Comment by geocar

> Well, first light does 500 miles in 3ms, but the connect signal needs to come back, right? So it should be 250 miles, at most?

I don't think this is terribly important (NB my examples have nothing to do with networking), but in the author's case it was probably the other way; maybe 10msec and a bit more: Copper gets up to ~0.6c but I think this detail makes the story less amusing, and is a distraction from wondering why does select() take so long...

> I imagine there can be a large variation between physical installations and different types of hardware

There is probably not as much as you think, and Sendmail retries, so with whatever variation that exists, only the bounds really matter.

> Or am I missing something?

Modern unixish systems have the same log-scale delay coming out of select() so this has almost nothing to do with the hardware being slower or variability in the network.