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computer science > Networks > Flashcards

Networks Flashcards

Exchanging data

1
Q

What is protocol

A

A set of rules for communication between devices

They allow different devices to make sense of the data they receive and transmit.

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2
Q

What is meant by layering

A

The principle of dividing a complex problem into separate, independent sub-problems

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3
Q

How can packets travel across the internet

A

Each packet has layers of further data added to it

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4
Q

What are some of the features of layering

A
  • Allows for the creation and maintenance of parts of a system without having to take into account the whole system
  • Networks use layering with protocols
  • Protocols on each layer communicate only with the layers above and below.
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5
Q

What does the transmission control protocol/ Internet protocol (TCP/IP) stack consist of

A
  • Application layer
  • Transport layer
  • Internet layer
  • Link layer
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6
Q

What is the purpose of the application layer (TCP/IP stack)

A

It specifies what protocol needs to be used to relate the application that’s being sent.
- For example, if the application is a browser then it would select a protocol

Examples - HTTP, HTTPS, IMAP

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7
Q

What is the purpose of the transport layer (TCP/IP stack)

A

Establish an end-to-end connection
between the source and recipient computer.

Splits data up into packets and labels them with:
- packet number, the total number of packets the original data was split
up into and the port number being used for communication.

  • If any packets get lost, the transport layer requests retransmission of these
    lost packets.

Examples - TCP

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8
Q

What is the purpose of the network layer (TCP/IP stack)

A

Concerned with providing links across different network types.
- Adds the source and destination IP addresses (socket address)

(router operates at this level)

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9
Q

What is the purpose of the Link layer (TCP/IP stack)

A

Passes data to the physical network.
- connection between the network devices (adds the MAC address identifying the NIC of the source and destination computers )

Example - Wi-Fi, ethernet

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10
Q

How is a packet sent across a network

A

Encapsulating the data
- The packet is sent down the stack, starting with the application protocol, and each protocol adds its own additional necessary data.

Decapsulating the data
- Once the data has arrived at its destination it is passed back up the stack and each protocol removes relevant data

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11
Q

What is a URL

A

Uniform resource locator
- The main part of the website address e.g. hodder.co.uk

We use them because they are easier to remember than an IP address

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12
Q

What is the purpose of a domain name server (DNS)

A

Converts URLs to IP addresses
- The system uses a series of servers that act like address books, matching URLs to their IP addresses.

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13
Q

How does the DNS work
(long answer)

A
  • First, your computer checks the local cache to see if the IP address has previously been found
  • If it doesn’t have a copy of the IP address, it checks one of the root servers. (root servers are the highest level of servers in the DNS that hold the locations of all the top-level domain servers)
  • If the root server doesn’t have a copy it points to a server matching the top-level domain (TLD) such as .com, .uk or .org
  • These may point to the second-level domains (e.g. .co.uk)
  • finally comes the authoritative name server that holds the IP addresses of the server being sought. This is sent back to the browser so it can visit the site

Once the address is found, as it gets passed back to each server the address is cached so it can be found more quickly next time

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14
Q

What is a LAN

A

Local area network
- Networks over a small geographical area
- Their infrastructure is owned by the organisation that uses it, and the organisation is also responsible for its upkeep

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15
Q

What is a WAN

A

Wide area network
- Network over a large geographical area
- Consists of interconnected LANs
- The internet can be considered a WAN

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16
Q

What is circuit switching

A

A pathway for the data is set up in advance of communication and then the data is sent across it. The pathways are closed after transmission. (provides an exclusive dedicated channel)

Usually used for live broadcasts eg. a phone call

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17
Q

What are the three stages of circuit switching

A
  • connection established
  • data transferred
  • connection released
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18
Q

What is packet switching

A

Packages of data are sent across a network. They may take different routes and are reassembled by the receiver.

19
Q

What is a data packet

A

Data is broken down into chunks called packets when sent across a network.

20
Q

What does a data packet contain

A

Header
- Source address and Destination address
- Packet sequence number (the order of the packet in the sequence)
- Protocol (the type of protocol being used)

Payload
- The actual data being sent

Trailer
- Checksum (used for error checking )
- End packet maker (denotes the end of the packet)

21
Q

How does packet switching work

A
  • Packets are sent across a network by whichever routes are available or most efficient
  • They may arrive in a different order to which they are sent
  • The receiver uses the sequence number to reassemble them into the original message
22
Q

What is good about packet switching

A
  • It doesn’t tie up large chunks of the network, making it perform better for multiple users
  • It is also part of what makes the Internet reliable; if one route is unavailable, there is always others
    (redundancy boosting reliablilty)
23
Q

define hacking

A

The process of gaining unauthorised access to a computer system

24
Q

what is a firewall

A

Software that can inspect and block incoming and outgoing network data

25
Q

What is a proxy

A

A server that sits between a network and the internet, through which internet data requests are made

26
Q

How do firewalls work

A

usually hardware devices but can be implemented as software

  • Inspect data entering and leaving the network
  • Can block these packets according to a set of rules
  • Can be configured to restrict access to certain sites or file types
27
Q

What are the functions of a proxy

A
  • Catching
  • Logging and monitoring traffic
  • Security
  • Privacy
28
Q

Describe catching (functions of a proxy) LA

A
  • Once a proxy receives a request for a file or website from the internet, a copy is stored on a proxy
  • Every subsequent person who requests the same file can get their copy directly from the proxy

This is quicker for the users and keeps bandwidth being used on the internet connection
However, the file or website on the proxy might get out of date

29
Q

Describe logging and monitoring traffic (functions of a proxy )

A

A proxy can monitor data going into a network. They can keep logs of all traffic in and out

30
Q

Describe how a proxy provides security (functions of a proxy)

A

External users are unable to see or access devices inside the network - their only contact is with the proxy

31
Q

Describe does a proxy provides privacy (functions of proxy)

A

Proxies can be external to a network and used to fetch web pages

As far as the website is concerned, the request comes from the proxy and therefore it is the proxy’s IP address that is logged on the website, not the user’s.

32
Q

What is Encryption

A

The process of making data unreadable to a third party. It has to be decrypted to be read.

33
Q

What are the two ways encryption can be used on a network

A
  • Stored data can be encrypted
    So it cannot be read by anyone who may gain unauthorised access to a private network
  • During transmission
    This is crucial especially if transmission is taking place across public communication channels or using wireless tech.
34
Q

What is a client-server model

A

This is when high-end computers (one or sometimes many) act as servers that provide services to users or clients.

35
Q

Give 4 examples of services provided to a user (client-server)

A
  • File storage and access
  • Printing
  • Internet access
  • Security features such as logins and audit trails
36
Q

4 advantages of a client-server model

A
  • client computers don’t need to be powerful do can be cheaper
  • It makes it easier to make data and software accessible from anywhere in the network
  • Banks of servers can be combined to make best use of their potential
  • Separate functionality can be devolved to virtual servers or physical servers
37
Q

What is a virtual server

A

A server that exists as a virtual machine, rather than a physical device dedicated to the task

38
Q

What is a peer-to-peer network

A

When each computer on the network has an equal status

39
Q

3 advantages of a peer-to-peer network

A
  • Cheap way of implementing a network
  • Popular way on the internet to pass files between users without the need to go through servers
  • Useful way to make use of distributed computing to promote collaborative working
40
Q

What is distributed computing

A

A collection of computers working together on a single task

41
Q

What is the HTTP

A

Hypertext Transfer Protocol
- Used for web page rendering, an encrypted version
HTTS is also becoming common

42
Q

What is the TCP/IP

A

Transmission Control Protocol/ Internet protocol
- This is a networking protocol used in the routing of packets through networks

43
Q

What is the POP3 and IMAP

A

Post Office Protocol
Internet Message Access protocol
- Mailing protocols, used for email access

44
Q

What is the FTP

A

File transfer protocol
- Used for the transmission of files over networks

computer science (19 decks)

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