Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!hayes!tnixon
From: tnixon@hayes.uucp
Newsgroups: comp.dcom.modems
Subject: Re: Uses of V.42 (bis?) data compression
Message-ID: <3911.28078baf@hayes.uucp>
Date: 13 Apr 91 22:52:31 GMT
References: <10334@pitt.UUCP> <3908.280363d4@hayes.uucp> <1991Apr12.132116.11546@hobbit.gandalf.ca>
Distribution: na
Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 32

In article <1991Apr12.132116.11546@hobbit.gandalf.ca>,
dcarr@hobbit.gandalf.ca (Dave Carr) writes: 

>>Also, the compression acheivable in the modem is limited by 
>>the ratio between the DTE-DCE speed ..
> 
> I agree.  So why do modems and PC get it together and get a decent
> interface worked out.  Why not Ethernet ?

Well, we do have EIA-530 now, which goes up to 2.1 Mbps, and is 
pin-compatible with EIA-232.  And TIA TR-30.2 just started work on a 
52 Mbps interface standard.  SCSI is another option, as are various 
LAN methods.  The easiest way to get high speed, of course, is to 
use an internal modem and have it right on the bus, but it seems 
that most people want external modems these days.

>>and the carrier speed.  
> 
> I don't see this at all.  Perhaps the link level protocol.
> Perhaps the line error rate.  But the compression should be
> independant on the carrier speed. 

I said the _ratio_ between the DTE-DCE speed and the carrier speed.  
If the DTE-DCE speed is 38400 and the carrier speed is 9600, it's 
hard to get more than 4-to-1 compression, because you're 
underrunning the transmitter.

-- 
Toby Nixon, Principal Engineer    | Voice   +1-404-840-9200  Telex 151243420
Hayes Microcomputer Products Inc. | Fax     +1-404-447-0178  CIS   70271,404
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