From owner-freebsd-stable  Fri Feb  1  7:30:13 2002
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Date: Fri, 01 Feb 2002 07:29:59 -0800
From: Michael Sierchio <kudzu@tenebras.com>
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To: Alexey Luckyanchikov <alexl@alkar.net>
Cc: freebsd-stable@freebsd.org, freebsd-net@freebsd.org
Subject: Re: Weird path MTU autodiscovery problem in 4.5-RELEASE
References: <20020201125326.GA3036@alkar.net>
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Alexey Luckyanchikov wrote:


> 14:06:48.477578 server.7 > client.1371: . 1437:2897(1460) ack 10001 win 65535 (DF) (ttl 64, id 25428, len 1500)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Server send packet with size 1500 bytes
> 
> 14:06:48.682558 router > server: icmp: client unreachable - need to frag (mtu 1476) for server.7 > client.1371: [|tcp] (DF) (ttl 61, id 25428, len 1500) (ttl 253, id 2491, len 56)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Router say to server that he must to decrease packet size
> 
> 14:07:04.477857 server.7 > client.1371: . 1437:2897(1460) ack 10001 win 65535 (DF) (ttl 64, id 52781, len 1500)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> But server ignore this information and still send 1500 bytes packets


What's the result of 'sysctl net.inet.tcp.path_mtu_discovery'  ??  Not that
I can imagine, at the moment, what would set it to 0....


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