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Path: utzoo!mnetor!uunet!husc6!rutgers!labrea!jade!saturn!eshop
From: eshop@saturn.ucsc.edu (Jim Warner)
Newsgroups: comp.protocols.tcp-ip
Subject: Terminal server efficiency
Message-ID: <1135@saturn.ucsc.edu>
Date: Sun, 15-Nov-87 20:11:26 EST
Article-I.D.: saturn.1135
Posted: Sun Nov 15 20:11:26 1987
Date-Received: Tue, 17-Nov-87 06:06:15 EST
Organization: U.C. Santa Cruz, CIS/CE.
Lines: 27
Keywords: Bridge, TCP-window, terminal server


How important is the offered TCP window size for Ethernet
terminal servers?  

Our Bridge LS1 terminal server offers a maximum window size
of 164 bytes.  Our Micom terminal server offers a 384 byte
window.  The small window forces our computers to send a full
screen update as many small packets instead of fewer larger
packets.  It seems to me that this is expensive in terms
of CPU bandwidth both for the connected computer and any
intervening gateways.  What do people think?  Is this important?

Here's some data.  I logged in to a 4.3BSD computer, read a 7
screen file (154 line, 10430 byte) with unix 'more' and logged out.
In all cases the terminal baud rate was 9600.  "Total packets"
includes those necessary to log in and give the commands.

Terminal           software      Max Offered        Total packets
attached to        version       rcv window         (both ways)

Bridge LS1         13000          164                481
Micom NTS-100      V1.3-AC        384                241
VAX 750            4.3BSD        4096                159


Our Micom NTS-100 is running software that is still in beta test.
The production software offers a 320 byte window.