Abstract definition:

A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

Let’s break it down with an analogy.

Example 1: Protocols Applied in Human Interaction - Water Cooler

Protocols are quite common.

In Australia, the Monday morning water-cooling protocol is as follows:

Colleague: How’s it going?

Boss: Good. You?

Colleague: Did you watch the footy?

Boss: Yes. How good were the Hawks?

Colleague: Very good. Smashed the Dees.

Boss: Get back to work.

Colleague: Yessir.

Boss: Good bye.

This is a standard protocol.

Note: there is an introduction, then an exchange of information. Questions, then answers. Then finally, a termination.

Example 2: Protocols Applied in Human Interaction - The Nerd Dating Protocol

Boy: Hi. My name is –

Girl: Bye

A very simple one.

This example is analogous to a protocol - the TCP protocol: there was a TCP connection request, and the connection response was brutally rebuffed. There are may others.

So why do we need protocols?

We need protocols - rules in order to: (i) communicate, and (ii) do so effectively.

You use them everyday without realising: it applies in everything e.g. when we send letters: we need to write the address on an envelope - the address must be agreed upon, as must the language, as well as the written characters. We pack a certain amount content in a letter. We might even ask if the address is deliverable.

Protocols when computers communicate with each other applies in much the same way it applies to human beings.