Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
18 Cards in this Set
- Front
- Back
|
Hybrid Topology
|
Hybrid networks use a combination of any two or more topologies in such a way that the
resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network connected to a tree network is still a tree network, but two star networks connected together exhibit a hybrid network topology. A hybrid topology is always produced when two different basic network topologies are connected. Two common examples for Hybrid network are: star ring network and star bus network. A Star ring network consists of two or more star topologies connected using a multistation access unit (MAU) as a centralized hub. A Star Bus network consists of two or more star topologies connected using a bus trunk (the bus trunk serves as the network's backbone). |
|
|
Mesh Topology
|
Mesh networking is a way to route data, voice and instructions between nodes. It allows for
continuous connections and reconfiguration around broken or blocked paths by “hopping” from node to node until the destination is reached. A mesh network whose nodes are all connected to each other is a fully connected network. Mesh networks differ from other networks in that the component parts can all connect to each other via multiple hops, and they generally are not mobile. Mesh networks are self-healing: the network can still operate even when a node breaks down or a connection goes bad. As a result, this network is very reliable. This concept is applicable to wireless networks, wired networks, and software interaction. A mesh network in which every device connects to every other is called a full mesh. Partial mesh networks also exist in which some devices connect only indirectly to others. |
|
|
Hubs
|
In the old days the LAN comprised mostly of devices called hubs or a concentrator in other
words. A hub or a concentrator was a way of concentrating network connections in a single point. Hub’s ran at 10Mbps and essentially if you put 10 machines into a wire that was running a 10Mbps you would see that every machine could probably only transmit at 1Mbps even if they were transmitting at their maximum. Hubs were shared, they were slow, they were not optimal, primarily because you had a certain number of devices that you plugged in and the performance of Ethernet would degrade to such an extent that it was preferable not to even work on the network. |
|
|
Network 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 circuitboard) |
|
|
Switch
|
A switch, like a hub, is a device that connects a number of computers together to make a LAN.
The typical use of a switch is at the centre of a star network (or as part of a hybrid network) - the switch has cables plugged into it from each computer. 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. |
|
|
Router
|
A 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). The router will typically have the Internet cable plugged into it, as well as a cable, or cables to computers on the LAN. |
|
|
Proxy Server
|
A proxy server is a computer setup to share a resource, usually an Internet connection.
Other computers can request a web page via the proxy server. The proxy server will then get the page using its Internet connection, and pass it back to the computer who asked for it. 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. |
|
|
Bridge
|
A bridge is a network device that typically links together two different parts of a LAN. Whereas a router is usually used to link a LAN to a WAN (such as the Internet), a bridge links independent parts of a LAN so that they act as a single LAN.
|
|
|
Firewall
|
A firewall is a device, or a piece of software that is placed between your computer and the rest of the network (where the hackers are!)
If you wish to protect your whole LAN from hackers out on the Internet, you would place a firewall between the LAN and the Internet connection. A firewall blocks unauthorised connections being made to your computer or LAN. Normal data is allowed through the firewall (e.g. e-mails or web pages) but all other data is blocked. |
|
|
Modem
|
Before the days of broadband Internet connections, most computers connected to the Internet via telephone lines (dial-up connections).
The problem with using telephone lines is that they are designed to carry voices, which are analogue signals. They are not designed for digital data. The solution was to use a special device to join the digital computer to the analogue telephone line. This device is known as a modem. A modem contains a DAC and an ADC. The DAC in the modem is required so that the digital computer can send data down the analogue telephone line (it converts digital data into noises which is exactly what the telephone line is designed to carry.) The ADC in the modem is required so that the analogue signals (noises) that arrive via the telephone line can be converted back into digital data. |
|
|
Physical Security
|
The first thing to make sure of is that no unauthorised people can physically access (sit down in front of) any of the computers on your network.
For example, by keeping office doors locked. |
|
|
Use a Username and Have a Good Password
|
The most common way to protect your computer’s data is to setup user accounts with usernames and passwords. Anyone not having a username, or not knowing the correct password will be denied access.
For this to be effective passwords must be chosen that are not easy to guess. Passwords should be a random combination of lowercase letters, uppercase letters and numbers (and symbols if this is allowed): •‘Weak’ passwords: password, 123456, david, 27dec1992 •‘Strong’ passwords: s63gRdd1, G66ew$dQ, gdr298783X Some computer systems replace the typing of usernames and passwords with other forms of user identification such as ID cards, fingerprint readers, voice-print recognition, etc. |
|
|
Always Install and Use a Firewall
|
A firewall is a device, or a piece of software that is placed between your computer / LAN and the rest of the network / WAN (where the hackers are!)
You can read about firewalls in the Networking Hardware section. |
|
|
Securing Your Data
|
Often we have data that is private or confidential. This data needs to be protected from being viewed by unauthorised people. This is especially true if the data is to be sent via a public network such as The Internet.
The best way to protect data is to encrypt it... |
|
|
Data Encryption
|
Encryption is the process of converting information into a form that is meaningless to anyone except holders of a ‘key’.
For example, if Alice wants to send important, personal messages to Bob, she must go through the following steps... Alice must then give a copy of this key to Bob. She must make sure that nobody else can get to the key (So maybe Alice will visit Bob and give him a copy of the key on a memory stick or floppy disc). Now that Bob has a copy of the key, each time Alice needs to send him a message she starts by encrypting it using special encryption software and the secret key. The encrypted message now looks like a jumble of random letters and numbers. Alice then sends the encrypted message to Bob. She can use a public network like the Internet, since, even if it gets stolen, the encrypted message cannot be read or understood without the key. When Bob receives the message, he uses special decryption software and his copy of the secret key to decrypt the message. Bob can no |
|
|
Setting Up a Small Network
|
If you were asked to build a small, Internet-connected network from scratch, what would you need to do?
You would need to buy some hardware: •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) You would need to organise some other things: •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 |
|
|
Intranets
|
An 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 |
|
|
The Internet
|
The Internet is a world-wide network that has grown and evolved from an experimental network (ARPANet) created by the US military back in the 1960s. Over the years, as more and more computers and networks have connected to this network, it has grown into the Internet that we know today. The Internet connects millions of people, and thousands of businesses, governments, schools, universities and other organisations. What Can We Use the Internet For?The Internet provides the network connections that links computers together. There are many ways that we can use these connections:
•View web pages on the WWW (World-Wide Web) •Sending and receiving e-mail messages •Sharing files •Communicating using voice (VOIP) and video (video-conferencing) •Playing multi-player games •Listening to streamed music or watching streamed video |
