A protocol architecture is the layered structure of hardware and software that supports the exchange of data between systems and supports distributed applications,such as electronic mail and file transfer.
At each layer of a protocol architecture, one or more common protocols are implemented in communicating systems. Each protocol provides a set of rules for the exchange of data between systems.
The most widely used protocol architecture is the TCP/IP protocol suite, which consists of the following layers: physical, network access, internet, transport, and application. Another important protocol architecture is the seven-layer OSI model.
...
The application layer contains the logic needed to support the various user applications. For each different type of application, such as file transfer, a separate module is needed that is peculiar to that application
The physical layer covers the physical interface between a data transmission device (e.g., workstation, computer) and a transmission medium or network.
The network access layer is concerned with the exchange of data between an end system (server, workstation, etc.) and the network to which it is attached. The sending computer must provide the network with the address of the destination computer, so that the network may route the data to the appropriate destination. Standards : circuit switching, packet switching (ex. frame relay), LANs (ex. Ethernet), etc… It is concerned with access to and routing data across a network for two end systems attached to the same network. In this cas, we need procedures (Internet Layer plays that role).
The Internet Protocol (IP) is used at the Internet layer to provide the routing function across multiple networks. This protocol is implemented not only in the end systems but also in routers (processor that connects two networks and whose primary function is to relay data from one network to the other on its route from the source to the destination end system).
The host-to-host layer, or transport layer is the mechanisms for providing reliability, mechanism shared by all applications : TCP (Transmission Control Protocol) is the most commonly used protocol to provide this functionality.