Can Linux handle > 28.8 modems?

Can Linux handle > 28.8 modems?

Post by Michael Jose Alfr » Wed, 06 Mar 1996 04:00:00



Newsgroups: comp.os.linux.hardware,comp.os.linux.setup,comp.os.linux.misc
Subject: Can linux handle > 28.8 modems?
Summary:
Followup-To:
Distribution:
Organization: University of Delaware
Keywords: modem
Cc:

        I am having problems receiving files with my USR Courier
V.Everything.  Using zmodem I get CRC errors and Data subpacket too
long errors.  Using ftp or ncftp's get, the file will start out at
3.5KBps and freeze for a few seconds and then pick up again, reducing
the ending rate at 1.3KBps for a 1MB file (I have tried different
files).  I used to have a Intel 14.4 modem that worked fine.  I am
connecting to the same type of modem (USRC V.*).  But putting 1 MB
files with ftp and ncftp goes at the normal 3.5KBps.  Also everything
works under win95 (zmodem, getting and putting).

        I have tried some of the AT commands, but with no success.  I
called US Robotics and they told me that it might be the size of the
receive buffer linux is using.  I think they might be right because
when I get the first error it is usually around 40K and that's when I
hear my hard drive spin and the light goes on.  Then it will go a
little further and do the same thing.  Any help or ideas would be
greatly appreciated, because I use linux a lot more than win95 and I
don't want to have to switch. :)

I am using slackware 3.0 and linux 1.3.70 (I have tried others).

        Thanks,

        Mike

 
 
 

Can Linux handle > 28.8 modems?

Post by Saint Erroneo » Sun, 17 Mar 1996 04:00:00




Quote:>    Interestingly, under Win95, I've been getting *very* high
>transfer rates, about .4K/s greater than Linux (3.3 vs 2.9).  I am using
>PPP in Win95, and slip in Linux.  From Win 3.1, I would only get about
>2.4, using Trumpet.  Under DOS 6, I'd get about 2.8 in a regular dialup
>terminal.

IIRC ppp does (some) error checking across the phone-line connecion, while
slip only does error checking between the internet source and your
machine.  Thus, if you've got a fuzzy phone line ppp should involve less
delay whenever you get a bad packet.

Or I could be talking bollox...
-michael
--
-St. michael (mainly) Erroneous http://www.st-and.ac.uk/~www_sa/personal/mpv
 "You have been changed. You are Joshua. That is your name. It is also your
    access-code. All the answers you will ever need are available to you.
      All you have to do is say your name." - Gap 2, Stephen Donaldson

 
 
 

Can Linux handle > 28.8 modems?

Post by Mike Cast » Tue, 19 Mar 1996 04:00:00






>>        Interestingly, under Win95, I've been getting *very* high
>>transfer rates, about .4K/s greater than Linux (3.3 vs 2.9).  I am using
>>PPP in Win95, and slip in Linux.  From Win 3.1, I would only get about

Slip or cslip?  If just slip, have you tried cslip?  Or have you
tried ppp?  

Theoretically, cslip and ppp should have the same performance.
However, quality of implementation can have great impact.
Perhaps trying cslip under win95 may give different results,
indicating that perhaps your ISP is using a higher quality ppp
implementation?

Quote:>>2.4, using Trumpet.  Under DOS 6, I'd get about 2.8 in a regular dialup
>>terminal.

>IIRC ppp does (some) error checking across the phone-line connecion, while
>slip only does error checking between the internet source and your
>machine.  Thus, if you've got a fuzzy phone line ppp should involve less
>delay whenever you get a bad packet.

If you have error correcting modems, wouldn't software
correction not make much difference most of the time? (Most/all
of the errors being caught at the hardware level, and the
software never seeing them).

mrc
--
Mike Castle .-=NEXUS=-.  Life is like a clock:  You can work constantly


    We are all of us living in the shadow of Manhattan.  -- Watchmen

 
 
 

1. Can Linux handle > 28.8 modems?


Subject: Re: Can Linux handle > 28.8 modems?
Date: 7 Mar 1996 16:50:49 GMT

        It could be that the buffer is too small, but I've never noticed
an option for changing it.  Maybe I'll need to dig in the kernel source
a
bit.  Anyhow, I also have a USR Sportster 28.8 internal, but I don't
have
that sort of problem.  Sportsters are supposed to have the serial port
set to 57.6, so check the setserial manpage for the correct command.
If
I set it to anything else, very poor performance results.  Also, you
may
want to play with your MTU.  The smaller the MTU, the better the error
recovery, but the transfer rate will be lower.  Check with your
internet
provider to see what they recommend.
        Interestingly, under Win95, I've been getting *very* high
transfer rates, about .4K/s greater than Linux (3.3 vs 2.9).  I am
using
PPP in Win95, and slip in Linux.  From Win 3.1, I would only get about
2.4, using Trumpet.  Under DOS 6, I'd get about 2.8 in a regular dialup
terminal.


:       I am having problems receiving files with my USR Courier
: V.Everything.  Using zmodem I get CRC errors and Data subpacket too
: long errors.  Using ftp or ncftp's get, the file will start out at
: 3.5KBps and freeze for a few seconds and then pick up again, reducing
: the ending rate at 1.3KBps for a 1MB file (I have tried different
: files).  I used to have a Intel 14.4 modem that worked fine.  I am
: connecting to the same type of modem (USRC V.*).  But putting 1 MB
: files with ftp and ncftp goes at the normal 3.5KBps.  Also everything
: works under win95 (zmodem, getting and putting).

<snip>

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