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From: sdempsey@UCSD.EDU (Steve Dempsey)
Newsgroups: comp.sys.sgi
Subject: Ethernet controller differences between 4D/340 and 4D/25
Message-ID: <9101182254.AA12177@chem.chem.ucsd.edu>
Date: 18 Jan 91 22:54:25 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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				Warning!
People prone to nervous breakdowns when dealing with network problems
		are advised to stop reading this now!
			     -------------

Hardware:
	4D/340VGX with IO2 i/o controller
	4D/25TG

Software:
	all machines at 3.3.1

Situation:
    When I attempt to transmit a file from our 340 to a remote site with
    'ftp' or 'rcp' the transfer is either very slow or terminates with a lost
    connection.  I then disconnect the 340 from the net by unplugging the
    drop line from the 340 I/O panel and plug the drop line into the I/O
    panel of the 4D/25TG, to insure that both machines use the same physical
    net connection.  Now I attempt the same file transfer from the 4D/25TG
    and it goes without a hitch.

What I Know So Far:
    I have monitored our subnet to watch the packets.  What I see is that
    packets from the 340 appear with varying frequency.  The time between
    delayed packets will double from 1 to 2, then 4, 8, 16, 32, and finally
    64 seconds will elapse between packets.  On occasion six consecutive
    packets will be delayed by 64 seconds, at which point the connection is
    summarily dropped.  More frequently the timeout resets back to 1 second
    and then starts doubling again.  When the 4D/25TG is used all of the
    packets are sent within a second or two without any unusual delays.

    The only clue I have from the 340's point of view is that if I run
    'netstat -p tcp' while the transfer is in progress I see these counts
    incrementing:
       6241 retransmit timeouts
	   11 connections dropped by rexmit timeout

    This problem has been reported to the HOTLINE (call # H2774) on 10Jan91
    but no answers yet.  Our FE tried replacing the IO2 board but it had no
    effect.

    A 240GTX on the same subnet also experiences these delays, and several
    other PIs also on the same subnet have no problems.

The Big Question:
    What is different about the 240/340 and 25 that would account for this
    behavior? 

---------------------------------------------------------------------------
Steve Dempsey					voice:	  (619) 534-0208
Dept. of Chemistry Computer Facility, 0314	UUCP:	  ucsd!sdempsey
University of Calif. at San Diego		BITNET:	  sdempsey@ucsd
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La Jolla, CA 92093-0314				fax:	  (619) 534-0058