7) The Application Layer:  – Closest layer to the end user. Receives information from users and displays incoming data to users.  – This layer does not include Applications themselves but it facilitates communications through lower layers in order to establish connections with applications at the other end.  – Applications will have access to network services from this layer. Web browsers, TelNet, and FTp are examples of communications that rely on layer 7.
6) The Presentation Layer:  – In this layer, Data encryption is carried out, and it will make sure that the data will be in the usable format.  – It represents the preparation or translation of application format to network format or vice versa.  – This layer presents data for the application or network
5) The Session Layer:  – It is used for controlling sessions and ports. When two computers or other network devices need to speak to one another, a session needs to be created and this is done at the Session Layer.  – Functions at this layer involve setup, coordination and termination between the applications.
4) The Transport Layer:  – It is Responsible for the end-to-end communication across the network. It makes use of UDP and TCP transmission protocols.  – It takes data transferred in the Session Layer and breaks it into segments at the transmitting end.  – It reassembles the segments on the receiving end, turning it back into data that can be used by the session layer  – It carries out flow control, sending data at rates that matches the connection speed of the receiving device, and error control, checking if data was received correctly and if not, requesting it again.
3) The Network Layer:  – The responsibility of the Network layer is to provide communication routes.  – This is where the router operates. A router forwards packets of information between computers on a network and it is where an IP address comes from.
2) The Data Link Layer:  – Determines the format of the data and is responsible for encoding and decoding the data.  – It establishes and terminates a connection between two physically-connected nodes on a network.  – It breaks packets into frames and sends them from source to destination.  – Has 2 parts: a. Logical Link Control (LLC) – identifies network protocols, performs error checking and synchronizes frames. b. Media Access Control (MAC) – uses MAC addresses to connect devices and define permissions to transmit and receive data.
1) The Physical Layer:  – It transfers the raw data by the communication medium.  – It is the electrical and physical representation of the system, e.g. cable type, radio frequency link (WiFi network), layout of pins, voltages, etc