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'[OT]: 56k modem at 250k'
2002\09\10@211534 by Jinx

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Quite often when d/l from ftp sites my connection seems to
be accepting data at a much faster rate than it normally does.

I use NetMedic to monitor the line and generally see a 50.6k
connection, and data comes in anywhere from 30k to 44k

Getting some pdfs from Microchip this morning the transfer
rate was up over 250k, as it has done before (it seems to be
true as NetMedic shows, as the files do d/l a lot faster), and
this time I thought I'd ask how that works. So, how does that
works ?

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2002\09\10@212216 by lexandre_Guimar=E3es?=

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Simple.... Compression.. Like a zip file.

----- Original Message -----
From: "Jinx" <spam_OUTjoecolquittTakeThisOuTspamCLEAR.NET.NZ>
To: <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Tuesday, September 10, 2002 10:14 PM
Subject: [OT]: 56k modem at 250k


{Quote hidden}

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2002\09\10@221452 by Jinx

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> Simple.... Compression.. Like a zip file.
>
> > Quite often when d/l from ftp sites my connection seems to
> > be accepting data at a much faster rate than it normally does.

The files aren't any smaller, they just sometimes download very
much faster. Normally a 6MB pdf (specifically the F452 data
sheet) would take around 25 minutes. Today it took 6 minutes,
but it's still 6MB

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2002\09\10@221907 by M. Adam Davis

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Some browsers start downloading the file while you're still choosing
where to save it, but don't count that as download time, so when the
dialog finally shows up it's downloaded half the file at one second.
Your modem and the modem you're calling also have fairly decent on the
fly compression built in, so you can transfer simple files fairly
quickly.  Lastly many web servers are configured to zip a file on the
fly when a compatible browser can unzip it on the fly.  It reduces
bandwidth and speeds up the transmission.

I'm still surprised you get 250K bytes, are you sure it isn't reading in
bits per second?

As an aside, some PDFs are not precompressed and since they have a
fairly simple structure they can compress very well.  To get a really
good idea of the actual speed try downloading a large compressed
(zipped) file, such as MPLAB.

-Adam

Jinx wrote:

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2002\09\10@221914 by Rick C.

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part 0 44 bytes
his is a multi-part message in MIME format.
part 1 1350 bytes content-type:text/plain; charset=iso-8859-1 (decoded quoted-printable)

Compression is good! ;-)
Rick

Alexandre Guimar„es wrote:

> Simple.... Compression.. Like a zip file.
>
> {Original Message removed}
part 2 12303 bytes content-type:image/gif; (decode)


part 3 144 bytes
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2002\09\10@223103 by Sean H. Breheny

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Hi Jinx,

He means compression on the fly. Modems can compress files as they send
them and transparently decompress on the other end. Try zipping one of the
ones that went really fast and see if it zips much. Note that it is (I
would guess) more reliable to zip a file first than to rely on the modem's
compression.

Sean


At 02:11 PM 9/11/2002 +1200, you wrote:
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2002\09\11@005255 by Jinx

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part 1 656 bytes content-type:text/plain; (decoded 7bit)

> He means compression on the fly. Modems can compress files
> as they send them and transparently decompress on the other end.

Hmmm. OK, consider this. These two captures of NetMedic (a great
little utility BTW) show a download of 39564a.pdf from the same
Microchip link 10 minutes apart. Spot the difference ? One of them
took a really long time, the other was going like a stolen car in the
fast lane

> Try zipping one of the ones that went really fast and see if it zips
> much.

Using WinZip8 it compresses 5.8MB to 3MB. 3MB @ 56kbps
should still take around 12-13 minutes, not 6

Must be Wednesday




part 2 6069 bytes content-type:image/gif; (decode)


part 3 131 bytes
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2002\09\11@005900 by Russell McMahon

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May possibly be loading out of your cache - have you downloaded them before
& not realised (until you read this :-) ) ?


> I use NetMedic to monitor the line and generally see a 50.6k
> connection, and data comes in anywhere from 30k to 44k
>
> Getting some pdfs from Microchip this morning the transfer
> rate was up over 250k, as it has done before (it seems to be
> true as NetMedic shows, as the files do d/l a lot faster), and
> this time I thought I'd ask how that works. So, how does that
> works ?

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2002\09\11@010835 by Sean H. Breheny

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Which one came first? The fast or the slow one? Also, did you ever DL this
file before?

Sean

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2002\09\11@014633 by Dale Botkin

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On Wed, 11 Sep 2002, Jinx wrote:

> > He means compression on the fly. Modems can compress files
> > as they send them and transparently decompress on the other end.
>
> Hmmm. OK, consider this. These two captures of NetMedic (a great
> little utility BTW) show a download of 39564a.pdf from the same
> Microchip link 10 minutes apart. Spot the difference ? One of them
> took a really long time, the other was going like a stolen car in the
> fast lane

Two words:


Browser cache.

Dale

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2002\09\11@014656 by Jinx

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> May possibly be loading out of your cache - have you
> downloaded them before & not realised (until you read
> this :-) ) ?

No. I did not complete the second load of the file. I abandoned
it after 11 minutes and it was less than 1/2 loaded. Cache was
cleared after the first load. Plus I saved it as 16F452.pdf, not
39564a.pdf. I don't think it would be got from cache under a
different name. The fact remains that one load was 5 times
faster than the connection would suggest it could be

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2002\09\11@014820 by Jinx

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> Which one came first? The fast or the slow one?

The fast one - pre-empts your cache question

> Also, did you ever DL this file before?

No, never

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2002\09\11@020322 by Dale Botkin

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On Wed, 11 Sep 2002, Jinx wrote:

> No. I did not complete the second load of the file. I abandoned
> it after 11 minutes and it was less than 1/2 loaded. Cache was
> cleared after the first load. Plus I saved it as 16F452.pdf, not
> 39564a.pdf. I don't think it would be got from cache under a
> different name.

Caching is done based on the object's URL, which would be the same no
matter what name you gave it when saved.


> The fact remains that one load was 5 times
> faster than the connection would suggest it could be

Right, and I think that indicates it is getting at least partially pulled
from cache.  I believe Internet Exploder will also keep partial downloads
and resume from the point it left off if it can, but I could be wrong.

Try this: Clear your browser cache.  Kill the browser, delete files from
\windows\temp also.  Restart the browser and try it again.  Bet it's slow
again, or there's another cache I've forgotten.  Windows will bend over
backwards to keep from downloading the same thing twice.

Dale

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2002\09\11@021111 by Jinx

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> Two words:
>
> Browser cache.
>
> Dale

Two words

Oh no it wasn't

I've just found exactly the same thing with 41159a.pdf,
which I have never ever downloaded before. 6MB came
down at 210kbps, which again is faster than compression
would suggest, unless it's a truly wonderful compression

Surely someone has seen this before ? Maybe it's because
I have a line monitor running that I notice

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2002\09\11@043606 by Roman Black

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Jinx wrote:

> > Browser cache.

> Oh no it wasn't
>
> I've just found exactly the same thing with 41159a.pdf,
> which I have never ever downloaded before. 6MB came
> down at 210kbps, which again is faster than compression
> would suggest, unless it's a truly wonderful compression
>
> Surely someone has seen this before ? Maybe it's because
> I have a line monitor running that I notice


Many of the "line monitor" things use a crude averaging
system, the displayed transfer speed starts very high
and will slowly approach a realistic speed by the end
of a large file.

With smaller files the displayed speed may be way off.
However you did say 6Mb file? I would expect that to take
a LOT more than 6 minutes.

I think the one fact you CAN rely on is that a 56k
modem is NOT going to give you 250k download speeds.
:o)
-Roman

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2002\09\11@043826 by Russell McMahon

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> Hmmm. OK, consider this. These two captures of NetMedic (a great
> little utility BTW) show a download of 39564a.pdf from the same
> Microchip link 10 minutes apart. Spot the difference ? One of them
> took a really long time, the other was going like a stolen car in the
> fast lane

That seems to confirm my previous suggestion - once downloaded the file is
in your cache and a reload simply requires a files transfer from cache to
where-ever you are putting it. This suggests that the fast loading Microchip
files have already been downloaded recently. Maybe your short term memory
(as opposed to your PC's is getting to be like mine :-)


           RM

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2002\09\11@050815 by Jinx

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> This suggests that the fast loading Microchip files have already
> been downloaded recently. Maybe your short term memory (as
> opposed to your PC's) is getting to be like mine :-)

Oh 'sakes ;-)  To summarise - I have never ever loaded any 18F
pdfs before. They are not in cache. 6MB loaded damn fast the
first time (@ roughly 1MB / min). It happens to me with many ftp
sites. I'm not convinced compression is the answer

> I think the one fact you CAN rely on is that a 56k modem is NOT
> going to give you 250k download speeds.
> :o)
> -Roman

Ye canna change the laws of physics cap'n ? I'd agree with that.

But - why do I see this at ftp sites and not during normal surfing
(or not to the same degree, sometimes data rate does go way
over the "speed limit"). NetMedic does have an actual and an
averaging read-out. They are different, and they concur

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2002\09\11@052601 by ichard Phillips

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> > This suggests that the fast loading Microchip files have already
> > been downloaded recently. Maybe your short term memory (as
> > opposed to your PC's) is getting to be like mine :-)
>
> Oh 'sakes ;-)  To summarise - I have never ever loaded any 18F
> pdfs before. They are not in cache. 6MB loaded damn fast the
> first time (@ roughly 1MB / min). It happens to me with many ftp
> sites. I'm not convinced compression is the answer

one thing that could explain this is that link compression is employed on
56k modems, i think - so depending on the file type, you may get an
'increase' in download speed.

so a compressed file, such as a zip, will download at the true link
bandwidth, whereas something like a text file will be compressed and appear
to be downloading at a speed above that of the connection.  i've seen
similar things quite often myself..

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2002\09\11@054727 by Katinka Mills

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> -----Original Message-----
> From: pic microcontroller discussion list
> [PICLISTspamKILLspamMITVMA.MIT.EDU]On Behalf Of Roman Black
> Sent: Wednesday, 11 September 2002 3:50 PM
> To: .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
> Subject: Re: [OT]: 56k modem at 250k

<elsnipo>

> With smaller files the displayed speed may be way off.
> However you did say 6Mb file? I would expect that to take
> a LOT more than 6 minutes.
>
> I think the one fact you CAN rely on is that a 56k
> modem is NOT going to give you 250k download speeds.
> :o)
> -Roman

One other thing, I assume this is an external modem plugged into a PC serial
port ?

If so , the max speed you can get is 115Kbps (unless you have a special high
speed serial card)

If you can do this repetably, I would love to know how, as I use a 512Kbps
ADSL link, and would love to get ~10 times more data though it (/me dreams
of files being here before I go looking ;o)


Regards,

Kat.

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Electronic and Software Engineering.
Perth, Western Australia.
Ph +61 (0) 419 923 731
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2002\09\11@072652 by Jinx

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> One other thing, I assume this is an external modem plugged into
> a PC serial port ?

Nope. Bog standard internal Lucent on Com3

> If so , the max speed you can get is 115Kbps (unless you have
> a special high speed serial card)

It's set in Control Panel to a max of 115k2, but generally I'd
see it at 30-40. I think I'll have to get an opinion from my ISP

> If you can do this repeatably, I would love to know how

Well, that's my point. If there is something going on, how could
I capitalise on it ? Mostly I'm happy with the good ole phone
line but now and then a little more speed would be just ducky

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2002\09\11@075006 by ar=E3es?=

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Hi, Jinx

> It's set in Control Panel to a max of 115k2, but generally I'd
> see it at 30-40. I think I'll have to get an opinion from my ISP

   There is no way you can get transfers faster than that unless things are
cached. The modem compression is a little different from a regular zip and
you can get much better or much worse results depending on the files but you
can never get higher than the 115k. It it is happening it is inside you
computer, cached somehow and somewhere :-)

> > If you can do this repeatably, I would love to know how
>
> Well, that's my point. If there is something going on, how could
> I capitalise on it ? Mostly I'm happy with the good ole phone
> line but now and then a little more speed would be just ducky

   That would be magic ;-) The cache is the best magic that can happen. Do
you have any kind of download accelerator installed ? Some of them try to
download the files before you look at them. They watch the hyperlinks on the
page and if transfer is idle they start the download in the background. That
might explain your huge transfer rates and also explain why it works in one
site and not in the other with the same file. It does not work with JAVA
pages, for example.

   There has to be a reasonable explanation somewhere.......

Best regards,
Alexandre Guimaraes

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2002\09\11@075422 by Alan B. Pearce

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>It's set in Control Panel to a max of 115k2, but generally I'd
>see it at 30-40. I think I'll have to get an opinion from my ISP
>
>> If you can do this repeatably, I would love to know how
>
>Well, that's my point. If there is something going on, how could
>I capitalise on it ? Mostly I'm happy with the good ole phone
>line but now and then a little more speed would be just ducky

It will be as others have said, the compression that can be available across
the modem link. This is on top of the 56k line speed, and could well give
you the 250k rate you report. I cannot remember the name of the compression,
but remember settings for enabling and disabling it in external modems.

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2002\09\11@092903 by Jim

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  > But - why do I see this at ftp sites and not
  > during normal surfing


Hmmm ... the diff between multiple TCP sessions being
opened for 'file' transfers back and forth thusly:

1) PC/Browser submits request  for a particular .html file
2) server returns the HTML file (these all require TCP sessions)
3) browser parses HTML
4) Browser begins to open multiple TCP sessions - one
  for each component on web page.

- versus basically one unidirectional FTP session (well, one
and control one data channel) being opened?


RF Jim

{Original Message removed}

2002\09\11@111004 by Herbert Graf

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> Quite often when d/l from ftp sites my connection seems to
> be accepting data at a much faster rate than it normally does.
>
> I use NetMedic to monitor the line and generally see a 50.6k
> connection, and data comes in anywhere from 30k to 44k
>
> Getting some pdfs from Microchip this morning the transfer
> rate was up over 250k, as it has done before (it seems to be
> true as NetMedic shows, as the files do d/l a lot faster), and
> this time I thought I'd ask how that works. So, how does that
> works ?

       v.42bis, IIRC, it's compression, usually does nothing since most downloads
are already compressed, but quite good when delaing with straight text. Just
happens that pdfs generally compress REALLY well. Of course, had the pdf
been compressed before transmission you would have probably gotten an even
faster equivalent transfer rate. TTYL

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2002\09\11@111211 by Herbert Graf

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> > Simple.... Compression.. Like a zip file.
> >
> > > Quite often when d/l from ftp sites my connection seems to
> > > be accepting data at a much faster rate than it normally does.
>
> The files aren't any smaller, they just sometimes download very
> much faster. Normally a 6MB pdf (specifically the F452 data
> sheet) would take around 25 minutes. Today it took 6 minutes,
> but it's still 6MB

       True, it's compression over your 56k link, perhaps everlier you did get the
compression since it wasn't done during init with the other modem. TTYL

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2002\09\11@111215 by Herbert Graf

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> Hi Jinx,
>
> He means compression on the fly. Modems can compress files as they send
> them and transparently decompress on the other end. Try zipping one of the
> ones that went really fast and see if it zips much. Note that it is (I
> would guess) more reliable to zip a file first than to rely on the modem's
> compression.

       I wouldn't say it's more reliable, it is however much more efficient. The
on the fly compression modems do is quite good, but it's nothing compared to
something like zip. TTYL

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2002\09\11@111423 by Herbert Graf

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> > He means compression on the fly. Modems can compress files
> > as they send them and transparently decompress on the other end.
>
> Hmmm. OK, consider this. These two captures of NetMedic (a great
> little utility BTW) show a download of 39564a.pdf from the same
> Microchip link 10 minutes apart. Spot the difference ? One of them
> took a really long time, the other was going like a stolen car in the
> fast lane

       That looks like you might have been getting the file from a cache or
something like that, do you have a caching program? What did you use to
download it? TTYL

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2002\09\11@114313 by Mike Singer

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Jinx wrote:
.
.
> Oh 'sakes ;-)  To summarise - I have never ever loaded any 18F
> pdfs before. They are not in cache. 6MB loaded damn fast the
> first time (@ roughly 1MB / min). It happens to me with many ftp
> sites. I'm not convinced compression is the answer
.
.

Once, in August at night I've downloaded 70082a.pdf (5.72M) for
about 14 min. (~24Mb/hour, usually 12-15Mb/hour)
I used:
WWW site, not FTP
FlashGet 0.96, W2K
ZyXel Omni 56K, connected at 40K V90 to my ISP
Local telephone commutator(~500m): stepping relay based,
produced in 195x.

I didn't downloaded it before, but the speed
24Mb/hour=400k/min=7kbyte/s=56kbit/s seems to be achievable,
taking into consideration the compression.

Mike.

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2002\09\11@115734 by Jim

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#1 ----

Does anybody know about the compression that can be agreed
upon during an LCP (Link Control Protocol) negotiation on
a PPP link between two modems, compression like Van Jacobson
Compressed TCP/IP?

May I guess that this compression is done my the main CPU
in a Winmodem - and by the on-board processor on a full
US-Robotics DOS-capable FAX-Modem?

#2 ----

It has also been shown that PCI modem ping-times are like
100 ms longer that the same modem but in an ISA slot -
documentation of this item upon request ...

(I know some Gamers that have caught onto this little item.)

RF Jim


{Original Message removed}

2002\09\11@125940 by Michael Rigby-Jones

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{Quote hidden}

The ping issue has nothing to do with the PCI slot per se, it's just that
the overwhelming majority of PCI based modems are either "softmodems" and
use the host CPU for virtualy all DSP work, or are at least "controllerless"
which puts somewhat less overhead on the CPU, but still far more than a
"proper" hardware modem.  Most (but not all) ISA based modems were purely
hardware solutions, effectively the guts of an external modem and a UART on
the same board.  USB modems are also nearly always controllerless.  The only
way to guarantee to get a decent modem (which will also work with Linux etc)
is to buy an external one that uses a proper serial port connection.

Regards

Mike

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2002\09\11@142121 by Jim

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  "The ping issue has nothing to do with the PCI
   slot per se"

I've got some guys reporting that ping times to a local
node from an ISA-based modem are always half those of of
a PCI-based modem.

I'm going to check with these guys and see whether their
PCI-based modem was a brainless Win-modem or not ...

RF Jim



----- Original Message -----
From: "Michael Rigby-Jones" <@spam@mrjonesKILLspamspamNORTELNETWORKS.COM>
To: <KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU>
Sent: Wednesday, September 11, 2002 11:07 AM
Subject: Re: [OT]: 56k modem at 250k


> > {Original Message removed}

2002\09\11@142909 by M. Adam Davis

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I'd say it has nothing to do with the slot, since th ISA bus is simply a
PCI to ISA bridge, meaning any ISA signals go through the PCI buss
before they reach the ISA bus.

If anything it's a driver or OS issue (winmodem, bad drivers, bad OS
handling of PCI stuff, etc)

-Adam

Jim wrote:

{Quote hidden}

>>>{Original Message removed}

2002\09\11@144550 by Jim

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The ping times using a serial port to an external
modem *also* report back with half the time reported
when using PCI-based modems. Now, I fully realize
that the usual standard serial ports nowadsys sits
off some other bus as opposed to the usual UART
that used to sit right off the CPU data bus - I just
don't know where they reside in today's machines.

And since I haven't researched all this 'ping time'
stuff myself, I'm only reporting on what these guys
have 'discovered' - this one individual did tests
with a number of different modems, both PCI and
ISA-based in order to arrive at his conclusions.

RF Jim


{Original Message removed}

2002\09\11@151134 by Dominic Stratten

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Could it be anything to do with the fact that most PCI modems are "software
modems" i.e. they use the computers CPU for all the processing ? I've always
had (as an ex IT manager) terrible problems with these software modems with
sluggish response, high CPU overheads and dropped lines. Any modem that sits
on the serial port is a hardware modem as is any ISA Modem on the market (I
will only buy and use ISA Modems). They have their own onboard CPU and will
operate quite independently from the main system.

Just a thought

Dom
{Original Message removed}

2002\09\11@162214 by Andrew Hooper

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Another thing you may like to take into account is that almost all ISP's
use a proxy server of some kind, Im not sure but I think clear use a
SQUID cluster and have slingshot enabled. This will dramatically
increase the speed of your downloads as it would look like the file was
being retrieved from the remote site when in fact it was coming from the
ISP's cache.

Most ISP's and service providers now put a limit on the available
bandwidth from FTP servers on their sites to prevent abuse and provide a
certain amount of balancing.

Often in a perfect world it is easy to get a dialup connection to your
ISP with very fast response time then the delays come as you go out that
ISP's connection.

Try thins next time.

Tracert ftpservers.ip.adress    (traceroute on linux)
Check the hops.
Look at the 2nd and 3rd hop and record the IP address

Ping the ftpservers.ip.adress
Average the ping times.

Ping the 2nd and 3rd hop IP. And check out the average.

I don't think this will take into account that you are running
compression or that the line is setup for compression and should give
you raw ping time.

And before you ask, testing an FTP from clear would not be a good
comparison as im sure they are limiting the FTP speeds.

Regards
Andrew Hooper
Server Operations
BestNet
021 212-9200






{Original Message removed}

2002\09\11@184142 by Peter L. Peres

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On Wed, 11 Sep 2002, Jinx wrote:

>Quite often when d/l from ftp sites my connection seems to
>be accepting data at a much faster rate than it normally does.
>
>I use NetMedic to monitor the line and generally see a 50.6k
>connection, and data comes in anywhere from 30k to 44k
>
>Getting some pdfs from Microchip this morning the transfer
>rate was up over 250k, as it has done before (it seems to be
>true as NetMedic shows, as the files do d/l a lot faster), and
>this time I thought I'd ask how that works. So, how does that
>works ?

Maybe the servers compress the file on the fly. Or you d/l'd it before and
it is lurking in your browser cache. The latter is the most likely
explanation for 250k.

Peter

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2002\09\11@184158 by Peter L. Peres

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On Wed, 11 Sep 2002, Jim wrote:

>#1 ----
>
>Does anybody know about the compression that can be agreed
>upon during an LCP (Link Control Protocol) negotiation on
>a PPP link between two modems, compression like Van Jacobson
>Compressed TCP/IP?

There is VJ compression and BSD compression. The latter is seldom used. VJ
is used by default in most systems and involves compressing the IP
datagram header (which header contains a lot of redundant information).
The header is a small part of an IP packet, unless it's a ICMP or other
low protocol packet, so the gain is minimal, and mostly manifests itself
in packet assembly/disassembly speed afaik. Of course it affects ICMP
packets strongly (since they are short).

>May I guess that this compression is done my the main CPU
>in a Winmodem - and by the on-board processor on a full
>US-Robotics DOS-capable FAX-Modem?

No, the compression is done by the TCP/IP protocol stack implementation,
i.e. the main CPU, in both cases.

>#2 ----
>
>It has also been shown that PCI modem ping-times are like
>100 ms longer that the same modem but in an ISA slot -
>documentation of this item upon request ...

Most PCI modems are winmodems. The latency is due to the main CPU playing
DSP to send/receive data. This also shows up as frame count drop in a
highly demanding application (video, games, math). The modems with
controller use lookup tables (like caches) and DSP math tricks to get
bytes in and out through the codecs, fast, with low latency.

It pays to examine the modem datasheet to make sure that it does not
accept slow and uncompressed connections (MNP, Vxxx etc), and alter the
modem setup strings accordingly.

Peter

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2002\09\12@120830 by Michael Rigby-Jones

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{Quote hidden}

The ping issue has nothing to do with the PCI slot per se, it's just that
the overwhelming majority of PCI based modems are either "softmodems" and
use the host CPU for virtualy all DSP work, or are at least "controllerless"
which puts somewhat less overhead on the CPU, but still far more than a
"proper" hardware modem.  Most (but not all) ISA based modems were purely
hardware solutions, effectively the guts of an external modem and a UART on
the same board.  USB modems are also nearly always controllerless.  The only
way to guarantee to get a decent modem (which will also work with Linux etc)
is to buy an external one that uses a proper serial port connection.

Regards

Mike

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'[OT]: 56k modem at 250k'
2003\02\02@214136 by Jinx
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technology.nzoom.com/technology_detail/0,1608,165245-113-380,00.html

Bin there, dun that

----- Original Message -----
From: "Jinx" <EraseMEjoecolquittspamclear.net.nz>
To: "pic microcontroller discussion list"
Sent: Wednesday, September 11, 2002 2:14 PM
Subject: [OT]: 56k modem at 250k


{Quote hidden}

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2003\02\02@234520 by Sean H. Breheny

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Did you ever figure out what was going on? Cache/compression of some kind?

Sean

At 03:43 PM 2/3/2003 +1300, you wrote:
>http://technology.nzoom.com/technology_detail/0,1608,165245-113-380,00.html
>
>Bin there, dun that
>
>{Original Message removed}

2003\02\03@015230 by Jinx

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> Did you ever figure out what was going on? Cache/
> compression of some kind?
>
> Sean

Nope - still happens too. Some pdfs from an ftp site the
other day came into the PC almost 4x as fast as their sizes
suggested they should have, ie transfer was 1 minute/meg.
I'm convinced that on odd occassions a 56k modem can
go faster, but I appreciate there are Doubing Thomases
amongst you with good technical reasons/opinions why it
shouldn't happen

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2003\02\03@032528 by William Chops Westfield

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See if the files compress more than expected with winzip/etc as well?

BillW

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2003\02\03@035050 by Jinx

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> See if the files compress more than expected with winzip/etc
> as well?
>
> BillW

No, it doesn't. Possibly there's some compression at their end
and exapnsion at my end and NetMedic is displaying the post-
modem (ie PC-side expanded) volume, even though the actual
volume into the modem is compressed. Might pop off a mail to
NetMedic and get their opinion, still makes me wonder every
time I see it

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2003\02\03@072130 by Alan B. Pearce

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>> Did you ever figure out what was going on? Cache/
>> compression of some kind?
>>
>> Sean
>
>Nope - still happens too. Some pdfs from an ftp site the
>other day came into the PC almost 4x as fast as their sizes
>suggested they should have, ie transfer was 1 minute/meg.
>I'm convinced that on odd occassions a 56k modem can
>go faster, but I appreciate there are Doubing Thomases
>amongst you with good technical reasons/opinions why it
>shouldn't happen

Well it is dependant on a number of things.

1. It is possible that the browser is downloading the file into a temporary
file while you are still fiddling around determining where to save it. You
can see this happening if you use Opera, as there is a download activity bar
at the bottom of the window. On small files the download into the temporary
file can be completed before you have finished selecting the save location.
Incontinent Exploder also saves to a temporary file before transferring to
the final save location, so I believe it does the same thing. It is possible
for this action to hide a reasonable piece of the download time.

2. If you are using your ISP's cache facility then the file can be
downloaded into that from the original location lightening fast, and your
download is then only at the speed/activity level of your ISP and you. This
can save considerable time in a large download, as you are not having to
send acknowledgements to packets considerable distances over a potentially
busy internet, your ISP has already done this in downloading into its cache.

3. AFAIK all 56k modems use compression on the data stream to achieve higher
than 56k equivalent data rates at the (equivalent) DB25 connector. For this
reason it is often possible to use 115k to connect to an external modem, and
subject to network traffic, achieve more than 56k actual data transfer
rates.

4. Do not forget that doing other browsing while downloading can
considerably slow down a file download. :)) If you have wandered away
thinking that you have started a large file which will take a while, and
leave the browser alone, you may be surprised at how much faster it runs
with no other activity.

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2003\02\03@094702 by Sean H. Breheny
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Well, the biggest problem I have with the idea that a 56k modem could go
faster than 56k (truly faster, not just on compressible data) is that
AFAIK, the codecs in the phone system which digitize the analog signal only
do so at a 64kbps rate (8000 8bit samples per second), unless that has been
changed (and even then it would be strange that the 56k modem would have
the ability to take advantage of that and they would not advertise such a
great capability!).

Sean

At 07:52 PM 2/3/2003 +1300, you wrote:
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2003\02\03@103810 by M. Adam Davis

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Not only that, but many systems encode the clock into the signal by
toggling the smallest bit every byte, giving us (tada!) 56,000 bits per
second.  That the modem's today can characterize the miles of wire,
devices, and codec such that they can use even 85% of that bandwidth
(for 48k) is neat, when you think about all the digital signal
processing that that sort of thing takes.

Only ISDN/T1/etc is able to achieve the full channel bandwidth.  I
assume they have built in clock encoding and regeneration.

-Adam

Sean H. Breheny wrote:

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2003\02\03@104635 by M. Adam Davis

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Web servers and browsers have built in zip type file compression on the
fly.  When you go to a site, your browser tells the web server its
capability in this regard, and the webserver will compress if it can
(which depends on who set it up).

Companies with smart webadmins who want to reduce bandwidth usage are
very aggressive in this respect, and one of the reasons you need a fast
computer to serve a relatively slow (1Mbps) line.  A 486 webserver can
saturate a regular 10Mbps line, but it takes a fast machine with gobs of
memory to compress several files at once for different viewers and still
saturate that line with the compressed data.  This also increases the
user-friendlyness of a web site, since html files are compressed ( which
typically compress a *lot*) and load faster, and the end users don't
have to worry about dealing with .zip files.  Download the exe, pdf, etc
and use it directly.

-Adam

Jinx wrote:

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2003\02\03@154936 by Peter L. Peres

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On Mon, 3 Feb 2003, Sean H. Breheny wrote:

*>Well, the biggest problem I have with the idea that a 56k modem could go
*>faster than 56k (truly faster, not just on compressible data) is that
*>AFAIK, the codecs in the phone system which digitize the analog signal only
*>do so at a 64kbps rate (8000 8bit samples per second), unless that has been
*>changed (and even then it would be strange that the 56k modem would have
*>the ability to take advantage of that and they would not advertise such a
*>great capability!).

I regularly see true d/l speeds of 6,7,8,9 kBps with a 56k modem connected
at 45.5 or so. The modem has compression and it works well for text. The
high speed is seen especially when browsing (mostly text). For binary data
and images it goes as slowly as the link (45k or below).

Peter

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