If you know what ARP is, you can see where this is going. It's not a subprotocol of IP, like TCP and UDP. For reference, take a look at Understanding the Internet Protocol Suite. I explained that ARP does not travel inside IP packets. At this point, it gets real weird. The induhvidual tells me that they must, otherwise 'how can they travel over the Internet'. I stated that they do not travel over the Internet. I then tried to explain to him, calmly mind you, what ARP does. He stops me mid-sentence and claims 'I know what ARP does, you don't have to tell me. I know all about ARP and what it does'. Fine, I say, then you know there is no need for it to travel over the Internet. But it does, he states, ARP is a protocol under IP, just like TCP.
I wanted to deck him. My blood pressure was rising, and my fists clenched. He didn't want to listen, he just wanted to insist. I said "Then, this is a pointless conversation." and I walked away. I'm still seething today...some people just piss me off.