Internet/E-commerce- Transmission Control Protocol/ Internet Protocol (TCP/IP) Reference Models

The TCP/IP reference model is the network model used in the current Internet architecture [19]. It has its origins back in the 1960's with the grandfather of the Internet, the ARPANET. This was a research network sponsored by the Department of Defense in the United States. The following were seen as major design goals:

• ability to connect multiple networks together seamlessly
• ability for connections to remain intact as long as the source and destination machines were functioning
• to be built on flexible architecture

The reference model was named after two of its main protocols, TCP (Transmission Control Protocol) [12] and IP (Internet Protocol).
They choose to build a packet-switched network based on a connectionless internetwork layer.
  
Figure 2.1:  TCP/IP Network Protocol

A detailed description of the reference model is beyond the scope of this document and project. The basic idea of the networking system is to allow one application on a host computer to talk to another application on a different host computer.
The application forms its request, then passes the packet down to the lower layers, which add their own control information, either a header or a footer, onto the packet. Finally the packet reaches the physical layer and is transmitted through the cable onto the destination host. The packet then travels up through the different layers, with each layer reading, deciphering, and removing the header or footer that was attached by its counterpart on the originating computer. Finally the packet arrives at the application it was destined for. Even though technically each layer communicates with the layer above or below it, the process can be viewed as one layer talking to its partner on the host

Source: www.csn.ul.ie