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From: casey@gauss.llnl.gov (Casey Leedom)
Newsgroups: comp.dcom.modems
Subject: Re: Telebits "PEP" protocol
Message-ID: <87673@lll-winken.LLNL.GOV>
Date: 12 Dec 90 00:48:12 GMT
References: <1990Dec8.025415.2920@amd.com> <8sHZT4w163w@mudos.ann-arbor.mi.us> <3592@jaytee.East.Sun.COM>
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| From: gsteckel@vergil.East.Sun.COM (Geoff Steckel - Sun BOS Hardware)
| 
| >From: mju@mudos.ann-arbor.mi.us (Marc Unangst)
| >
| >>From: ncpmont@brahms.amd.com (Mark Montgomery)
| >>
| >> ... why isn't some modem manufacturer that already has a handle
| >> on V.32, V.42, bis, etc putting PEP into their products?
| >
| >Mostly because Telebit also owns the PEP protocol.  They invented it,
| >and they can decided who gets to use it.
| 
| Open letter to Telebit:  if you think PEP is worth anything, license it
| (with or without fee).  Otherwise it will be bypassed by a (possibly
| inferior) but widely available standard.  V.32 is coming up fast.

  Telebit's DAMQAM (Dynamic Adaptive Multicarrier Quadrature Amplitude
Modulation) has a couple of definite features over V.32 and possibly even
the upcoming V.32bis standard:

    o	Ability to handle line noise and changing line conditions.

    o	Higher raw bandwidth -- in one direction at a time.

From what I understand, PEP (Packetized Ensemble Protocol) is simply a
special packetizing and error detection/correction protocol designed to
live on top of DAMQAM and provide a simulated full duplex interface.  The
spoofing of various higher level protocols to increase overall throughput
rates are a completely separate issue and could be layered on top of any
``error free'' channel.

  The protocol spoofing is nice, but mostly a because of stupidity in the
higher layer protocols -- notably a fixed window size of 1.  (From what I
understand, SLIP spoofing, when it becomes available, will actually be
making up for the half duplex nature of DAMQAM.)  Nevertheless, in this
world of stupid higher level protocols, the spoofing is a definite
advantage.  My only complaint is that I should be able to do it over any
``error free'' channel, such as V.32/V.42/V.42bis.

  PEP is simply a packetization protocol.  Who cares?  Please feel free
to flame me if I'm misstating the extent of PEP's features.

  But, the real winner is DAMQAM.  After struggling with a V.32
connection for the last couple of weeks with the best length of connection
being ninety minutes I've changed my mind about telling people to forget
``PEP'' modems and just go with V.32.

  My only problem is I can't stand using PEP.  The echo delays are
terrible to behold when I try to use my X terminal and it's just barely
passable with a normal terminal.  Visual editors are gruesome.

  It would be really nice if Telebit could come up with a follow on to
DAMQAM that was ``TRUE'' full duplex ala the V.32/V.32bis echo
cancellation.  Really nice.  Incredible nice.  Can you imagine it?
Roughly 18Kbps full duplex and reliable over the worst lines?  Layer
V.42/V.42bis on top of that and you'd have one mean communications link
...  such a modem would also, of course, have to support ``TRUE''
38.4Kbps ... :-)

  Oh course, in line with the note that I'm following up, it would have
to be licensed very cheaply for such a scheme to become widely used or
adopted as a new CCITT standard ...

Casey