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From: laird@slum.MV.COM (Laird Heal)
Newsgroups: comp.sys.mac.comm
Subject: Re: Should I get MNP5 or V.42bis?
Message-ID: <1990Sep18.010556.1739@slum.MV.COM>
Date: 18 Sep 90 01:05:56 GMT
References: <44782@apple.Apple.COM>
Followup-To: comp.dcom.modems
Organization: dis
Lines: 61

In article <44782@apple.Apple.COM>, das@Apple.COM (David Shayer) writes:

>I'm going to be buying 2 9600 bps modems, so my partner and
>I can send files back and forth.  I want to get data compression,
>but most companies seem to offer V.42bis OR MNP5.  Which is
>better?  Which one is the world going to go?  I don't want
>to buy the system that is going to obsolete next year.

V.42/bis is better by far than MNP 5.  Sorry, but I do not have any
real-world figures to quote.  I have some comp.dcom.modems articles 
saved off, and if you want to see them, send me mail.

>I would also welcome any advice on which modem to get.
>I'm currently looking at the Intel 9600EX, which has V.42 and
>V.42bis.  The list is $819, but mail order its only $549.

                                      vvvv      vvvv
Let me caution you to look harder for V.32 than V.42.  V.32 describes 
how the data is sent down the wire.  I mean, compressing the data is 
one thing, sending and receiving is another.  V.32 is a full-duplex 
mechanism (both ways at 9600bps per).

There are other 'ping-pong' implementations.  These are for transfers
mostly in one direction at a time.  Telebits have PEP, with 19.2kbps 
the nominal transfer rate.  US Robotics has HST, now at 14.4kbps, and 
there are others like V.29 going one way at at time at 9600bps.

My US Robotics HST-DS has V.32 and HST modulation.  It worked well for 
calling bulletin boards.  Maya had a good price, too.  Compressed data
often transfers at 16.6kbps, as if the HST modems 'play hooky' and drop
the start-stop bits.  I never timed any (MNP 5) text transfers, I just 
zoomed the window in as far as I could so my Portable could keep up.  

I now have the V.42 upgrade kit, but the only V.42 modem I can call is 
a Hayes, which must be the most incompatible high-speed modems around.
Even a Telebit connects decently at 1200-2400, but those V-series Hayes
are trouble even to connect to!  Shucks.  Then again, folks that do have 
a V-series Hayes just won't use anything else...

Telebits are reported to deliver reliable 12k-14kbps on voice-grade
lines.  Ask your uucp administrator.  Yesterday my news feed at 2400bps
took six hours on my HST-DS, so getting a Telebit is on my mind.

>Any help would be appreciated.

- Telebits handle line noise exceptionally well, but turnaround is said 
  to be poor for interactive sessions at high-speed.  They also have 
  protocol spoofing, which I will not go into here.
- The US Robotics HST has a great real-world transfer rate when the lines 
  are clean and is also better interactively, "due to more bandwidth on 
  the back-channel", or so it is said. 
- Both of the above are 'ping-pong' half-duplex modems where the direction
  of high-speed transmission is allocated according to requirements.  You
  might desire two-way transmission, as for Async AppleTalk or SLIP, and
  that means using V.32 modulation.

I have redirected followups to comp.dcom.modems, where this topic belongs.

-- 
Laird Heal	laird@slum.MV.COM	Talk is cheap.
(Salem, NH)	+1 603 898 1406		Whiskey costs money.