Path: utzoo!censor!comspec!becker!bdb
From: bdb@becker.UUCP (Bruce Becker)
Newsgroups: comp.sys.amiga
Subject: Re: Dnet
Keywords: Dnet, Telebit Trailblazer
Message-ID: <5717@becker.UUCP>
Date: 10 Mar 90 05:57:37 GMT
References: <25358@swrinde.nde.swri.edu> <1990Mar7.000117.6984@ncsuvx.ncsu.edu> <25373@swrinde.nde.swri.edu> <1990Mar8.231002.21288@ncsuvx.ncsu.edu>
Reply-To: bdb@becker.UUCP (Bruce Becker)
Distribution: na
Organization: G. T. S., Toronto, Ontario
Lines: 45

In article <1990Mar8.231002.21288@ncsuvx.ncsu.edu> ml@ecerl3.UUCP () writes:
|[...]
|OK, I guess I'm laboring under a misconception here.  I thought the
|9600 bps rate was achieved using a large symbol set (ie 512 frequencies)
|but that the higher rates (up to around 18000 bps -- PEP enabled)
|was by adding compression techniques as well.
|But I'm no expert here.
|
|My real points in the prior response were:
|
|  1)  It's fast.  Comfortably faster than 2400 bps.
|  2)  It wasn't as fast as expected (not really 9600 bps or higher)
|  3)  I don't think the modem is the culprit for (2).
|  4)  I suspect serial port handshaking IS the culprit.  
|      No proof.  I could be way off base here.

	The Telebit uses half-duplex communication,
	which can really slow things down for any
	packet-oriented traffic requiring acks
	on an immediate basis. I don't know the
	details of the Dnet protocol but I'm
	pretty sure it uses some kind of end-to-end
	handshaking to guarantee delivery.
	This is incompatible with half-duplex
	technology due to the time it takes for the
	modems to negotiate line turnaround.
	600 cps is pretty good for this kind of
	use on a Telebit - TCP/SLIP is apparently
	even worse in performance using those
	modems.

	Telebits can emulate uucp, xmodem and kermit
	very effectively in terms of throughput, but
	only because of some builtin smarts in the
	firmware. If Dnet was somehow able to be
	emulated, or Dnet able to use one of the
	above protocols for communication, you'd see
	up to 1400 cps throughput...

Cheers,
-- 
  (__)	 Bruce Becker	Toronto, Ontario
w \@@/	 Internet: bdb@becker.UUCP, bruce@gpu.utcs.toronto.edu
 `/v/-e	 UUCP: ...!uunet!mnetor!becker!bdb
_/  \_	 "They never tell you shit like this in high school!" - J. R. Dobbs