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000333_news@newsmaster….columbia.edu _Tue Dec 2 05:41:13 1997.msg
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From: jrd@cc.usu.edu (Joe Doupnik)
Newsgroups: comp.protocols.kermit.misc
Subject: Re: Kermit DOS Performance?
Message-ID: <rN9z2nZx0SE4@cc.usu.edu>
Date: 1 Dec 97 18:07:46 MDT
References: <65t342$k91$1@goanna.cs.rmit.edu.au>
Followup-To: poster
Organization: Utah State University
Lines: 44
Xref: news.columbia.edu comp.protocols.kermit.misc:8127
In article <65t342$k91$1@goanna.cs.rmit.edu.au>, rwi@yallara.cs.rmit.edu.au (Ross Irvine) writes:
> Hi All,
> I'm trying my best to get kermit for dos (3.15) to transfer files
> as fast as possible. It's currently about half the speed of z modem.
>
> I've set the following :
> set block 3 ;
> set window 4 ;
> set receive packet-length 9000 ;
> set control prefix all ;
>
> I'm transfering data via an Async Bonded ISDN line (The bonding combinds
> 2 64K B channels into one. Giving me 128k to play with).
>
> I'm only getting around a 6000 cps rate. I can see that my problem is the
> set control prefix all line. As I'm sending ZIP's, this is probably
> making kermit send twice as much data.
>
> I've tried setting unprefix all and prefixings 0,1 and 129 but I keep
> getting strange parity errors on the recieving end. Both sides of the
> xfer are Kermit for DOS 3.15.
>
> What do I need to prefix for kermit to send at it's fastest to another
> kermit using CTS/RTS folow control and for the transfer's to work without
> the strange parity errors. This is using 8 data non parity and 1 stop.
---------
MSK itself needs only protect the start and end of packet delimiters,
normally Control-A (1) and Control-M (13), plus Control-C (3) to interrupt
a Kermit server, and their high bit set counterparts. Leaving all control
codes prefixed adds only 4/32nds overhead, there being 32 C0 controls,
32 C1 controls (high bit set), plus DEL (127) and its mate 255, out of
a total of 256 combinations in one 8-bit byte.
More than likely your comms channel is not really 8-bit clean and
thus some bare control codes are being mangled/intercepted/doing bad things.
This is in the nature of the beast, and the primary reason Kermit defaults
to using printables. The only suggestion we can make is try code after code
until the guilty parties own up.
9KB packets are expensive when damaged, and that long has exceeded
the breakeven point. Try going back to 1-2KB packets and only if necessary
use more window slots.
As you are probably aware, MSK itself is really fast. In local
development tests I'm getting about 400KB/sec over regular Ethernet, and
hope to increase that value. Headers are not counted as payload here.
Joe D.