ABSTRACT
Fundamental changes take place by changing the mode of communication from the well-known broadcast technique where the information bearing signal is modulated and sent out into open space and each receiver picks it and demodulates it for display to routing and multicasting. The changes involve not only discretizing the signal, but also assembling the information-carrying bits into packets and assigning headers to packets. Depending on the access techniques, different packets are formed. For example, an IP packet is an IP datagram that carries a TCP datagram. Similarly, an Ethernet packet has an IP datagram inside an Ethernet frame. In general, a datagram is the basic unit of data transfer in an IP environment.
