Path: utzoo!utgpu!watserv1!maytag!xenitec!zswamp!root
From: root@zswamp.fidonet.org (Geoffrey Welsh)
Newsgroups: comp.dcom.modems
Subject: Re: New Modems
Message-ID: <5718.27549624@zswamp.fidonet.org>
Date: Wed, 28 Nov 90 15:21:20 EST
Organization: Izot's Swamp BBS - Kitchener, Ontario

Marc Unangst (mju@mudos.ann-arbor.mi.us ) wrote:

 >david@twg.com (David S. Herron) writes:
> 2-- It's half-duplex.  The rapid-turnaround mode is a help, but I haven't
>       ever used v5 ROMs so I don't know what improvements were in them.
>       Still -- the UUCP spoofing is extra development cost & effort that
>       wouldn't be necessary of it were full-duplex.

 >Actually, I believe that each of the 512 subchannels that PEP uses 
 >can
 >be either send or receive, so you *could* (in theory) split the line
 >into two 6Kbps pieces and send data in both directions.  The
 >Trailblazer doesn't usually do this, because there's usually much 
 >more data flowing in one direction than the other.

   In theory, this could be done. It would probably be a vast improvement to 
the TB+ interactive capability if it split the channels based on dynamically 
monitored adta flow statistics.

   However, the TB does in fact send data in only one direction at a time. Some 
Telebit propoganda leads me to believe that there is a backchannel, but 
experience leads me to believe that it would be used only for PEP-related 
information (e.g. ACK/NAKing of PEP blocks) and not at all for user data.

 >Also, the UUCP spoofing would be useful even if it was full-duplex.
 >The UUCP 'g' protocol will top out at around 700cps on a 9600bps 
 >link,
 >simply because of the protocol overhead and the time necessary for an
 >ACK to get to the other end.  With the UUCP spoofing, ACKs only have
 >to go from the serial port to the modem, so things are much faster.

   Absolutely. I remember some old Microcom propoganda mentioning protocol 
spoofing, but I don't see it mentioned in their current Qx/V.32c spec sheet.
 

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