TCP/IP Reference Model


The application layer: This is the layer at which communication partners are identified — Is there someone to talk to? 
Network capacity is assessed — Will the network let me talk to them right now? 
And where the data or application is presented in a visual form the user can understand. 

The transport layer: This layer manages packetization of data, then the delivery of the packets, including checking for errors in the data once it arrives. On the internet, TCP and UDP provide these services for most applications as well.

Network Access Layer: This layer corresponds to the combination of Data Link Layer and Physical Layer of the OSI model. It looks out for hardware addressing and the protocols present in this layer allows for the physical transmission of data.
Internet Layer: This layer parallels the functions of OSI’s Network layer. It defines the protocols which are responsible for logical transmission of data over the entire network.