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CS GCSE > Unit 3 > Flashcards

Unit 3 Flashcards

(51 cards)

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1
Q

What is the internet

A

A collection of interconnected networks

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2
Q

What are Ipv4 and 6 addreszes

A

Each network has a unique address and they are used to identify them. Ipv4 is made up of 8 octet values and ipv6 is 8 groups of 16 bits (4x ipv4)

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3
Q

What is circuit switching and what do we use instead

A

When a dedicated connection is made between 2 devices, this is called packet switching. Theres not enough lines for the amount of data being sent so packet switching is used

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4
Q

How does packet switching work

A

The data is split into 5 packets of equal size and they are given a header containing:

IP address its going to

IP address it has come from

sequence num on packet

num of packets in whole communication

error checking data

recipient computer reorders packets in the correct order and each packet is checked for errors

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5
Q

What happens to lost packets

A

Any packets not acknowledged after a set amount of time will automatically be resent by the sending computer

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6
Q

Purpose of a router

A

To direct data packets across nodes which are less busy and will get to the destination more effectively

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7
Q

What is a DNS

A

A Domain Name System allows you to type a name like google.com into the web browser and it will translate it into the required IP address

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8
Q

How do DNS servers work

A

There are 13 root DNS servers worldwide, and they keep a complete database of all the TLD (top level domain) names (ie: .com, .org…)

When a DNS server receives a request not in its database, it passes the request onto another server until it reaches the one with a matching name/IP address

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9
Q

What is a URL

A

Uniform Resource Locator is used to specify a means of accessing a resource across a network and its location

Protocol + domain name of the resource = URL

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10
Q

What is a NIC

A

Built into every network device
A network interface controller (NIC) provides a method of connecting to a network.
Can be wired/wireless (So it can hold up to 2 MAC addresses)

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11
Q

What is a MAC address

A

Assigned to every NIC by manufacturer

May have more than one (one for wired/wireless/bluetooth)

Made up of Hexadecimal

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12
Q

Role of MAC address

A

Unlike IP addresses, MAC address never change wherever you are.

When you request a web page, each router uses each other MAC addresses to send the packets along its way

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13
Q

What is one computer not connected to a network and what is a LAN

A

Standalone

A network of computers that covers a small geographical area. All hardware is owned by org using it. Wired with UTP cable, fibre optic or wireless using WiFi

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14
Q

Difference between router switch and hub

A

Router:

Sends data packets on their way in the best direction

Hub:

Central, multi plug adaptor for computers and printers in a network

When a data packet is received it broadcasts the packet to all devices on network

Switch:

Smart, multi plug adaptor, only sends packets to intended recipient using its MAC address

Reduces Network Traffic and increases speed

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15
Q

Adv and dis of networking

A

Advantages:

sharing resources (ie: printers) saves money

You can access your files from any computer in the network

Data is easy to back up as its stored on the central server

Disadvantages:

Purchasing network hardware is expensive

Managing a large network is complicated

Viruses can infiltrate the network and harm every computer

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16
Q

What are the 2 different topologies for LANs

A

Star and mesh

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17
Q

Adv and dis of star network

A

Advantages:

Fast data transfer as fewer collisions
If one cable fails other workstations are not affected
Disadvantages:

Requires additional hardware (ie: Switch)
If central device fails (switch) whole network goes down

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18
Q

What is a wireless mesh network

A

One node has a wired internet connection, no other cabling/infrastructure is necessary
More nodes = more the signal can travel
Ie: A node with broadcast distance of 3 other nodes will have triple the bandwidth.

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19
Q

Adv and dis of mesh networking

A

Advantages:

No single point of failure: self healing network
Expansion/modification can be done without disrupting the network
data can be transmitted from different devices simultaneously
Disadvantages:

Can involve redundant connections
Expensive to install cabling is using wired connections
Network maintenance/administration is difficult

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20
Q

What are ethernet protocols

A

Describes how devices should format data ready for transmission between computers on the same network

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21
Q

Whats a virtual network

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A

A network that can securely connect geographically unrelated devices via the internet

virtual network servers create a network with no physical connection but one that allows file sharing and communication

22
Q

Whats a WAN

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A

Covers large geographical area and connects multiple LANs

Infrastructure between LANs is hired from telecommunication who own/manage it

WANs are connected with telephone lines/fibre optics/satellite links

Internet is the biggest example of a WAN

23
Q

What is a WAP

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A

Wireless access point is a device which allows wireless devices to connect to a wired network using WiFI

24
Q

How does wireless data transmission work

Adv and dis of the 2 most used channels

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A

Using WiFi frequencies/channels, mostly using 2.4GHz or 5GHz channels

Advantages:

2.4GHz:

Greater distance/coverage
5GHz:

Less crowded space, 23 non-overlapping channels with higher data transmission rates
Disadvantages:

2.4Ghz:

More interference from other devices and only 3 non overlapping channels

5GHz:

Fewer devices can use 5Ghz frequencies, less able to penetrate through walls.

25
Plaintext
Original message to be encrypted
26
Ciphertext
Encrpted message
27
Encryption
Process of converting plaintext into ciphertext
28
Key
A sequence of numbers used to encrypt or decrypt, often data using a mathematical formula
29
Encrypton algorithm
formula for encrypting plaintext
30
Encryption techniques
Private key (symmetric): A single key is used to encrypt and decrypt a message Public Key(asymmetric): 2 keys are used. One to encrypt and one to decrypt. This is safer as you can give someone the encryption key but never have to reveal your decryption key
31
Caesar shift
An encryption method where each letter is replaced "n" letters away in the alphabet
32
What is client server model and uses of the 2 devices used
There is a client computer and a server. The server waits for a request, performs any processing required, then the request data is sent to the client. The client is a device that requests this resource, waits for a reply and receives the resource/reply.
33
5 servers and what they do
File server Holds all data files and databases and manages data backups Print server Organises printing on different printers Email server: Manages emails (Ie: receives, blocks, sends emails) Web server May host the schools website Database server May hold student records
34
Adv and dis of client server model
Advantages: With file servers, just one file server needs to be backed up and can be accessed by many computers Email servers provide a central place for emails which is then accessed by many devices One print server can manage all files being printed which allows one printer to print from many computers Disadvantages: If the server is down then all the data cannot be retrieved. Same goes for security
35
P2P network and features
Peer to Peer network is basically a mesh structure Features: Suitable for smaller companies with fewer computers No central server controls files/security All computers can see files on all other computers all computers can communicate with each other without going through a server
36
P2P adv and dis
Advantages: Easier to set up No need for dedicated server equipment individual computers can share different hardware (eg: printer) Users can communicate with each other and share each others files Disadvantages: Viruses/malware is easily transferred over as there is no central firewall Each computer has to backup their own data Files aren't stored centrally so its harder to access a specific file from another PC If a PC is switched off, data from there cannot be retrieved
37
What is hosting
Service offered by web pages which will host web pages/files for websites They will often provide database servers Companies which provide more general hosting (ie: Backup servers) are known as hosting service providers
38
What is the cloud
A term used to refer to services delivered across the internet. They can sometimes give (SaaS) Software as a service. It is typically used on a subscription basis and doesn't need to be installed on a local machine
39
Adv and dis of cloud
Advantages: You can access data anywhere at any time You dont need a powerful storage computer You dont need to back up data Disadvantages: Personal data is stored elsewhere You need internet to access data Slow internet = slow connection Sometimes the provider can't back up the data properly due to some issue.
40
Adv and dis of copper cables
Advantages: Tried and trusted tech Relatively inexpensive Disadvantages: Signal affected by magnetic fields and electricity low bandwidth heavy cables
41
Adv and dis of fibre optics
Advantages: Fast data transmission Low loss of signal over distance Not affected by electricity or magnetic fields Disadvantages: High investment cost Need for expensive equipment
42
Adv and dis of wireless transmisson
Advantages: No need for Trailing Wires (safer) Allows devices to be used anywhere (if there's a signal) easier to add devices to a network Disadvantages: Data transmission rate less than wired systems Signals can be blocked by objects/walls increased security issues
43
What is transmssion media
The way you connect computers
44
4 things sffecting network performance
Bandwidth - Amount of data that can be carried through a connection at a time Latency - Length of time a packet takes to travel through the network Error rate/collisions Num of devices connected
45
What is HTTP(S) protocol
Hyper text transfer protocol is used for accessing and receiving web pages in the form of HTML HTTPS encrypts the data so that it cannot be understood if hacked
46
What is the use of FTP
File Transfer Protocol is used for sending/receiving files to or from a remote server/computer
47
What is POP3 and IMAP used for
They are both used to transfer an email from a server to a computer POP3 will download the whole email and send it off to you IMAP will only download the message header onto your computer and just leave the rest on the server until opened
48
What is SMTP used for
Simple Mail Transfer Protocol is an email protocol used for transferring emails between remote email servers
49
What is the TCP/IP protocol
Transmission control protocol: Breaks up data into packets reassembles packets Detects errors Resends packets IP Protocol: Routes the packets
50
What is in the TCP/IP protocol stack and purpose
Application Layer Selects the correct protocol (ie: FTP, SMTP...) to use depending on which application and what you're trying to do Transport Layer Creates connection between 2 computers/hosts Hosts agree on the communication settings and the size of packets sent/received Network Layer Routers operate here and transport the packets Link Layer Physical hardware which connects the 2 hosts (ie: NIC and cabling)
51
Adv of layers
Layers are self contained You can edit one layer without affecting the others Different hardware can work together if they're on different layers Ie: One guys router on network layer can work with another guys NIC on link layer

CS GCSE (7 decks)

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