RE: [Nolug] Cox Connection Dropping - Packet Loss Topic

Hi Scott.

Making ICMP low priority doesn't create packet loss unless the router is
topped out or close to it. But I agree with you that as long as it passes
ICMP, even though it doesn't respond itself, this is good enough.

One of the nice features of some of the various combo ping/traceroute programs
is that they attempt to ping all the hops in a route in very quick succession.
This lets you see the effect of a busy router blocking pings to hops behind
it, even if it is sporadic. Note that it isn't the number of pings per hop
which is fast, but that when 1 hop is pinged all are (at nearly the same
time).

While the Cox article you mentioned is generally good, they are wrong in one
respect. No core router should ever be configured to block all ICMP. It's
bad enough tat many firewalls do this, but for a core router to do so would be
unforgivable!

John

    John Souvestre - Southern Star - (504) 888-3348 - www.sstar.com

As charles noted, It's really typical now for cable ISP's to make ICMP
very low priority at the CMTS. Which means pings and traceroutes appear
to have packet loss at the first hop. If you run ping plotter, a couple
of varying traceroutes, or mtr (http://freshmeat.net/projects/mtr/ ) the
symptom is seeing only loss at the first hop and not at subsequent hops.
   if you're seeing the loss across all links starting at the first hop,
then perhaps you've got signal problems or routing issues. The next
step would be to look at the CM stats page to see what the modem's
signal levels are and report them to Cox (or just send your CM MAC to
charles and he'll take a look)

This page (from a cox engineer) is informative
http://members.cox.net/coxengr/dslr_help/dslrtool_tools.html

-- 
Scott Harney <scotth@scottharney.com>
"Asking the wrong questions is the leading cause of wrong answers"
gpg key fingerprint=7125 0BD3 8EC4 08D7 321D CEE9 F024 7DA6 0BC7 94E5
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