TRANSPORT LAYER

This is the fourth layer of the OSI Model. I like to call it the heart of the OSI Model. This is where much attention is required.

It is responsible for the transmission of data segments between points on a network, including segmentation, acknowledgment and multiplexing. It provides a reliable means of transferring data of variable length from one host to another across a network, while every other functionality is not affected. This protocol can be connection-oriented or connectionless. Most times, this usually requires the breaking down of data into segments (smaller lengths), because the network layer has a maximum number of data lengths it accepts.

The most common protocol used in this layer of the Internet originated in the development of TCP/IP. The best-known transport protocol of the Internet protocol suite is the Transmission Control Protocol (TCP), it is used for connection-oriented transmissions, whereas the connectionless User Datagram Protocol (UDP) is used for simpler messaging transmissions. The TCP is a more complex protocol, due to its design incorporating reliable transmission and data stream services.

A few functions of the Transport Layer are:

• Connection-Oriented Communication

• Reliability

• Flow Control: This is to improve efficiency and the rate of data transmission between nodes.

• Multiplexing, etc.

The transport layer is said to be responsible for delivering data to the appropriate application process on the host computer. With a source and the destination IP address, the port numbers are set to constitute an identification address of the process-to-process communication.

Below are some lists of protocols that are in the Transport Layer;

• NORM, NACK-Oriented Reliable Multicast

• RDP, Reliable Data Protocol

• RUDP, Reliable User Datagram Protocol

• SCTP, Stream Control Transmission Protocol

• SPX, Sequenced Packet Exchange

• SST, Structured Stream Transport

• TCP, Transmission Control Protocol

• UDP, User Datagram Protocol, etc.