Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!ncar!news.miami.edu!umiami!ian
From: ian@umiami.ir.miami.edu
Newsgroups: comp.sys.mac.comm
Subject: Re: ZTerm transfers (again...)
Message-ID: <1991Jun4.131205.10392@umiami.ir.miami.edu>
Date: 4 Jun 91 17:12:04 GMT
References: <009496DA.C7E09C00@uclapp.physics.ucla.edu>
Organization: Univ of Miami IR
Lines: 64

In article <009496DA.C7E09C00@uclapp.physics.ucla.edu>, price@uclapp.physics.ucla.edu (John Price) writes:
> Hi all:
> 
> I have a question about just how ZTerm does file transfers.  I transfer 
> files from a VAX running VMS (rz 3.01, sz 3.03) to either a Plus (at 2400 
> bps) or a IIcx (at 19200 bps) and back.  Transfers *from* the VAX work 
> great - I get 237 cps (!) to the Plus, and about 1050 cps to the IIcx.  I 
> don't expect to be able to improve either speed by too much - certainly not 
> the Plus...
> 
> However, going from either Mac to the VAX is painful.  I keep getting ZRPOS 
> errors.  The fastest transfer I can get on the IIcx is about 500 cps.  I 
> tried playing with the Zmodem parameters a bit - I noticed that changing 
> the "subpacket length" didn't have much effect, but changing the "Window 
> limit" did seem to help.  
> 
> Initially, there was no window limit - the box was empty.  Not having the 
> slightest idea what I was doing, I put 100 there and tried the transfer 
> again.  This time, it appeared as if the program wasn't trying to send as 
> much data at one time as it had before - the "bytes sent" field updated 
> much more quickly than before.  When I looked at the window limit again, to 
> try a different number, I saw that the program had automatically changed it 
> to 256.
> 
> OK, I can deal with that.  It wants multiples of 256.  I have no idea why, 
> but now I at least have a handle on how to affect the program's operation.  
> I found that the larger I made this number, the faster I was able to 
> transfer data.  This effect seems to flatten out with a window limit of 
> about 4096 (it's currently set to 16384).
> 
> Now, my questions to Dave Alverson (or anyone who has more of a clue about 
> this than I do - that shouldn't cut too many people out  :) are the 
> following:
> 
> 	1: What is the "subpacket length"?
> 	2: What is the "window limit"?
> 	3: How can I optimize the transfer speed *to* the VAX without 
> 	   affecting the transfer speed *from* the VAX?
> 	4: (to Dave Alverson specifically) Could you put at least a cursory 
> 	   description of this in the docs for the next version?  
> 
> Thanks a lot in advance!
> 
>            John Price * * * * price@uclapp.physics.ucla.edu
>            Where there is no solution, there is no problem.

Someone probably already said this...
I  had the same problem here...Check to see whether the VAX end of the
connection is 8bit..I believe Z-Term will only transfer to an 8 bit connection..
Course I could be wrong..:)
-- 
Scruffy
Ian Sullivan
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