Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!pacbell.com!tandem!netcom!gandrews
From: gandrews@netcom.COM (Greg Andrews)
Newsgroups: comp.unix.sysv386
Subject: Re: Equinox question reply
Summary: (just picking a couple of nits)
Keywords: Telebit uucp spoofing details
Message-ID: <24307@netcom.COM>
Date: 16 Feb 91 12:25:59 GMT
References: <1991Feb14.224748.18446@pcserver2.naitc.com> <1991Feb15.083043.11636@pegasus.com> <1991Feb15.164415.19733@rwwa.COM>
Followup-To: comp.unix.sysv386
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 44

In article <1991Feb15.164415.19733@rwwa.COM> witr@rwwa.COM 
(Robert W. Withrow) writes:
>
>In the case of Telebit modems, for PEP and Direct V.32 (but not V.42
>LAP-M) connection, the modem ``spoofs'' the `g' protocol, and thus the
>pacing (aka flow-control) is performed by the modem in this way.
>

Protocol support for uucp (or kermit or x/ymodem) is available only
in two modes: PEP and V.32/MNP.  "Direct V.32" (by which I understand
you to mean V.32 without error control) does not have protocol support.

>
>With other modems (and telebit modems using LAP-M), the pacing is done
>by the two computers via the `g' protocol.  In cases where the
>DTE-to-modem bit rate is higher than the modem-to-modem bit rate,
>modern modems generally have enough buffer capacity to run UUCP `g'
>protocol without using *any* DTE-to-modem flow control!
>

OTOH, the modem-to-DTE flow control can still have its little say.  If
the uucp data exceeds the modem's XOFF threshold, the modem will send
an XOFF, causing an alarm on many systems.  My info on the buffering
in Telebit modems says the modem sends an XOFF after there are 30-40
bytes in the buffer.  Since uucp "g" can spit out 192 bytes (3 x 64)
the computer may be able to fill the buffer past the threshold when
there's a large difference between the DTE speed and the connection
speed (such as 19200/2400 or 19200/1200).

The above is on links without error control.  MNP or LAP-M links may have
different thresholds.  PEP links have completely different thresholds.

>
>I have my DTE speed set at 38400 BPS,
>and have successfully performed UUCP `g' to other modems operating at
>2400, 4800, and 9600 BPS.
>

38400?  Hope you're using a T1600 (or a non-Telebit modem). <smile>

-- 
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| Greg Andrews      |   gandrews@netcom.COM |
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