides the video chatting and conferencing with peoples more than two person.
9. Fax handlings - Like PBX fax messages can send over the phone line and controls the message for authorizations.

#### The cost of equipment and installation

For Townsville police department, there would be six main phone lines and forty-five extensions will be required. Each hub costs around 35 dollars and there are six hubs so its costs around 210 dollars. Each extension costs around 60 dollars and there have forty-five extensions and its total is around 2700 dollars. Other fees cost around 300 dollars so total equipment fees are around 3210 dollars.

For the setting up of the whole system, installation of head quarter and each district workstations costs around 50 dollars and crime squad costs around 150 dollars. So, total installation costs will be around 400 dollars.

#### The costs of operating the system

The costs of operating the system depend upon the duration of the phone usage. The duration will be set on minutes. Each minutes of usage will costs around 0.15 dollars to 0.75 dollars. And the monthly fees of maintenances and extra services will be around 50 dollars for whole Townsville Police Department.

#### Recommendation

For the Townsville police department I suggested PBX system rather than VOIP system. Video conversations, audio conferencing, online transferring, three-way calling in video system are too enormous for a police department. As an online data transferring, VOIP system is lower security level than the PBX system although cheaper than PBX. For PBX, features for extensions and local communications are more advanced than VOIP and It is also a secure conferencing for a government police department. So, PBX is more suitable than the VOIP system for the Townsville Police Department.