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Computer Science > 3.5: Computer Networks > Flashcards

3.5: Computer Networks Flashcards

1
Q

What is a computer network

A

A computer network is made up of 2 or more computers connecting together physically or wirelessly to exchange information and share network recourses

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2
Q

What is the internet

A

Connection of networks
Collective ownership as no one person owns it

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3
Q

What is the world wide web

A

A service that is offered on the internet

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4
Q

Benefits of computer networks

A

communication, sharing peripherals, sharing files, roaming, Centralised management, Remote management

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5
Q

Risks of computer networks

A

Viruses, Hacking, Hardware reliance, Network speed

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6
Q

What is a Personal Area Network

A

connects devices centered around a single person
wired or wireless
Bluetooth

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7
Q

What is a Local Area Network

A

A Local Area Network is a location devices connected together physically or wirelessly across a small geographic location such as a house which is completely owned by a single person

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8
Q

What is a WAN

A

A Wide Area Network is a network that extends over a large geographic. Computers communicate using recourses shared by a 3rd party service such as BT. It is a collective ownership. The internet is the largest WAN is it extends all over the world

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9
Q

What is a standalone

A

An isolated network that is not connected to any over device. Businesses use it to test for viruses as it won’t affect every computer

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10
Q

What is a data packet

A

. Packets are a small piece of data transmitted over a network. Packets are numbered by their number out of how many
packets there are in total
. The payload is the actual data in the packet
. Each packet also has the packet number, source and destination IP addresses

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11
Q

What is an IP address

A

. Every computer has a Internet Protocol address
. IP addresses are four 8 bit numbers separated by dots 32 bits in total
. It is set in software and can be changed
. It is hierarchical (contains lots of different bits of information) - this means that it includes the . network, subnet and host
components
. It is used by routers
. Written in dotted decimal

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12
Q

what is circuit switching

A

. When you make a telephone call a dedicated connection is set up between you and the person you are calling
. Impractical for billions of people

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13
Q

What is packet switching

A

the file is broken down into packets of 512 bytes each which take their own path across the internet

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14
Q

What is a Router

A

Routers are a piece of hardware that capable of routing packets from one place to another based on the IP address

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15
Q

what is a Network Interface card

A

Each device has a NIC which allows a full time connection to a network
It can be wireless or wired

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16
Q

What is a MAC address

A

each NIC has it’s own MAC address which is unique
It cannot change as it was assigned by the manufacturer in the hardware
Computers can have more than one MAC address for ethernet and WIFI
12 characters of hexadecimal 48 bits in total

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17
Q

What is a Switch

A

switches connect each node in a network
They send packets to the correct computer using the MAC address

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18
Q

What is a Hub

A

A switch that sends packets to all nodes in a network

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19
Q

What does a Router do when moving packets from LAN to WAN

A

. Looks at the destination IP address of packets and sends them to the network that is closer to the destination

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20
Q

What is a network Topology

A

Physical and logical arrangement and connection in a network

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21
Q

What is a star topology

A

Every node is connected to a switch/hub

Advantages

Better performance as the network wont be affected by traffic increase
If one cable fails the rest of the computers won’t fail
No collision - if switch used
Better security

Disadvantages

using a hub has data security risks
using a hub makes more data collisions which impacts the speed
expensive
relies on central device

22
Q

What is a bus topology

A

All nodes are connected to a central backbone cable with terminators on each end to stop data bouncing back and corrupting other data

Advantages

Cheaper to install as there are less cables
easy to add more devices

Disadvantages

Reliant on central backbone cable
Potential security risk as all packets are broadcast to the network
Many collisions of data

23
Q

What does a switch or hub do

A

connects the computers to a LAN

24
Q

What is a modulated demodulator (Modem)

A

. Required to connect to the internet
. Usually combined with a router inside a single device

25
Q

What does a Wireless Access Point do

A

Connects wireless devices to a network

26
Q

What is an ethernet cable

A

Made out of copper
ethernet is sent through twisted copper cables`

27
Q

What is a coaxial cable

A

Copper core with an insulated outer coating
used to carry data and video signals

28
Q

What is a fiber optic cable

A

Made of glass or plastic
Speed of light

29
Q

What are the risks of public networks

A

Man in the Middle Attack

. Someone positions themselves between you and the access point

. They intercept your packets and read them and then relay it on

Evil Twin Attack

. Duplicate the name of the network

. They think they are with the actual network but, it comes straight to hacker

Malware Infiltration

. Hackers infect an unsecured WI-FI connection with malware, which then infect the devices that connect to it

Snooping

. Hackers can eavesdrop on unsecured Public Wi-Fi networks using special software

. An attacker on the network can what you are doing

30
Q

How can you be secure on public networks

A

Use a virtual private network to encrypt data
select a secure network
only use websites with https as it is encrypted
avoid public networks when possible

31
Q

What are four methods networks can be secure

A

Authentication
Encryption
Firewall
MAC address filtering

32
Q

what is encryption

A

encoding of data so that it can no longer be understood

33
Q

what is ciphertext

A

encrypted text

34
Q

what is a key

A

A sequence of numbers that are used to encrypt or decrypt data

35
Q

What is private key encryption

A

1 key is used to encrypt and decrypt data
not great as you must tell the person the key without letting anyone else know

36
Q

what is public key encryption

A

a public key is used to encrypt data and a private key is used to decrypt data

37
Q

What is a firewall

A

Firewalls are used to separate a trusted network from an untrusted network
Inspect all the packets entering and leaving your network
Could be hardware or software
usually positioned at the router

38
Q

What is MAC address filtering

A

Allows and blocks MAC addresses so they cannot use the WI-FI
Not very practical
. Very labour intensive to keep it up to date
. Use another device if filtered

39
Q

What is a network protocol

A

A set of rules that allow devices to communicate

40
Q

What are the application protocols

A

HTTP - hyper text transfer protocol is used for web pages. It requests a web page from the web server

HTTPS - hyper text transfer protocol sec is Used for sensitive data as it encrypts your data

SMTP - simple mail transfer protocol is for sending emails. It passes emails between servers and waits at the closest server until accessed

FTP - File transfer protocol for transferring files

POP - automatically download every new message as it appears. not good for multiple people

IMAP - Downloads a copy from the server so multiple people can access the message. when it is deleted it will also delete it from the serve

41
Q

What is the TCP / IP stack

A

. Gives a set of protocols for any device to be able to communicate on the internet
. It will make sure that packets are delivered to their destination
. Data is resent if it doesn’t arrive
. makes sure that the Security of data is maintained
. 4 layers that enable communication on the internet

42
Q

What is the purpose of the Application layer

A

. Applications create data to send to this layer
. could be web browsers, email clients

43
Q

What is the purpose of the Transport layer

A

. creates a connection between the two hosts
. divides the data into packets and adds packet number
. resends packets if not delivered correctly (only when TCP is used not UDP)
Uses TCP and UDP

44
Q

How does UDP differ from TCP

A

UDP will not resend packets if they didn’t arrive and is only used for fast paced live software like games and video calls

45
Q

What is the function of the Internet layer

A

. adds the source and destination IP
. responsible for routing packets
. gets the packets ready for transmission

46
Q

What is the function of the Link layer

A

. Where all the hardware is including the NIC, device drivers and the MAC address
. Uses the Ethernet and WIFI protocols
. sends data along cables

47
Q

How is the TCP/IP stack used in sending data

A

Application - computer applications produce data for sending
Transport - divides into packets and adds the number
Internet - gets the packets ready for transmission, adds the source and destination IP addresses
Link - Mac address is added, data sent along cables

48
Q

How is the TCP/IP stack used in receiving data

A

Link - removes the MAC address
Internet - removes the source and destination IP addresses
Transport - reassembles packets in order
Application - uses the correct protocol to display the data

49
Q

How is a router used when sending data

A

opens up a single packet to expose the IP address at the internet layer then it repackages the packet and sends it

50
Q

What is a network layer

A

. A division of network functionality
. each layer has its own specific function
. operates independently from any other layer

51
Q

what are the advantages of layers

A

. The functionality of one layer can be changed without affecting the functionality of other layers
. Ensures interoperability between providers and systems this means that manufacturer’s routers operating on the Internet layer, will operate with another manufacturer’s Network Interface Cards (NICs) operating on the Link layer

Computer Science (7 decks)

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