From: syscrc@pickle.gsu.edu (Randy Carpenter)
Subject: Re: NCSA Telnet problems--HELP!
Organization: Georgia State University
Date: Fri, 22 Jan 1993 18:51:46 GMT

matt@wardsgi.med.yale.edu (Matt Healy) writes:

>We have been having some really *weird* problems with NCSA Telnet
>2.5 connecting to a Silicon Graphics workstation.  They went away
>for a couple of months but now they seem to be coming back...
>
>1. THE PHYSICAL NETWORK IS ABSOLUTELY OK:
>
>   --Ethernet packet analyzer finds few bad packets/collisions
>   --AppleTalk/AppleShare work perfectly over the same Ethernet
>
>2. BOTH MACHINES INVOLVED HAVE *GOOD* IP CONNECTIONS:
>
>   --The SGI can ping the Macs involved just fine, even at high
>     speed
>
>   --The Macs involved can use Network Time to get correct time
>     of day information from the SGI even when the problem is
>     happening
>
>   --Email between the SGI and the rest of the universe works
>     just fine
>
>   --When certain Macs cannot log in to the SGI, other Macs in
>     our lab can log in without problems using NCSA Telnet
>
>   --Those Macs which cannot log in to the SGI workstation
>     can login without problems to every other host we have
>     tried, even hosts that are thousands of miles away
>
>   --Finger queries from the Macs involved (using finger 1.3.5
>     by Peter Lewis, a Macintosh finger utility) work OK
>
>3.  THE PROBLEM IS NOT SPECIFIC TO VERSION 2.5 OF NCSA TELNET:
>
>   --we have tried other versions; same symptoms!
>
>So, I have listed all the things which *are* ok; what's the
>problem?  At unpredictable times certain Macs have difficulty
>logging-in to the SGI workstation, even when others work ok.
>Severity ranges from very slooooow response to failure to
>connect at all.  Sometimes, when a connection attempt fails,
>I *can* start an ftp session; then after the ftp session has
>been established suddenly telnet logins work.  Once an interactive
>login is working, I close the ftp session and the interactive
>session continues OK.  This leads me to suspect the glitch has
>something to do with Telnet protocol negotiation.
>
>I am cross-posting this to comp.sys.sgi.admin, comp.sys.sgi.misc,
>and comp.sys.mac.comm because I have no idea whether this is a
>MAC problem, an SGI problem, or some complex interaction.
>
>I AM AT MY WITS' END; I HAVE TRIED EVERYTHING I CAN THINK OF.
>
>HELP HELP H E L P.
>
>Matt Healy
>"I pretend to be a network administrator; the lab
> net pretends to work!"
>
>matt@wardsgi.med.yale.edu

I don't know if this will help, but we had a problem with early versions
of Lan Workplace for DOS and Wollingong TELNET on PCs.  The would almost
connect to our SGIs.  The solution was to reduce a couple of TCP window sizes
in IRIX.  In /usr/sysgen/master.d/master.c we changed:

  unsigned long tcp_sendspace = 60 * 1024;      /* must be < 64K */
  unsigned long tcp_recvspace = 60 * 1024;      /* must be < 64K */

to...

  unsigned long tcp_sendspace = 24 * 1024;      /* must be < 64K */
  unsigned long tcp_recvspace = 24 * 1024;      /* must be < 64K */

and it fixed the problem.

-- 
===========================================================================
Randy Carpenter                    rcarpent@gsu.edu          % Got a light?
Georgia State University           (404) 651-2648            No match.
Wells Computer Center                                        %