Modem speed or lack thereof.....

Modem speed or lack thereof.....

Post by Chas... » Sat, 08 Mar 1997 04:00:00



If anyone can help me witha slightly perplexing question it would be greatly
appriciated.

Ok, so I have made a successfull PPP connection to my ISP (Worldnet).
I find my connection much slower then that made with a (I hate to say it..)
windows connection. I am setting my modem speed to spd_vhi using the setserial
command in my/etc/rc.d/rc.local ie. /etc/rc.d/rc.local /bin/setserial
/dev/cua1 spd_vhi.  I have confirmed that the speed is set at 115000 with
/dev/cau1.

The problem is that the modem seems sluggish and stalls alot.

Does anyone have a suggestion on how to get things humming?

Thanks for any input.


 
 
 

Modem speed or lack thereof.....

Post by Steve La » Sat, 08 Mar 1997 04:00:00



>/dev/cua1 spd_vhi.  I have confirmed that the speed is set at 115000 with
>/dev/cau1.
>The problem is that the modem seems sluggish and stalls alot.
>Does anyone have a suggestion on how to get things humming?

    irqtune and lower the port speed.  I use 115200 on my ISDN line.  If
you're running a modem with 33.6k there is little reason to go over 57600
and only a marginal reason to see anything over 38400.

--
                      -   -  - ---===+{ }+===--- -  -   -
                                 Steve C. Lamb
  i got a feeling we're gonna be close real pals i like the way you shake and
  scream and run away when all i want to do is play with your mind to see how
    long it takes before you crack and lose your strength i'm gonna be your
       closest friend who else would terrorize you.......................
                                          -- Happy Rhodes, "Cohabitants"

 
 
 

Modem speed or lack thereof.....

Post by Jim Bianc » Sun, 09 Mar 1997 04:00:00



>If you are moving stuff like uncompressed text (news) there is PLENTY
>of reason to go higher. a 33.6 modem can (and does) easilly tranfer >57600
>when moving stuff that is highly compressable. Problem is more likely
>an old motherboard with unbuffered UARTS and an external modem but
>the original posting has expired from my server so I can not read it.

        A friend of mine and I made some tests once. He had a new 28.8kbps
modem and I a new 14.4kbps. Using DOS and COMMO (terminal pgm), I called him
and established a connection (he used DOS and COMMO also). Using COMMO, it's
easy to change parms -- such as the pooter<=>modem rate and etc. One of us
set his to 57,600 and the other to 38,400 at first, then we both reset to
57,600, and used zmodem to tfr a pair of test files (a fairly long ASCII
text file and a ZIPed copy of DOOM.WAD).

        Not only did the uncompressed ASCII text file tfr faster when both
ends were set to 57,600, but the compressed ZIP of DOOM.WAD tfr'd signif-
icantly faster too. I forget the figures, but we're talking several minutes
difference on the ZIP file. Both ways (uloading and dloading.)

        I've always set this figure (pooter<=>modem bps rate) to 4x the
expected modem<=>modem rate. For 14.4kbps this works out to 57,600. The
reason is that v.42bis, the most common hardware compression protocol in use
for high-speed modems, is capable of attaining a four times compression
rate. Of course, this figure and these results aren't always seen. For
general BBS work, where unless a file is being tfr'd, the data is mostly
short bursts of uncompressed data (ANSI screens and ASCII text), it makes no
difference what speed is being used (IMHO 2400 is prob fast enough for most
BBS work that doesn't involve tfring dense ANSI screens). It is when a file
tfr is done that these speeds become meaningful.  

        I'm a firm b'liever in using the highest pooter<=>modem speed
possible. Now that I have a new USR Sportster 33.6 (with x2 coming rsn),
I've changed this figure to 115,200 in both my DOS and Linux modem setups.
Sure, a lower speed will work as well, but the link won't be operating at
full efficiency.  

--

Eclectic Garbanzo BBS, (707) 539-1279

 
 
 

Modem speed or lack thereof.....

Post by Steve La » Sun, 09 Mar 1997 04:00:00



Quote:>If you are moving stuff like uncompressed text (news) there is PLENTY
>of reason to go higher. a 33.6 modem can (and does) easilly tranfer >57600

    I charge you to one day account for all the data that you're moving
across the link and see just how much is uncompressed.  Fact of the matter
is slower speed = reliable.  When you've got a crappy link 0% of 115200 will
ALWAYS be < 100% of 38400.  Furthermore, most people have compression on the
protocols turned on so hardly anything that goes through is plaintext.

    I used to be a speed demon, believe me.  I remember setting my 9600bps
modem to 38400 to get maximum throughput.  But years later of SysOping,
being on the internet and being in tech support have taught me otherwise.
If you can do the speed, fine, but there is no "Need" to go that fast.

    Look at the average web page.  1k of text, 5k of gif/jpg.  FTP... I nab
moe in FTP in a day then I grab in news in a month.  Fact of the matter is
most of what people transfer is already compressed and, again, there is no
need to push speed at the expense of reliablity.

Quote:>when moving stuff that is highly compressable. Problem is more likely
>an old motherboard with unbuffered UARTS and an external modem but
>the original posting has expired from my server so I can not read it.

    Even with a 16550AFN in there higher speeds can be a problem.

--
             Steve C. Lamb             | Opinions expressed by me are not my
    http://www.calweb.com/~morpheus    | employer's.  They hired me for my
                                       | skills and labor, not my opinions!
---------------------------------------+-------------------------------------

 
 
 

Modem speed or lack thereof.....

Post by Vern Hox » Mon, 10 Mar 1997 04:00:00




>If you are moving stuff like uncompressed text (news) there is PLENTY
>of reason to go higher. a 33.6 modem can (and does) easilly tranfer >57600
>when moving stuff that is highly compressable. Problem is more likely
>an old motherboard with unbuffered UARTS and an external modem but
>the original posting has expired from my server so I can not read it.

>Note that I had all kinds of trouble with one link until I went to
>115200. Seems two different brands of modems did not like to handshake
>when moving data that they were compressing. Moving plain text at 38400
>on the port caused the other end all kinds of distress.

It is much better to precompress your files before sending them.
Throughput then appraches the connection speed of you modem.  Relying on
the modem to do your compression does indeed affect throughput.

Get my "serial_suite.tgz" via ftp from 'scicom.alphacdc.com'.  It is a
collection of serial port utilities along with several blurbs about
configuring the ports under a Unix type system.

When logging in as "anonymous" on 'scicom', you must use your entire e-mail

vern

--
Vernon C. Hoxie                                           scicom!zebra!vern

Denver, Colo., 80212        uucp: 303-455-2670          voice: 303-477-1780
               Unix is what MSDOS will be when it grows up.

 
 
 

1. Modem recognition (rather, lack thereof)

i'm attemptin to get my ppp connection configured.  i should be able to
handle the scriptin and call to pppd and chat (then again, mayhaps this post
denies that).  anyhow, my prob is that i cannot access the modem from w/in
the shell at all.

minicom works fine, so i know the modem, as well the /dev/modem link, work
fine.  after ensurin that, i tried to echo to the modem (juss a bunch o 9's,
tryin to get somethin).  when that failed i sent my modems init string plus
the dials...still nothin.  that is, i exit w/zero, but the modem neither picks
up or responds.

as for the messages from my attempts w/ pppd/chat, all i get is non-zero exit's
and nothin else.  
although i dont think the prob lies in the pppd/chat calls--mainly because
the scripts run and exit due to the lack of modem usage.  

essentially, how can i get the modem recognized?  that is, chat and echo do
not pick up the line...

danks in advance

xan

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