# Enterprise networking

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1. Topology of a network refers the logical and physical connection between nodes(workstations). Logical Topology explains how the data transfer is going to take place while the Physical Topology is concerned with how the nodes are going to be connected by means of wires, cables or other medium.
2. Basically, there are two types of logical topology:

• Bus
• Ring

Physical Topology of a network can be star or mesh or something else but its logical topology has to be anyone of Bus or Ring.

### Bus Topology:

Bus networks uses 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 hear, but only the intended recipient actually accepts and processes the message (Network Topologies). At the ends of the bus attached are Terminators which device terminates any signal that has been left unattended and occupies the backbone preventing the transfer of other signals. But there are always high probability of collisions in buses which can be avoided by CSMA/CD.

### Ring;

In a ring network, every device has exactly two neighbors for communication purposes. A special pattern of bits revolves around the ring called the Token. A node in the network can only transmit data when it recieves the Token. It attaches the data to the Token with the destination address and then sends it. After recival a confirmation is given to the sender. 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. But this problem can be avoided to an extent when Dual Ring is adhered.

3. Suitable media types available for forming the network are:
1. Unshielded Twisted Pair(UTP) Cables.
• Category 5e
• Category 6
• Category 7
• Optical Fibre Cable.
2. Wireless Communication.
• Microwave.
• Infrared.

### Unshielded Twisted Pair(UTP) Cables:

• Less expensive and comparably efficient.
• Available.
• Easy to install.
• Many categories to choose from.

• High Cost maintainence.
• Susceptible to corrison quickly.
• Probability of being theft.
• Vulnerable to crosstalk and noise.

### Optical Fibre Cable:

• It provides a higher transmission capacity.
• It is easily transportable.
• Immune to electromagnetic interference.
• Capacity to transmit all forms of communication (voice, data and video).

• Used only in particular circumstances.
• Very expensive.
• Fragile than other kinds of cables.

### Wireless:

• Workstations can be added easily.
• Workstations can be mobile.
• Installation less difficult.
• Environment remains neat and clean due to no wires.

• Lower bandwidth due to limitations of signals.
• Costs more than wired devices.
• High probability of interference occuring.
• Many security threat implications.
4. For logical topology Dual Ring would be best suitable because the chances of collisions will be decreased greatly and for physical topology, Extended Star will be applicable because there will be multiple worstations connected from multiple sites and it will also ensure reliablity in case of a node breakdown. The only medium suited for the network would be a category of UTP Cable and it should be Category 7 because it is shielded and immune to crosstalk or noise. Optical Fibres will be overhead because the communication is in-house. Wireless transmission cannot be implemented because there will be many openings to information theft and protecting the signals will add more cost to the budget.

1. Based on what topology and medium type has been chosen previously, Broadband Internet Service will be best suited for a Police Department because Broadband Service provides very high speed data transfer rates. Broadband services are available in half and full duplex communications. For this kind of organization, Full Duplex communication is best suitable so that, incoming transmission does not hinder outgoing transmissions. Broadband services also allows for many choices of transmission rates as required ranging from ~1Mbit/s to ~160Gb/Bits. The braodband service can be unreliable at times but if a very trusted ISP is chosen for the service and dedicated service is chosen then there will not be any room for compromise.
2. Connection speed suitable would be 55 MB/s .
3. The ISPs providing best of services and reliable are as follows:
• BDCOM Online Ltd.
• IS PROS Limited.
4. According to the ratio of price to service. Link3 has a very good reputation. Therefore, Link3 should be chosen. Their package is as follows:

Package: Broadband (Dedicated) - 1MB/s*55=55 MB/s.

Monthly Charge: 55 MB/s*18,000 BDT= 9,90,000 BDT.

### The method for Two-way voice communications available is PTMR(Private Trunked Mobile Radio).

Its characterstics are as follows:

• Point to multi-point communications (as opposed to cell phones which are point to point communications).
• Push to talk, release to listen - a single button press opens communication on a radio frequency channel.
• Large coverage areas.
• Closed user groups.
• Communication on a single channel(half duplex).
• Use of VHF or UHF frequency bands.
• Requires license from govermental department.
• Bandwidth and channel availability limited.

In general narrow band frequency modulation is the chosen form of modulation for PTMR. Typically a deviation of 25kHz is used for FM and this enables a channel spacing of 12.5kHz to be implemented. As the demands for PTMR are high, it is necessary to make effective use of the channels available. This is achieved by re-using the frequencies in different areas. Base stations must be located sufficiently far apart so that interference is not experienced (Professional Mobile Radio).

### Licensing Gudelines:

1. The Licensee shall establish, operate and maintain the BWA Services as provided in the License.
2. In order to ensure proper competition among the BWA Services licensees, total 3 (three) licenses will be issued to provide nationwide BWA Services in 2.3 GHz and 2.5 GHz spectrum bands. An additional BWA license (fourth license) may be issued to Bangladesh Telecommunications Company Limited (BTCL) in the same terms and conditions including the License Acquisition Fee (to be fixed by way of auction) as shall be applicable to the other BWA licensees.
3. Two licenses will be awarded to the prospective Applicant(s) to provide nationwide BWA.
4. Services in 2.3 GHz and one license will be awarded in 2.5 GHz spectrum bands.

5. The duration of the Licenses, shall initially be for a term of 15 (fifteen) years. Upon expiry of the initial term, the License may be renewed for subsequent terms, each of 5 years in duration, subject to the approval from the Commission and to such conditions, including the payment of any fees, as may be specified herein and/or by the Commission under the Act.

### Frequency Distribution:

1. Spectrum bands 2.3 GHz and 2.5 GHz have been considered for BWA Service License.
2. A contiguous 30 MHz of unpaired spectrum from 2.3 GHz band (23xx-23xx MHz and 23xx-23xx MHz) will be assigned to 2 licensees. (Licensing Guidelines).
3. A contiguous 30 MHz of unpaired spectrum from 2.5 GHz band (25xx-26xx MHz) will be assigned to 1 licensee. 2615-2620 MHz is kept as guard block between TDD and future FDD assignment.
4. 30MHz contiguous channel will be allocated to each operator to provide BWA services. Per channel bandwidth should be either 5 or 10 MHz.
5. The spectrum assignment will be inclusive of guard bands needed for the operation of the equipments to avoid causing harmful interference to adjacent equipments operating in adjacent bands. No separate spectrum shall be kept as guard band between two assignments in 2.3 GHz band. (Licensing Guidelines).

### Fees and Charges:

The spectrum charges shall be calculated using the following formula:

Spectrum Charges in Taka = STU x CF x BW x AF x BF.

Where, STU=Spectrum Tariff Unit=Tk. 60.00 per MHz per Sq.km.

CF=Contribution Factor.

BW=Bandwidth Assigned for Access Frequency in MHz.

AF=Area Factor for Access Frequency=147570 Sqkm.

BF=Band Factor.

### Limitations:

The operators, within 1 year of issuance of license, shall have to install minimum 5 full fledged Base Station Transceiver (BTS) radio sites in areas covering each Divisional Headquarters and 3 BTS covering each District.

Frequency Range: 2.3 Ghz - 2.5Ghz.

Channel Spacing: 12.5 Khz.

Interference: Co-channel Interference, Adjacent Channel Interference and Intermodulation (Operating frequency range explained, 2008).

### To implement PTMR a network of stations are set up.

If more range is to covered than the frequency coverage can be increased by the use of repeaters. A repeater can be a useful tool to increase the operating range of a radio system. With its relatively high transmitting power & external antenna, a well-sited repeater will provide an excellent platform to boost signals beyond the range of non-repeater networks. Whether it is sited at the centre of operating network or at a location prone to weak coverage, the repeater will instantaneously re-transmit received audio without any noticeable delay (Repeater applications explained!).

The above recommendation has been given due to many advantages explained in other Tasks but as an overview will be briefed below as the advantages of implementing the:

PTMR communications system:

• Improved communication and liaison between users.
• Increased intelligence exchange.
• Increased safety and confidence for users.
• A more effective early warning system enabling the users to provide a more pro-active approach.
• Support and backup.
• Crime deterrence, public safety and improved confidence for them.
• Greater knowledge of criminals, especially for retail operative.
• Quicker responses.

1. The organization investigated was a Computer Sales Plaza called IDB.
2. The Adminstration department of IDB has a Hosted PBX(Private Branch Exchange) installed from BRTC. Every shop in IDB is connected through the Adsminstration office so that calls can be routed to specific shops. Since it is a hosted PBX, all the equipments are in BRTC's premises. So the following names of equipments are based on assumptions and references.

The equipments more or less required are:

• The PBX's internal switching network.
• Microcontrolleror microcomputerfor arbitrary data processing, control and logic.
• Logic cards, switching and control cards, power cards and related devices that facilitate PBX operation.
• Stations or telephone sets.
• Outside Telco trunks that deliver signals to (and carry them from) the PBX.
• Console or switchboard allows the operator to control incoming calls.
• Uninterruptible Power Supply(UPS) consisting of sensors, power switches andbatteries.
• Interconnecting wiring.
• The PBX features the following features from mail to optional ones:

### Main:

• Establishing connection between two telephone sets of two users.
• Maintaining connections as long as user requires.
• Dial outside lines.
• To make an extension query while connected to and on hold another external call.
• Transfer an external call to the extension that has been enquired.

• Auto-attendant.
• Calls are answered automatically by a pre-recorded message or a menu system.

• Automated directory services.
• Where callers can be routed to a given employee by keying or speaking the letters of the employee's name.

• Call Diversion.
• Calls will be diverted to an extension when a given condition will be fulfilled.

• Saved Number Dialled.
• Allows to save an incoming number and re-dial it at a later time.

• Call park.
• A feature of sometelephone systemsthat allows a person to put a call on hold at one telephone set and continue the conversation from any other telephone set.

• Hunt Groups.
• If one extension is busy then the call will be routed to the available extension in the Hunt Group number.

3. Since the organization is using a Hosted PBX. They have disclosed the following costs.
4. The hardware and setup cost included = 1,30,000 BDT/Month.

5. If something goes wrong with the telephone sets or wiring in the user premesis then the users has to confront the costs. Their monthly cost on PBX requires as follows:
6. Replacing damages sets= 2,850 BDT/Telephone set.

Wiring Replacement= 25 BDT/Feet of wire.

Any damage occuring at the provider premesis is maintained by them.

7. The Hosted PBX is the best solution for any organization can afford. Because most of the problems are handled by the provider including any necessary cost(varies with provider). Other advantages of PBX are detailed below:
1. It allows all employees to share phone system lines, thus reducing overall telecommunication expenses.
2. The PBX system is totally programmable and can support complex installation or integration requirements.
3. There are a wide variety of standard, as well as additional features with the PBX system.
4. The PBX system is easily expandable as the organization grows.
5. The physical PBX hub is low profile and does not require a large amount of space.
6. Installing PBX may require investment of a big amount but on the long run, it is profitable.
7. Save money with no PBX hardware to purchase or lease and no labor or maintenance ever needed
8. PBX provides the best sounding telephone conversations with digitally optimized voice handling

Due to all the above advantages over other telecommunication alternatives. It is recommended that Hosted PBX be used and if possible better provider and more features be adhered to.

Executive Summary:

This report will be consisted of the following:

1. Topology that will be suitable for the Police Department Networking.
• Which Physical and Logical Topolgy.
• ecommendation for a Topology and its associated medium.
2. Internet Connection Requirements for the Police Department.
• Type of Internet Service.
• Bandwidth most suitable.
• Providing ISPs available and the associated costs.
• Recommendation of an ISP.
3. A Two-way voice communication method that can be implemented.
• Possible voice communication methods.
• Legislation.
• Costs and charges.
• Limitations and coverage.
4. Recommendation for Telephone Systems to be purchased.
5. Equipments required with related system.
6. Features available with system.
7. Cost of equipment, installation and maintainence.
8. Recommendation for a Telecommunication system.

### Introduction:

The compilation of this tasks forms an output which will provide a whole network structure required to operate large single-site organizations such as The Police Department. Since, imlementing such big network gets governmental, legal requirements are also required which have also been mentioned.

### Topology that will be suitable for the Police Department Networking:

To suggest a topology for the Police department, information about the topologies are also required. But before that, What is a Topology? Topology of a network refers the logical and physical connection between nodes(workstations). Logical Topology explains how the data transfer is going to take place while the Physical Topology is concerned with how the nodes are going to be connected by means of wires, cables or other medium. Why a Topology is required for the network? A topology is required because it gives the network an architecture or a structure to follow which will house the communications between the nodes and on the web. After a through analysis, it has been recommended that a logical ring implemented as a physical star(extended) be adopted. Because ring topology compared to bus has many advantages and reduces the cost of maintaining equipments which increases the efficiency of the network like CSMA/CD used in bus topologies. Physical star will be most suitable because there will be multiple sites connected to a server. If star is adopted then multiple sites can be connected with the help of hub/switch to form a centralized structure to the server.

### Internet Connection Requirements for the Police Department:

Internet is required by any official departments. So, The Police Departments requires one too. Now, it might get very confusing about what Internet Service will be most suitable for the department. To narrow the search, concentration be put into the requirements of bandwidth and consumers. Since there are great number of bandwidth consumers, whose list will be provided below:

Wrok stations in each office in each district(x4):

District Commander= 1

Deputy District Commander= 1

Seargents= 1

Constables= 5

Total= (1+1+1+5)x(4)+21= 53 Workstations required

Therefore, 76 Workstations total in 4 Districts.

Assuming that all of the wokstations more or less is going to be active, high abdnwidth is required. Therefore, it is suggested that Broadband Internet Services be implemeted with the high bandwidth package the ISPs has to offer. The connection speed for this big of an organization as a whole should be from 50 MB/s to 55 MB/s. Calculation will be done to minimum because ISP providers vary from place to place and their related charges. According to the ratio of price to service provided. Link3 has a very good reputation. Therefore, Link3 should be chosen. Their package is as follows:

Monthly Charge: 55 MB/s*18,000 BDT= 9,90,000 BDT.

### A Two-way voice communication method that can be implemented:

There are many methods through which two-way communication could be achieved. They are PTMR, cellular Radio, MPDN and etc. But the system that is popular and implementable is the PTMR(Private Trunked Mobile Radio). PTMR has been used and is still being used by many Police forces around the globe. Therefore, it is perfect for the Townsville Police Department also. This method consists of Radio Devices which can be used to do both talking and hearing though the communication is half-duplex that is why use of phrases such as 'over and out' is essential. Every police officer will be carrying one of the radio devices and base stations will be set up in the district offices and the headquarters. Use of repeaters can also be implemeted if signals are distorted. Repeaters can increase the radius of signals thus, covering more distance. Encryption is encouraged because Police conversation is very important and sensetive so, its leak can create havoc and increase crimes. Signals can be protected through Encryption and prevent from getting captured by Scanners.

There are many legislation requirements for implementing the PTMR. The legislation is directly not named the PTMR rather named BWA(Broadband Wireless Access) which when obtained can be used to register frequency and then the vendor equipment license. There are rules and regualtions to be followed for registration. The rules are as follows:

1. The Licensee shall establish, operate and maintain the BWA Services as provided in the License.
2. In order to ensure proper competition among the BWA Services licensees, total 3 (three) licenses will be issued to provide nationwide BWA Services in 2.3 GHz and 2.5 GHz spectrum bands. An additional BWA license (fourth license) may be issued to Bangladesh Telecommunications Company Limited (BTCL) in the same terms and conditions including the License Acquisition Fee (to be fixed by way of auction) as shall be applicable to the other BWA licensees.
3. Two licenses will be awarded to the prospective Applicant(s) to provide nationwide BWA Services in 2.3 GHz and one license will be awarded in 2.5 GHz spectrum bands.
4. The duration of the Licenses, shall initially be for a term of 15 (fifteen) years. Upon expiry of the initial term, the License may be renewed for subsequent terms, each of 5 years in duration, subject to the approval from the Commission and to such conditions, including the payment of any fees, as may be specified herein and/or by the Commission under the Act.

The operators, within 1 year of issuance of license, shall have to install minimum 5 full fledged Base Station Transceiver (BTS) radio sites in areas covering each Divisional Headquarters and 3 BTS covering each District.

Frequency Range: 2.3 Ghz - 2.5Ghz.

Channel Spacing: 12.5 Khz.

Interference: Co-channel Interference, Adjacent Channel Interference and Intermodulation (Operating frequency range explained, 2008).

### Recommendation for Telephone Systems to be purchased:

Now, what is left for the police department is a Telecommunication system. The best possible solution is the PBX(Private Branch Exchange). Housing personal machines and equipments to implement a PBX is a big hassle. Therefore, it is popular and advisable that Hosted PBX be implemented. As the name suggests, a provider of PBX will do all the necessary work to implement the PBX and most of the equipments will be in their premises which decreases the cost and problem of maintaining the equipments. And as of privacy and security, the providers can be signed with for a QoS(Quality of Service) which will include rules and regulations of security and privacy of the client's communications through PBX.

A Hosted PBX includes the following costs and charges:

The hardware and setup cost included = 1,30,000 BDT/Month.

If something goes wrong with the telephone sets or wiring in the user premesis then the users has to confront the costs. Their monthly cost on PBX requires as follows:

Replacing damages sets= 2,850 BDT/Telephone set.

Wiring Replacement= 25 BDT/Feet of wire.

Any damage occuring at the provider premesis is maintained by the providers themselves.

### Assumptions:

• Investigation source has concealed right information.
• ISP will fulfill the requirements at the claimed price.
• PTMR is mostly used in Bangladesh for Two-way communication.
• Equipments that are required for PBX are roughly the same as denoted above.
• The features investifation source claimed they have for PBX are true and accurate.
• Hosted PBX in Bangladesh is at the price claimed above.
• PTMR can be implemented in Bangladesh as claimed above.
• Legal Requirements obtained from the BTRC web site are accurate.