Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!rutgers!columbia!cunixc!lih
From: lih@cunixc.columbia.edu (Andrew Lih)
Newsgroups: comp.sys.mac
Subject: Re: Comm Programs
Message-ID: <611@cunixc.columbia.edu>
Date: 22 Apr 88 13:25:34 GMT
References: <683@cerebus.UUCP> <353@hudson.acc.virginia.edu>
Reply-To: lih@cunixc.columbia.edu (Andrew Lih)
Distribution: na
Organization: Columbia University
Lines: 43
Keywords: xmodem ymodem communications

In article <353@hudson.acc.virginia.edu> wrp@biochsn.acc.Virginia.EDU (William R. Pearson) writes:
>>
>>Yesterday, I tried downloading a 250K+ file from our UNIX machine to my
>>Mac using Red Ryder at 2400 baud...well, it worked but I can write faster
>>that it downloaded! :-)/2
>
>>VT-100 Emulation, and FAST DATA TRANSFERS.  (RR at 2400 baud had an
>>abysmal throughput of 137 cps.)

Hmm...well if you were using XMODEM, then 137 cps is not THAT bad
considering the overhead for XMODEM.  Since there are only 128 bytes
per packet, if you go through the math, it really is not that bad.
( I am too lazy to go through the math, and I also don't want another
  flinging of combinatorics and icon posibilities :-)

>	You do not say how you did the download.  If you were using
>kermit, this would be the expected speed, because of kermit overhead.
>If you were using xmodem I would expect faster transfer.

Yeah, with a 94-byte packet constraint, then you are talking sub
1000 effective baud rate.  

>	I use Versaterm and kermit with long packet sizes (1000 bytes).
>This works well at 2400 baud (or 19,200 to my IBM-PC over a direct
>line).  But long packets can kill you if you have a noisy line.
>Unix kermit got long packets relatively recently, so you may have to
>upgrade.

I use MacKermit 0.9(36) which has the capability to go up to 1000 bytes
per packet.  I normally use 512 byte packets, and get about a 1600-1700
effective baud rate, which I consider pretty good.  The resend on 
1000 bytes can be rather lengthy, which is the reason why I use 512.
And the fact that when my refrigerator kicks in, you can see {{{eas{{
on the line...

>	(I have to use kermit because my connection to the unix
>machine is over a LAN which interprets ^P, ^S and ^Q, and the
>LAN's modem interprets ^Q and ^S without letting it get to the LAN).

OK, so where is the Mac implementation of sliding-windows?  
Who shall come to the rescue and write this bugger?  :-)

>Bill Pearson
>wrp@virginia