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qwerty uiop

on 10 February 2013

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Transcript of Networks

Networks By: Rita Lucas Why use Networks? Why not use Networks? because this means: For example, by using a computer connected to the internet, we have to be: For example, by using a computer connected to the internet we can: What is a Network? Network connections between computers are mainly created using cables, but they can also be created using radio signals (wireless/wi-fi), telephone lines, or via satellite links, for very long distances. To share files and data easily
To share resources like, internet, printer...
To communicate with other users
To store data centrally
To keep our settings centrally to use any workstation Use on-line services like, shopping, banking...
Get access to information for research
Access forms of entertainment like games, videos...
Join on-line communities like My Space, Facebook... The computer is vulnerable to hackers
The network might break, therefore many tasks become difficult
Your computer can get viruses more easily Careful about revealing personal information
Careful to avoid websites that might contain malware
Aware that the information on the internet isn't always reliable or correct A network is two or more electronic devices connected together so that they can exchange data. It allows computers to share files, users to message each other, a whole room of computers to share a single printer, and so on. Computers in a Network Clients These computers, also called workstations, are normal computers that people sit at Servers These are special, powerful computers that provide 'services' to client computers on the network. These 'Services' include: Providing a central, common file storage area
Sharing hardware like printers
Controlling who can or can't access the network
Sharing internet connections Servers are built to be reliable, which means they are much more expensive than normal computers.
In a small network a server might provide all these services, but in a large network many servers share the work. Types of Networks Local Area Network (LAN) This is a network limited to one building or site. It is usually a private network that belongs to an organisation or business. It is relatively small, so uses cables or wireless for connections. Wireless Local Area Network (WLAN) This is a LAN that uses WiFi to connect computers instead of cables. At the centre is a wireless switch or router, which is used to send and recieve data to computers. This is difficult to make safe, as anyone can try to connect to it. Networking Hardware Network Interface Card (NIC) Network Cable Wide Area Network (WAN) This is a network that extends over a large area. It is often created by joining lots of LAN's together. For example if a business has offices in different countries, they link the office LAN's together. They use optical fibre cables, satellite radio links, microwave radio links and so on, for connections. Bluetooth (Personal Area Network) This is a wireless networking technology, made for very short-range connections. The idea of this technology is to connect between computers without using lots and lots of cables. These contain low-power radio transmitters and recievers. Uses of bluetooth:
Connecting a wireless keyboard to a computer
Connecting a wireless mouse to a computer
Using a wireless headset with a mobile phone
Printing wirelessly from a computer or a PDA
Transfering data/music from a computer to an MP3 player
Transfering photos from a phone/camera to another device
Synchronising calendars on a PDA and a computer All computers that are to connect to a network need this NIC. The more modern computers have them built into the motherboard. The others have to add an extra expansion card. The Internet Intranets Setting up a small network Network and Data Security You need these cables to connect together different devices to make up a network. Nowadays a lot of networks ude wireless, but these are still used as they carry much more data per second, and are safer (less hacking). Hub This is a device that connects lots of computers together to make a LAN. The hub has cables from each computer plugged into it. If the hub recieves a message, it sends it to all computers on the network, it isn't very safe. Switch This is also a device that connects lots of computers together to make a LAN. It also has cables plugged into it from each computer. The main difference between this and a hub is that when a switch recieves a message, it checks who it is adressed to, and only sends it to that specific computer. It is safer, although more expensive. Router Proxy Server Bridge Firewall This is a device, or piece of software, that is placed between your computer and the rest of the network. If you want to protect your LAN from hackers you need to place this device between the LAN and the internet connection. This then blocks unauthorised data and connections being made, and only allows normal data through. This is a network device that connects two or more networks together. A common use of this is to join a home or business network (LAN) to the internet (WAN). The router can have the internet cable plugged into it, or the LAN connection might be wireless, making the device a wireless router. This is a computer setup to share a resource, normally the internet. Other computers can request a web page through this, and then this will get the page using its internet connection, and pass it back to the computer that asked for it. Lots of times these are used instead of routers. This is a network device that links together two different parts of a LAN. This device links independent parts of a LAN so that they acts as a single LAN. The internet is a world-wide network, which has grown and evolved alot into the internet we know today. This connects millions of people, and thousands of businesses, governments, schools, universities and other organisations. What is it used for? It provides the network connections that link computers together. These connections can be used in many ways. For example: To view webpages
To send and recieve emails
To share files
To communicate using voice and video
To play multi-player games
To listen to music or watch videos An intranet is a private network that provides similar services to the internet, like e-mail, messaging, web pages and so on, but these services are only for the users of the intranet, they are private. They are normally used by businesses. Uses of an intranet would be: Viewing internal webpages
Internal e-mail and instant messaging between workers
Sharing of internal documents To build a small network you need some hardware: Switches/hubs- to link devices together
Network cables- to connect devices to the switch... Seperate wireless access point- to allow wireless devices tojoin the network
Router- to connect LAN to the internet
Firewall- to protect network from hackers
Bridge- if you already have a section of network and want your new network to connect to it
Servers- to manage network functions like: security, file storage, shared resources Set up an account with an Internet Service Provider
Get an Internet connection from the ISP to your location
Configure hardware and software so everything works with the network You would also have to: When you connect your computer to a network you have to think of security, because as soon as you're connected to a network everyone can gain access to it. These people are usually called hackers. Preventing unauthorised Access You can take several security measures to prevent hackers from accessing your computer. Physical Security: Make sure no unauthorised people can physically access any computer on your network, and you can do this by locking office doors. Using Usernames and Passwords: By using these anyone that doesn't know the correct answer will be denied. Passwords should be hard to guess, random combinations Installing and using a Firewall: A firewall is a device or a piece of software that is placed between your computer and the rest of the network. Securing your Data Usually everybody has confidential, private data that has to be protected. If you want to send that data through the internet with protection, the best way is to encrypt it. Data Encryption: Encryption is the process of converting information into a form that is meaningless to enyone except holders of a key. If, for example Alice wants to send personal messages to Bob, she has to follow these steps: 1. Alice has to generate a secret key, which is usually very long and random numbers 2. Alice has to then give a copy of this key to Bob, making sure no one else can get to it. 3. Now Bob has a copy of the key. Alice sends him a message by encrypting it using special encryption software and the secret key. The message now looks like a jumble of numbers and letters. 4. Alice sends the message to Bob. She can use a public network because if anyone steels it, they can't read anything without the key. 5. Bob recieves the message, and uses special decryption software and the secret key to decrypt the message. After doing this he can read the original message from Alice
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