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Computer Science Ongoing Flashcards > Set 3 > Flashcards

Set 3 Flashcards

1
Q

What is the Internet?

A

The worldwide collection of networks that use the Internet Protocol Suite (TCP/IP)

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2
Q

What is a router?

A

A device that receives packets on a network and forwards them to correct destinations based on an IP address

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3
Q

What is a gateway?

A
  • A device that receives packets on a network and forwards them to correct destinations based on an IP address
  • A gateway is able to deal with packets travelling between networks using different protocols, by stripping off all of the header data and adding a new header in the format needed for the destination network
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4
Q

What is a domain name server?

A

A server that contains databases of IP addresses and their corresponding FQDNs.

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5
Q

What is an IP address?

A

An IP address uniquely identifies a device on a network, and defines where it is located geographically.

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6
Q

What is the link between a Domain Name and an IP address?

A

A domain name is a string that corresponds to an IP address.

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7
Q

What is a packet and what are the main components of a packet?

A
  • A packet is what data being transported across a network is split into.
  • A packet is made up of the header and the payload.
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8
Q

What is an NIC?

A
  • A hardware component that connects to the motherboard and is hardwired with a unique MAC address
  • It allows a computer to connect to a network
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9
Q

What are the steps in packet switching?

A
  1. Data is split into packets.
  2. Header is added to packet
  3. Packets are sent along the network, not necessarily along the same route
  4. Once packets arrived, they are re-ordered using their sequence number
  5. Acknowledgements sent from recipient to sender for each packet
  6. Transmission of a packet happens again if no acknowledgement is received
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10
Q

What does TCP/IP stand for?

A

Transmission Control Protocol / Internet Protocol

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11
Q

What are the four layers of the TCP/IP protocol stack?

A
  1. Application Layer
  2. Transport Layer
  3. Network Layer
  4. Link layer
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12
Q

What does the transport layer do?

A

The transport layer establishes end to end communication
The destination and source application level client (or server) is identified by the port numbers
The TCP layer uses these port numbers to route reassembled requests (or responses) to the correct application layer
client (or server)
The TCP layer splits and reassembles requests (or responses) into packets
Packets are numbered by transport layer
The transport layer deals with error control i.e. acknowledgements and retransmission

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13
Q

What does the application layer do?

A
  • It uses an appropriate protocol relating to whatever application is being used to transmit data
  • It also interacts with the user via appropriate application software or the users system
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14
Q

What is the transport layer responsible for?

A
  • establishing the “end-to-end” connection
  • splitting the data into packets once the connection is made
  • sends and receives acknowledgments
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15
Q

What does transport layer add to each packet?

A
  1. The sequence number
  2. The total number of packets
  3. The port number the packet should use
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16
Q

What protocol does network layer use?

A

IP (Internet Protocol)

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17
Q

What protocol does transport layer use?

A

TCP (Transmission Control Protocol)

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18
Q

What is a MAC address?

A

A unique 12-digit hexadecimal address hardcoded on each NIC for use as an address in network communications to uniquely identify any device.

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19
Q

What does the link layer do?

A
  • Adds the MAC addresses of the source and destination device
  • The MAC addresses are changed at each hop on the route
  • It moves packets between 2 internet hosts
  • It deals with physical connections (and cabling)
  • It includes network card (and drivers)
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20
Q

What is a socket?

A

A socket is the IP address (provided by the IP protocol) combined with the port (provided by the TCP protocol)

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21
Q

What is a port?

A

The port determines what application on the device needs the packet

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22
Q

How does SSH work?

A

SSH uses for port 22. It uses public key encryption to authenticate the user and prevent unauthorised access.

  1. The client initiates the TCP connection by contacting the server
  2. The server sends a public key to the client
  3. The server and client agree communication rules and open a secure channel
  4. The user can now login to the remote server host operating system and can issue application layer commands such as GET for HTTP, and SMTP and POP3 commands for sending and retrieving emails
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23
Q

How does SMTP work?

A

SMTP sends the email from the client device to the linked mail server or forwards the email to the recipient’s mail server.

24
Q

How does POP3 work?

A
  1. Retrieves email from a mail server
  2. Removes it from the server
  3. Transfers it to your device
25
Q

How does HTTPS work?

A

HTTPS uses encryption to secure the data being transferred, and authenticates the web server through certificates.

26
Q

How does HTTP work?

A

The web client sends a request message to a web server and the web server sends back a response message containing the data needed to display the webpage (or other web resource).

27
Q

How does FTP work?

A
  • FTP commands can be issued from a command line interface, but more commonly a user interacts with an FTP client, which sits on top of the actual FTP protocol.
  • Once logged in, the user can access directories on the FTP server and can download and upload files.
  • FTP sites which are publicly available are known as anonymous FTP.
28
Q

What does SMTP stand for and what is its purpose?

A
  • Simple Mail Transfer Protocol
  • Used to send emails from client device to the linked mail server or to forward the email to the recipient’s mail server
29
Q

What does SSH stand for and what is its purpose?

A
  • Secure Shell
  • Used to provide an encrypted connection for remote access to another computer
30
Q

What does POP3 stand for and what is its purpose?

A
  • Post Office Protocol (v3)
  • Used to retrieve emails from an email server.
31
Q

What does HTTPS stand for and what is its purpose?

A
  • Hypertext Transfer Protocol Secure
  • HTTPS is used for accessing a webpage from a web server securely. HTTPS encrypts data between the client and server.
32
Q

What does HTTP stand for and what is its purpose?

A
  • Hypertext Transfer Protocol
  • HTTP is used for accessing a webpage from a web server
33
Q

What does FTP stand for and what is its purpose?

A
  • File Transfer Protocol
  • Used to move files between two devices. (commonly used to transfer data and programs as opposed viewable content)
34
Q

What is a URL?

A
  • A Uniform Resource Locator (URL) is the address of a webpage or other internet resource
  • It indicates the location of a resource as well as the protocol used to access it.
35
Q

‘www.w3schools.com’ is an example of a…

A

Fully qualified domain name

36
Q

‘www’ is an example of a…

A

Host name or subdomain

37
Q

‘w3schools.com’ is an example of a…

A

Domain name

38
Q

‘/cs/cs_operators.asp’ is an example of a…

A

Path

39
Q

What is the purpose of a domain name?

A
  • A domain name identifies an organisation or individual on the internet.
  • They use alphanumeric characters which make them easier for humans to remember than IP addresses
40
Q

What is the purpose of a domain name server?

A

To translate a fully qualified domain name into its corresponding IP address

41
Q

What is the domain name system?

A
  • The domain name system is a distributed database of mappings from FQDNs to their corresponding IP addresses
  • DNS servers are organised into a hierarchy
42
Q

What is the operating system?

A

A collection of programs that control the operation of computer hardware and provide an interface between the user and the computer

43
Q

What are the main roles of the OS?

A
  1. To hide the complexities of the hardware from the user
  2. To manage the resources which processes compete for (NB to get marks here you need to state WHICH resources).

Give a concrete example, e.g. “To allocate I/O devices to processes”

44
Q

How does the OS hide the complexities of the hardware from the user?

A

By presenting the user with a virtual machine to interact with.
e.g.
- Graphical User Interfaces (GUIs)
- Command Line Interfaces (CLIs)
- Application Programing Interfaces (APIs)

45
Q

What is a virtual machine?

A

A virtual machine is the apparent machine or interface that the OS presents to the user

46
Q

What is an API (in the context of the operating system)?

A
  • An application programming interface
  • APIs are layers of software that allow the application programmers use the functions the OS provides
47
Q

What is a process?

A

A process is an instance of a program being executed

48
Q

What resources does a process compete for?

A
  • (Secondary) Storage
  • I/O Devices
  • Memory
  • Processor time
49
Q

How does the OS manage storage?

A
  • Allocating space on storage devices to files
  • Organising files into directories
  • Determining where on the device to save a file
  • Manages which process/user can access (read/write/modify) different files and directories
50
Q

How does the OS manage I/O devices?

A
  • By allocating I/O devices to different processes
  • And managing communication between the processes and devices
51
Q

How does the OS manage memory?

A

By allocating different parts of main memory for all the processes. (Locations may not be contiguous)

52
Q

How does the OS manage processors?

A

By allocating processor time to each of the processes (aka processor scheduling)

53
Q

Simplify A . (A+B)

A

A
(can be a useful shortcut)

54
Q

How does routing work?

A
  • Routers are organised into a hierarchy
  • The path to take is selected by each router, determined by the Network ID of the destination IP address
  • Each router decrements the “time to live” of the packets
  • Source and destination MAC addresses changed at each hop
  • Network Address Translation will occur at routers at either end
55
Q

What is the difference between Physical vs Logical topology?

A

Physical: The physical layout of the connections between computers on the network

Logical: How the packets flow around a network

56
Q

What is a well known port number and why are they used?

A

Well known port numbers are reserved for common TCP/IP applications. They range from 0 to 1023.
When there is a client/server communication, they allow client applications to easily locate the corresponding server application processes on other hosts.

57
Q

When are port numbers selected from the dynamic range?

A

When there is a client/server communication, the client port numbers come from the dynamic range.

Computer Science Ongoing Flashcards (11 decks)

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