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DIGITAL TECHNOLOGY A21 > BOOKLET 1 > Flashcards

BOOKLET 1 Flashcards

1
Q

LAN#

A

-Local area networks
-A network of computers that is spread over a small geographical area
-E.g. school

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2
Q

Advantages of LAN#

A

-Devices dont have to be physically connetcted
-Additional devices can be added using a wireless card

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3
Q

Disadvantages of LAN#

A

-Security can be a risk unless the system is password protected

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4
Q

MAN#

A

-Metropolitan area networks
-A small WAN that is optimised to connect computers within a large city or campus
-E.g. university

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5
Q

WAN#

A

-Wide area network
-A network of computers that are spread by large geographical distances
-E.g. the world wide web

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6
Q

Server-based networks

A

A network organised around one or more servers. The server maintains a database of authorised users, passwords and access rights

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7
Q

Features of a server-based network

A

-There is a controlling node
-The client is a ‘dumb’ terminal
-Clients request resources
-The server then allocates the resource

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8
Q

Advantages of a server-based network

A

-Better security (all data stored on servers which hold access rights)
-Easier to update (data storage is centralised)

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9
Q

Disadvantages of a server-based network

A

-Overloading (if the number of simultaneous client requests increases)
-Lacks robustness (if a critical server fails, client’s requests cannot be fulfilled)

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10
Q

Peer-to-peer networks

A

A network that provides shared resources such as printers and storage, but may offer little else in the wayof additional features such as file security. There is no controlling node

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11
Q

Advantages of peer-to-peer networks

A

-Low installation costs as there is no need to resource a dedicated server
-Robust
-Performance is greater as each node increases the bandwidth

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12
Q

Disadvantages of peer-to-peer networks

A

Low level of security as cannot be controlled centrally

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13
Q

NIC#

A

-Network interface card
-Provides the physical connection between the network and the computer workstation

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14
Q

Switched hub#

A

-‘Intelligent hub’ that sends data packets straight to the destination without being copied to all the computers
-Stores all the addresses directly or indirectly connected to it which increases network performance and offers greater security

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15
Q

Server functions#

A

-Stores all programs and data
-Logs all file accesses
-Controls access to software and user data
-Provides a backup facility

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16
Q

Repeater#

A

-As electrical signals travel down a cable, their initially clean signal gets ‘smeared’ and indistinct with distance, the role of the repeater is to clean up the signal by regenerating it so it can pass long a further segment

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17
Q

WAP#

A

-Wireless access point
-Networking hardwarre device that allows a wifi compliant device to connect to a wired network
-AKA hotspot

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18
Q

Media converter#

A

-Flexible and cost-effective devices for implementing and optimising fibre links in all types of networks.

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19
Q

IP address#

A

-Internet protocol address
-Uniquely identifies any device connected to the internet
-Data is transmitted as packets, containing data in the ‘body’ and the IP address of the sender and receiver in the ‘header’
-Large ietms of data are split into several packets that are reassembled by the receiving device

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20
Q

MAC address#

A

-Media access control address
-Unique identifier assigned to network interfaces for communications at the data link layer of a network segment

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21
Q

Router#

A

-Used to determine an efficient route for data transfer between computer systems and to transmit web pages to users throughout the world

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22
Q

IP definition#

A

A protocol is a standard set of rules used to ensure the proper transfer of infromation between computers on the internet. It defines how data is to be structures and what control signals are to be used

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23
Q

TCP/IP#

A

The set of working practices that allow all internet users and providers to communicate with eachother whatever their equiptment is. Specifies how individula signals are sent over the internet

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24
Q

TCP/IP functions#

A

-Used tpo transmit actual data packets on the internet
-Responsible for transmitting data between LANs ansd WANs regardless of the type of hardware and software being used

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25
TCP layer#
Responsible for the correct delivery of packets and reassessment of packets at the destination, if they are incorrect, an error message is displayed
26
IP layer#
Responsible for transferring packets of data from node to node, detects errors or lost data
27
Bus network definition#
Each network node is connected directly to a common/shared communication line
28
How does a bus network send data#
-The data is sent by one computer to the address of another computer -Travels along the backbone until it reaches it's destination
29
Advantages of a bus network#
-Inexpensive as each node only requires a network card and cabling -Easy to build and maintain -Works well as long as traffic is light
30
Disadvantages of a bus network#
-A break in the main cable causes network failure -Data packets can collide due to two nodes sending data packets at the same time -Performance rapidly falls if traffic is high
31
How do you add a new node to a bus network?#
The new computer is connected by it's own cable to the backbone, causing the backbone to have to be broken
32
Ring network#
-There is no controlling node -Each node can communicate with any other node in the network
33
Sending data on a ring network#
-A token is passed around the network ready to carry data -When it reaches a node with data to send, it picks up the data and travels around the ring to the destination -A signal is then attached to the token and it returns to the node that sent the data -The token is then free to move around the network again -Nodes can add a message to a token or remove one if it is addressed to
34
Ring networks are most suitable where...#
-Large number of nodes with heavy traffic, can transfer data quickly -Where a cable fault must not disrupt the entire network -Devices are frequently added or removed
35
Advantages of a ring network#
-Very fast and reliable as there is no collisons because the data moves in one direction -No node can dominate the network, so all can use the network without clogging
36
How do you add an additional node to a ring network#
An existing connection between two nodes must be split, and a new computer added between the two connections
37
Star network#
-Each node is connected to the central node by a dedicated line -The central node is in control of the whole network
38
Sending data on a star network#
-Central computer where all nodes are directly connected -All data is sent to this central computer -The central node redirects the data to the destination
39
A star network is most suitable where...#
-Large number of computers with heavy traffic -Where a cable fault must not disable the entire network -Devices are frequently added and removed
40
Advantages of a star network#
-If one node fails, none of the other nodes fail -Easy to expand the network -Collisions are greatly reduced since each computer is directly connected to the central node -Security is high as the central node is in complete control
41
Disadvantages of a star network#
-Failure of the central node causes failure of the whole system -Network uses a large amount of cabling as each node is direcly connected to the central node -Central node can be expensive and requires software
42
How is another computer added to a star network#
If there is a free access point, the computer can simply connect the cable with no disruption to the system
43
Protocols definition#
Protocols enable hardware devices from different manufacturers to pass data to one another in a coherent way using a strict set of rules and preocedures regarding data formats
44
Communications software controls transmission by specifying:
-Speed of transmission -Direction of data flow -Type of parity used -Which device has control -How errors are detected/corrected
45
Why do we need communications protocols#
Common standards led to open systems which allow users to use components from more than one manufacturer. Users are not restricted to one paerticular manufacturer
46
Advantages of protocols#
-Can connect different manufacturer's devices -Users not confined to one manufacturer -Greatly assisted the development of WANs -Very effective for the communication and sharing of data
47
Disadvantages of protocols#
-Prevents new enterprise/ stops innovation -Agreeing a common standard can be time consuimg and difficult -Protocol may not be the best but it happens to be the most common
48
OSI model definiton#
A set of protocols allowing computers of different origins to be linked together
49
OSI model functions#
-Each layer interacts only with the layer immediately beneath it and provides facilities for use by the layer above -Each layer deals with a specific functionality (control is passed from one layer to the next)
50
Wi-fi definition#
Wi-fi is a wireless networking technology that allows computers and other devices to communicate over a wireless signal, using radiowaves toprovide high-speed internent and network connections
51
Wi-fi features#
-Enables two or more devices to connect wirelessly for data sharing -It can connect wirelessly to a wireless router over a limited distance (60-90m) -Wi-fi networks can either be open (anyone can use them) or closed (a password is needed)
52
To set up a small wi-fi network you would need:#
-A broadband connection to the internet -A router -Wi-fi enabled computers
53
Advantages of wi-fi#
-Ethernet LANs can be set up without cables -Can be used to extend the range of a LAN -Wi-fi hubs can act as hardware firewalls, giving an extra layer of security
54
Disadvantages of wi-fi#
-If security is not properly configured, then anyone within a certain radius can access sensitive data -Wi-fi transceivers may drain batteries in portable devices very quickly -Devices on the edge of the hub's range may be disconnected, unless repeaters are used
55
Bluetooth definition#
A wireless technology for exchanging data over short distances. Bluetooth is an example of PAN technology, and is most associated with connecting mobile phones to earpieces or sharing data between handsets
56
Bluetooth features#
-It uses radiowaves to send information between two devices in close proximity that have been paired together -A protocol which defines the communications standard -It uses very little power -The range is affected by obstacles eg furniture and walls
57
Advantages of bluetooth#
-Ad hoc networks are easy to setup -Wireless devices such as phones, can share sound files,videos and images without being charged by a network
58
Disadvantages of bluetooth#
-Security is low in cases where developers have been lax when implementing software, and even novice users haveaccess to security settings (no password=low security) -Short distances (10m)
59
Bandwidth definition
Bandwidth is the measure of the amount of data which a network or trasnmission media can carry at once (mbps)
60
Features of fibre optic#
-Uses light -Consists of glass or plastic wires bundled together and encased in a jacket -Very secure form weather and hackers as it has cladding which reflects light back along the core -Not susceptible to interference (cutting the sheathing will immediately disrupt the flow of data)
61
Advantages of fibre optic#
-High bandwidth -Less signal degradation -Difficult to intercept -Not subject to interferance -Non-flammable -Lightweight -Flexible -Non-corrosive
62
Disadvantages to fibre optic#
-More expensive per metre than copper
63
Error detection and correction
-Typically happen because of some sort of interference eg loose or damaged connectors/cables -Many errors occur invisibly when a user transmits data, but the network protocols normally corrects them without user intervention
64
Two strategies of error detection and correction
-Error detecting coding (Sending a small amount of redundant data that allows a receiver to deduce that an error has occurred) -Error correcting coding (sending each block of data with a large amount of redundant data that allows the receiver to detect an error and deduce what the transmitted data must have been)
65
Why is error detecting coding the most common?
Less redundant data is needed and retransmission is very quick and efficient in the event of an error
66
Parity checking definition
The technique of checking whether data has been lost or written over when it's moved from one place in storage to another or when transmitted between computers
67
Parity checking technique
-A parity bit (8th) is added to each byte -In an even parity, the total number of on or '1' bits in every byte must be even , odd must be odd -When data is moved from one location to another in memory, the parity bits are checked again at the receiving end, and if they are different, an error message is displayed
68
Weakness of parity checking
In an even parity check, if the number of bits that have 'flipped' is even, no error will be detected
69
Echo checking definition
When data is received, a copy is transmitted back to the sender where it is compared with the original. If it differs, the original data is retransmitted
70
Disadvantages of echo checking
-The method is slow -A character may have been received correctly by the host device and an error could corrupt it on it's way back, the operator has no way of knowing where the error occurred -Error correction is manual
71
Checksum
-Data is transmitted over a transmission line between computers in blocks of approx. 256 bytes -Each block has a mathematical calculation applied to it -The remainder of this calculation is sent with the block of data as part of it's header information -The receiver performs the same calculation and the new checksum is compared against the transmitted checksum -If the numbers do not match, an error is detected and re-transmission is required
72
OSI model in order#
1- Physical layer 2- Data link layer 3- Network layer 4- Transport layer 5- Session layer 6- Presentation layer 7- Application layer
73
Physical layer
Defines how a cable is attached to the network and what transmission technique is used to send data over the cable
74
Data link layer#
Packages raw bits into frames and transfers them from one computer to another without errors
75
Network layer
Ensures that packets of data are routed efficiently over the network and manages traffic problems
76
Transport layer
Hnadles error recognition and recovery. Makes sure packets of data arrive at the correct destination in the correct sequence
77
Session layer
Establishes dialogue between the two computers in a session using a communication link
78
Presentation layer
Manages security by providing encryption and compresses data so that fewer bits need transferred on the network
79
Application layer#
Represents services that directly support applications, such as database access and email

DIGITAL TECHNOLOGY A21 (2 decks)

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