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Networks Flashcards

1
Q

Why are networks used

A

To read/write personal files on a central server- provides extra storage and back up facility
To access shared files among several users
To send data to a shared printer
To communicate with each other

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2
Q

What are 4 different types of network

A

LAN- Local Area Network
WLAN- Wireless local area Network
WAN- wide area network
PAN- Personal Area Network

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3
Q

Explain LAN

A

Local area network
is a network connecting computers in a single site
It is used by a organisation in the site
Transmission media will be a twisted pair of WiFi

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4
Q

Explain WLAN

A

Wireless Local Area Network
A wireless router allows all computer devices in a household such as printers and external hard drives

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5
Q

Explain WAN

A

Wide area network
Each site has one or more LANs, and they are connected together to form a WAN
The networked computers are 1000s of kilometres apart and it allows employees from different sites to communicate and share data.

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6
Q

Explain PAN

A

Personal area network
Network used for data transmission over short distances by computer devices
The devices usually communicate wirelessly over short distances up to 10m

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7
Q

Explain Client-Server network

A

Architecture where a client runs a application provided by a server on a network
At least 1 server, which is a powerful computer that provides a service to the clients in the networks
The server will authenticate the user and then give the user access to the relevant authorized files

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8
Q

Explain Peer-to-Peer computer model

A

operates with each peer storing some of the files
Each peer can therefore act as a client and request a file from other peer or it can act as a server when another peer requests the download of a file
No dedicated server

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9
Q

What is the CSMA/CD method, why is it used

A

Carrier sense multiple access with collision detection
As there is a shared medium for message transmission causes messages that are transmitted to corrupt due to collision

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10
Q

What is the procedure of CSMA/CD method

A

Transmitter follows the procedure
1. Check voltage of the transmission medium to see if the line is busy
2. If this indicates activity, wait a random time before checking again
3. If no activity detected, start transmission
4. Continuously check for a collision
5. If no collision detected, continue transmission
6. If a collision is detected, stop transmission of the message and transmit a jamming signal to warn all end stations, after a random time try again- go to step 1

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11
Q

Wired communication media

A

Physical connection between the computer and the network
Most are made of copper wire and carries electrical signals
Also can be fibre-optic cable, which is made of either glass or plastic and carries light signals
Fibre optic cables transmits data far faster and allow signals to travel over greater distances than copper wire

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12
Q

Wireless communication media and eg

A

Does not require physical connection between devices
Most transmits and receives radio-signals
Infra-red can be used over limited distances
Examples include mobile phone network, Bluetooth and Wi-Fi

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13
Q

Advantages of wired connectivity

A

Faster than wireless connectivity
More security- harder to intercept or eavesdrop on data

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14
Q

Disadvantages of Wired connectivity

A

Expensive to install and configure
Requires many cables at a premise
Requires site preparations to prevent health hazards

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15
Q

Advantages of wireless connectivity

A

No need for a cable to connect
Allow users to use their own device
High mobility of devices within the range
A wider range of devices can communicate within each other/a network

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16
Q

Disadvantages of wireless connectivity

A

Data transmission makes it slower
Interference from other device can hinder performance
Walls and other objects can hinder performance
Data needs to be encrypted to prevent eavesdropping or interception

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17
Q

What is Network data speed

A

speed that data can be transmitted through a communication medium

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18
Q

What is Bandwidth

A

Amount of data that can be carried from one point to another on a network in a given period usually expressed as bps

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19
Q

What is the Latency of the network connection

A

Any delay that data might experience when travelling through a network

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20
Q

What are protocols

A

A set of rules for data transmission which are agreed by sender and receiver for the transmission of data
A protocol is a set of rules that control how communications between devices and how these communications will be sent/received
Without protocol, different computers and other hardware would be unable to communicate with each other

21
Q

What details would a protocol contain?

A

Transmission speed that a user shouldn’t exceed
The address- how the computer will be identified
Routing information- which route data will take to get to its destination
Error checking- how errors will be found and deal with
Whether each part of a message should be acknowledged as received correctly
The procedure when incorrect data is received
How data/message is formatted
How the data is sequenced- send in order or later put in to correct order
How the speed of the sender and receiver can be synchronized- occur at the same time or operate at the same rate

22
Q

What are the email protocols

A

SMTP, POP3, IMAP

23
Q

What is SMTP

A

Simple Mail Transfer Protocol
Used when sending a email through the internet
It is a “push” protocol
It details the format that messages are sent in, what commands email server should understand and how they should reply to them

24
Q

What is POP3

A

Post Office Protocol version 3
Used to retrieve email from an email server
It is a “pull” protocol
Emails are downloaded onto the client computer and the message in the server gets deleted
i.e. emails are locally stored
Emails are only accessible from the one client system

25
What is IMAP
Internet Message Access Protocol Used to retrieve an email from an email server It is a "pull" protocol Emails aren't downloaded, they remain stored on the server until the user deletes them Server can be accessible from any client- tablet, mobile phone etc This makes it suitable for anyone on the move or if someone is using a system other than that normally used
26
What are the Network Protocols
Ethernet, WI-FI, HTTP, HTTPS, FTP
27
What is Ethernet
Data link protocol Family of protocols used in wires LANs Cover everything from physical parts of a networks, such as type of cable or optical fibre and type of connectors to be used, to the logical parts, such as how data is sent and checked for errors and the speed at which data can be transmitted
28
What is WI-Fi
Digital communication protocol that sets out how data is transmitted on wireless LANs It is a trademarked term that is owned by Wi-Fi alliance
29
What is HTTP
HyperText Transfer Protocol Used in the application layer Used when sending and receiving data between web browsers and web servers This covers how data should be formatted, what commands the web browser and web server should understand and how they should react to each commend -e.g. 404 error indicates that requested wed page does not exist in the web server
30
What is HTTPS
HyperText Transfer Protocol Secure Secure version of HTTP Used in the application layer Data sent between the devices is encrypted Prevents data from being read/accessed by a third party
31
What is FTP
File Transfer Protocol Includes rules that must be followed when files are being transmitted between computers
32
What is TCP
Transmission Control Protocol This is the transport layer protocol Connection oriented protocol Provides a reliable connection between computers Makes sure that no data sent is missing and the data sent is correct by Used when web pages are accessed, send/receive emails or upload/download files
33
How does TCP make sure that no data sent is missing and the data sent is correct by
Acknowledgements sent by receiving computer/devices Using checksum to ensure that data received is accurate Flow control- to give time for the receiving device to process data by telling the sending computer to slow down Ensure that data sent up to the application layer contains no duplicates and is in the correct order
34
What is UDP
User datagram Protocol Transport layer protocol Connectionless protocol Packets are just sent to the recipient Does not check that they have been received Used when speed is desirable and error correction is not necessary Frequently used for live broadcast
35
What is IP
Internet protocol Internet layer protocol Deals with the addressing system to identify individual computers/servers on the internet Adds the source and destination addresses to the packets (header)
36
What is Checksum
A technique for finding errors A mathematical formula is applied to the data and resulting number value (checksum) is transmitted with the data The recipient computer applies the same formula to the received data It then compares the checksum sent with the calculated checksum If checksums do not match, error has occurred, and the recipient computer request data to be resent
37
What is the TCP/IP suite
Transmission Control Protocol/Internet protocol Protocol stack- collection of protocols that work together Consists of four layers Data to be transmitted or to be received must pass through the layers Each layer performs specific tasks and can communicate/interact with the adjacent layer/layers in only
38
What are the benefits of using network layers
Makes model easier to understand by dividing it into functional parts Each layer is specialized to perform a particular function The different layers can have different interfaces to communicate with each other/ can be combined in different ways One layer can be developed or changed without affecting the other layers Makes it easier to identify and correct networking errors and problems Provides a universal standard for hardware and software manufacturers to follow so communication between layers and between different devices is not a problem
39
What are the layers of the protocol stack
Application Transport Network Data link
40
Explain the application layer
top layer of the stack The layer which interacts with the user to provide access to services and data that is sent/received over the network Layer where applications such as web browsers and email clients operate It is where requests are made to web servers or where emails are sent/received Protocols used in this layer include HTTP FTP Email protocols- SMTP, POP3, IMAP Requests are passed to the transport layer
41
Explain the transport layer
Concerned with host to host connection Layer sets up communication between the 2 hosts They agree settings such as language and size of packets When sending data Data received from the application layer is divided into packets of the correct size and include the packet sequence number, and error checking-checksum Checks that data packets have arrived safely and if not, re-send the packet When receiving data Performa a check on data received-checksum If the data has been received correctly send an acknowledgement to the sender If not, send a request to re-send the packet Once all the packets are received correctly it assembles the packets in order of the packet sequence number and send it to the application layer Protocols used TCP UDP
42
Explain the network layer
Adds the source and destination addresses to the packets from the received from the transport layer It deals with sending data across multiple networks (possibly the internet), from the source to the destination- routing When a packet is received it checks the destination address and if it matches then send it to the transport layer Protocols used IP
43
Explain the data link layer
Controls the transmission and reception of data to/from a local network using the protocols of a specific network This is where the network interface card (NIC) and the device drivers are located Protocols used in the ethernet
44
What is mobile communication
Wireless network distributed through cells Each cell includes a fixed location transceiver known as a base station These cells provide wireless coverage over a large geographical area Each cell offers coverage of between 9 and 21 miles Handover- when a user moves out of range, signal falls and the base station makes a request to transfer control to another base station that is receiving the best signals without notifying the subscribers European Telecommunications Standards Institute develop a standard for mobile communications called the Global Systems for Mobile Communications (GSM) to describe the protocols to be used The generations are 2G, 3G, 4G, 5G
45
Explain 2G
First to use digital communications Enabled text messages to be send Introduced a multi-media messaging service (MMS)
46
Explain 3G
Increase data transmission to 2mbits/s Gave wireless access to the Internet Enables video calls, downloading and streaming Use IP-based protocols for data
47
Explain 4G
Provide much higher transmission speed Gave rise to mobile gaming A film that takes 5hrs to download on 3G takes less than 8 minutes Has a much higher capacity- can support greater number of users at the same time Gives a more immediate response to a user's commands Useful when playing online games Use IP-based protocols for data and voice calls
48
Explain 5G
Smarter, faster and more efficient than 4G Achieves peak speeds of 100 Gbps, 100 times faster than 4G and faster than most broadband networks Has far lower latency Will be able to handle current devices and emerging technologies such as driverless cars and connected home products
49
How does TCP make sure that no data sent is missing and the data sent is correct by
Acknowledgements sent by receiving computer/devices Using checksum to ensure that data received is accurate Flow control- to give time for the receiving device to process data by telling the sending computer to slow down Ensure that data sent up to the application layer contains no duplicates and is in the correct order

Computer science (12 decks)

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