Subj : Pure DOS TelNet ZMoDem
To   : Bo Simonsen
From : Stephen Hurd
Date : Sat Oct 16 2004 09:58 pm

  Re: Pure DOS TelNet ZMoDem
  By: Bo Simonsen to Stephen Hurd on Fri Oct 15 2004 23:32:21

 >  SH> Because XModem and YModem both send a block, wait for confirmation,
 >  SH> rinse and repeat... this means that (for XModem) every 128 bytes
 >  SH> requires a round trip to be completed before the next 128 bytes are
 >  SH> sent...
 > 
 > Yes but it's doesn't make them more optimized for modems than for telnet.. :
 > Or does it?

It most definately does... XModem *will not* send the next 128 bytes util the
previous 128 bytes have bee nrecieved by the remote system AND the remote
system has replied saying it has recieved them.  If you pink the other host for
example, you get the round trip time...

My round trip time to vert.synchro.net is currently 645.339 ms.
That is the time between EVERY 128 bytes in an XModem transfer... so say I want
to transfer a 5k file...
5*1024 = 5120
5120/128 = 40
40 * .645339 = 25.8

This means that 25.8 seconds will pass while my vert is just sitting there
waiting for my system to acknoledge the previous 128 bytes... 5k can be
transferred by both systems in under 1 second.
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 * Origin: FreeBSD Synchronet - telnet://FreeBSD.synchro.net (1:140/17)

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