Setting up DSL

June 30, 2004 11:15 AM

The New House, part four: Help me set up my DSL. Please! [more inside, naturally enough]

I've signed up for DSL through Qwest out here in Portland, Oregon. They shipped me a smallish, black Actiontec DSL modem/wireless router. It didn't detect the DSL signal.

They sent out a service tech, who was very helpful. He checked the line and told me, "The modem needs 8db to 'train up', and your line is showing 16db, which is pretty good for your distance from the C.O." He spent an hour futzing with things to no avail. He even tried two other Actiontec modems of the same model, but none of them detected the DSL signal.

Then he tried an older model (bigger, white, no wireless router). It got the signal fine. He left the older modem with me and told me to call him when the replacement modem new model arrived. Well, it arrived yesterday, but like its three brethren, it doesn't detect the DSL signal.

I e-mailed the tech support woman whose been helping me. She's not only crediting me for two months of free DSL (without my asking!), she's forwarding my problem to her brother, "a supervisor in the DSL center".

So what's my question?

Simple: Why does the older Actiontec modem detect the DSL signal, but the new models don't? The service tech was completely puzzled by it. The tech support woman says I can buy my own DSL modem, but she recommends that I buy Actiontec (they're the only brand officially supported by Qwest).

Which Actiontec DSL modem should I buy? Or — since I'm not really that concerned about owning an "officially supported" model — can you recommend other DSL modems I should consider?

[I'm a fairly techie guy. I have my own small computer consulting firm. I'm comfortable with both Macs and PCs. I'm fine tinkering with the internals of a wireless router, etc.]

p.s. Is the thing I'm calling a DSL modem actually a modem at all? Or is it simply a router? I mean, if I plugged my existing Linksys wireless router directly into the DSL line, would it work fine? Or is there some vital component needed to process the DSL signal?

posted by jdroth to computers & internet (13 comments total)

This is a W.A.G, but I recently had a problem with my DSL connection. I wound up spending a lot of time with upper-level tech support, and we discussed a number of different possibilities (it turns out that somebody had taken down my connection and failed to bring it back up, but this wasn't immediately apparent for some reason).

One of the possibilities we discussed was that I needed a new modem; the tech guy suggested I buy one, see if that made a difference, and if so, keep it. In order for this to work, he said, he'd need to change my "virtual path" (this is a low-level ATM thing) setting--my old modem was using VP0 and newer ones use VP8 (or something like that). So it's conceivable that it's a misconfiguration at the CO, such as the wrong VP.

PS: No, it's not really a modem. I believe the technically correct term is "gateway." I'm pretty sure you do need a DSL, err, modem.
posted by adamrice at 11:33 AM on June 30, 2004

Get a Cisco 678. A bit pricey, but they last forever. Plugging anything aside from a DSL modem into the jack won't work.
posted by cmonkey at 11:37 AM on June 30, 2004

Why don't you keep the old model and just add an Ethernet -> 802.11b bridge to it? Or even add a real wireless router to it?

It's better than futzing about with things that don't work, IMHO.
posted by shepd at 11:52 AM on June 30, 2004

Yes, a DSL modem is really a modem. It modulates digital signals to analog for transmisson over the phone line, it demodulates analog signals back to digital. Same with cable modems.
posted by kindall at 11:54 AM on June 30, 2004

I have the newer Actiontec modem/gateway/whatever with the wireless router, and I'd say to avoid it if you can. The signal strength for the wireless is really bad; while I know people with other types of wifi routers who can work from their back yard, I can't connect too well from the far side of my (smallish) apartment.
posted by COBRA! at 11:57 AM on June 30, 2004

If you have a modem that works (that old one the tech left you with), just get a wireless router to plug in behind it.
posted by Mayor Curley at 12:03 PM on June 30, 2004

I've always just considered the DSL modem part of "their stuff" and used my own router, etc behind it. I think it probably is wise to use an "officially supported" model if possible, even if only because not doing so will give them an excuse not to help you out if you have problems.

I'm not sure about the "modem" thing. I don't know if the signal is actually ever analog. Most phone calls are converted to digital as quickly as possible, because that signal is cheaper to carry. Perhaps I'm thinking of "cable modems." Homework necessary, but I tend to trust kindall on this kind of thing.
posted by scarabic at 12:52 PM on June 30, 2004

If you have a modem that works (that old one the tech left you with), just get a wireless router to plug in behind it.

Right. So I should have made it clear that I'd already done that. I know how to get the wireless connection. That's not a problem. The problem is receiving the DSL signal.

A geeky friend, via e-mail, advised the following (which I'm sharing here in the hope that it will help others):

The DSL 'modem' is not a modem, it is indeed a router. Sort of. But it also has DSL-specific hardware to pick up the data transmission off the phone line and convert this to and from ethernet.

A 'cable modem' is the same thing, really.

If your existing router has both a cable-modem port AND a DSL port, then yes, you should be able to just use it.

In theory.

I note the following:

"i have been working with the actiontec gt701-wg for about a week now and i am VERY unhappy with it and their tech support. although the device functions it does so just barely and will NOT work with my VPN!"

The same forum has lots of praise for the Cisco 678.

Dunno.

The only thing that occurs to me is that there's something funky in your wiring. DSL has four basic issues — distance from the central office (which doesn't appear to be an issue, as you have a strong signal), a loading coil (this is something which they ought to know already, or easily diagnose — it's an analog way of boosting the voice signal that horks the frequency range that DSL is using), or possibly a 'tail' — somewhere on your voice line there's a y, one leg of which is hooked to your house, one to the central office, and one to nothing (this happens in older neighborhoods when someone orders a second phone line or something like that). A 'y' won't mess up an analog voice signal much, but it goofs up the frequency response for high speed signalling (this was a problem with old 10-base-2 ethernet wiring, too).

The thing is, for your line to qualify for DSL, it has to be free of all those things, and even if the phone co. didn't know it, the tech should have been able to find it.

AND, if any of them was the problem, NO DSL 'modem' should be able to train up properly.

So why one does and another doesn't is a bit of a mystery...

So that's a second vote for the Cisco 678. I'll have to see if the Fry's in Wilsonville carries them...
posted by jdroth at 2:17 PM on June 30, 2004

I'm not sure about the "modem" thing. I don't know if the signal is actually ever analog.

Yes, it is. It's modulated at a frequency above the range of human hearing, which is why DSL and voice service can share a line. Common modulation schemes used are CAP (Carrierless Amplitude) and DMT (Discrete Multitone), both of which are variants of QAM (Quadrature Amplitude Modulation, the same modulation scheme used in analog modems). More info.

Cable modems of course use frequencies in the range used for television broadcasting, since that's what cable TV networks are optimized for, but the technology is similar.
posted by kindall at 2:49 PM on June 30, 2004

I'm not sure about the "modem" thing. I don't know if the signal is actually ever analog. Most phone calls are converted to digital as quickly as possible, because that signal is cheaper to carry. Perhaps I'm thinking of "cable modems." Homework necessary, but I tend to trust kindall on this kind of thing.

If you can plug an ordinary analog phone into the jack, get a dialtone, and place calls, you have an analog phone line. You need a modem in order to transmit signals over the analog phone line. DSL modems are different from the traditional hayes modem in that they do not interfere with analog voice communications. But they still convert signals between digital and analog.

The DSL 'modem' is not a modem, it is indeed a router. Sort of. But it also has DSL-specific hardware to pick up the data transmission off the phone line and convert this to and from ethernet.

Wrong. and Wrong. Routing occurs at layer 3 of the OSI seven-layer model. DSL is a layer-1 technology, and the DSL modem provides translation services between layer-1 and layer-2. Routers often have ethernet interfaces, but more importantly, they understand layer-3 protocols like IP. Your DSL modem may have an IP address, but that is just for the management interface. It couldn't examine an IP packet, even if it wanted to.

Back at the ISP, a router is typically connected to the DSLAM via ATM. The DSLAM is what is placed in the "central office" close to your house. A T3 or maybe OC-3 digital line runs back to the router in your ISP's server room.

Digital lines are cheaper because they allow more bandwidth and more hetrogeneous services to be aggregated over a single wire or fiber pair. Unless you have a large number of phone lines at home, it is unlikely that a digital line is cheaper for the phone company than your existing analog line + DSL.
posted by Kwantsar at 3:06 PM on June 30, 2004

The more advanced DSL modems (like the Cisco 675 and 678, the only models I have experience with actually) do function as routers. You can simply plug them into the uplink port of a switch/hub and have them redirect traffic via NAT, etc. The Cisco 67x series have this little operating system inside that you need to program.
posted by neckro23 at 3:28 PM on June 30, 2004

jdroth: I don't think you can buy them new anymore, which is why I put the link to ebay in my post. If you do get the 678, make sure you upgrade the CBOS to the latest version.
posted by cmonkey at 3:56 PM on June 30, 2004

I have the new Actiontec Gateway thing (after the clueless tech failed to tell me the modem I had wouldn't work, despite the fact that the new specs had been in place for three months, but that's Qwest), and it really sucks. The way Qwest has it set up port forwarding doesn't work at all (v. important if you're trying to Torrent things), and I have been unable to find a way to do so. If you have something that works, stick with it. If the modem is in good condition, it can only be a problem on Qwest's end if something goes down.
posted by calistasm at 12:13 AM on July 1, 2004