Date: Wed, 4 Jun 2003 07:10:21 -0700 From: "Crist J. Clark" <crist.clark@attbi.com> To: "Giovanni P. Tirloni" <gpt@tirloni.org> Cc: freebsd-stable@freebsd.org Subject: Re: Very weird network behaviour with 4.7-RELEASE-p10 (large) Message-ID: <20030604141021.GA83754@blossom.cjclark.org> In-Reply-To: <20030601071255.GC123@pixies.tirloni.org> References: <20030601071255.GC123@pixies.tirloni.org>
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On Sun, Jun 01, 2003 at 04:12:55AM -0300, Giovanni P. Tirloni wrote:
> Hi,
>
> I have been doing some tests using hping2 and TCP SYN
> pings targeting local and remote hosts from two FreeBSD
> 4.7-RELEASE-p10 and one Linux 2.4.18 host.
>
> The three machines have the same hardware configuration
> and have been running for 6 months now. The average load
> isnt too high (usually 0.01 to 0.15) on the FreeBSD machines.
>
> Here is the output from hping2 (excuse me the line wrap),
>
> root:~# hping -S -p 80 -c 6 www.freebsd.org
> HPING www.freebsd.org (fxp0 216.136.204.117): S set, 40 headers + 0 data bytes
> len=46 ip=216.136.204.117 ttl=50 DF id=20997 sport=80 flags=SA seq=0 win=57344 rtt=212.6 ms
> len=46 ip=216.136.204.117 ttl=50 DF id=21140 sport=80 flags=SA seq=1 win=57344 rtt=212.3 ms
> len=46 ip=216.136.204.117 ttl=50 DF id=21301 sport=80 flags=SA seq=2 win=57344 rtt=212.3 ms
> DUP! len=46 ip=216.136.204.117 ttl=50 DF id=21494 sport=80 flags=SA seq=0 win=57344 rtt=3207.3 ms
> len=46 ip=216.136.204.117 ttl=50 DF id=21498 sport=80 flags=SA seq=3 win=57344 rtt=212.3 ms
> DUP! len=46 ip=216.136.204.117 ttl=50 DF id=21650 sport=80 flags=SA seq=1 win=57344 rtt=3209.4 ms
>
> --- www.freebsd.org hping statistic ---
> 5 packets tramitted, 6 packets received, -20% packet loss
> round-trip min/avg/max = 212.3/1211.0/3209.4 ms
[snip]
> Any help is welcome and sorry if this email doesn't have all the
> information needed to solve this problem. I'll be happy to provide
> more details and do more tests if needed.
Errr... What problem? The hping2 and tcpdump output all look
normal. You send a SYN to a remote host, it keeps sending SYN-ACKs
back trying to establish the connection. You get long "RTTs" due to
the time elapsed between the initial SYN and the continuing
responses. That RTT has nothing to do with how fast a packet crosses
the network.
--
Crist J. Clark | cjclark@alum.mit.edu
| cjclark@jhu.edu
http://people.freebsd.org/~cjc/ | cjc@freebsd.org
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