The primary success for the internetworking technologies is performed by through OSI model. OSI it is not Protocol It is the reference model. OSI it contains seven layers
It is seventh layer. It is used for FTP, SMTP, Email, web browser application.
Example download a file from ftp site in the internet then highest layer in Ftp operation is Application Layer.
It is sixth layer. It is used for encryption and decryption purpose.
It is manage and terminate session between two communicative tools. Example client software.
It is fourth layer. These layer break up the date from sending host and then reassemble in the receiver. Transport Layer is responsible for ensuring reliable end to end delivery data. These layer associated with acknowledgement of transmission, sequencing and flow control.