Karteikarten
Networks
Karten in diesem Stapel (21)
- 1Unit 4-Computer NetworksTheory Notes
- 2What is a Network?A network is two or more computers, or other electronic devices, connected together so that they can exchange data.
For example a network allows computers to share files, users to message each other, a whole room of computers to share a single printer, etc.
Network connections between computers are typically created using cables (wires). However, connections can be created using radio signals (wireless / Wi-Fi), telephone lines (and modems) or even, for very long distances, via satellite links. - 3Why Use Networks?Using a computer connected to a network allows us to…
•Easily share files and data
•Share resources such as printers and Internet connections
•Communicate with other network users (e-mail, instant messaging, video-conferencing, etc.)
•Store data centrally (using a file server) for ease of access and back-up
•Keep all of our settings centrally so we can use any workstation
In particular, if we use a computer connected to The Internet, we can…
•Make use of on-line services such as shopping (e-commerce) or banking
•Get access to a huge range of information for research
•Access different forms of entertainment (games, video, etc.)
•Join on-line communities (e.g. MySpace, Facebook, etc.) - 4Why Not Use Networks?Using a computer connected to a network means that…
•The computer is vulnerable to hackers
•If the network breaks, many tasks become very difficult
•Your computer can more easily be attacked by a virus
In particular, if we use a computer connected to The Internet…
•We have to be careful about revealing personal information
•We have to be careful to avoid suspect websites that might contain malware
•We have to be aware that information found on The Internet is not always accurate or reliable - 5Computers in a Network-ClientsClient computers, or workstations, are the normal computers that people sit at to get their work done.
- 6Computers in a Network-ServersServers are special, powerful computers that provide ‘services’ to the client computers on the network.
These services might include:
•Providing a central, common file storage area
•Sharing hardware such as printers
•Controlling who can or can’t have access the network
•Sharing Internet connections
Servers are built to be very reliable. This means that they are much more expensive that normal computers.
In a small network one server might provide all of these services. In a larger network there might be many servers sharing the work. - 7Types of Network-LANA Local Area Network is a network confined to one building or site.
Often a LAN is a private network belonging to an organisation or business.
Because LANs are geographically small, they usually use cables or low-power radio (wireless) for the connections - 8Types of Network-WLANA wireless LAN (WLAN) is a LAN that uses radio signals (Wi-Fi) to connect computers instead of cables.
At the centre of the WLAN is a wireless switch or router - a small box with one or two antennas sticking out the back - used for sending and receiving data to the computers. (Most laptops have a wireless antenna built into the case.)
It is much more convenient to use wireless connections instead of running long wires all over a building.
However, WLANs are more difficult to make secure since other people can also try to connect to the wireless network. So, it is very important to have a good, hard-to-guess password for the WLAN connections - 9Types of Network-WANA Wide Area Network is a network that extends over a large area.
A WAN is often created by joining several LANs together, such as when a business that has offices in different countries links the office LANs together.
Because WANs are often geographically spread over large areas and links between computers are over long distances, they often use quite exotic connections technologies: optical fibre (glass) cables, satellite radio links, microwave radio links, etc. - 10Network Interface Card (NIC)Any computer that is to be connected to a network, needs to have a network interface card (NIC).
Most modern computers have these devices built into the motherboard, but in some computers you have to add an extra expansion card (small circuit board - 11HubA hub is a device that connects a number of computers together to make a LAN.
- 12SwitchA switch, like a hub, is a device that connects a number of computers together to make a LAN.
A switch is a more ‘intelligent’ device than a hub: if it receives a message, it checks who it is addressed to, and only sends it to that specific computer. Because of this, networks that use switches are more secure than those that use hubs, but also a little more expensive - 13RouterA router is a network device that connects together two or more networks.
A common use of a router is to join a home or business network (LAN) to the Internet (WAN). - 14Proxy ServerA proxy server is a computer setup to share a resource, usually an Internet connection.
Proxy servers are often used instead of router since additional software can be easily installed on the computer such as anti-virus, web filtering etc - 15BridgeA bridge is a network device that typically links together two different parts of a LAN.
- 16FirewallA firewall is a device, or a piece of software that is placed between your computer and the rest of the network
- 17IntranetsAn intranet is the name given to a private network that provides similar services to The Internet: e-mail, messaging, web pages, etc.
However, these services are only for the users of the intranet – they are private, not public (unlike Internet services which are generally public).
Businesses and other organisations often have intranets for use by their employees.
Typical uses of an intranet would be:
•Viewing internal web pages (e.g. company calendars, etc.)
•Internal e-mail and instant-messaging between workers
•Sharing of internal documents - 18Setting Up a Small Network?If you were asked to build a small, Internet-connected network from scratch, what would you need to do?
•One or more switches / hubs - to link devices together
•Network cables to connect devices to the switch, etc.
•A separate wireless access point (or this could be part of the switch) - to allow wireless devices (e.g. laptops or smart-phones) to join the network
•A router to connect your LAN to the Internet (WAN)
•A firewall to protect your network from hackers
•Possibly a bridge if you already have a section of network and you want your new network to connect to it
•Server(s) to manage network functions such as network security, network file storage, shared resources (such as printers - 19Setting Up a Small Network?-Cont.•Set up an account with an Internet Service Provider (ISP)
•Get an Internet connection installed from the ISP to your location
•Configure various bits of hardware and software so that everything worked with the network - 20Network & Data Security-Preventing Unauthorised AccessPhysical Security
-Use a Username and Have a Good Password
-Always Install and Use a Firewall - 21Securing Your Data-Data EncryptionEncryption is the process of converting information into a form that is meaningless to anyone except holders of a ‘key’.
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- Karteikarten am Networks, erstellt von poynton am 06/05/2016.
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