Well, first you have to decide whether you need ADSL2+ or can work with
ADSL.
I've only had a couple ADSL modems here. The first one, came as a rental
with my Sympatico account. It ran cool enough, that the unit had no
vents, just a metal box with status LEDs on it. I could leave that
running, without worrying about anything. It lasted as long as I had the
account (years and years), and because it was a rental, made the
supplier a bundle.
My current ADSL modem supports ADSL2+ (it seemed a good idea at the
time), but my service is still capped at 5 megabits/sec. So a plain ADSL
modem would have been sufficient.
I got a Speedtouch ST546v6 and it runs hot. It seems to have a few
regulator chips inside, and has no cooling other than some vents cut in
the plastic. I've mounted a fan next to it, to aid cooling.
The unit is a combined modem/router/switch, with four Ethernet ports.
The firmware is so bad, I run it in bridge mode, and use an external
router that at least I can program with a web browser. There are some
protocols I'd like to turn off on the Speedtouch, but I need to master a
command line interface (with about a hundred different commands
available), to make that happen. Rather than bother with scripting, I
just turned off the router, and used bridged mode to turn the box into a
"straight piece of wire".
There seems to be a trend to incorporate modem and router in the same
box. If they put the effort into doing firmware which the end-user could
use, I'd be all in favor of that trend.
So what lessons did I learn ?
1) The product I bought, seemed designed to please the ISP selling it,
rather than being designed to help the end-user. For example, the
ISP has the ability to "lock" certain features in the unit, and if
the user doesn't have the password for that admin level, there is
nothing you can do. Fortunately, the modem belongs to me, so every
function is available (even if I'm not interested in spending a
couple weeks learning the CLI).
2) I really should have insisted on a proper manual, before buying it.
I assumed I'd eventually find a manual, as the documentation I could
find seemed a bit brain-dead. The unit does have a web interface,
but it doesn't appeal to me.
Where should you look instead ? Look for something by TP-Link. That is a
company that clones other designs, and the retail price is quite
reasonable. If it turns out to be a bust, and you hate it, you'd be out
a few less dollars than for the thing I bought.
The TP-Link products may be a challenge to understand (numbering scheme,
what you're getting and so on), and threads on this site may help you.
http://www.dslreports.com/forum/r19475347-have-you-heard-about-TPLINK- dsl-modemrouter
http://www.dslreports.com/forum/r23681143-TPLink-TD8816-GOOD-MODEM
In the table here, you can see that some of the modems share the same
main chip. Finding a picture and details of what is inside, should allow
you to track down how well that particular chip is known to work.
http://www.dslreports.com/r0/ download/1242980.thumb600~32cd8a5fee2b43b8f50707c1ae9e636c/table.gif/
thumb.jpg
There is a piece of software called DMT, that displays stats from the
modem. I haven't tried it on mine, because I don't know if my operating
the unit in bridged mode, makes a difference or not. What DMT does, is
give you some idea how much SNR you have, and whether your profile can
be raised safely or not. For example, I'm not getting my full 5
megabits/sec, and I think I have excessive margin that could be
converted into usable bitrate. If I bothered to run DMT, I'd have the
necessary proof, to phone the ISP and get it bumped up. The "versions"
of DMT are sorted according to the modems or chipsets they support.
http://dmt.mhilfe.de/
http://img.mhilfe.de/DMT.gif
The controls on there, may be sensitive to the version of firmware
running in the modem. In some cases, if you're a real enthusiast, you
want to load an older firmware, that supports some of the sliders in the
interface.
So whether you can get statistics from the unit, might be another slight
concern. That gives you some options, if you're given a profile that is
less than what you're paying for. They do that, as a function of the
signal to noise ratio. They'll turn down the link, in the interest of
guaranteeing it will sync each time you use it.
Paul