Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!rutgers!bellcore!faline!thumper!ulysses!terminus!rolls!mtuxo!mtune!rkh
From: rkh@mtune.ATT.COM (964[jak]-Robert Halloran)
Newsgroups: comp.dcom.modems
Subject: Re: hayes 9600 vs. trailblazer
Message-ID: <2988@mtune.ATT.COM>
Date: 13 Apr 88 16:17:41 GMT
References: <8804110136.AA16978@ucbvax.Berkeley.EDU> <15612@onfcanim.UUCP> <494@edsews.EDS.COM>
Reply-To: rkh@mtune.UUCP (Robert Halloran)
Organization: AT&T ISL Middletown NJ USA
Lines: 40

In article <494@edsews.EDS.COM> roberts@edsews.EDS.COM (Ted Roberts) writes:
>I realize that news is normally compressed by the system before transmission
>partly due to the modems that don't do data compression in the hardware.
>However, I'm curious if in a this is actually the best method for the
>Trailblazer.  Is the modified Lempel-Ziv data compression algorithm used
>by the news better than the type used by the Trailblazer?  What algorithm
>is used by the TB?

	It is my understanding that the Telebit uses L-Z compress.  If
	you run a file through it that has already been compressed, though,
	the modem will expend needless cycles trying to improve the 
	compression.

>If the data compression used by the news is better, though, there are still
>other types of data to send that are not compressed.  For this type of data
>(mail comes to mind) I would disagree that doing compression in the modem
>is counterproductive.  This is by no means a flame, I personally don't know
>much about the data compression techniques used and would like to learn a
>bit more.

	Agreed about compression of non-news data.  It remains to be
	seen whether throughput is better when the host does the compress
	vs. the modem.  You would have to sum host-time-to-compress with
	transmission-of-compressed-file with modem's compress disabled
	against transmission-of-uncompressed-file with modem's compress
	on.
>
>-- 
>Ted Roberts                         |  My opinions are not necessarily those
>EDS Technical Services Division     |  of my employer.  Does that mean I'm
>UUCP: roberts@edsews.EDS.COM        |  wrong?


						Bob Halloran
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