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.

Yes

[krow]

I have done this before. The best I could ever get it to work was for 22K feet. The thing you need is two DSL modems that can speak together. Most of what is being sold today expects an expensive backend CO unit and a cheaper frontend modem.
I suspect that if you want to do this cheaply you would be best off finding an ISP that experimented with "rolling its own" around 1998-99.

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!

One caveat

[splattertrousers]

Are there any caveats or precautions?

Sharing the connection is probably against the DSL provider's terms of service. Your friend might want to look into that before sharing the connection.

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.

Re:ummmm......

[Guspaz]

Read the article, he's 2 miles away. Ethernet doesn't do 2 miles.

Also, you're wrong about 100 feet being the max length of ethernet. It does 100 meters using UTP (Unshielded Twisted Pair), which is 300 feet.

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.

We have 4 of these...

[RobbieW]

I own a very small ISP in rural North Carolina. We started it mainly to allow us to have broadband in our programming office.

Until about a year ago, Sprint would allow us to order these point-to-point dry pairs. Since we didn't have any other type of broadband (except Sprint's "reasonably priced" frame-relay circuits ~$700 for a fracT1) we used these circuits with PairGain 300S sDSL modems. These are manually adjustable from 128kbps up to 2048kbps depending on the distance and quality of the lines. They work very well. We were able to use them with circuits approximately 2-3 miles long at speeds of 384kbps and in one case the line quality was good enough to support 768kbps.

There is a huge difference between a modem and 384kbps circuit. I highly recommend them.

That being said, these modems are very expensive. I haven't priced them in several years but they were about $900 for a pair a couple years ago.

Check Out Zyxel DSL Modems

[kzanol]

So, anyone have 2 DSL modems working point to point, back to back? Are there any caveats or precautions?
Check out the SDSL / GSDSL Devices from Zyxel; I'm using a lot of these in back-to back configurations covering distances in the range from ~ 300ft to 4 miles.
I'm using two differnt models: the older Prestige 681 SDSL Modems/Routers and newer Prestige 782R G.SHDSL Routers.
Both have a max. linespeed of ~2Mbits; what you actually can get depends both on line quality and distance. Under identical conditions, the newer 782R will get about 20-30% higher troughput.
From my experience I'd expect to get about 1 - 1.5 Mbits over a 2 mile link if it's reasonable quality.
There's probably lots of other devices that would also work, it's just that I've successfully used these myself. Prices (new) in Europe are about $480 each; with a bit of luck you should be able to get them used for a lot less.

Why hasn't anyone posted this url yet?

[Judg3]

OdessaOffice.com
This guy lives in rural washington, and had the same problem. This is his complete step-by-step how to on how he did it, including modem brands & models, problems he had while setting it up, how he overcame obstacles, etc. Very very good read and I would think it'd be your first stop for rolling your own.