OSI Model

Lets start with the basics, what is the OSI model and what does it do. OSI stands for Open Systems Interconnect and this model talks about how a network communicates and transmits data. OSI model constitutes of 7 layers - Physical, Data Link , Network, Transport, Session, Presentation and Application. Best way to remember this  - (P)lease (D)o (N)ot (T)hrow (S)tuffed (P)izza (A)way

Physical Layer ( layer 1 )- This provides the hardware for communication between devices. Ex - copper cable, optical cable, wireless 802.11N technology, patch panel.

Data Link Layer( layer 2 )- This is your link layer, provides a link between the connected devices. Ex - switch

Network Layer( layer 3 ) - This layer deals with the logical addressing ( IPv4, IPv6), determines best route for data transmission( static or dynamic routing) and fragmentation ( breaking the message into smaller pieces so it can fit into the frame)

Transport Layer( layer 4 )- This deals with reliable data transmission( TCP,UDP), flow control, sequencing( making sure all the packets are in the correct order) and segmentation ( segments the messages into smaller peices so as to suit the requirements of the network layer)

Session Layer ( layer 5 )- This layers opens up communication between devices to start data transmission

Presentation Layer ( layer 6 ) - In this layer ASCII data is converted into readable format at the destination port and vice verson on the source port

Application Layer ( layer 7) - This layer interacts with the applications. Ex - outlook, http, ftp

 Diagram to help understand : 

In short :)