Date: Sat, 17 May 2003 10:55:24 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: brett@lariat.org Cc: net@FreeBSD.org Subject: Re: Ping results are sometimes wrong Message-ID: <200305171755.h4HHtOM7063475@gw.catspoiler.org> In-Reply-To: <200305171558.JAA16811@lariat.org>
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On 17 May, Brett Glass wrote: > Just noticed that FreeBSD's ping program was giving me inaccurate stats when > pinging hosts on the local subnet (but not on remote subnets). Some > investigation has revealed why: the delay for the very first ping includes the > time (if any) it takes to use ARP to discover the MAC address of the target. > This introduces an outlying data point that messes up the stats; it makes them > look as if there are extra delays or congestion on the network. > > Perhaps the program should make sure that the MAC address of the target (if > it's on the local network) has been resolved before starting to ping? You could have the same problem when pinging through a router that doesn't have the MAC address of the target, and ping doesn't have a way to check that. It would be simpler to just ignore the first sample when calculating the statistics.
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