November 27th, 2007

monkey pirate


I'm walking across a parking lot coming back from 7-11 with a cup of coffee. Another person ( drmanhatten for the record) was walking past me. I call out "Hey man. What's up?" he says, "Not much, you?"

The triviality of this exchange knocked around in my head for a little while. I have this exchange or a variation on that theme, at least a dozen times a day. One offers greetings. The other queries, re: wellness. Obligatory mild response - incident forgotten. Why do we do this?

And then it hit me. ARP/RARP packets.

When your computer establishes a network connection, whether it's for email, web, chat - whatever - the first thing it does is send out a packet that says, "you there?" and the intended recipient says, "I'm here, who're you?". Your computer replies. A transaction occurs. The connection terminates, usually with a "you done?" "Yep." This is what happens for a temporary connection.

But sometimes you have to keep a more lasting connection going - like when you log on to your PC. Chances are good you've got a cable or DSL modem hooked up to an internal router. At least, I do. When I log on, my computer has already established a previous relationship with the router. So it says, "Still there, bud?" the router replies. "You know it!" and they resume their prior acquaintance. This is a stateful connection - and even though the same process of query and identification occurs at first, it will also periodically renew, just to be sure the other partner in the connection hasn't dropped off.

That's what those little "How are you?", "Good, good." conversations are. Just checkin' in. Doesn't mean much - just wanted to know you're still there.
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