Given a connectionless network absolute delivery is impossible (well, not completely, but just about...) Here is a theme I'm going to mention a few times today: the complexity class of probabilistic algorithms is the one that matters most for practical applications. Which is to say, that when you have a partially unreliable connectionless network, you can't, can not, can never _assure_ delivery. You can, however, set up the protocols so that the assurance in delivery is arbitrarily close to probability one, even though it can't ever actually reach it. Here's the fallacy which is common, that something which is probabilistically bounded but is not deterministically bounded is somehow flawed. Or, rather, you can trust expected values. Hal's random-send spool has an expected value of latency which is approximately the size of the spool but has no deterministic upper bound for that latency. Fine. Great. No problem. There should be zero hesitation here, because the expected value -- the probabilistic average -- is what you want. When you start off with probabilistic assumptions about the underlying reliability of the network, the best you can get is probabilistic answers. Even if the network components are deterministic, you still get probabilistic results. Adding probabilistic components also gives you probabilistic results. So what's the bid deal? The hesitation to accept a probabilistic measurement is still all-too-frequent. I will refrain from commenting on why I think that is, and merely admonish folks not to pull their punches and bewail a probabilistic result about device behavior. Eric