Using DSL Modems for Point to Point Connections?

Tommydog asks: "Any techies out there? I'm living in a rural area and would like to know from anyone qualified, if I can hook up 2 DSL modems point to point, and connect to a neighbor's home network who is running Internet Sharing. We do have a dry pair (we can only get one pair) of TELCO wires between our houses, which are about 2 miles apart. Before investing in a couple of single pair modems (T-1's require 2 pair), I'd like to know if anyone has been able to make something like this work. It turns out that I'm just a bit too far for DSL, but this neighbor does have it and will share it if I can get a good connection going. So, anyone have 2 DSL modems working point to point, back to back? Are there any caveats or precautions? Thanks!"

Comments

cut the cord...use high-powered wireless antennae

[avi33]

There's an article on I, Cringely that describes this exact scenario.

However, he wanted to sit in a coffeeshop in town and use his home network, so he claims he installed a couple of high powered "pringle antennae" climbed tree, installed another one as a repeater in a tree somewhere (to get around a mountain) and he was in business. Shouldn't be too hard to line-of-sight something 2 miles.

Re:Yes

[ivan256]

Older SDSL modems should do the trick. I know that the SpeedStream 5250 not only works, but when used at both ends can totally autoconfigure a DSL bridge for ethernet at the highest speed your pair is capable of. The best part is that they're old and cheap. You can find them for $10 on eBay, so if you buy them and find out there's a problem with your loop, you're only out $20.

I've seen these things work at 11,000 feet, and the manual for mine says it's possible to use for up to 18,000 feet (measured by line impedance). If you're 2 miles drive from your friend's house you could have 20k+ feet between the two of you, or worse, your line could go through the CO on the way there. If you're too far out for DSL from the CO, you're definatly too far from your friends house if your line makes a stop at the CO first!

This will sound insane.

[NoMoreNicksLeft]

But assuming that you own the property in between...

Have you considered putting in a fiber link? On ebay, I just saw a 9k ft spool for ~$200 buyitnow awhile back. $30 for some 10baseT transcievers at each end. Renting a trencher for a weekend would cost what? Hell, it might be alot of work, but in 2 years when you decide you want a 100baseT link, or even gigabit, you buy some more (by then) cheap transcievers. For that matter, you might even be able to find the equipment to multiplex cable tv over the damn thing, if you wanted.

Just a thought.

link to older Slashdot discussion

[falsification]

This was usefully discussed a couple of years ago on Slashdot. Link.

BTW, if your phone company won't take your order for a "dry pair," ask for an "alarm circuit."

You should be able to just plug both of them in, configure your TCP/IP stacks to use the DSL "modem" as a gateway, and you're off to the races.

Etherloop

[Fallon]

Go to http://www.paradyne.com/ and check out their Etherloop 1020 modems. I'm not sure if they technically use DSL signaling, but they work GREAT. Up to 10 megabit and up to about 22,000 feet (I think) range. Bandwith drops as distance increases a bit, but it blows most DSL out of the water on range and bandwith.

We are currently using them to phase out some ISDN lines. At $175 a pop (need 1 on each end) it's pretty economical. Currently "modem to modem", but we have some actual DSLAMS were going to be installing shortly.

They will work on just a dry pair, or a pair with tone on it. The builtin POTS splitters work fine, even modem to modem. The only issues are getting access to the cabel plant... not that big a deal for "us" as we are on a military base and own the plant, but probaly dificult for normal telco lines.

Their documentaion is kind of poor, but the products are great. You have to call them and track down a re-seller which is a pain, but worth it.

possible for some DSL flavors, but not others

[fist_187]

here's a quick guide to DSL:

there are many types of DSL... ADSL, SDSL, HDSL, VDSL, SHDSL, etc. they are divided into 2 main groups: Symmetric and Asymmetric.

the "symmetry" of a DSL modem refers to the way the frequency spectrum is divided up. above the voice spectrum, there is an upstream data spectrum followed by a downstream data spectrum. in Asymmetric DSL types, the upstream spectrum is much smaller than the downstream spectrum. in Symmetric, they are the same size.

since ADSL modems have different size spectrums for upstream and downstream, they do not connect to each other.

Symmetric modems, on the other hand, are more readily connectible to each other. but, most need to be configured so that one will act as the "central office" device, and the other will act as the "consumer premise" device.

the other thing that needs to happen in order to connect symmetric devices is configuring the ATM settings properly. DSL devices use Asynchronous Transfer Mode to transfer data across the line (this has nothing to do with your local network). most devices use a PVC of 8/35; it doesnt matter which one you use, as long as they're both the same.

so, your best bet would be to use two Symmetric modems with consoles that you have access to.