THE TRANSPORT LAYER(PART 1)

Definition:-

The transport layer is the core of the Internet model. The application layer programs interact with each other using the services of the transport layer. Transport layer provides services to the application layer and takes services from the network layer.

Duties of Transport Layer:-

Transport layer is meant for the process to process delivery and it is achieved by performing a number of functions.

Following are the functions of transport layer:-

1. Packetizing:

• The transport layer creates packet out of the messages received from the application layer. Packetizing is a process if dividing a long message into smaller ones.
• These packets are then encapsulated into data field of the transport layer packet and headers are added .
• The length of the message which is to be divided can vary from several lines to several pages.

2. Connection Control:

• Transport layer protocols maybe divided into following two categories:
• Connection oriented delivery- A connection oriented transport layer protocol establishes a connection I.e. virtual path between sender and receiver. This is a virtual connection. The packet may travel out of order. The packets are numbered consecutively and communication is bidirectional.
• Connectionless delivery- A connectionless transport protocol will treat each packet independently. There is no connection between them. Each packet can take it’s own different route.

3. Addressing:-

• The client needs the address of the remote computer it wants to communicate with.
• Such a remote computer have a unique address so that it can be distinguished from the other computers.

4. Providing reliability:-

• For high reliability the flow of control and error control should be incorporated.
• Flow of control provided by transport layer and is used to perform end to end flow rather than across a single link.
• Error correction is generally achieved through retransmission.

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