Path: utzoo!attcan!uunet!husc6!bloom-beacon!apple!bionet!agate!pasteur!ames!coherent!dplatt
From: dplatt@coherent.com (Dave Platt)
Newsgroups: comp.dcom.modems
Subject: PEP still wins over V.32 (was Re: V.32 will dominate the marketplace)
Summary: Pure-V.32 modems may have other disadvantages for USENET sites
Message-ID: <13458@coherent.com>
Date: 6 Nov 88 21:26:55 GMT
References: <9515@conexch.UUCP> <1125@vsi1.UUCP> <299@telebit.UUCP>
Reply-To: dplatt@coherent.com (Dave Platt)
Distribution: na
Organization: Coherent Thought Inc., Palo Alto CA
Lines: 70

There's another issue w.r.t. V.32 modems vs. Telebit PEP modems that
I'm not sure has been mentioned.  It may well be true that the V.32
modems may take over the bulk of the synchronous (SDLC/SNA) market and
perhaps also the high end of the general-purpose interactive-dialup
market.

However, I'm not sure that these modems (in their "pure" V.32 form)
will be all that useful in the USENET world.  The reason is simple:
Telebit modems (from the TrailBlazer Plus onwards) support protocol
spoofing;  none of the V.32 modems I've seen discussed have included
this feature.

UUCP-protocol spoofing is a _big_ win for those of us who use UUCP as
our primary connection to the outside world.  The fact that our hosts
receive UUCP handshakes from the modem, rather than from the host at
the other end of the phone line, has several very large advantages:

1) The sending host receives a packet-acknowledgement immediately,
   rather than having to wait for the packet to travel to the far-end
   host and be acknowledged.  There's probably a small throughput-gain
   even over short (local-call) distances;  there's an IMMENSE
   throughput gain when a call is routed over a long-delay link such as
   a geostationary satellite route.

2) Neither host must retransmit packets due to transmission-line
   lossages; the modems' PEP error-detection-and-retransmission handles
   all necessary data retransmission, and does it in a much more
   time-effective fashion than UUCP (which has an _very_ long
   packet-timeout value).

I'm willing to believe that a standard V.32 modem could equal the UUCP
performance of a PEP modem, _IF_ the PEP modem didn't support UUCP
protocol spoofing.  I have real doubts as to whether a V.32 modem could
compete with a UUCP-spoofing PEP modem.  I also expect that similar
results would obtain when a file-transfer protocol such as XMODEM,
YMODEM, or Kermit were being used.

Those who favor V.32 as the New Standard can certainly argue that
small-window protocols such as UUCP, XMODEM, and Kermit are
fundamentally obsolete, and that people "should" use "better"
protocols such as SDLC/SNA, TCP/SLIP, ZMODEM, and other large-window
protocols.  That's a valid route for us to take in the future... but it
doesn't do us any good _today_.

Let's face it, folks... there are a lot of us out here who must work
with the host/micro software that we have today.  We here at CTI depend
heavily on Sun's rather out-of-date UUCP software to stay in touch with
the outside world... we don't have sources, and don't have the luxury
of rebuilding our UUCP driver to support a larger window or packet
size(as would be necessary if we wanted UUCP to work decently over a
V.32 modem at 9600 baud during cross-country calls).  We don't have
ZMODEM or sliding-windows Kermit, don't have SLIP (nor any place with
which to connect), and don't care much about SDLC at the moment.

For us, there are precisely two practical choices when it comes to
modems:  TrailBlazers, and 212/V.22bis modems.  We use both... one
'Blazer for UUCP, and a bank of USR Couriers for UUCP and interactive
dialin.

The TrailBlazer Plus we bought last year has already more than paid for
itself in reduced UUNET connect charges.  It was the _only_ modem we
could buy at the time that we could simply "drop into place" and have
work effectively with our primary protocol (UUCP).  If we retire it in
a couple of years because a still-more-effective solution has arrived,
I won't weep... it will have served its purpose, and paid for itself
several times over.  Very few investments do as well!

Perhaps, someday, a V.32 modem manufacturer will release a V.32 modem
that supports UUCP protocol spoofing.  When that day arrives, I'll
consider buying one.