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Computer science > Networks > Flashcards

Networks Flashcards

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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
Q

What is IMAP

A

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
Q

What are the Network Protocols

A

Ethernet, WI-FI, HTTP, HTTPS, FTP

27
Q

What is Ethernet

A

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
Q

What is WI-Fi

A

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
Q

What is HTTP

A

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
Q

What is HTTPS

A

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
Q

What is FTP

A

File Transfer Protocol
Includes rules that must be followed when files are being transmitted between computers

32
Q

What is TCP

A

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
Q

How does TCP make sure that no data sent is missing and the data sent is correct by

A

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
Q

What is UDP

A

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
Q

What is IP

A

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
Q

What is Checksum

A

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
Q

What is the TCP/IP suite

A

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
Q

What are the benefits of using network layers

A

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
Q

What are the layers of the protocol stack

A

Application
Transport
Network
Data link

40
Q

Explain the application layer

A

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
Q

Explain the transport layer

A

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
Q

Explain the network layer

A

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
Q

Explain the data link layer

A

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
Q

What is mobile communication

A

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
Q

Explain 2G

A

First to use digital communications
Enabled text messages to be send
Introduced a multi-media messaging service (MMS)

46
Q

Explain 3G

A

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
Q

Explain 4G

A

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
Q

Explain 5G

A

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
Q

How does TCP make sure that no data sent is missing and the data sent is correct by

A

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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