As far as I know, protocols is just a rule for communications, but there's one thing that I don't understand. I have read about IPX protocol, so
it responsible for encapsulating packages into frames and send them to another layer, but if it just a rule, how the rules gonna do that? I don't get it.
Let's assume that protocols are like the law, if someone doesn't obey the law, he will get caught by police, not by law. So for the same reason, I think the one who encapsulates packages into frames is software or hardware, not the protocols. Is that correct?

 

Correct, if you want to get all legalistic.

When we talk about protocols, the context of the discussion determines if we are talking about the protocol in terms of what the specification states or whether we are talking about something that operates in accordance with that protocol (and that expects others to behave likewise).

 

A protocol is a standard/convention/rule.
The software/hardware implements the protocol.
If the transmitter/receiver does not obey the protocol the message received would be garbage.

 

So can I consider the protocols as a wall?
It only lets the things that have the same shape pass through. Is this idea correct?

 

It can also allow 'garbage' data to arrive if the proper protocol is not observed, an example is if the data TX/RX is asynchronous and the transmission rate is not identical, the result can be corrupted information recieved.
Max.

 

So can I consider the protocols as a wall?
It only lets the things that have the same shape pass through. Is this idea correct?

Huh????

A protocol is an agreed upon way of doing something. Don't make it harder than it is.

There are all kinds of protocols about all kinds of things. You have protocols that define the electrical signals to be used (for instance, RS-232 specifies that certain voltage level will be used to mean certain things while a 4-20 mA current loop protocol might specify current levels to indicate the same things) . You have protocols that define how information is to be encodes (for instance, ASCII is a protocol that was used for a long time to control teleprinters and is still widely used to exchange text information). You have TCP and IP protocols that specify how information is to be packaged in order to successfully send them over networks using those protocols. You have encryption protocols that aim to achieve information security goals by requiring that the sender and receiver do certain things.

Most communications activities involve simultaneously adhering to a number of different protocols. Some of these rely on everyone playing nice and following the rules (cooperative protocols) while others assume the existence of people that aren't going to follow the rules (adversarial protocols).

 

A protocol is an agreed upon convention.

Yes means yes and no means no.
Green means go and red means stop.

What happens if you twisted the rule or you received the wrong message?

 

As far as I know, protocols is just a rule for communications, but there's one thing that I don't understand. I have read about IPX protocol, so
it responsible for encapsulating packages into frames and send them to another layer, but if it just a rule, how the rules gonna do that? I don't get it.
Let's assume that protocols are like the law, if someone doesn't obey the law, he will get caught by police, not by law. So for the same reason, I think the one who encapsulates packages into frames is software or hardware, not the protocols. Is that correct?

Hello there,

I think you may be accidentally confusing the rules with the implementation. The rules are more general that allow for different implementations depending on various other factors that do not change the basic rules.

But really if you want to understand a given protocol like that you have to read up on it. You have to learn the rules and the structure and stuff like that. If you only know a little about it then it might not make much sense or you might create an implementation that does not work in every case.
For example, if you thought RS232 was only allowing 9600 baud then your system would not work with a system that was purely 14400 baud.