OSI is a sevel layer conceptual model that is logically used to present the logical layers between which the data is going to travel. the below seven layers are described below, the data is sent from 1-7 from source machine while on client computer it travels from 7 to 1, the one in brackets.
Upper data layer:
it contains of three top layers of OSI:
1.(7) Application layer, the top layer that actually contains applications like telnet, http, DNS or any other layer that actually is responsible for starting the communication or with whom the user directly interacts.
2.(6) Presentation layer: this layer provides the context for the communication like the ASCII characters or the ASCII characters, and SSL comes here.
3.(5)Sessions layer; responsible for the creating the sessions between the computer, netbios and sap.
4.(4) transport layer: TCP and UDP resides here, this layer is responsible for the segmenting the data, end to end connection and reliability is a consideration along with flow control.
5.(3) network layer: the data is further broken into the packets. IPv4 and IPv6 work here. data is broken into packets. Routing and switching happens at this layer.
6.(2) Data link layer: Provides the connection between the two hosts that are in the same subnet, componenets like MAC address resides here.
7.(1) Physical layer: the layer where actual data is transmitted across. it includes all the cabling and other hardware stuff.