David Miller wrote:

From: Rick Jones <redacted>
Date: Wed, 29 Aug 2007 16:06:27 -0700

quoted

I belive the biggest component comes from link-layer retransmissions. 
There can also be some short outtages thanks to signal blocking, 
tunnels, people with big hats and whatnot that the link-layer 
retransmissions are trying to address.  The three seconds seems to be a 
value that gives the certainty that 99 times out of 10 the segment was 
indeed lost.

The trace I've been sent shows clean RTTs ranging from ~200 milliseconds 
to ~7000 milliseconds.

Thanks for the info.

It's pretty easy to generate examples where we might have some sockets
talking over interfaces on such a network and others which are not.
Therefore, if we do this, a per-route metric is probably the best bet.

This is exactly what I was thinking.  It might even help discourage 
users from playing with this setting who should not. ;)

   -John