A layer can offers two different types of services to the layer immediately above it – connection-oriented and connectionless service. In connection oriented service user establish a connection at first, communicates over the connection and at last release the connection. It is similar to a telephone system. In connectionless service no connection is established beforehand. Instead, like in a postal system, every message caries its full destination address and each routed independently to its destination,…"Connection-Oriented and Connectionless Service."