We have already hinted on the diversity of networking. Many different systems have to talk
to each other. And they have to speak the same language. They also have to understand the same language the same
People often think that body
language is universal. But it is not. Back in my early teens, my father took
me to Bulgaria. We were sitting at a table in a park in Sofia, when a vendor approached
us trying to sell us some roasted almonds.
I had not learned much Bulgarian by then, so, instead of saying no, I shook my head
from side to side, the ``universal'' body language for no. The vendor quickly started serving us some almonds.
I then remembered I had been told that in Bulgaria shaking your head sideways meant
yes. Quickly, I started nodding my
head up and down. The vendor noticed, took his almonds, and walked away. To an uninformed
observer, I did not change the body language: I continued using the language of shaking
and nodding my head. What changed was the meaning of the body language. At first, the vendor and I
interpreted the same language as having completely different meaning. I had to adjust my
own interpretation of that language so the vendor would understand.
It is the same with computers: The same symbols may have different, even outright
opposite meaning. Therefore, for two computers to understand each other, they must not
only agree on the same language,
but on the same interpretation of