eshop@saturn.ucsc.edu (Jim Warner) (11/16/87)
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.
hedrick@ATHOS.RUTGERS.EDU.UUCP (11/19/87)
Our tests also showed that a small window can significantly increase the CPU time on hosts that are talking to a terminal server. Thus I regard small windows as a significant problem.
JBVB@AI.AI.MIT.EDU.UUCP (11/20/87)
If the window is smaller than the MSS, the MSS doesn't matter much - you'll never see a packet bigger than the window. I have observed the 164-byte window feature in Bridge, and the fact that at least one of their products only sends 82 bytes (I hesitate to guess why..) in a packet, no matter how much output is pending. This is a box that serves as a milking machine, attached to a host via async lines. I think window (or MSS, whichever is the limiting factor) is an important consideration. I have found that it affects throughput a lot, even in telnet output situations. jbvb
lamaster@pioneer.arpa (Hugh LaMaster) (11/23/87)
In article <8711191851.AA13481@athos.rutgers.edu> hedrick@ATHOS.RUTGERS.EDU (Charles Hedrick) writes: >regard small windows as a significant problem. Does anyone know how the Encore Annex behaves? Hugh LaMaster, m/s 233-9, UUCP {topaz,lll-crg,ucbvax}! NASA Ames Research Center ames!pioneer!lamaster Moffett Field, CA 94035 ARPA lamaster@ames-pioneer.arpa Phone: (415)694-6117 ARPA lamaster@pioneer.arc.nasa.gov (Disclaimer: "All opinions solely the author's responsibility")