Why we need protocols in data communication ?
 

Review:

  • A bus protocol consists of a rigid set of steps that communicating devices must follow to complete a data transfer operation successfully
 

But why do we need follow the the steps rigidly ??

I will illustrate with a cooking example....

Illustrating a protocol using a real life task
 

Steps to fry an egg successfully:

  1. Turning on the stove
  2. Putting a pan on the stove
  3. Poor oil in the pan
  4. Break the egg and put it in the pan
  5. Wait until the egg is cooked
  6. Remove the egg and turn off the stove

To fry an egg successfully, these steps must be followed in the specified order !!!

You cannot do: (1) put the egg in, (2) fry it and (3) then poor the oil - the eggs won't fry correct (it will burn !!!)
Human have the common sense to understand that without oil, the egg will burn. But the computer does not have common sense !!!)

Notice this fact in the protocol
 

Steps to fry an egg successfully:

  1. Turning on the stove
  2. Putting a pan on the stove
  3. Poor oil in the pan
  4. Break the egg and put it in the pan
  5. Wait until the egg is cooked
  6. Remove the egg and turn off the stove
 

The protocol will need to use a signal to indicate a READY/NOT READY state !!!