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From: Kevin_Crowston@XV.MIT.EDU
Newsgroups: comp.sys.xerox
Subject: tcp fragments handled badly in koto
Message-ID: <0.43520.29067.16609.9588@XV.MIT.EDU>
Date: Tue, 1-Dec-87 18:58:19 EST
Article-I.D.: XV.0.43520.29067.16609.9588
Posted: Tue Dec 1 18:58:19 1987
Date-Received: Sat, 5-Dec-87 01:07:48 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
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I seem to be having a problem with TCP fragments. I'm running Koto on an 1108. The date on the TCP file is 18-Dec-86 17:39:57; it's the same as the one currently on {SUMEX-AIM.Stanford.EDU}KOTO>.
A host is sending me large packets that are getting broken up along the way across the internet. When I get them there are two fragments (identified by the MIT PC/IP netwatch program as TCP Fragments), one of 1004 bytes and one of 516 bytes. This makes me think that the originating host is sitting on an ethernet pumping out 1.5K packets. I'm not sure what exactly happens, but the Dandelion doesn't seem to be able to reassemble the packets and after getting a few repeats it sends back some TTL Exceeded I
CMP packets, first one to a bogus host (with an address like 111.113.22.22) and then two to the originating host. After this, I think the connection dies. (I'm a little vague on the details since I'm not using the Dandelion, only watching the packets go by on the network and seeing the final result of the connection, which is a mail message with no contents.)
Anyway, is this a known bug? I suspect the originator shouldn't really be sending such large packets, but I also suspect the dandelion should be doing a better job of catching them. Is there a fix?
Kevin Crowston
MIT Sloan School of Management