Advantages And Disadvantages Of Star Topology Computer Science Essay

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.)

Star Topology is the most common type of network topology that is used in homes and offices. In the Star Topology there is a central connection point called the hub which is a computer hub or sometimes just a switch. In a Star Network the best advantage is when there is a failure in cable then only one computer might get affected and not the entire network.

In a Star Network the entire network is dependant on the hub so if the entire network is not working then there could be a problem with the hub. This feature makes it easy to troubleshoot by offering a single point for error connection ad at the same time the dependency is also very high on that single point.

Star Topology Advantages

• A Star Network Topology is very easy to manage because of its simplicity in functionality.

• The problems can be easily located logically in a Star Topology and therefore is easy to troubleshoot also.

• The Star Topology is very simple in format so it is very easy to expand on the Star Topology.

Star Topology Disadvantages

• The Star Topology is fully dependant on the hub and the entire working of the network depends on the hub or the switch.

• If there are many nodes and the cable is long then the network may slow down.

Since all the computers on the network have independent control of their networks and only dependant on the central hub computer, the failures in transmission and other possible problems in this area are less likely. Also if the hub is safe then every computer in the network is safe. This type of network also offers more privacy than any other network.

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All the computers in the network are communicating with one main centrally located computer and there is no peer to peer coordination. If the peer to peer coordination takes place it is routed through the central hub. This way the privacy of each and every computer on the network is maintained.

b).

UTP Cable

Advantage:

1. The main advantage of cable lan is that it is capable of transmitting data at very high speed rates : even much faster to that data that can be transmitted over telephone.

2.It is cost effective as no excess hardware is required.

3. It is secure way of communication as no external virus interrupt.

4. It is stable as it show irs effect in smaller area.

Disadvantage:

1.The Disadvantages to a twised pair cable (AKA A Cross Over Cable):

2.It will require direct p2p (peer to peer) connections , e.g. straight from one computer to another (Mostly Via Ethernet or Com)

3.It will be incompatiable if talking to more then 1 computer by going throught a switch or hub.

4.Cross Over Cables should only be used when one computer needs to talk to another one right next to it, or if you are connecting to a router (via the console port) to configure it.

Wireless advantages and disadvantages

One of the major problems that presents itself is the already limited spectrum available for communications. The remaining free spectrum has to be used to its maximum potential, spread spectrum technology presenting itself as a suitable means of increasing performance. Splitting up of the environment into a number of small cells also increases the overall accessible bandwidth of the communication system, but also increases the cost as more cell sites are required. Techniques such as diversity combining can also be used to increase the available bandwidth through improved reception capabilities.

Where a large number of devices, each being of a low power, are transmitting, a sizable amount of radio power is being generated. The effects of radio communication on human health are being examined , however much more work is required in this area before large scale communication systems are developed.

The unconstrained nature of the communication medium of radio requires the issue of network security to be addressed. Verification of communication entities must also be performed to ensure that only registered devices may communicate using the network, and that only registered devices may receive the data.

c).

Reason for why I choose star topology:

• A Star Network Topology is very easy to manage because of its simplicity in functionality.

• The problems can be easily located logically in a Star Topology and therefore is easy to troubleshoot also.

• The Star Topology is very simple in format so it is very easy to expand on the Star Topology.

Task-02

a).

The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic and optical networking technologies. The Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents of the World Wide Web (WWW) and the infrastructure to support electronic mail.

Most traditional communications media including telephone, music, film, and television are being reshaped or redefined by the Internet. Newspaper, book and other print publishing are having to adapt to Web sites and blogging. The Internet has enabled or accelerated new forms of human interactions through instant messaging, Internet forums, and social networking. Online shopping has boomed both for major retail outlets and small artisans and traders. Business-to-business and financial services on the Internet affect supply chains across entire industries.

b).

Banglalion starts the shopping mall activation. you can know about Banglalion WiMAX & enjoy our subscription at your nearest shopping Mall. following is the activation Calender. Shopping Mall Date Dhaka Pink City, Gulshan 5 June, 2010 Anam Rangs Plaza, Dhanmondi 11 June, 2010 Shah Ali Market, Mirpur 12 June, 2010 North Tower, Uttara 18 June, 2010 Eastern Plaza, Hatirpool 19 June, 2010 Multiplan Center, Elephant Road 25 June, 2010 Concord Twin Towers (Shantinagar) 26 June, 2010 Metro Shopping Mall 2 July,

Qubee is a new and exciting company from Augere providing fast and reliable broadband internet services to residential and business customers across Bangladesh. We believe that everyone should be able to enjoy trouble-free access to the internet and the world of opportunities that it brings. Our aim is to make a magical internet experience available to everyone, everyday, without exception.

Qubee is the creation of a group of global telecoms professionals who saw that a new technology called WiMAX could really change the internet experience for millions of people worldwide. WiMAX means that you don’t need telephone lines or cable to get connected: all you need is to live close enough to a transmitter to receive the internet wirelessly. As you read, we’re busy building a network of base stations to offer our brand of internet access right across Bangladesh. We’re starting in Dhaka, but quickly plan to do the same in cities nationwide.

c).

Bangla Lion

Advanced Data Network (ADN)

Qubee

d).

Qubee introduces range of new packages to suit your monthly need. Be it speed, volume; Qubee has the solution which is fast and reliable. Now you can enjoy the fast and reliable 512 kbps speed @ Tk 1250. Enjoy Skype, streaming YouTube, download and browse your Facebook profile faster.

Qubee offers 5 GB, 10 GB and Sky solution for all three speeds.

Whether you use email, Skype, connect through social network, browse information, listen to internet radio, and download movies or songs: you can choose the volumes according to your need.

Monthly Usage Allowance*

Speed

5GB

10GB

Sky **

256 Kbps

BDT 850

BDT 950

BDT 1,250

512 Kbps

BDT 1,250

BDT 1,450

BDT 2,250

1Mbps

BDT 2,250

BDT 2,750

BDT 5,250

*Additional charge of BDT 0.15/MB beyond Usage Allowance is applicable in all packages except Sky. BDT figures in above table indicate monthly fee.

Task-03

a).

Frequencies:

A recent innovation in assessing community vitamin A status is the Helen Keller International food-frequency method, which is based on weekly intakes of key foods among pre-school children. Since it excludes breastmilk, we investigated whether the amount of breastmilk received by 40 children aged one to three years in a rural area of Bangladesh contributed significantly to their vitamin A intake. Vitamin A intake was indirectly calculated from the consumption of breastmilk, which was quantified over a 9-hour period by a test-weighing technique. The estimated mean 24-hour milk intake was 548 g for the 97% who were breastfed at 12 to 23 months and 312 g for the 73% who were breastfed at 24 to 36 months. This represents an average daily intake of 41% and 23% of the safe recommended daily intake (400 RE) for vitamin A, respectively. The Helen Keller International food-frequency method should be revalidated for settings where breastfeeding is sustained beyond infancy.

The Helen Keller International food-frequency method approach has certain advantages.

The Helen Keller International food-frequency method has been validated against serum retinol in three countries: the Philippines, Guatemala, and Tanzania [16]. However, the majority of vitamin A deficiency is located in South Asia, where such studies have not yet been conducted. At the same time, the tradition of sustaining breastfeeding beyond the first year is stronger in this region than anywhere else in the world. In Bangladesh, for example, the 1996-1997 Demographic and Health Survey found that the mean duration of any breastfeeding was 28 months, based on current status data for children less than three years of age [17], and the median was 36 months. This is comparable to the mean of 27 months reported in 1975-1976 [181, suggesting that no decline in duration has occurred since then.

Half Duplex:

A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. (The term multiplexing is used when describing communication between more than two parties or devices.)

Duplex systems are employed in many communications networks, either to allow for a communication “two-way street” between two connected parties or to provide a “reverse path” for the monitoring and remote adjustment of equipment in the field.

Systems that do not need the duplex capability include broadcast systems, where one station transmits and the others just “listen”, and in some missile guidance systems, where the launcher needs only to command the missile where to go, and the launcher does not need to receive any information from the missile. Also, there are spacecraft such as satellites and space probes that have lost their capability to receive any commands, but they can continue to transmit radio signals through their antennas. Some early satellites (such as Sputnik 1) were designed as transmit-only spacecraft. Pioneer 6 has transmitted for decades without being able to receive anything.

Full Duplex:

A full-duplex, or sometimes double-duplex system, allows communication in both directions, and, unlike half-duplex, allows this to happen simultaneously. Land-line telephone networks are full-duplex, since they allow both callers to speak and be heard at the same time. A good analogy for a full-duplex system would be a two-lane road with one lane for each direction.

Examples: Telephone, Mobile Phone, etc.

Two-way radios can be, for instance, designed as full-duplex systems, which transmit on one frequency and receive on a different frequency. This is also called frequency-division duplex.

b).

This Site and our business change constantly. As a result, at times it may be necessary for BD to make changes to this Privacy Statement and Consent. BD reserves the right to update or modify this Privacy Statement and Consent at any time and from time to time without prior notice. Please review this Statement periodically, and especially before you provide any Personal Data. This Privacy Statement and Consent was last updated on August 1, 2002. Your continued use of the Site after any changes or revisions to this Privacy Statement and Consent shall indicate your agreement with the terms of such revised Privacy Statement and Consent.

“User Data” includes all information passively collected from users of the Site that does not identify a particular individual, including, by way of example, statistical information on Site usage.The terms “you”, “your” and “yours” when used in this Privacy Statement and Consent means any user of this Site.

Information That You Give Us: We collect Personal Data such as your name, date of birth, e-mail or mailing address from you when you voluntarily choose to register for or use certain BD Services at this Site. We use the Personal Data that we collect in an effort to provide you with a superior customer experience on the Site and to improve and market BD Services. BD may store such Personal Data itself or it may be stored in databases owned and maintained by BD’s affiliates, agents or service providers. BD retains its rights to these databases and the information contained in them.

If you register with BD or use certain other of the personalized options we offer, we will create a profile that includes your name, mailing address, e-mail address, and other information that you provide that is pertinent to your specific situation. We may combine such information with data gathered from other sources. For instance, if incorrect postal codes are received, we may use third party software to correct them. We also may collect e-mail or other addresses from prospect lists of other companies, for example, in connection with a joint marketing effort. When we do so, (1) we acknowledge in our correspondence how the recipient was added to our list and (2) we provide a means for recipients to opt out of further communications from us. In addition we may ask you for Personal Data if you enter an educational program, contest or promotion sponsored by BD.

c).

The Microsoft Volume Licensing program agreements are refreshed annually. This year’s changes, effective October 1, 2010, will help clarify language, bring alignment among Volume Licensing agreements, and implement significant program enhancements that will help simplify licensing and improve the customer and partner experience.

Your existing agreement remains unchanged, as the changes apply to agreements signed after October 1, 2010 (December 1, 2010 for all Select Plus for Academic, Select License for Academic, and Open Program agreements). No action is required until your agreement renewal. See your Microsoft reseller for additional information on the program updates.

d).

UTP Cable Limitation

1.The Disadvantages to a twised pair cable (AKA A Cross Over Cable):

2.It will require direct p2p (peer to peer) connections , e.g. straight from one computer to another (Mostly Via Ethernet or Com)

3.It will be incompatiable if talking to more then 1 computer by going throught a switch or hub.

4.Cross Over Cables should only be used when one computer needs to talk to another one right next to it, or if you are connecting to a router (via the console port) to configure it.

Wireless Limitation:

One of the major problems that presents itself is the already limited spectrum available for communications. The remaining free spectrum has to be used to its maximum potential, spread spectrum technology presenting itself as a suitable means of increasing performance. Splitting up of the environment into a number of small cells also increases the overall accessible bandwidth of the communication system, but also increases the cost as more cell sites are required. Techniques such as diversity combining can also be used to increase the available bandwidth through improved reception capabilities.

e).

Ever notice how you can speak to a dog in a happy, sing-song tone, but tell them something horrible, and they will still be really happy you’re talking with them?  Tone of voice is often more important in communication than we realize. The way we send the message is often just as important as the content of the message itself, even to those of us with opposable thumbs and the ability to understand more than a few words of language.

When training animals, consistency is key. Similarly, in order to “train” one’s customers about one’s brand, a company needs to have a consistent message to all customers in every interaction with every part of the business. Dealing with a company that is always changing its look, sound, and values can be confusing. If part of a business’s marketing materials are very serious, and part of it is surfer talk or chatty girl-talk, it can create accessibility problems for current and potential patrons and partners. How can you trust the company, or trust that it knows who it is and what it is doing, if it doesn’t have a consistent message? The tone of voice should communicate your brand’s values and qualities. A company needs to decide not only the message it wants to get across, but the best way to deliver that message.

Task-04

a).

A good portion of this web site is devoted to mapping locations and the identification of cellular transmission equipment across Canada. This includes the maps for Victoria, Vancouver, Nanaimo, Kelowna, Whistler, Windsor, Halifax, plus new maps planned for the near future (e.g., Edmonton and Calgary) as well as the Cellular Equipment Identification Guide. Although I show each wireless provider’s locations on these maps, I do not mention the steps that each of the wireless providers took to establish their network in each of these locations. This article deals with why a wireless service provider would set up a wireless network in a particular market and the steps required to setup a new network.

b).

If you’ve looked into setting up, or have set up a home office, or a small business, you’re probably aware of how far technology has come in terms of what’s available to the average consumer. What used to take up a whole room can now fit neatly under a desk. You can have a multi-server wireless network with a handful of workstations and all the bells and whistles. But is this right for you? Maybe not, but a wireless network may be the key to making your

Workplace more efficient.

c).

Wireless networks, also known as Wireless LANs (WLANs), allow for wireless communication between computers and the Internet without the need for cables between the networked devices. Simple wireless networks can be set up for the home or small office using one’s existing Internet access. Typically, a person who is familiar with setting up a computer can install a home wireless network in about an hour by following the guides and manuals.  Typical costs:

Wi-Fi technologies conform to several wireless standards that allow the network devices to communicate and interact with one another. There are currently four wireless standards: 802.11a, 802.11b, 802.11g and 802.11n. Every wireless networking device will list what standards it follows on the box.

802.11g and 802.11n are the prevalent wireless technologies, though most routers still support older standards.

Wireless-G (802.11g) broadband routers typically cost less than the newer and faster Wireless-N (802.11g) ones. These 802.11g routers range from $40 to $60. The Linksys WRT54G2 Wireless-G Broadband Router is well-reviewed option in this price range.

Wireless-N broadband routers cost more and offers the fastest speed and longest range. These routers cost anywhere from $70 to $170 depending on what features and capabilities get implemented. The D-Link DIR-655 Extreme N Wireless Router at $90 is good choice. The higher priced Netgear Rangemax WNDR3700 Dual Band Wireless-N Gigabit Router at $160 offers twice the bandwidth using Netgear’s RangeMax technology.

What should be included:

The wireless broadband router and a network cable to connect to your home internet cable or DSL modem.

User manuals and quick start guides to help install and set up the router for the wireless network.

Additional costs:

In order for one’s computer or laptop to communicate to the newly set up wireless network, network adapters such as wireless USB adapters, PCI cards or laptop PC adapters may also be needed. Most newer laptop and notebook computers already have built-in wireless capabilities.

Discounts:

TIP: Sometimes bundles will be offered at a better price and these often include a wireless router and a USB adapter to be used on a computer.

TIP: Many of the networking companies also provide some online or telephone support if there are installation issues, thus saving on any outside professional servicing costs.

Shopping for a wireless network:

The companies Linksys by Cisco, D-Link, Netgear and Belkin are major manufacturers of wireless routers and adapters.

Store retailers such as OfficeMax, Best Buy, Staples, and Office Depot all sell wireless networking equipment.

Online retailers such as Amazon.com, Newegg.com and CompUSA also sell wireless computer components.

TIP: All of the various networking companies also offer their products for sale on their websites. However, the prices there are often not as discounted as what one would find either in a store or from online retailers.

d).

Almost as important as properly sizing hvac equipment, is the estimation of annual heating and cooling costs. Most prospective hvac system buyers don’t really care what size of a unit they need, they only care about costs, both initial and annual operating costs. To remain competitive, today’s hvac contractor must be able to present a credible analysis showing the probable operating cost of a proposed system.

A quick, ballpark estimate of operating costs can now be obtained for standard air conditioners and heat pumps listed in the directory published by the American Refrigeration Institute (ARI). In an attempt to compare all models on an equal basis, the ARI directory shows an average national operating cost for each unit listed. As expected, units with low estimated cooling costs also have high SEER (Seasonal Energy Efficiency Ratios) values. And heat pumps with low heating costs have high HSPF (Heating Seasonal Performance Factors) values .Using the guidelines given above, an have a contractor should be able to find a number of operating cost programs that can greatly aid equipment sales. The biggest difference a contractor can look forward to is the situation where a customer is facing the decision to repair an old, inefficient unit or buy a new, high efficiency model.

.

Task-05

Mobile Technology For the place where no electrical power and fixed telephone line:

Here you will learn about mobile technologies, mobile phones, wireless communication introduction, overview to gsm, gprs, sms and mms reviews. A cellular or mobile phone is a long range portable electronic device for communication over long distance.

Current Mobile Phones can support many latest services such as SMS, GPRS, MMS, email, packet switching, WAP, Bluetooth and many more. Most of the mobile phones connect to the cellular networks and which are further connected with the PSTN (Public switching telephone network). Besides mobile communications, there is a wide range of mobile products available such mobile scanners, mobile printers and mobile labelers.

Mobile Network Technology

Mobile phones and their network vary very significantly from provider to provider and country to country. However the basic communication method of all of them is through the electromagnetic microwaves with a cell base station. The cellular companies have large antennas, which are usually mounted over towers, buildings and poles. The cell phones have low-power transceivers that transmit voice and data to the nearest sites usually within the 5 to 8 miles (8 to 13 kilometers away).

When a mobile device or phone is turned on, it registers with the mobile telephone exchange or switch. It is a unique identifier and is alerted by the mobile switch when there is an incoming phone call.

The handset listens for the strong signals from the nearest base stations. When a user moves, the mobile device handoff to various nearest sites during phone calls or while waiting between calls it reselect the nearest cell phone sites.

Cell sites have relatively less power radio transmitters. They broadcast their presence and relay communications between the mobile handsets and the switch. On the other hand, the switch connects the call to the same or another mobile network or subscriber.

The dialogue between the mobile phone handset and the cell phone site is a stream of the digital data, which includes the digitized audio. This technology depends on the same system as of mobile phone operator. Some mobile phone technologies have adopted the AMPS for the analog communication and D-AMPS, CDMA2000, EVDO, GSM, UMTS, and GPRS for the digital communication. Each mobile phone network has a unique radio .

Task-06

In Task-01 I will try to describe the star topology, advantage and disadvantage of star topology, advantage and disadvantage of medium and why I should like 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 conduit to transmit messages.[1] Thus, the hub and leaf nodes, and the transmission lines between them, form a graph with the topology of a star. 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.

Advantages

Better performance: star topology prevents the passing of data packets through an excessive number of nodes. At most, 3 devices and 2 links are involved in any communication between any two devices. Although this topology places a huge overhead on the central hub, with adequate capacity, the hub can handle very high utilization by one device without affecting others.

Isolation of devices: Each device is inherently isolated by the link that connects it to the hub. This makes the isolation of individual devices straightforward and amounts to disconnecting each device from the others. This isolation also prevents any non-centralized failure from affecting the network.

Benefits from centralization: As the central hub is the bottleneck, increasing its capacity, or connecting additional devices to it, increases the size of the network very easily. Centralization also allows the inspection of traffic through the network. This facilitates analysis of the traffic and detection of suspicious behavior.

Simplicity: This topology is easy to understand, establish, and navigate. Its simplicity obviates the need for complex routing or message passing protocols. Also, as noted earlier, the isolation and centralization it allows simplify fault detection, as each link or device can be probed individually.

Easy to install and wire.

Easy to detect faults and to remove parts.

No disruptions to the network when connecting or removing devices.

Disadvantages

High dependence of the system on the functioning of the central hub

Failure of the central hub renders the network inoperable

The performance and scalability of the network depends on the capabilities of the hub

Network size is limited by the number of connections that can be made to the hub

Other nodes may see a performance drop if traffic to another node occupies a significant portion of the central node’s processing capability or throughput.

Wiring up of the system can be very complex and expensive.

In Task-02 I will try to describe the service for the new system and also Internet connection speed and the requirements of ISP. An Internet service provider (ISP), also sometimes referred to as an Internet access provider (IAP), is a company that offers its customers access to the Internet.[1] The ISP connects to its customers using a data transmission technology appropriate for delivering Internet Protocol packets or frames, such as dial-up, DSL, cable modem, wireless or dedicated high-speed interconnects.

ISPs may provide Internet e-mail accounts to users which allow them to communicate with one another by sending and receiving electronic messages through their ISP’s servers. ISPs may provide services such as remotely storing data files on behalf of their customers, as well as other services unique to each particular ISP.

End-user-to-ISP connection

ISPs employ a range of technologies to enable consumers to connect to their network.

For users and small businesses, the most popular options include dial-up, DSL (typically Asymmetric Digital Subscriber Line, ADSL), broadband wireless, cable modem, fiber to the premises (FTTH), and Integrated Services Digital Network (ISDN) (typically basic rate interface). For customers with more demanding requirements, such as medium-to-large businesses, or other ISPs, DSL (often SHDSL or ADSL), Ethernet, Metro Ethernet, Gigabit Ethernet, Frame Relay, ISDN (BRI or PRI), ATM, satellite Internet access and synchronous optical networking (SONET) are more likely to be used.

In Task-03 I will try to describe how each method works legal requirements of my country to operating the new system, cost estimate for operating and install the system, Limitation of the method and how voice communication established.

Operating systems

Quick links

Operating System ABCs

Operating System types

Operating System overviews

Troubleshooting