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Computer science A level theory > Communication and internet technologies > Flashcards

Communication and internet technologies Flashcards

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1
Q

What is a protocol ?

A

It is a set of rules governing the transmission of data (communication) over a network

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2
Q

Why is a protocol used ?

A
  • It sets a standard for communication
  • It enables communication between devices from different platforms
  • If two devices were sending messages to each other but using different protocols, they would be unable to communicate properly
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3
Q

What are the four layers of the TCP/IP protocols and how does it work ?

A

APPLICATION LAYER
TRANSPORT LAYER
INTERNET LAYER
LINK NETWORK

When sending data, move downwards
When receiving data, move upwards

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4
Q

What is the TCP/IP protocol suite ?

A
  • It is a layered stack made up of 4 layers
  • It uses a set of protocols for the transmission of data
  • The layers are Application, Transport, Internet and Link
  • When sending data, move downwards
  • When receiving data, move upwards
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5
Q

What is the application layer ?

A
  • It contains all the programs that exchange data, e.g : - web browser
  • It sends files to the transport layer
  • It defines the protocols used
  • It handles the access to and provides user services
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6
Q

What are the protocols used in the application layer ?

A
  • HTTPS or HyperText Transfer Protocol
  • FTP or File Transfer Protocol
  • SMTP or Simple Mail Transfer Protocol
  • POP or Post Office Protocol
  • IMAP or Internet Message Access Protocol
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7
Q

What is HTTP(s) ?

A

HyperText Transfer Protocol, it is used for the transfer of web pages from the server to the client.

It is used by browsers to fetch web pages

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8
Q

What is FTP ?

A

File Transfer Protocol, it is used for interactive file transfer, it is used for the sending and receiving of files between two devices over a network.

It is used when downloading and uploading files over the internet

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9
Q

What is SMTP ?

A

Simple Mail Transfer Protocol, it is a protocol used for the sending of emails. It is a push protocol

It is used my mail servers to forward emails, it can only send text.

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10
Q

What is POP ?

A

Post Office Protocol, It is used for the receiving of emails. It is a pull protocol.

  • It is used by email clients to receive email messages from a mail server
  • The mail is held in the remote mail server until it is downloaded
  • It does not keep the server and client in sync, when an email is downloaded by the client it is deleted from the server
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11
Q

What is IMAP ?

A

Internet Message Access Protocol, It is used for the receiving of emails. It is a pull protocol

  • It is used by email clients to receive email messages from a mail server
  • It keeps the client and the server in sync, the original mail is still held in the server, only a copy is downloaded by the client.
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12
Q

What is the transport layer ?

A
  • The transport layer breaks the data down into manageable packets
  • It sequences the packets and adds a packet header to each one
  • It controls the flow of packets
  • It handles packet loss or corruption
  • It receives data from the application layer and sends data to the
    internet layer
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13
Q

What is TCP ?

A

Transmission Control Protocol, it is a protocol working at the Transport layer which sets up and maintains a connection between two nodes on the internet and ensures the delivery of data between them.

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14
Q

What is the internet layer ?

A
  • The internet layer identifies the intended network and host
  • It transmits the packets to the Link layer
  • It routes the packets independently and through the most optimum
    route
  • It addresses packets with their source and destination IP addresses
  • It then uses an IP address and port number to form a socket
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15
Q

What is IP ?

A

Internet Protocol, it is a protocol working at the Internet Layer which provides the rules for the exchange of packets over the internet. It decided the path for transmission of each packet.

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16
Q

What is the link layer ?

A
  • It converts the electrical data into analog signals and sends it, allowing the upper layers to access the physical medium
  • It formats the data into frames for transmission and maps IP addresses to MAC addresses
  • It ensures the correct network protocols are followed
  • It verifies the checksum when receiving a message and then sends it to the internet layer.
17
Q

Summary of TCP/IP

A

Application layer : - Handles access to services and defines protocols used

Transport layer : - Handles the forwarding of packets

Internet layer : - Handles the transmission of data using IP addresses

Link layer : - Handles how data is physically sent

18
Q

What is Ethernet ?

A

It is used to send/receive data along a cable for local area networks

19
Q

What is WiMAX ?

A

It is used to provide wireless broadband where there is no wired infrastructure.

20
Q

What is BitTorrent ?

A

It is a protocol used for peer-peer file sharing, it allows for the decentralized distribution of data.

21
Q

How does BitTorrent work ?

A
  • The BitTorrent client software is made available
  • A computer joins a swarm by using the software to load a torrent descriptor file
  • A server called a tracker records all the computers in the swarm and shares their IP addresses allowing the computers to connect to each other
  • At least one computer in the swarm must have a complete copy of the torrent to be shared
  • The torrent is split into small pieces
  • These pieces are downloaded and uploaded
  • Once a computer in the swarm has downloaded a piece or the whole file it becomes a seed and uploads it
  • Leeches download more data than they upload
22
Q

Hows does TCP/IP work from SENDERS side ?

A

Application layer : - Encodes the data in the appropriate format
Transport layer : - Breaks the data down into packets
Internet layer : - Adds the Source and destination IP to the header and adds checksum value
Link layer : - It formats the data into frames and maps IP addresses to MAC addresses. Converts the electrical data into analog data and sends it.

23
Q

How does TCP/IP work from the RECEIVERS side ?

A

Link layer : - Receives the packets and computes and verifies the checksum, removes the checksum from the packet header
Internet layer : - Reads the header and assembles the packet in the correct order
Transport layer : - Reads the header to determine the application protocol to be used. Removes the protocol from the header and sends it to the relevant application
Application layer : - Receives the message and performs the requested operation

24
Q

What is circuit switching ?

A

A dedicated circuit is established before transmission starts and it is released when transmission ends

The data is transferred using the same route and using the whole bandwidth of the circuit

It is implemented at the physical layer

25
Q

What are the pros and cons of circuit switching ?

A

Pros

  • Fast method of data transfer
  • Whole of the bandwidth is available
  • Data can’t get lost
  • Data arrives in the same order it was sent so reassembly is not
    required
  • Data is transmitted at a fixed data rate
  • It is a simple method of data transfer
  • Better for real-time data transfer
  • All data follows the same route

Cons

  • No one else can use the circuit even if it is idle
  • Less data security as it is easier to intercept since the same route is used
  • Not flexible
  • No alternative route in case of failure
  • The bandwidth can’t be shared
26
Q

When is circuit switching used ?

A

It is used where a dedicated path needs to be sustained throughout the communication and the whole bandwidth is required.

It is usually used where real time communication is used like video streaming

27
Q

Why is circuit switching used ?

A
  • A dedicated channel can use all the bandwidth to allow for two way real time communication
  • There is no delay as there is no switching and reassembly is not required
28
Q

What is packet switching ?

A
  • Data is broken down into a group of smaller chunks called packets, where each packet has a header and a payload.
  • The header will contain the source IP, destination IP and the sequence number.
  • Each packet will be sent independently and may travel along different paths.
  • The packets may arrive out of order and they are reassembled at the destination.
    -If any packets are missing or corrupted a re-transmission request is sent.

It is implemented at the internet layer

29
Q

What are the pros and cons of packet switching ?

A

Pros

  • It doesn’t use the whole bandwidth
  • Packets can take the least congested route
  • Packets can be rerouted if there are any problems
  • Transmission errors can be detected and packets can be resent
  • Better data security as packets are sent using different routes

Cons

  • Packets can be dropped/delayed
  • Time delays to correct errors and reassemble
  • Unsuitable for real-time transmission
  • Requires complex protocols
30
Q

When is packet switching used ?

A
  • It is used to send large data files which don’t need to be live
    streamed
  • It is used when the communication has to be secure
  • It is used for high volume data transmission
  • It is used when it isn’t necessary to use the whole bandwidth of the
    circuit

E.g : - Email, text messages and documents

31
Q

Why is packet switching used ?

A
  • It makes the best use of the available bandwidth by using alternative routes
  • It is more secure as packets use various routes
32
Q

What is the purpose of a packet header ?

A

It stores data about the packet and its routing to ensure that it reaching its destination and the message can be properly reconstructed

33
Q

What is the role of a router in packet switching ?

A
  • It examines the packet header
  • It reads the destination IP address
  • It accesses its routing table and decides the best route
  • Sends the packet on its next hop
34
Q

What items are stored in a packet header ?

A
  • Senders IP address
  • Destination IP address
  • Source port
  • Destination port
  • Checksum
  • Number of packets the message consists of
  • Packet ID
  • Packet length
  • Max number of hops
  • Protocol used
35
Q

What items are stored in the routing table ?

A
  • Network ID
  • IP address of network destination
  • Routing metric
  • Next hop

Computer science A level theory (4 decks)

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