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From: mcmahan@netcom.UUCP (Dave Mc Mahan)
Newsgroups: comp.sys.amiga
Subject: Re: Question about a possible transfer protocol
Message-ID: <16485@netcom.UUCP>
Date: 9 Nov 90 04:38:40 GMT
References: <45220@eerie.acsu.Buffalo.EDU>
Organization: Dave McMahan @ NetCom Services
Lines: 36


 In a previous article, v128ll9e@ubvmsd.cc.buffalo.edu writes:
>
>	I was thinking late at night on how I could make a brand new and really
>fast transfer protocol.  This is (I think) a completely new idea. It occured to
>me that the only way to really speed up a transfer is the have the receiving 
>computer send NO information back to the sending computer.

Not quite true.  To take advantage of the maximum rate of your modem, you have
to ensure that the transmitting end is always full and there are no pauses in
the outbound character stream.  Transmission rate in one direction does not
depend on transmission rate in the other direction (for modems that are
true full duplex).  

>	The way that it would work (for error checking) is have the sending
>computer would send a CRC check every 1024 bytes.  The receiving computer would
>independently compute the CRC and compare them, if they are different, then and
>only then would the receiving computer send anything back.

I think this is pretty much the concept behind Z-modem.  If you get a fast host
and a fast term program that are optimized for Z-modem speed, you will see
the back channel light flicker only occasionally and you should never see the
outbound data light stop and wait for it.  I use JR-Comm for the amiga (nice
job on the software, Mr. Radigan!) and a Sun-4 host.  I regularly get 235
characters per second coming in (out of a possible 240 cps with a 2400 baud
modem) even with heavy usage of the host computer.  I have seen this number
go up to 239 or 240 cps when little else is taking CPU time or disk accesses
from my host.  I almost always get 240 cps when I send files to my host.

>-Rich

   -dave

-- 
Dave McMahan                            mcmahan@netcom.uucp
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