1.3.3 - Networks

Question 1

What is a protocol?

Answer 1

A set of rules defining common methods of data communication.

Question 2

What is TCP/IP and what is its purpose?

Answer 2

Transmision Control Protocol/Internet protocol
Set of networking protocols that work together as four connected layers, passing incoming and outgoing data packets up and down the layers during network communication.

Question 3

What are the four layers of the TCP/IP stack

Answer 3

Application layer
Transport layer
Internet layer
Link layer

Question 4

Explain the application layer

Answer 4

The application layer sits at the top of the stack
Selects and uses protocols relating to the application transmitting data over a network, usually the internet.
If the application is a browser, for example, it would select an appropriate higher-level protocol for the communication such as HTTP, FTP or POP3.

Question 5

Explain the transport layer

Answer 5

Uses the transmission control protocol to establish an end-to-end connection with the recipient computer.
The data is then split into packets and labelled with the packet number, the total number of packets and the port number through which the packet should route.
This ensures its handled by the correct application on recipient computer - port 80 is usually used by HTTP.

Question 6

Explain the internet layer

Answer 6

Adds the source and destination IP addresses.
Routers operate on the network level and will use these IP addresses to foward the packets on to the destination.
The addition of an IP address to a port number forms a socket.

Question 7

Explain the link layer

Answer 7

Physical connection between network nodes
Adds the unique Media Access Control (MAC) addresses indentifying the Network Interface Cards (NIC) of the source and destination computers.
This means that once the packet finds the right network using the IP addresses, it can then locate the correct hardware.
The MAC address varies as it always points to the next address the packet is to be sent to. EG this could be a router to start off with.

Question 8

Explain the TCP/IP process when recieiving the transmitted data.

Answer 8

1. MAC address is stripped off by the link layer
2. IP addresses are then removed by the internet layer
3. Port numbers are removed and the packets are reassembled into the correct order by the transport layer.
4. Resulting data is then presented to the user by the application.