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24 Cards in this Set
- Front
- Back
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Network |
1. A network is defined as two or more devices connected through wires or wireless
Examples of networks: -LAN, WAN, Internet
A network can be designed in two ways: a) Client-Server model b) Peer-to-Peer
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Benefits of using a network |
1. File sharing: users can share files easily through a network.
2. Hardware sharing: users can share devices such as printer,thus reducing cost.
3. Communication: users can communicate using emails or instant messaging.
4. Data back-up: Storing data and files centrally on the server makes it easier to perform backup and implement security measures.
5. Software sharing: users can share software applications.
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Drawbacks of using a network |
1. Cost: Setting up a network can be costly
2. Management: Large networks may be difficult to manage
3. Malware: malware such as virus or spyware can spread easily on networks
4. Hacking: connected computers are easier to hack 5. Malfunction: breakdown of devices, such as file servers, can affect the whole network |
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Local Area Networks (LANs) |
- A LAN consist of a group of devices connected through cables, within a small geographical area ; these devices can share data and communicate with each other.
Example of where LANs are used: - In a company's office - In a household Size of a LAN: 10m to 1km |
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Wide Area Networks (WANs) |
-A WAN consists of a group of devices connected through leased communication lines or satellites, within a very large geographical area
-A WAN is generally the connection of several LANs that are far from each other.
Example of WAN : Internet
Size of a WAN: 100km to over 1000km |
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Servers |
A server is a computer that provides data or resources to other computers, known as clients, on the network
Example of servers: - File server: it store all files that other client computers can use and update.
- Web server: it store webpages and provide them to client computers connected to the internet.
- Print server: it control a printer on a network. In the client server model, servers are very important computers as they perform a lot of processing and store a large amount of data ; hence they are usually powerful computers. |
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Client-Server Model |
A client is a computer that request and consumes the service (data) of a server.
There are two types of clients: -Thin-client -Thick-client Example: a browser (client) consumes the service of the webserver.
Clients and servers communicate using request-reply protocol.
How it works? 1. The client computer sends a request to the server. 2. The server processes the request and send back a reply to the client. |
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Features of Client-Server |
1. It uses separate dedicated servers and specific workstations. 2. Sharing of data is the most important aspect of this type of network. 3. Once logged in, a user can only access resources that the network manager allows them to use. 4. It is a more stable system since there is centralised backing up of files. |
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Benefits of using client-server |
Why Client-Server should be used? 1. All files and resources are stored centrally, hence easy to perform backup and manage security.
2. Access to the resources stored on the server can be controlled/monitored.
3. Client computers can be less powerful machines, hence less expensive.
4. The model can be used with very large number of computers. |
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Drawbacks of using Client-Server |
1. If the server is overloaded or breaks down, the whole system is affected. 2. The is usually powerful, hence expensive. |
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Peer-to-Peer |
A peer performs both the role of a "client" and a "server",that is, it can request and provide services to other peers.
A group of connected peers is called a swarm.
A tracker is a "server" that keeps the details of all peers in a swarm.
A seed is a peer that has part of or a whole file and offers it for upload.
The P2P model uses the Bit-Torrent Protocol.
How it work? 1. Each peer can request and provide resources. 2. Peers are connected between each other without the need for a central server. 3. Each peer on the network can share its files with the other peers and will have its own data. |
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Features of Peer-to-Peer |
1. Connectivity is the most important aspect of this type of network. 2. It has no central storage and doesn't require authentication of users. 3. Has no central server, each workstation shares its files/data with the other workstations. 4. Performance and management issues can occur if the number of workstations exceeds ten. |
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Benefits of Peer-to-Peer |
1. The system is not affected by any computer being overloaded or breaking down. 2. It allows users to download different parts of files separately. 3. Files are smaller, hence transmitted faster. 4. It prevent network congestion when multiple clients are trying to download files simultaneously. |
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Drawbacks of Peer-to-Peer |
1. There is no control of which computer can download a file. 2. There is no control on security. 3. Only suitable for small amout of computers (around 10). |
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Thin-client |
A Thin-client is a device or software that performs very little processing and is heavily dependent on the server. It cannot function if disconnected to the server Example: -Web browser (software thin client) -Moblie phone apps -Point of sale terminals (hardware thin client ) |
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Benefits and Drawbacks of thin-client |
Adv: 1. Less expensive to expand as low-powered and cheap devices can be used.
2. Data updates and software installation are done centrally.
3. More secure as server can offer protection against hacking and malware.
Disadv: 1. Dependent on server, cannot function if disconnected to server.
2. Start-up cost are more expensive |
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Thick-client |
A Thick-client is a device or software that can function even when disconnected to the server. It is still able to do some processing whether it is connected to a server or not. Examples: -laptop (hardware thick client) -computer game (software thick client) |
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Benefits and Drawbacks of Thick-client |
Adv: 1. More robust as it can out processing even when not connected to server
2. Clients have more control Disadv: 1. Less secure as it relies on clients to keep their own data secure. 2. Each client need to update data individually 3. Data integrity issues, since many clients access the same data which can lead to inconsistencies.
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Differences between thin client and thick client |
Thin: cannot function if disconnected to server. Thick: can still function if disconnected to server.
Thin: relies very few local resources Thick: relies heavily on local resources
Thin: more secure Thick: less secure
Thin: cheaper Thick: expensive
Thin: requires a fast and reliable network connection. Thick: more tolerant on slow network connection. |
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Network topologies |
A network topology is the way a network and its connected devices are connected. Example of network topologies : 1. Bus 2. Star 3. Mesh 4. Hybrid |
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Bus Topology |
Description: 1. All connected devices are connected through a central cable. 2. There are terminators at both ends of the channel, hence preventing packets from bouncing back in the channel. 3. The cable transmits data in half-duplex. 4. Typically peer-to-peer
Adv: -It is cheaper to set up as fewer cables are needed. -It is easy to expand the network by adding more devices. -Even if one node fails, the system continues to function.
Disadv: -No confidentiality: packets sent to one computer can be "listened" by all the other computers.
-Data transmission speed is slow: only one computer can send packets at a time.
-Transmission is not reliable: if collisions of packets occurs, data will be lost.
-If the main cable is broken, the whole network stop functioning.
Uses: -There are suitable for situations with a small number of devices with light network traffic occurring.
-Used in LANs, in a small company or office.
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Star Topology |
Description: 1. All devices are connected to a central switch. 2. There is dedicated communication link between each computer and the switch. 3. The switch reads the Mac address of packets received and forwards them to the intended receiver only. 4. Transmission is full-duplex 5. Typically client-server
Adv: -Confidentiality maintenaned: the switch forwards a packet to the intended receiver only along a dedicated cable between the switch and the computer.
-Data transmission is fast: each computer is connected to the switch using a dedicated cable and transmission is full-duplex. -Transmission is reliable: No collisions of packets occurs. -Easy to expand network: Computers can be added by just connecting them to the switch. -When a cable is broken, only one device is disconnected from the network.
Disadv: -More expensive to set up as more cables are required. -The network is heavily dependent on the switch, if the switch is broken, the whole network fails.
Uses: -It is suitable where many computers are required, network need to expand often and high transmission speed is important. -It suits for heavy data traffic. -Creation of office LANs. |
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Mesh Topology |
Description: 1. A device is connected directly to all other devices using a dedicated cable. 2. Transmission is in full-duplex.
Adv: -Confidentiality maintenaned: a packet goes from one computer to another directly.
-Transmission is very fast: packets move directly to other computers without any delay.
-If one cable is broken, the devices may still communicate through other devices.
-Easy to expand network.
Disadv: -Most expensive to set up as cabling is very complex. -Setup and maintainance is difficult and complex.
Uses: -In the internet and WANs -In medical monitoring of patients in a hospital.
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Hybrid Topology |
Description: 1. It is a mixture of two or more different topologies. 2. They are very complex to install, configure and maintain. The main advantages and disadvantages depend on which types of network are used to make up the hybrid network. Additional advantages: -They can handle large volume of traffic. Additional advantages:-They can handle large volume of traffic. -It is easy to identify where a network fault has occurred. -They are very well suited to the creation of larger networks. -It is easy to identify where a network fault has occurred. -They are very well suited to the creation of larger networks. |
