What is Transport layer and its use in OSI Model? What are protocols of Transport layer?

Transport Layer : Process to Process delievery of data is done by transport layer .

=> Transport Layer has two major protocols  : TCP and UDP .

=> Which Transport layer protocol will be used either tcp or udp depends upon Application layer protocol.

example : Telnet , Ssh , Ftp , Http , Https these are applications layer protocols which will use TCP at Transport Layer.

==> Transport layer is responsible for providing Reliablity to application layer protocols.

TCP ( Transmission Control Protocol ) :

1. Connection Oriented Protocol    1.1 . Establish a virtual connection - using TCP THREE WAY HANDSHAKE.

                                                  1.2. Data transfer.

                                                  1.3. Terminate the connection

2. Reliable  : get acknowledgment for every message it sends.

3. Provides Error Correction and Error Detection.

4. Sequencing and Recovery  : Using Sequence number and Acknowledgment number .

UDP ( User Datagram Protocol ) : 

1. Connection Less- Protocol  - Direct Data Transfer.

2. Unreliable  : Doesn't provide acknowledgment.

3. Provides Error Detection.

4. No Lost Data Recovery.