TCP/IP Protocol (Packet Layers)

When data is being transmitted through a network the following process is used (TCP/IP):

Application Layer - This is the top layer of TCP/IP protocol suite. This layer includes applications or processes that use transport layer protocols to deliver the data to destination computers. Each different piece of software uses a different protocol so the correct one is selected. 

 The most common types of protocol used are: 
  • HTTP (Hypertext transfer protocol)
  • FTP (File transfer protocol)
  • SMTP (Simple mail transfer protocol)
Transport Layer - divides the data (coming from the application layer) into proper sized chunks and then passes these chunks onto the network (packets). It acknowledges received packets, waits for the acknowledgments of the packets it sent and sets timeout to resend the packets if acknowledgements are not received in time. The term ‘reliable connection’ is used where it is not desired to loose any information that is being transferred over the network through this connection.

Network Layer - This layer is also known as Internet layer. The main purpose of this layer is to organise or handle the movement of data on network. IP addresses of the sender and recipient are assigned at this stage so we now where the data/requests have come from/where they are going. 

Data Link Layer - This layer is also known as network interface layer. This layer normally consists of device drivers in the OS and the network interface card attached to the system. Both the device drivers and the network interface card take care of the communication details with the media being used to transfer the data over the network (is it wired or wireless). MAC addresses are assigned to the packet so we know specifically which device that data/request has come from. 

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