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Date:      21 Apr 1999 11:26:09 +0200
From:      Julien Oster <sysadm@sysadm.cc>
To:        "Julian Stacey" <jhs@muc.de>
Cc:        garyj@fkr.dec.com, freebsd-isdn@FreeBSD.ORG, isdn-dev@hcs.de
Subject:   Re: Fritz!card PCI and sPPP
Message-ID:  <7jogki2uku.fsf@gandalf.midearth.fuzzys.org>
In-Reply-To: "Julian Stacey"'s message of "Wed, 21 Apr 1999 01:53:28 %2B0200"
References:  <199904202353.XAA03900@jhs.muc.de>

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>>>>> "Julian" == Julian Stacey <jhs@jhs.muc.de> writes:

    Julian> Reference:
    >> From: Gary Jennejohn <garyj@mofo.fkr.dec.com> Reply-to:
    >> garyj@fkr.dec.com Date: Tue, 20 Apr 1999 14:50:51 +0200 Message-id:
    >> <199904201250.MAA30165@mofo.fkr.dec.com>

    Julian> Hi, Gary Jennejohn wrote:

    >> > has anybody using the Fritz!Card PCI with sPPP observed strange
    >> behavior ?  > I mean, the connection is made OK and things like ping
    >> and nslookup work, > but other services like telnet, ftp, popclient,
    >> etc., do not.

    Julian> ping is ICMP, nslookup might be too (traceroute is I believe)
    Julian> (ans. in src/ of course) the rest I guess are all tcp/udp.  I used
    Julian> to suffer a problem on my HDLC (ipr0) ISP, till Gary diagnosed the
    Julian> ISP was limiting my max buffer size or some such, before that I
    Julian> recall similar phenomena)

ping is ICMP, right. Name Server lookups are mostly been done by UDP. The can
(sometimes) be made by TCP, but that is almost never done. traceroute _sends_
UDP packet and waits (_receives_) for ICMP Time to Live exceeded packets, so
it uses UDP and ICMP (but under BSD you may use any other protocol to send
than TCP, however, this does not always work)... so it seems like that TCP is
the only thing not working.

My guess: MTU/MRU are too high (especially MTU). Normally, that doesn't cause
TCP-Services to refuse working at all, but they may stall when receiving to
much data. But if the MTU/MRU is much too high, it could make it stop working
at all...

So try lowering the MTU and MRU, first to a value of 500 or such (better use
534, that's 20 bytes for the IP header and 512 bytes for the payload). If that 
works, then you have the problem. You can now experiment by raising the value
to things like 1600 and go down step by step until it works again (though 1600 
may also be fine... if it is, then you can try to even increase it, if you
desire that)... test it with large FTP file transfers. If they stall (and
won't come up again), MTU/MRU are too high.


[...]



-- 
  /--/ Julien Oster /---/ www.fuzzys.org <---> www.sysadm.cc /---/
 /--/ OpenBSD  2.5 /---/ Greetings  from  Munich,   Germany /---/
/--/ contact me : /---/ talk fuzzy@fuzzys.org or e-Mail me /---/


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