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Home > Archive > Cheap Linux Hardware > December 2007 > multiple xDSL connections from one ethernet connection.
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multiple xDSL connections from one ethernet connection.
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| Weird request I guess.
I have a classroom and access to an ethernet socket on the wall.
I would like each student to have their own DSL line to
their desk so they can install and configure their own DSL
modem pci card. Then ideally go through the rest of the
course using that as their internet connection for
downloading software.
Since they would (or should) all be downloading the same
software, a web cache machine could be placed at the
ethernet connection.
I never get to see this side of the ADSL hardware. It all
happens back at the local telephone exchange, but this is
what I'd like to achieve.
It easy enough to turn a linux beige-box into an ethernet
switch, and I would like to think I could do the same but
with DSL modem cards instead of ethernet cards, but I need
pointers so some software here.
What problems can anyone forsee?
Cheers
Andy Richardson
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| Henrik Carlqvist 2007-12-10, 1:24 am |
| Andy <andy-at@mrbumpy-dot.co-dot.uk> wrote:
> I would like each student to have their own DSL line to their desk
It is possible to buy such equipment. There are different brands to choose
from.
> so they can install and configure their own DSL modem pci card.
Why a PCI card? This will limit your choices of brands.
> I never get to see this side of the ADSL hardware. It all happens back at
> the local telephone exchange, but this is what I'd like to achieve.
There is really nothing difficult with this.
> It easy enough to turn a linux beige-box into an ethernet switch, and I
> would like to think I could do the same but with DSL modem cards instead
> of ethernet cards, but I need pointers so some software here.
If you go the route with PCI cards you will of course need drivers for
those cards. Except from that, there is nothing different in the DSL
software setup compared to any normal network. You might want to consider
things like DHCP and firewall settings.
> What problems can anyone forsee?
Your biggest problem might be to find a reseller of DSL modems. In sweden
we have a reseller at http://www.direktronik.se/ but that one is the only
one I know of.
regards Henrik
--
The address in the header is only to prevent spam. My real address is:
hc1(at)poolhem.se Examples of addresses which go to spammers:
root@localhost postmaster@localhost
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| Jordan Hazen 2007-12-12, 7:20 am |
| In article <fjgldq$1fam$1@energise.enta.net>,
Andy <andy-at@mrbumpy-dot.co-dot.uk> wrote:
>Weird request I guess.
>
>I have a classroom and access to an ethernet socket on the wall.
>
>I would like each student to have their own DSL line to
>their desk so they can install and configure their own DSL
>modem pci card. Then ideally go through the rest of the
>course using that as their internet connection for
>downloading software.
Assuming you mean ADSL, this requires different equipment at each end
of the wire pair. It isn't possible to operate a pair of normal,
consumer-type ADSL modems back-to-back.
Some "SDSL" standards do allow point-to-point use over a try pair.
SDSL needs a different type of modem, which tends to be more
expensive and harder to find.
>Since they would (or should) all be downloading the same
>software, a web cache machine could be placed at the
>ethernet connection.
>
>I never get to see this side of the ADSL hardware. It all
>happens back at the local telephone exchange, but this is
>what I'd like to achieve.
The device on the telco side is called a "DSLAM" (DSL Access
Multiplexer). This contains a number of individual modems, designed
to operate on frequencies complementary to the user's side --
transmitting on its receive channel, and vice versa (there are more
subtle differences also... e.g. modems at each end play different
roles during the "sync up" process.
Most DSLAMs gather traffic from the individual modems onto a DS-3
port, running ATM encapsulation. You then have to feed this into an
ATM-capable router, which can break out the individual PVCs (virtual
circuits) and extract the IP data payload from each.
Both pieces of equipment tend to be expensive, since only telcos and
ISPs buy them, and they can be difficult to set up. You might check
eBay for used gear.
There's such a thing as an "IP DSLAM", relatively new, which combines
both units into one, stripping off the ATM layer internally, and
giving you plain Ethernet on the uplink side (no DS-3).
>It easy enough to turn a linux beige-box into an ethernet
>switch, and I would like to think I could do the same but
>with DSL modem cards instead of ethernet cards, but I need
>pointers so some software here.
Why do you want to use DSL? As compared to plain Ethernet, its added
complexity (allowing for longer distances, and data transport over
wiring never designed for such, while sharing a loop with voice) would
be mostly wasted in your enviroment.
If you only want to restrict per-user bandwidth, there are several
ways of doing that entirely in software over normal Ethernet.
>What problems can anyone forsee?
>
>Cheers
>Andy Richardson
--
Jordan.
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| David Schwartz 2007-12-12, 7:16 pm |
| On Dec 9, 3:58 am, Andy <andy...@mrbumpy-dot.co-dot.uk> wrote:
> I would like each student to have their own DSL line to
> their desk so they can install and configure their own DSL
> modem pci card. Then ideally go through the rest of the
> course using that as their internet connection for
> downloading software.
That seems like a very odd thing to want. Why not just give them each
their own Ethernet connection? You are making things *very* hard. Do
you have a *really* good reason? Is there something you think Ethernet
won't or can't do?
DS
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