Network

osi model

1  physical      Raw bit stream over physical medium
2  data link.    Defines the format of the data on the network.
3  network.      Desides which which physical path the data will take.
4  transport     Transmits data using transmission protocol. (tcp, udp...)
5  session       Maintain connection and is responsible for controlloing port and sessions.
6  presentation  how two devices should encode, encrypt, and compress.
7  application   User end applications.