Subject: statistics on retransmitted packets
To: None <>
From: Laine Stump <>
List: netbsd-users
Date: 11/11/2000 17:24:05
Is there a simple way to get statistics out of IP about the percentage
of retransmitted TCP packets over a period of time? My cable line (RCN
in the Boston area) is getting progressively worse, with RTTs to the
next hop often > 500ms, ping lossage commonly above 50%, and frequent
total outages of several minutes, and the only thing RCN will do is
give me all sorts of incantations involving various combinations of 1)
shutting down my machine, 2) unplugging the coax and waiting for 1
minute, 3) unplugging the power to the cable modem and waiting for 1
minute, and 4) using *yet another* different NIC and/or machine. They
seem unwilling to admit any of: 1) other people are having the same
problem (I don't know, but I suspect so), 2) they have severely
overloaded their network, 3) the problem even warrants investigation
on their part.

I keep statistics on the RTT and loss percentage of pings sent from my
machine to their headend (the next hop in IP terms) (50 pings every 2
minutes), and can show them that the RTT and lossage both go up
considerably during times that you'd expect more people to be online,
but they insist that ping statistics are useless, as their routers are
configured to drop pings as soon as they get busy. They instead want
to hear whether or not I can "get to the web".

So, I want to have some data that is more difficult for them to
refute. If I could show what percentage of my TCP packets had
retransmitted packets, and what the average ack time was, maybe they'd
be more willing to listen. (Actually, probably not - they'll most
likely blame it on backbone congestion, and I'll end up cancelling RCN
service and going to something a bit less ridiculous anyway. But it's
worth a try...)

P.S. If anyone has any other tactics they've used in the past for
getting ISPs to recognize they have a problem, I'd appreciate hearing