Quick questions on Communication system functions and protocols in HSC Information Processes and Technology

At its simplest a communication system has a source that creates a message, a transmitter that encodes and sends it, a transmission medium that carries it, a receiver that decodes it, and a destination that uses it. Noise can interfere along the medium, which is why error detection matters. This model frames the transmitting and receiving information process: moving data from one place to another and arriving with it intact.

A protocol is a set of agreed rules that governs how two devices communicate. Because a sender and receiver may be built by different makers, they must agree on the format of the data, how it is addressed, the timing of signals, and how errors are handled. Without a shared protocol, devices cannot interpret each other's signals. Examples include HTTP for web pages, SMTP for email, and FTP for file transfer, each running over the underlying internet protocols.

Handshaking is the exchange of control signals that establishes and agrees the parameters of a connection before data is sent. The devices confirm they are ready, agree on speed and format, and acknowledge receipt. A familiar example is the exchange that sets up a connection between two devices before payload data flows. Handshaking ensures both ends are synchronised so data is not lost or misread.

Because communication involves many jobs, protocols are organised into layers, each handling one part and passing data to the layer below for sending or above for receiving. The OSI model describes seven such layers as a teaching framework; the TCP/IP model used on the internet groups them into four. IP handles addressing and routing of packets across networks; TCP handles reliable delivery, breaking data into packets, numbering them, and requesting retransmission of any that are lost. Layering means a change in one layer, for example a new physical medium, does not force a rewrite of the others.