Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!cs.utexas.edu!news-server.csri.toronto.edu!torsqnt!geac!maccs!beame
From: beame@maccs.dcss.mcmaster.ca (Carl Beame)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: telnet and pc's
Message-ID: <2698A174.13868@maccs.dcss.mcmaster.ca>
Date: 9 Jul 90 15:23:31 GMT
References: <8285@b11.ingr.com>
Organization: McMaster University, Hamilton, Ontario, Canada.
Lines: 44

In article <8285@b11.ingr.com> griffin@b11.ingr.com (Tommy Griffin) writes:
>
>We're experiencing some difficulty communicating between our
>workstations and PCs using Telnet over TCP/IP.  The PCs are running
>Sun's PC/NFS product through the 3-Com Ethernet card.
>
>The problem occurs when a Telnet session has been established from a
>PC to a workstation, and the workstation is generating a continuous
>stream of output to be displayed by the PC.  The PC begins to display
>the output, but instead of displaying a continuous stream of data, new
>data is displayed at intermittent intervals with 1-20 second delays
>between bursts of output.  The delay usually ramps up to 20 seconds
>and stays there.
>
>The problem seems to be caused by the PC's inability to receive and/or
>process Ethernet/TCP frames which arrive within 5 milliseconds of each
>other.  Our workstation sends output to the PC in TCP frames carrying
>64 bytes of data.  The 512 byte TCP window offered by the PC's TCP
>allows us to send up to 8 frames inside one window, so these frames
>can arrive with very little inter-frame spacing.  When the PC drops a
>frame, we have to retransmit the data that was lost.  The Jacobson
>algorithm in our implementation of TCP causes us to *DOUBLE* our
>retransmission timer each time we have to retransmit data.  We
>eventually increase the retransmission timer to  its maximum value, 20
>seconds, which explains why we're seeing bursts of data every 20
>seconds.
>
>Any light that can be shed upon this matter would be greatly
>appreciated.
>
>
>Tom Griffin
>griffin@ingr.com

	At McMaster University they are running CS/100s  to the IBM 7171
and IVECS cards in the Vaxen. They had the same problem (originaly the 
IVECS cards had a 16 second retry time). What I did was allow the
Telnet window size to be changed. The CS/100s and IVECs cards buffer
up to 82 bytes per packet. By setting the window size to 82, everything works
and you can get reasonable through-put with telnet.

	Carl Beame
	Beame & Whiteside Software Ltd.
	Beame@McMaster.CA