Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ames!mailrus!utah-gr!uplherc!sp7040!obie!wsccs!terry
From: terry@wsccs.UUCP (Every system needs one)
Newsgroups: comp.dcom.modems
Subject: Re: need help with xenix Kermit to PC procomm
Summary: question...
Message-ID: <620@wsccs.UUCP>
Date: 31 Aug 88 03:04:42 GMT
References: <20302@neabbs.UUCP> <11744@oberon.USC.EDU>
Lines: 57

In article <11744@oberon.USC.EDU>, blarson@skat.usc.edu (Bob Larson) writes:
> In article <20302@neabbs.UUCP> richard@neabbs.UUCP (RICHARD RONTELTAP) writes:
> >I suggest you get the rzsz modules.
> 
> This isn't a horrible idea, but you should be warned that XMODEM based
> protocols are sometimes will corrupt the data on a single noise
> character, and are picky about the types of systems and communications
> equipment they run on.

Not if they are using a CCITT CRC-16!

> >Kermit is VERY  slow on binary files and many versions are
> >incompatible. (also the 'super' implementations)
> 
> This is just plain wrong as far as I know.  The main "incompatability"
> problem I know of is different default parity.

This is right.

> All versions of kermit are able to transfer files to each other.

Not true.  Try try talking to an IBM 4300 with MS-Kermit 1.0!  Not only
does the mainframe want turnaround characters that DOS can't provide,
but a lot of other things are not there as well!  (besides, there are
numerous weird implementations -- for instance, I have one in LISP).

> This does not seem "VERY" slow in comparison to me.
> (ZMODEM or WXMODEM is faster than non-windowing kermit, but windowing
> kermit is faster than XMODEM or YMODEM.)

Windowing protocols require large buffers... Xenix has 128 bytes of
buffer.  Windowing protocols on most multitasking operating systems
have realtively teeny buffers.  The only way that'll work is with
some sort of flow control -- either rts/cts or xon/xoff, and xon/xoff
requires a non-binary protocol.

> I have yet to see a
> comparison of ZMODEM to windowing kermit from a non-biased source, I
> would expect windowing kermit to be about 5% slower on a typical file
> mixture.

Actually, I think windowed Kermit is faster by about 8% (from several
10 meg transfers on my equipment).

The main problem with a windowed 7-bit protocol is that there is no way
to get out of a kernal-mode xoff (alarms are queued around kernal-mode
code, and they all go off when you get an xon..) short of putting a
timer in the driver.  This means you have to handle xoff's in user mode
code and this puts you in never-never land if you're swapped out.  This
means no way to gracefully recover.


| Terry Lambert           UUCP: ...{ decvax, ihnp4 } ...utah-cs!century!terry |
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