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Date:      Thu, 17 Aug 2000 10:12:29 -0600 (MDT)
From:      Nate Williams <nate@yogotech.com>
To:        sthaug@nethelp.no
Cc:        dhw@whistle.com, achilov@granch.ru, Egon.Rath@lsr-ooe.gv.at, freebsd-security@FreeBSD.ORG
Subject:   Re: AW: deny incoming icmp
Message-ID:  <200008171612.KAA23225@nomad.yogotech.com>
In-Reply-To: <57904.966523813@verdi.nethelp.no>
References:  <200008171414.HAA02662@pau-amma.whistle.com> <57904.966523813@verdi.nethelp.no>

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> > >Traceroute uses ICMP types 0 (Echo Reply), 8 (Echo request) and 11 (TTL
> > >expired) to determine the route to the host.
> > 
> > That didn't seem quite right to me, so I looked (in
> > /usr/src/contrib/traceroute/traceroute.c); there is a rather large
> > comment block near the beginning of the file tagged
> > 
> >  *  -- Van Jacobson (van@ee.lbl.gov)
> >  *     Tue Dec 20 03:50:13 PST 1988
> > 
> > that explains how & why the program uses high-numbered UDP datagrams for
> > the probes.  It does rely on ICMP (time exceeded; ICMP type 11) for
> > receiving notification from a router, though.
> 
> The Microsoft implementation of traceroute uses ICMP instead of UDP
> though...

Not as far as I can tell, since it wouldn't work with my firewall if it
did.  However, I haven't done any explicit testing to see what exactly
it does.



Nate


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