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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!"
Are there any caveats or precautions?
You may have already considered this, but most ISPs that I'm aware of have a line in the ToS that states that you may not share the connection with other people. And they do check; I remember a friend getting his house checked by Road Runner due to his daughter using P2P out the wazoo.
This statement is false.
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.
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.
You can't grep a dead tree.
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.
Maybe not enough power to electrocute someone, but there is enough power on a phone line to cause a tingle (especially if you touch the bare copper while a ring is sent through). Thing is, dry pairs aren't the only ones that can do that... all lines can do that.
keep poking your test leads into the can, you should find another dry pair for the Telco to, ahem, 'lease' to you.
i dont suppose you have any sort of cable (ie co-axial) connection running down those poles do you? might be able to get a dry line there and convince an old BNC'd ethernet card to shove data down it.
also remeasure your distance. is he two miles straight down the road or two miles across a field and thru the woods?
looks around im sure ive seen some people using microwave, wi-fi, laser, and radio over those distances jsut in case your DSL doesnt go.
yea im sure this post helped you a lot.
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.
Prohibiting an action that could take business away from the ISP is entirely logical, but prohibiting an action that has no effect on the ISP whatsoever is not. If I'm paying for a 768Kbps DSL line and I'm not reselling that bandwidth, the ISP should keep its nose out of my business. I'm paying for that bandwidth and what I use it for is up to me until it begins harming the ISP.
I also have a real problem with ISPs that crack down on users who do lots of filesharing. Since I pay my ISP for 24 hour 768Kbps access, I expect to be able to utilize all the bandwidth I'm paying for (minus TCP overhead, of course) all the time. An ISP telling me I can't use all 768Kbps all the time because they haven't got the capacity is like the cable company telling me I can only watch HBO fifteen days out of the month. It's their job to have the capacity, since I'm paying them for it.
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.
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.
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.
Somewhere on this page I have hidden my signature.
If you want the consumer-grade stuff (the 3com or dlink RTUs that you buy to hook up to your telco's network), then no. They need a DSLAM.
If you want to spend a few bucks ($1000 per end), Adtran makes some good HDSL gear - such as the Express-L768, and Express-L1.5, that will do what you want. The L-768 is probably what you want, as it uses a single pair, and runs 768K bidirectional. (The 1.5 runs at 1.5M, but uses 2 pairs.. it can also run 768K on a single pair.)
We use these at a number of sites, and they work pretty well.
There are caveats.. the maximum distance you can drive them is 18000 feet.. and if you're leasing copper from the telco, you have to watch the distance.. the telco here bills length as crow-flies distance, so unless you know their distribution network, you may not know the exact footage.. for example, we have two schools that are about 3 feet away from each other (next door), but the actual cable distance was over 20000 Feet. (The copper for each site runs back to the telco's distribution point.)
If you own the land between the sites, I'd do as another poster suggested, and run fiber)
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.
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.
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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.
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