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Date:      Tue, 20 Apr 1999 13:07:40 -0700 (PDT)
From:      Doug White <dwhite@resnet.uoregon.edu>
To:        Stanley.Hopcroft@ipaustralia.gov.au
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: NATD and packet fragmentation: fragements are not re-assembled or  delivered ?
Message-ID:  <Pine.BSF.4.03.9904201305500.1514-100000@resnet.uoregon.edu>
In-Reply-To: <4A256756.00078FAC.00@noteshub01.aipo.gov.au>

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On Sat, 17 Apr 1999 Stanley.Hopcroft@ipaustralia.gov.au wrote:

> Unfortunately it does *not* reliably transport the data between the mainframe
> and the LAN.
> 
> The tn3270 sessions and ftp data sessions hang intermittently.

FreeBSD release version?

> A tcpdump on the router shows that packets from the mainframe (which is via a
> frame-relay WAN)
> 
> . are bigger than 500 bytes
> . are fragmented by some intervening router into two 1480 byte packets (probably
> the FreeBSD router given the size of the fragments)
> . are not acknowleged by  the 199.19.99.0 end-system

Is the end-system even receiving the data?  .0 isn't a valid host address,
by the way.  Make it .2 or something non-special.

> The 199.19.99.0 end-system keeps acking earlier byte-ranges, the
> mainframe resends the packet (which appears as new fragements) until
> the end-system resets the connection.

The ACKs are getting dropped too.

> When I change the LAN (and router) to an address the mainframe can
> route to, and stop using natd, all is well.

Hm.  Try throwing some logging on a firewall rule and make sure the
packets aren't getting blocked or dropped.

Doug White                               
Internet:  dwhite@resnet.uoregon.edu    | FreeBSD: The Power to Serve
http://gladstone.uoregon.edu/~dwhite    | www.freebsd.org




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