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From: gillies@p.cs.uiuc.edu
Newsgroups: comp.sys.mac.comm
Subject: High Speed ZModem
Message-ID: <70900001@p.cs.uiuc.edu>
Date: 31 May 90 05:34:00 GMT
Lines: 37
Nf-ID: #N:p.cs.uiuc.edu:70900001:000:1643
Nf-From: p.cs.uiuc.edu!gillies    May 31 00:34:00 1990


I occasionally would like to upload 100k postscript files to another
machine at the maximum possible throughput.  Currently, I have tried
using zterm 0.85 at 38400 baud.  It runs fine for about 10k, then the
zmodem gets stuck, and often it wedges permanently.

My mac is connected as follows:

  Mac SE/030  ---RS232--->  Encore Annex ---Ethernet--->  Multimax
			     Box(68020?)		(or pyramid)

I am uploading through an encore annex box, which concentrates the
data using either (1) multimax call, (2) unix rlogin, or (3) telnet
protocol.  Since the ethernet should not be a bottleneck at these slow
speeds (3.2k/sec), I assume that the host is dropping packets, or the
mac is dropping responses, and someone is not timing out correctly
(because the Mac just hangs).

What can I do to improve the situation?  I have some questions

(1) will white knight 11.0 run zmodem at 38400, perhaps under
    scripting control?  Does it work as nicely as zterm 0.85?
(2) is there a later version of zterm 0.85?
(3) is there something wrong with my UNIX zmodem program?  I know it
    has bugs, because in the past uploads have terminated with the
    UNIX host being short about 2Kbytes out of 100K, needless to say, the
    upload was worthless.
(4) is there something I can do to the terminal concentrator, to xon-xoff,
    or elsewhere to reduce the rate of packet/ack dropping, or to get 
    UNIX/zterm 0.85 to restart more quickly after a transmission error?


Thanks,

Don W. Gillies, Dept. of Computer Science, University of Illinois
1304 W. Springfield, Urbana, Ill 61801      
ARPA: gillies@cs.uiuc.edu   UUCP: {uunet,harvard}!uiucdcs!gillies