Rlogin and ethernet packet size

[Dave Besselievre]

Chemical Abstracts Service is seeing the following problem on our DEC/SUN
network.  When using rsh/rlogin on an idle systems (local and remote) we
see keystrokes being broken into single character Ethernet packets when
being sent to the remote system.  This is ok when the user is entering
text, but during cursor movement, multi-character sequences are generated
for each keystroke the users types.  The sending of these packets
containing a single character, very quickly causes the packets to backup,
and more they one keystroke is then packaged into a Ethernet packet.  This
leads to the cursor movements being jerky. (ie. the cursor jumps 3 to 5
character locations at a time.  This behavior is seen by the user as if
the remote system is slow or not responding correctly.  As the system load
increases on the remote system this behavior becomes worse.

Now if the user uses "telnet" to connect to the remote system, this
behavior does not occur.  If you look at the Ethernet packets being sent
we see that multi-character keystrokes are being sent as one Ethernet
packets.  And the system never gets behind due to Ethernet packet traffic.

The problem is that rsh/rlogin provides features that are not available
under telnet (ie, automatic login and remote execution of programs).  Is
there any way to cause the rsh/rlogin process to package the
multi-character keystrokes as one Ethernet packet as the telnet program
does.

Could this problem be caused by any OS environmental problem?

Please send any suggestion on how to correct this to:

	dlb25 at chemabs!osu-cics
	dlb25%cas.BITNET at CUNYVM.CUNY.Edu
	dlb25%CAS at pucc.PRINCETON.EDU

David Besselievre
Chemical Abstracts Service
614-447-3600 X3545

Testing environment
~~~~~~~~~~~~~~~~~~

CAS has 12 VAX 785 running Ultrix 3.1 and one VAX 785 running Ultrix 4.0.
There are also 3 VAX 8820 running ULTRIX 4.0  We have 370+ Sparc 1+ WS on
the network running SUN OS 4.1 configured into tree Subnet.  The VAXS are
evenly distributed between the three subnets.

We have found that the problem occurs when the remote system is on local
or remote subnet; remote system is a VAX 785, 8820 or SUN WS; and under
SUN OS, Ultrix 3.1 or Ultrix 4.0.  This problem occurs under both programs
telnet and rsh/rlogin when they are executed from a sun window
environment, but the telnet program still performs better than the
rsh/rlogin program does when outside the windowing environment.  When
execution is between VAXs, there is not problem with the telnet keystroke
response.  And the SUN users do not feel that the telnet responsiveness is
poor in the SUN Windows environment.  But they find the rsh/login very
objectionable, in both the Sun windows and VAXs environments.

In a moderately busy remote system we are seeing as much as three to four
words being skipped in cursor jumps when the user performs a smooth cursor
scrolling to the right (ie. users hold down right arrow key), under
rsh/rlogin.  Where the same document and operation in a telnet connection,
provides smooth scrolling.