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Computing > 3.5 Computer Networks > Flashcards

3.5 Computer Networks Flashcards

1
Q

What is a network?

A

2 or more computers connected together that can communicate.

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2
Q

2 benefits of networking

A

Share resources
Communicate

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3
Q

2 risks of networking

A

Greater security risks - data could be open to unauthorised access
Greater cost in setting up

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4
Q

Types of networking

A

LAN - Local area network
PAN - Personal area network
WAN - Wide area network

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5
Q

What is PAN?

A

Uses Bluetooth
Used for connecting devices in a very small geographic area
Bluetooth is a wireless protocol
Slower than Wi-Fi
Easier to set up than WIFI
Uses radio waves over 79 bands

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6
Q

What is LAN?

A

Small geographic space (office block)
Owned by a single person or organisation
Often have connection to the internet
Often have file servers

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7
Q

What is WAN?

A

A computer network that spans regions, countries or even the world
The internet is a type of WAN
Often owned by specific network companies and leased to users

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8
Q

Positives of wireless networks?

A

+ Allows any device to connect if it has a wireless network interface
+ Easier to set up and connect new devices

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9
Q

Negatives of wireless networks?

A
  • Greater security risk as device does not need a physical connection
  • Potential to become overloaded with devices and limit access speeds
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10
Q

What are wired networks?

A

Use physical cables
Copper wires are less expensive and already exist
Fibre optic cables allow faster transmission of data than copper and have less data loss

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11
Q

What is a topology?

A

The shape of a wired network.

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12
Q

What is a star topology?

A

Every device is linked singularly to a central device (a switch)

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13
Q

2 benefits of star topology

A

+ Faster, uses full network capacity as each device has use of its own cable
+ One fault means only one device is affected

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14
Q

2 negatives of star topology?

A
  • More cables so more expensive
  • If the central node is faulty the whole network will fail
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15
Q

What is bus topology?

A

Every device is linked to the same cable.

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16
Q

2 positives of bus topology?

A

+ Easy to set up
+ Cheaper

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17
Q

Negative of bus topology?

A
  • One break in the cable means entire network breaks
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18
Q

What is a network protocol?

A

A set of rules that all the devices on a network must follow if they are able to communicate with each other.

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19
Q

What are the 3 types of data transmission?

A

• Simplex channel
• Half duplex
• Full duplex

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20
Q

What direction is simplex channel?

A

Unidirectional - one direction

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21
Q

What direction is half duplex?

A

Simplex communication in both directions over a single channel.

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22
Q

What direction is a full duplex?

A

Simultaneous communications in both directions but requires 2 channels.

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23
Q

What are the types of network protocols?

A

• Ethernet
• WI-FI
• TCP and UDP
• IP
• HTTP
• HTTPS
• FTP
• Email protocols: SMTP and IMAP

24
Q

Ethernet

A

Used for local area networks:
A computer communicates on the network by using a network interface card or network adapter.
The adapted plugs into the motherboard of the computer
The cable that plugs into the adapter allows the computer to communicate with the network
The data is transmitted in packets
The format and size of a frame is defined by the Ethernet protocol.

25
Q

Ethernet:
Checksum

A

This is an error detection scheme.
Each transmitted package is accompanied by a numerical value based on the number of set bits in the message.
The receiving station then applies the same formula to the message and checks to make sure the accompanying numerical value is the same.
If not it will have to be sent again.

26
Q

WI-FI

A

Invented to provide wireless connection between computing devices and enable these to connect to an access point between a WLAN (wireless LAN) and a wired LAN.
The Wi-Fi signals travel through a shared medium.
This means it is a multiple access medium
Access is co-ordinated and controlled

27
Q

TCP (Transmission control protocol)

A

When a computer requests a web page, the web page must travel through a packet-switched network.
The web page is split up into smaller pieces, called packets.
Each packet is labelled with a sequence number before being out on the network.
Packets do not necessarily follow the same path.
Packets may arrive out of sequence.
TCP reassembles the packets in the right order at the destination.

28
Q

What does TCP detect?

A

TCP detects error in packet transmission.
And the sender will expect to receive an acknowledgment of receipt of the packets
If not the sender will send the packets again.

29
Q

UDP (user datagram protocol)

A

UDP (like TCP) breaks a message down into smaller sized packets.
They are sent through the packet switched network to their destination.
The packets are called datagrams.

30
Q

Difference between UDP and TCP?

A

No check is made by UDP to check that the datagrams arrived correctly
UDP does not request a resend if an error is detected, the packet is just discarded.
UDP does not add sequence numbers.

UDP is efficient at transporting but not reliable.
It can be used in gaming, voice and video communications as data loss or corrupted data will not affect quality too much.

31
Q

IP (internet protocol)

A

Each computer using the internet needs to be uniquely identified.
Each computer must have an IP address.

32
Q

What are the 2 parts of the IP address?

A

NetID - identifies the network connected to the internet.
HostID - identifies the host connected to the network.

33
Q

TCP/IP

A

On the internet, TCP/IP (Transmission Control Protocol/Internet protocol) is the delivery model.
TCP is in charge of the reliable delivery of information.
While IP is in charge of routing, using the IP addressing mechanism.

34
Q

HTTP

A

This is an application protocol.
A client computer sends a request to a web server, using web browser.
The web server responds with a response message.
For a web page that could be HTML

TCP establishes the connection.

35
Q

HTTPS

A

This web protocol encrypts and decrypts user page requests
And the web pages returned by the web server
HTTPS uses secure sockets layer (DEL)

36
Q

FTP

A

This is an application layer protocol that allows a file from one host to be copied to another host.
The host runs FTP client software
The other runs an FTP server

FTP uses 2 ports
Port 21 for commands
Port 20 for data

37
Q

What are the 2 email protocols?

A

Simple mail transfer (SMTP)
Internet message access protocol (IMAP)

38
Q

SMTP

A

SMTP is used by e-mail clients to send an email.
A message is written and addressed to recipients.
SMTP is used by the email client to transfer the message to a mail server.
The mail server takes care of delivering the mail to the destination using SMTP.

39
Q

IMAP

A

IMAP is a protocol that allows access to emails stored on a remote server.
A user will connect to an IMAP server to read and organise their emails.
Remote access from any device is supported.
Emails are cached locally so they can be read again without contacting the server.

Your email program uses the IMAP protocol to copy or mirror emails stored on an email server to your desktop or device.

40
Q

SMTP VS IMAP

A

SMTP and IMAP are used to send and receive email messages.
The difference is in their function.
SMTP is a protocol for sending email towards its intended destination.
IMAP is a protocol that deals with managing and retrieving email messages from the server.

IMAP is used only between a client who is retrieving the mail, and the server where the emails are stored.
SMTP is used by the client to send emails to a server, but also used to push the email to another server as the sender and recipient might use different services e.g. gmail and outlook

41
Q

Methods of network security

A

• Authentication
• Encryption
• Firewall
• MAC Address filtering

42
Q

Authentication

A

Authentication is used to try and stop unauthorised users to gain access to a network. It is the process of identifying an individual.

A user can enter a username and password at a login screen and prove they ‘know’ that piece of information but not that they have permission to login.

43
Q

3 factors of authentication

A

1) Identification: Something you know - email address or user ID
2) Authentication: Something you have - smart card or OTP
3) Authentication: Something of you - fingerprint or other biometrics

44
Q

Encryption

A

Encryption is the process of encoding data or a message so that it cannot be understood by anyone other than its intended recipient.
Encryption means that data can be stored and transmitted securely by sending the data to the receiving computer.
The data or message is encrypted using an encryption algorithm.

45
Q

Firewall

A

A firewall is a combination of hardware and software that isolates an internal network from an external network e.g. the internet.
Some packets will be allowed through the firewall and some will be blocked.

This means that there is less internet traffic that the come through, making the network more secure.

46
Q

MAC address

A

Every network enabled device has a network interface adapter.
Each network interface adapter has a unique number, known as the MAC (Media Access Control) address.
It is a 48 bit, displayed as a hexadecimal number.

47
Q

MAC address filtering

A

A LAN will have routers that can filter traffic
It can manage a list of allowed MAC addresses
This will then block access to any devices not on the list
And the request to join the network will be rejected.

BUT if a spoofer learns the MAC address of a valid network adapter
They can change the data in a packet to have a valid MAC address that is on the filtered list.

48
Q

White list filtering

A

Only allows devices on a list to connect to the network.

49
Q

Black list filtering

A

Devices on the blacklist are blocked from accessing the network.

50
Q

TCP/IP model

A

How devices communicate across the internet.

51
Q

Order of the TCP/IP model

A

Application layer
Transport layer
Internet layer
Link layer

Goes up the other way when reaches other computer.

52
Q

Application layer

A

This is where the network applications such as web browser and email programs operate.

HTTP/HTTPS, SMTP, IMAP, FTP protocols

53
Q

Transport layer

A

This layer sets up the communication between the 2 hosts and they agree settings such as ‘language’ and size of packets.

TCP/UDP protocols

54
Q

Internet layer

A

Addresses and packages data for transmission. Routes the packets across the network.

IP protocols

55
Q

Link layer

A

This is where the network hardware such as the NIC (network interface card) is located. OS drivers also sit here.

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