[BoppreH]

That's not a very useful definition of "in-band signaling". For me, the main difference is an out-of-band protocol that says:

"The first two bytes represent the string length, in big-endian, followed by that many bytes presenting the string text."

and an in-band signalling protocol:

"The string is ended by a period and a newline."

In the second one, you're indicating the end of the string from within the string. It looks simpler, but that's where accidents happen. Now you have to guarantee that the text never contains that control sequence, and you need an escaping method to represent the control sequence as part of the text.