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A Level AQA Computer Science > TCP/IP protocol > Flashcards

TCP/IP protocol Flashcards

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1
Q

What are the layers of the TCP/IP stack from top to bottom

A
  • application layer
  • transport layer
  • internet layer
  • link layer
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2
Q

Purpose of the application layer

A

Uses protocols designed to work with specific types of applications

E.g. web browser uses HTTP, email client uses SMTP, IMAP and POP3

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3
Q

What is the purpose of the transport layer

A

Breaks the application data down into segments(TCP) and datagrams(UDP)

Sequence numbers allocated, source and destination port numbers are added to header.

For TCP, delivery acknowledged and lost segments retransmitted

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4
Q

Purpose of the internet/network layer

A

Encapsulates segments from the transport layer to create IP Packets.
Source and destination IP addresses are added at this stage

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5
Q

Purpose of link layer

A
  • Responsible for transporting IP packets across each individual link that make up path between client and server
  • Further encapsulates IP packets in Ethernet frames
  • At this level, networking protocols are used
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6
Q

Names of data block produced by each layer

A

Application- application data (HTTP, SMTP)
transport - segments or datagrams
Internet - Packets
Link - Frames

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7
Q

What protocols does the transport layer use

A

Transmission control protocol and user datagram protocol

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8
Q

What does the TCP do

A
  • keeps track of each generated segment, assigning a sequence number
  • at receiving end, TCP keeps record of incoming sequence numbers & acknowledges each segment
  • if sender doesn’t receive an acknowledgement, segment is resent
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9
Q

What does the UDP do

A

Transfers data at a fast rate

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10
Q

Uses of TCP compared to uses UDP

A

TCP - when complete data is required (reliable)

UDP - when speed of data transfer is the most important criteria (unreliable)

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11
Q

What is a socket

A

A combination of an IP address and a port number.
Persists throughout duration of the connection

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12
Q

What is the max amount of connections a server can keep track of

A

65, 534 per host

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13
Q

What does the socket facilitate

A

Asynchronous communication, meaning only one device can communicate at a time

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14
Q

What are the well-known port numbers

A

Port - protocol - use
20 - FTP(Data) - file transfer
21 - FTP(Control) - file transfer
22 - SSH - Secure remote access
25 - SMTP - Mail transfer
80 - HTTP - Website access
110 - POP - Mailbox access
143 - IMAP - Mailbox access
443 - HTTPS - Secure website access

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15
Q

What is a MAC address

A

Unique to a specific NIC
Physically tied to hardware of computer often referred to as physical address

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16
Q

What does HTTP do

A

Requests web pages and linked resources from the web server

17
Q

How does HTTP operate

A

Through requests and responses:
- server waits and listens for requests
- client sends HTTP request for web page to server
- server receives the request
- server sends HTTP response which encapsulates requested page
- client receives response and displays web page in web browser

18
Q

What are the extra steps for the HTTP operation for dynamic pages

A
  • database may be accessed for up-to-date images and prices for online shopping
  • profile may be accessed for more personalised content
  • processing may happen on client-side
19
Q

What are the HTTP request methods

A

GET - request data from resource
POST - submit data, create new resource
PUT - update/replace an existing resource
DELETE - removes a resource from server
HEAD - requests just header of data from server

20
Q

What does HTTPS do

A

Encrypts data exchanged between client and server

21
Q

How does HTTPS work

A
  • Provides digital certificate containing public encryption key.
  • authenticity is checked automatically in browser through number of root certificates
  • your browser uses key to encrypt data
  • only the authorised server has corresponding private key to decrypt it
22
Q

What does the FTP do

A

Used to move files between 2 devices

23
Q

How does the FTP work

A

Client-server application:
- client device runs FTP client software, responsible for initiation of all connections
- another device runs the FTP server & has access to disk space to store the files

24
Q

What can a user do once logged into the FTP client software

A
  • access directories on FTP server & request list of files in directory
  • user can choose to download or upload file
25
Q

Examples where FTP can be used

A
  • create web pages on own computer and then upload files to web server
  • download software
  • download music file
  • upload video clips to be embedded in web-page
26
Q

What types of FTP are publicly available FTP sites

A

Anonymous FTP

27
Q

Role of a traditional email system

A

user connects to their email server and downloads any messages they may have received

28
Q

Role of a modern email system

A

Most modern systems use ‘push’ technology.
New emails are pushed to client as soon as they arrive on mail server
Is optional

29
Q

What protocols does an email system use for sending and retrieving

A

uses POP3 and IMAP for retrieval and SMTP for sending

30
Q

What does POP3 do

A

Downloads emails onto client and deletes them from server

31
Q

What does IMAP do

A

Creates a copy on the local client device and syncs any deletion on both client and server

32
Q

What is preferred between POP3 and IMAP

A

IMAP as it offers the ability to manage your emails on multiple devices

33
Q

What does SSH do

A

Provides an encrypted connection for remote access to another computer

34
Q

How does SSH work

A

Encrypts messages sent between SSH client and SSH server, providing a secure link through which users can communicate with a remote computer

35
Q

How can encrypting data via SSH be described

A
  • creates a secure tunnel over the internet
  • means that SSH can be used to securely tunnel other protocols over the internet.
  • SSH hides actual protocol its encrypted
  • network doesnt see destination address or nature of data, just SSH data destined for SSH server
36
Q

Common uses of SSH

A

Network admins who need to access remote devices to start & stop devices, perform software upgrades, etc.
Allows person to securely manage multiple computers from one place

37
Q

What must you have to connect to another computer using SSH

A
  • an account in the computer you’re trying to connect to
  • sufficient administrative tight to carry out some operations
38
Q

What are the 2 ways to sign into a remote computer via SSH

A
  1. Use command line of your OS, type commands you SSH in remote device
  2. Use a GUI based SSH client

A Level AQA Computer Science (8 decks)

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