Baslinux mailing list

[James Miller <jamtat AT mailsnare.net>]

On Wed, 20 Apr 2005, Constant Brouerius van Nidek wrote:

> I will have the possibility to get ADSL which is what I assume the DSL you are
> talking about. As you did connecting DSL for a living you are the right
> person to ask my question.
> I thought that in order to connect an ethernet card to the digital line you
> need something like a router. Is that right?
> As far as I know my ethernet card there are two connectors, one for a shielded
> cable and one for a flat stecker for a more elaborate flat cable.
> Is there some box between these connectors and the ADSL connection?

I'm not David, but excuse me while I jump in and offer what I know. DSL = 
digital subscriber line. This is a digital technology that allow phone 
signals to be relegated to a certain frequency on the phone wire, and the 
remaining frequencies to be devoted to other traffic like internet 
packets. In short, it makes use of more of the bandwidth of a telephone 
line than an analog signal alone can. ADSL = asynchronous digitial 
subscriber line. Same as DSL, but allowing asynchronous connection (ok, so 
I'm not totally sure what synchronous means when talking about electrical 
signals travelling over a phone wire . . . :) ).

The ingredients of a DSL/ADSL connection are: [your computer with ethernet 
card]----[DSL/ADSL modem]----[phone jack]. If you have a working ethernet 
card and your phone line is DSL/ADSL-capable, all you need is a provider 
to activate DSL/ADSL on your line and a modem (and a cable to go from the 
ethernet card to the modem). The modem filters out typical phone traffic 
on the line and sends only internet traffic to/from your computer. In the 
US, the DSL/ADSL modem typically comes as part of the package you buy from 
the company that activates DSL/ADSL on your line ("free" if you sign a 
contract for a given period--usually at least a year). Not sure how it 
works wherever you may be, but you should look into how the DSL/ADSL modem 
get supplied.

Incidentally, all DSL modems I've seen take a typical phone cord in one 
side (the side that goes to the telephone wall jack) and UTP (unshielded 
twisted pair) with an RJ45 plug on the other. RJ45 looks much like 
(American) phone plugs but is a little wider. UTP is noticeably thicker 
than American phone wire. I've never seen a DSL modem that will take 
coaxial--or any other type of network connection for that matter. So, your 
ethernet card will most likely *have to have* an RJ45 plug. I can't tell 
from your description whether it does.

While you don't *need* a router between your computer and the DSL/ADSL 
modem, adding one will allow you to share the connection with other 
machines. If you get a firewalling router, you will help secure your 
computer(s) against hackers, too. Here, these firewalling routers are so 
cheap (ca. $30) that it just doesn't make sense to be without one if you 
have a broadband connection. Unless you're pretty adept at securing your 
Linux system against attack, or if you use any version of Windows, you 
should definitely have a firewalling router on your ADSL connection.

James