Oh, I can just see I am digging myself deeper here. Not mention further off
the thread

I stand corrected on most things.

> Upstream, 56Kbs modems are analogue so to speak, even the new V.92 ones,
so
> there's no conversion needed. The path to you is digital, however. Each
> voice circuit is actually a digital 64Kbps one already, so apart from
> equipment at the ISP end, there's not that much investment required to
make
> 56K modems work over the Telecom network. (This is simplified of course.)

Now as is my understanding V56 modems connect to an analogue phone line. If
there is a Analogue to digital converter at the other end they can use this
to encode information. They can also drop down to an analogue mode if line
conditions are not adequate. Even though the analogue to digital conversion
is done by the Telephone network the "digital" stream is not data, it is
encoded data to be sent over a standard telephone line. In order to convert
this back to "real" data you need some form of Digital Signal Processing.
This represents a processing overhead which I associated originally with an
increase in hardware. There for I think what I was proposing was that for
each dial in line a user consumed 64Kbs of digital bandwidth + 1 Digital
signal processor process. In the case of a "true" data connection the
processing overhead was routing and there was no "fixed" bandwidth
consumption. I then made the assumption that a router algorithm was cheaper
than an DSP algorithm and that the average bandwidth per user would be less
than 64Kb/s 24/7 . This represents raw 659Meg Bytes per day going into the
dsp processors per dial-in line if it were connected 24 hours . Thus I
surmised dial-in users were more expensive.

Oh and I think I better promise not to post any more against this thread.

Adam

----- Original Message -----
From: "Juha Saarinen" <juha@saarinen.org>
To: "Adam Bowden" <adam@datafreight.co.nz>; "Adsl@Unixathome. Org"
<adsl@unixathome.org>
Sent: Friday, October 06, 2000 12:09 PM
Subject: RE: clear/telecom deal

> %-> Fine those are the technical details don't loose the overall
> %-> picture. Sorry
> %-> I should have been more rigerous with the details but I was
> %-> just trying to
> %-> show a concept. I was just trying to get it clear that the DSL
> %-> represents
> %-> the conection to the ISP. Not the gateway to the internet that
> %-> is the ISP.
>
> Well, no, DSL doesn't represent the connection to the ISP. It's the
> connection to IPnet -- that's perhaps what you meant? And sorry, I didn't
> mean to imply that you weren't being rigorous with details or anything
:-).
>
>
> %-> I was also noting that dial in modems have a need for a fixed
> %-> continuious
> %-> 64kb/s per modem (digital to analogue conversion) and require
> %-> hardware to
> %-> decode the modems signals. This represents costs in hardware
> %-> and possible
> %-> multiple "telco" circuits. This to me seems more expensive than
> %-> having one
> %-> central ATM portal which handles all the DSL connections with one
router
> %-> etc.
>
> Upstream, 56Kbs modems are analogue so to speak, even the new V.92 ones,
so
> there's no conversion needed. The path to you is digital, however. Each
> voice circuit is actually a digital 64Kbps one already, so apart from
> equipment at the ISP end, there's not that much investment required to
make
> 56K modems work over the Telecom network. (This is simplified of course.)
>
> %-> Also Saying that DSL runs at 8 Mb/s is misleading. You need
> %-> something at the
> %-> other end which can serve 8MB/s. The rate at which the DSL runs
> %-> has got an
> %-> indirect link to the internet gateway. This is determined by
> %-> the ISPs desire
> %-> for quality of service. TCP/IP is packet based (atm more so) so that
> %-> "streams" of packets can easily be interleaved spreading the
> %-> badwidth across
> %-> multiple clients. Just because you have a link to your ISP of
> %-> 8MB/s does not
> %-> mean that your link to the internet is 8Mb/s you share the link to the
> %-> internet with other users.
>
> No, it's not really misleading, but it's important to take into account
what
> the network itself can handle. Last time I checked, I got 420KByte/s per
> single TCP session -- that's ~3.28Mbit/s. However, if you can aggregate
your
> TCP sessions, you can double that easily. I've done it with Mass
> Downloader...
>
> You might not be able to get e.g. 8Mbps out of a single server on the
> Internet, but with that sort of bandwidth, you have enough headroom to
open
> up several connections to different servers, so your aggregate bandwidth
> might get close to the max.
>
> However, as you point out, it's not just that the speed of the DSL link
that
> decides what performance you'll get. There are many more factors, such as
> traffic shaping by ISPs, etc.
>
> Incidentally, ATM is quite different from TCP/IP, but that's probably
> besides the point here.
>
>
>
> %-> I also note that note everybody is constantly using all their
bandwith.
> %-> Usage is bursty - you download, you browse. So this means on
> %-> average you may
> %-> use alot less than your total available bandwith.
>
> Yes, that's for sure. I don't think Telecom or anyone could support users
> running at full tilt 24-by-7...
>
> -- Juha
>
>
> This message is part of the NZ Broadband mailing list.
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>

This message is part of the NZ Broadband mailing list.
see http://unixathome.org/adsl/ for archives, FAQ,
and various documents.
To unsubscribe: send mail to majordomo@unixathome.org
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Received on Fri Oct 6 13:58:59 2000