NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/dcom/modems-part1/6566

Internet Message Format | 1996-08-05 | 5.6 KB

Path: dlmlap.supra.com!dan
From: [e-mail] (Dan Moore)
Newsgroups: comp.dcom.modems
Subject: Re: Supra will offer upgrade to 33.6!
Date: Thu, 29 Feb 1996 15:56:01 GMT
Organization: Supra Corporation
Message-ID: <[e-mail]>
References: <[e-mail]> <4ftaot$[e-mail]> <[e-mail]> <4g182k$[e-mail]> <[e-mail]> <4g3t66$[e-mail]> <[e-mail]> <dan.
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In article <4h0d2b$[e-mail]> [e-mail] (doug haire) writes:
>Dan Moore ([e-mail]) wrote:
>:         The behaviour of the modem when a failed rate renegotiation occurs
>: is not controlled by any S register or command.  It is specified in
>: recommendation V.34 and is not subject to user control.
>Let me get this straight. The %E0 command is meaningless? Why is it even
>mentioned or enabled then? Why has it changed in the last few code revisions?
>Why hasn't it been deleted since retrain initiation is not really
>controlled by this at all?

        The %E and %G commands control what is done when the line
conditions change.  When line conditions change, as reported by higher or
lower EQM levels, the modem may initiate a rate renegotiation or a
retrain to increase or decrease the data rate, or it may do nothing at all.

        Setting %E0 disables the use of retrains when intiating changes in
data rate due to changes in the line condition.   Retrains will only happen
if a rate renegotiation fails (as required by recomendation V.34) or if the
EQM reaches a fairly high value.  Effectively this means a retrain will occur
if the modem is about to lose RLSD (carrier detect) from the remote modem.
No matter what the setting of %E the modem will always respond to remote
retrain requests.

        Setting %E1 enables the use of retrains when initiating changes in
data rate due to changes in the line condition.   This effectively disables
the use of rate renegotiations when initiating changes in data rate.  Rate
renegotiation requests from the remote modem will be responded to normally.

        Setting %G0 disables the use of rate renegotitions when intiating
changes in data rate due to changes in the line condition.   Rate
renegotiation requests and retrains from the remote modem will be responded to
no matter what the setting of %G.

        Setting %G1 enables the use of rate renegotiations to intiate
changes in data rate due to changes in the line condition.

        Setting %E0 and %G0 tells the modem to not initate any retrains or
rate renegotiations to change the data rate of a connection.  The remote modem
may issue retrains or rate renegotiations and the local modem will respond.
If the EQM level is high enough that there is a risk of RLSD being lost the
modem will initiate a retrain request.   This retrain is not caused by an
attempt to adjust the data rate, it is an attempt to prevent RLSD from being
lost.  (This is a difference in intent not of effect.  The data rate after the
retrain will probably be lower.)

        Setting %E0 and %G1 (this is the factory default setting) tells the
modem to initiate rate renegotiations to change the data rate if the line
conditions as measured by EQM changes.   The remote modem may issue retrains
or rate renegotiations and the local modem will respond.   If a rate
renegotiation fails the local modem will initiate a retrain.  If the EQM level
is high enough that RLSD may be lost the modem will initiate a retrain.
Normally the EQM level will never be high enough to initate a retrain, before
it gets that high a rate renegotiation to a lower data rate would occur.

        Setting %E1 and %G0 tells the modem to initiate retrains to change
data rate if the line conditions change.  The remote modem may issue retrains
or rate renegotiations and the local modem will respond.

        Setting %E1 and %G1 tells the modem to initiate retrains to change the
data rate if the line conditions change.  (The %G1 setting is ignored.)  The
remote modem may issue retrains or rate renegotiations and the local modem
will respond.

>None of the answers make sense. You have a command %Ex which is alleged
>by the manual to control line monitoring and retrain initiation and this
>command has been modified in the course of code revisions. But you now
>say that the command means nothing when you use the default since V.34
>specs demand that lines be monitored and retrains initiated.

        I never said the commands mean nothing.   I said that recommendation
V.34 requires additional behaviour.  It defines what a failed rate
renegotiation is and then states that if a rate renegotiation fails a retrain
must be initiated.

        The behaviour controlled by the %E and %G commands has not been
modified in any firmware revision.  They have always worked this way since
they were first implemented in the first SupraFAXModem V.32bis about 4 years
ago.   The parser for the %E command did allow a invalid setting (%E2) to be
accepted in some firmware revisions.   This set %E1 but should not have been
accepted since the option is not legal in Supra products.

        The %E and %G commands control whether or not requests to change data
rates based on current line conditions are initiated and how that request
will be sent to the remote modem.  No matter how %E is set retrains
will be initiated if the line conditions are poor enough that RLSD could be
lost, this is independant of any attempt to increase or decrease data rates.

--
Dan Moore
Supra