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Date:      Thu, 13 Jan 2005 12:02:52 -0500
From:      Chuck Swiger <cswiger@mac.com>
To:        Kevin Oberman <oberman@es.net>
Cc:        freebsd-net@freebsd.org
Subject:   Re: IPv6 TCP transfers are hanging
Message-ID:  <41E6A9BC.9000406@mac.com>
In-Reply-To: <20050113153018.D2B4B5D07@ptavv.es.net>
References:  <20050113153018.D2B4B5D07@ptavv.es.net>

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Kevin Oberman wrote:
> What I don't understand is how this is happening. tcp.mssdflt is set to
> 1400 bytes and tcp.v6mssdflt is only 1024. If PMTU discovery was
> working, this should not be a problem. If PMTU discovery is not used,
> the MSS defaults should keep the packets small enough to work over the
> tunnel.

Doesn't IPv6 require a minimum MTU of 1280 bytes?  Try setting the IPv6 TCP 
MSS to 1350 or so, bigger than IPv6 code requires, but small enough to fit 
into the ~1400+ byte MTU effectively available when you tunnel the traffic.

-- 
-Chuck



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