Chapter 6 Flashcards
LAN
A collection of computers and peripheral devices connected together within a single site.
WAN
A collection of computers and LANs connected together over a geographically remote area, using leased infrastructure.
Topology
A description of how devices are connected together. Does not necessarily represent physical layout.
Bus
A topology where each device is connected to a main cable, referred to as the bus. Any device can transmit at any time but only one transmission can occur on the main bus at any one time.
Ring
A topology where each device is connected to the next in a loop. Uses a tokenpassingprotocol to allow transmission by one device at a time.
Star
A topology where each device has its own cable connecting it to a central device, which can be a switch or a server.
Peer-to-Peer
A method of organising devices in a network where devices are all of equal status rather than having specialised roles. Each computer can access resources on another computer, assuming access rights have been granted by the other computer.
Client-Server
A method of organising devices in a network where some computers havespecialised roles: servers. The servers provide resources and services to the other computers, known as clients. Management of the network and shared resources/files is centralised at the server.
Hub
A hardware device that provides connectivity to a LAN cable. A multiport box that has a connection to the LAN from one side and several computers on the other. Can be wireless or cabled.
Switch
A hardware device that is similar to a hub but it has built-in intelligence to direct traffic to the right place. Computers connected to a switch form a star topology LAN.
Wireless Access Point
The device to which a computer connects wirelessly. Can be a wireless hub or awireless switch.
NIC
Network Interface Card: the card that plugs into a computer to provide a connection to a LAN. Can be wireless or cabled. Holds the MAC address.
MAC Address
A unique hardware number allocated to every NIC. It is a 48-bit address, usually written in hex, e.g. 00-09-7C-F1-F7-85
Message
A communication between devices. Split into packets for sending over a networkand put back together again at the other end.
Packet
A fixed size chunk of a message created to send a message over a network. Ithas its own header containing data such as the destination address and packet number (so the message can be put back together in the right order).
Protocol
A set of rules that defi nes how devices communicate. E.g. IP, HTTP, HTTPS
Internet
A public worldwide network where computers and networks in geographicallyseparate locations are connected together using a variety of communication links.Devices communicate using Internet Protocol (IP).
Routers
The hardware devices that make up the backbone of the Internet as well as (smaller ones) providing connectivity from a LAN to the Internet. Use Internet Protocol to communicate with each other.
Modem
The hardware device used to convert the digital transmission from a computerinto an analogue signal that can be carried over the analogue telephone network.A method of accessing the Internet.
Digital
A transmission signal that is made up of separate values (numbers), as opposed tothe continuously changing signal in analogue transmissions.
Analogue
A transmission signal that is continuously changing, as opposed to being made upof separate values (numbers). Sound in the real world is analogue.
Broadband
A digital method of connecting to the Internet that allows more than one transmission at the same time, e.g: phone and computers. It may use the site’snormal phone line or a fibre optic cable to carry transmissions.
WWW
World-Wide Web: a collection of pages distributed on servers connected to theInternet. Uses HTTP to request and send pages to browsers.
HTTP
HyperText Transfer Protocol: the protocol used by a browser to send page requeststo a server and also by the server to send back the required page.
HTTPS
A secure version of HTTP where transmissions are encrypted.
IP Addressing
A method of labeling any device connected to the network with a uniquenumerical value. Uses four bytes usually expressed in this notation: 123.123.003.243
Domain Name
The text label for a website in the Internet: www.bbc.co.uk It corresponds to an IP address for that site.
DNS Servers
Domain Name System server: a database of domain names and associated IP addresses stored on servers. There are many DNS servers distributed across the Internet, which communicate with each other.
HTML
HyperText Markup Language: the programming language used to define the layout and content of a webpage. Uses tags in conjunction with a CSS to control how content is displayed.
CSS
Cascading Style Sheet: defines the formatting and layout of the content defi ned by the HTML code. E.g. may be 32pt Arial in Green.
Tags
Labels that go around the content (text, pictures etc) to define the page layout.Eg: A heading
User Access Levels
A network policy that defines which users can see which folders and files and the type of access they have to them. Eg: Read-Only or Read-Write.
Encryption
Where the data is changed, using a key, before it is transmitted so that it canonly be deciphered by another device with the appropriate key. To anyoneintercepting the message it would be unintelligible.
Acceptable Use Policy
An agreement that computer users will sign/agree to before being allowed access to a computer or the network.
Failover
When a hardware component fails, the computer switches over to a redundantcomponent without the service to the user being interrupted.
Redundant
Spare, ready to be used if another component fails. Relates to spare hardwarecomponents in fault-tolerant systems that use failover.
Fault-Tolerant
A system that has been designed to cope with hardware failures. Usesredundant hardware and failover usually.
Backup
A copy of data is taken from a live computer system as a precaution against system failure or corruption/deletion of individual files/folders. To be restored in the event of data loss.
Archiving
Files are removed from the main computer system but kept in long-term storage, just in case they are needed in the future or because the law requires they be kept. Creates space on main system.
Disaster Recovery
A collection of precautions that ensures the computer system can be reestablished very quickly after a catastrophe. Includes backup policy, complete hardware system available offsite at short notice and policies to restore data and applications on the replacement hardware.
Compression
Making files smaller for quicker transmission over a network.
Lossless compression
File is compressed with no loss of essential data.
Lossy compression
Files are compressed by removing some data that is less essential for the purpose. For example, using fewer colours in a picture (reduce colour depth).
What is an IP address?
A unique identifier which consists of 4 8-bit numbers
What is a MAC address?
Every computer today has some sort of Network Interface Card (NIC). Every NIC is created with a hardware number permanently “burned” into it. This permanent hardware number of known as the MAC (Media Access Control). MAC addresses are 48 bits in length and usually displayed as a 12 digit hexadecimal number.
What is a packet?
A packet is one unit of binary data capable of being routed through a computer network.
