Slashdot Mirror
Verizon - No DSL Over Hybrid Copper/Fiber Lines?
bziman asks: "Speaking of fiber, I've been waiting for DSL from Verizon here in Northern Virginia for more than a year now. Their excuse is that even though I'm well within the normal range limitations (I'm only 9,000 ft from the Central Office), I'm not eligble for DSL because half of the line between the CO and my house is fiber optic instead of copper, and they haven't figured out how to run DSL over fiber optic yet. I can
get no meaningful answers from Verizon, so I turn to the combined wit and wisdom of Slashdot." Note that it's the hybrid nature of the lines that's the problem, as Verizon already provides DSL for it's all-copper customers. I would think, that customers with all-fiber connections could just be wired directly into the Internet...or is this assumption a fallacy?
I actually live in DC and I was told by Verizon that they couldn't give DSL service in my area. I went to DSL.net and they were able to set me up via Covad. It is more expensive, but in the end I do have DSL service.
-- Solaris Central - http://w
This complicates competition. DSL CLECs can rent space from the incumbent in the CO to put in their own DLSAMs, but space in the street furniture is too tight to house several competitors' equipment. One answer is to open the data networks in the ATM network that carries the data back to the ISPs' routers, but that was not in the Telecom Act of 1996, which was written before the commercialization of the Internet.
VDSL will have to be deployed this way, since it can only reach 4000 feet. So either DSL competition goes away at that point, or we need a new Telecom Act.
I wrote parts of this stuff
Correct.
It tends to be called names like "remote subscriber terminal" (and possibly other things with "remote" and "subscriber" in them). Here's a tutorial on Digital Loop Carrier systems, that being the name of the technology. In effect, a digital loop (T1, or more, possibly fibre) is run to the "sub-station" (remote terminal), and subscriber phone lines are run to the "sub-station" as well. The "sub-station" performs some of the functions that would be performed at the central office for subscribers whose phone line goes directly to the CO, e.g. analog-to-digital and digital-to-analog conversion.
This multiplexes N phone circuits over the digital loop, so you only have to run that one loop to the neighborhood, not one loop per subscriber. (This is called "pair gain" because you can serve more subscribers with one or two pairs to the neighborhood.)
Unfortunately, this means that everything above about 4 KhZ or so on the subscriber's phone line gets lost - the remote terminal filters it out and spits out the standard 8000-samples-per-second digitized signal. As ADSL uses stuff well above 4 KhZ, you can't do ADSL with this.
However, one might then ask "well, as the stuff going back to the central office is digital anyway, why not convert the ADSL signal to a bit stream at the remote terminal and send that back to the central office?"
That's what SBC's Project Pronto, and probably some other projects of other phone companies, is all about; here's a discussion of "Digital Loop Carrier meets ADSL". The link to the neighborhood is fibre, not copper, and it runs, among other things, ATM back to the central office; ADSL carries ATM cells, and those cells get shipped back to the CO, and, ultimately, to your ISP.
If the original poster can't get ADSL "because they have fibre running to their neighborhood", it's probably because Verizon don't have one of those shiny new ADSL-capable remote terminals in their neighborhood.
My understanding is that DSL is a signalling protocol for copper lines, so they're correct that a hybrid fiber/copper feed won't work unless the copper-to-fiber bridge contains the DSLAM (Digital Subscriber Line Access Multiplexer) front end to convert the analog DSL signals into digital bits to go over the fiber.
Right now, DSLAMs like to live on racks in a CO, not one of those grey boxes by the side of the road where the copper-to-fiber conversion is likely happening. To run DSL, you need copper from you to the DSLAM. Hence the problem.
Presumably, whatever they use to bridge the copper over to fiber could be adapted for tranceiving high-bandwidth DSL signals as well, but it sounds like right now that's not in the cards.
That's my 0x02 cents...
--Joe--
Program Intellivision!
My understanding is that G.lite is a less computationally intensive version of DSL, and so it can be implemented on lower cost equipment. It also makes some compromises so that you can have a "splitterless" setup (you don't have a voiceband/DSL-band filter where the phoneline enters the house). The result is a lower-bandwidth DSL which is suitable for consumer applications.
G.lite still uses the same frequency bands as normal DSL, though, from what I recall. It may be slightly narrower, but it's still well outside the 300 Hz to 3300 Hz range that voiceband uses, because it's supposed to coexist with the household voiceband service on the same line. It's also supposed to coexist with voiceband modems and FAX machines. (Some of the performance tradeoffs in G.lite apparently have to do with the harmonics coming off of the things it might have to coexist with, including changes in loading due to people picking up handsets, incoming ring signals, and so on... In a non-G.lite setting, the splitter handles most of this. G.lite is supposed to make this easier on J. Random Consumer, again at the cost of some performance.)
Given all that, I'd be surprised if G.lite was any friendlier to fiber than regular DSL.
--Joe--
Program Intellivision!
We had the same problem (Fairfax, VA). What was our solution? We yelled and yelled and yelled. We bitched and moaned. We called them and complained over and over.
We got DSL very soon thereafter. Somehow the technical issues vanished, although they claimed a top speed of 780-something because of them.
Now, I titled this post YMMV, and I mean it. I don't want people to reply "But that's not possible!!!!!" over and over. It may very well not be possible; my suspicion is they (Verison) were lying when they said it wasn't possible (meaning, the lines in our area were just fine, etc). It wouldn't be the first time I'd caught them in a lie. What my point IS, is don't just wait. Make a stand, or just get a cable modem and tell them to fuck off.
ZOMG I WOULD LOVE TO KNOW ABOUT YOUR FEELINGS ON MACINTOSH VERSUS WINDOWS, VI VERSUS EMACS, AND HOW YOU'RE NOT A DORK
There was an article in the local paper about this. Qwest is apparently looking to push DSL into areas currently unreachable for whatever the reason -- distance, circuit quality or fiber muxes. They were planning on upgrading the little green boxes into larger green boxes with climate controls (I'd think they could fix the heat problem with lots of fans, but the humidty'd be a killer) and DSLAMs. I'd imagine the box/DSLAM vs. climate problem is easier to solve than the "DSL data backhaul problem", unless they're planning on upgrading the existing fiber muxes to something more data friendly.
One of the rich guys where I work lives on a cul-de-sac, way out of reach of DSL but both he and his neighbors can get it thanks to the whining of politically connected neighbors. He says that one day US West showed up and dropped what looked like 1/3 of a shipping container with an A/C where the dinky phone box had been. I think this represents basically the type of "upgrade" Qwest is talking about, a micro-CO, that can support interesting data bits on the inside.
There's probably a market for DSLAM vendors to come up with DSLAMs that need little more than power and good venting and can withstand wide environmental conditions, like heat and humidity, so that the Qwests of the world don't have to build buildings with A/C everywhere. Since the upgrade to "digital cable" in my neighborhood, I see a fair number of what look like school lockers bolted onto the phone poles. I think they must be breakout points for the cable system, they have power running into them and what looks like CATV coax running out. If they can do it, DSL can too..
After reading your question, I went out on the net and found this interesting document. It really runs down on what DSL technology is about (history, terms, and lots of good info)...
For the paranoid, the url is: http://www.telebyteusa.com/dslprimer/dslfull.htm
:)
---
Computer Science: solving today's problems tomorrow.
Price, Quality, Time. Pick none. What, you thought you had a choice?
You've gotten a half baked answer from them, and everyone one this thread:
The real answer is this:
Most likely what is going on, is your being serviced by a "sub-station". Thats not the real name, but I don't know the real one.
Basicly what they do, is put a mini-switch out in the feild in a envormentaly controled valt, either below ground, or above. So you are most likely being serviced by a "sub-station" (not the real name). Its not a fiber/hybrid.
What SBC is doing (Southwestern Bell, Pacbell, Ameritech, etc) is putting NEW "sub-stations" out in the field where people are to far from the CO, or where they are already serviced by a"sub-station" . These are equipment cabinets, in the field that take the copper, and put it into a DSLAM to provide DSL services, and into a switch interface, to provide phone service, and then backhaul it all with fiber.
SBC is spending something like 5 Billion on this project, and so far nothing has come of it, other then I have seen alot of these above ground cabinets pop up.
Anyway, I was quite annoyed that no one gave a straight answer (that was moderated up, I didn't read EVERY message) although I'm probably to late to get moderated up.
-Tripp
HEre is anotehr url that will help: http://www.iec.org/tutorials/adsl_dlc/
What it comes downto is older equipment cant handle dsl but newer stuff may be able to. Odds are they just say no to avoid any potential hassles since it is easier that way right now.
this space for rent
They might have put in a "(DSL?) hotel." That moves some of the gear from the CO to the other size of the fiber, but it requires money, space, money, available bandwidth on the fiber, money, equipment, and did I mention money?
Ironically, the odds of getting this are inversely proportional to how far the fiber runs. If fiber runs to your block (or building!), there's not enough potential customers to justify the expense. But if there's hundreds of potential customers, the phone company can be fairly confident that it can find customers to justify the investment.
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
Just get together with one of your local ISPs that offer DSL and conspire to get around Verizon. Order an alarm circuit which is a relatively easy thing to do, just don't mention ANYTHING about your true intentions of running data over the line.
Pass the info your conspiring ISP, (all the needed circuit id#'s, etc.) and they, if they have been in the DSL game for more than a year or two, will be able to get a DSL provider to provide service over that circuit.
As COVAD has moved from dedicated loop installs to line-sharing, you may or may not be able to get ADSL over the circuit, just the pricer SDSL.
Were there is a will, there is a way. And for more trials and tribulations check out dslreports.com. A virtual treasure trove of info there, aswell as people in a similiar position with the ILECs.
--
Yeap. They are called "Remote Offices". And at least with BellSouth, you get only what BellSouth wants to sell you -- which is consumer ADSL. There is zero colo in a remote office.
Fiber-in-the-loop means you don't have an end-to-end copper loop. DSL, with the exception of IDSL, requires a direct electrical connection to the CPE. There are a number of products that can be placed in concentrators (i.e. DSL line cards) that move the DSL termination to the nearest junction which then trunks everything back to a "DSLAM" (calling it an ATM cell mux would be more accurate.) The problem is, no one uses this technology. I've known about them since mid-'98.
<sarcasm>But DSL is better because you don't have to share your bandwidth like you do with cable. DSL is always fast.</sarcasm>
That said, I can't even imagine what it would be like to have several thousand ADSL customers sharing a single T1. If the bandwidth is that oversold you'd be better off with a 28.8 modem.
________________________
I don't want free as in beer. I just want free beer.
The phone company expects to only deal with 8,000 samples of 8 bits each per second, and when they multiplex the signals for 24 lines into one (to get 23 more phone services through a single pair of wires), then sample everything at that rate. They don't care about DSL, they only expect to provide voice service, and engineer appropriately.
If you were willing to pay for the labor and materials and increased expense of having to run completely new lines... they would still probably turn you down, because they are only interested in delivering voice service, at the aformentioned 64kbits/second encoding.
--Mike--
Its an electrical signal sent at a very high frequency. If it were a radio signal you wouldn't need a wire to get it!
"A plan fiendishly clever in its intricacies"- Homer Simpson
hmm, where to start? I work for Verizon, in engineering no less.
PairGain is a company that makes several products, all of which seek to expand existing copper facilities. Their most commonly used piece is called a Digital AML, which allows you to take one copper line and provide another line. This is predominantly used in areas that are not "feed rich", and in urban areas are the default used when a customer orders a second line.
The ADSL problem w/ fiber is simple- DSL technology (as has been previously posted) is meant to utilize the unused bandwith that copper wires can carry, in a higher frequency than the human ear can hear.
Finally, the fiber/ copper problem you were fed over the phone. Chances are, when you are quoted such a thing, Verizon went and installed a fiber remote hut, which is used to extend feed out from the CO. Fiber is brought out of the CO (usually in two different paths, for loop redundancy) to a hut or ManHole, and then copper is run from that hut for feed. When this is done, it is to provide more feed pairs in a certain route (which is how Verizon tracks fill rates and such, by distribution areas and routes that they determine). The most common technology used w/ the fiber huts is LiteSpan, and LiteSpan is not a DSLAM. Newer LiteSpan shelves can provide DSL facilities, but it would be impossible to find out the specifics of a LiteSpan unit unless you knew your local Outside Plant Engineer.
Before you despair, there is one caveat to the fiber hut- there's copper run from the CO to the hut as well. We are REQUIRED to run copper, b/c there are special circuits that we can't provide over fiber facilities- the best example is the alarm circuits in the hut, which must be on fiber.
OK, last thing- customer service, and how to get what you want. When you call, you receive an associate. Ask to speak w/ their supervisor, they have to put you through. From there, be prepared to complain loudly, insist that you know there are copper facilities there- you may cite lotto circuits and security circuits. Tell them you are prepared to call the PSC (Public Service Commission) or call the Verizon President's Hotline (which really escalates things). Ask them if they can give you your local Engineering office phone number.
They may tell you the copper feed portion at the hut already has circuits that preclude yours from receiving DSL- it is true that we can only provide one DSL circuit in every 25 pair of complement of copper wires, which is due to DSL's inherent limitations.
I think that answers all the questions- hopefully, seeing the post a day late, some will still check this and understand!
I'm sorry, but I do believe you are mistaken. DSL does NOT rely "completely on the absence of telephone company equipment between the DSL modems on each end of the line." Granted, each switch you touch degrades the signal by X, but there could be any number of switches betweeen your modem and the DSLAM.
Also, just because you have a fiber local loop does not mean you can't get DSL. Read this for a decent explanation of the hybrid network issue. IF your neighborhood has new enough equipment (read: installed in the last 4 years or so), you may be able to convince them. In my experience with Verizon (on the left coast) the tier 1 support staff often has NO idea of what services are offered, where a certain service is and is not offered, or even whether or not they actually have a pulse. As a for instance: The company I work for (a medium sized ISP) receives a fax from Verizon stating that they would be offering enhanced DSL services in our area, so our sales department happily started selling these services. When installation dates started popping up, the Verizon techs denied for weeks that the service the customer had been sold was available. After many hours of sitting on hold, arguing with rude technicians (IMNSHO), and finally speaking with someone far enough up the food chain to know what was going on, our customers did indeed get their service. </rant>
Twinkies sure taste good for something that is 68% air.
When we moved in, my roommates and I decided to set up a DSL line for out local LAN. Just like you said, the line test put us within the range for DSL - about 300 - 200 feet from the CO. Unfortunatly, Versizon (then Bell Atlantic) had aparantly added a coil of fiber inside the CO. That's right - according to Covad, there was fiber inside the CO, being used roughly as a patch cable. Thus, the whole Harbor Pont development (5000+ units, if I remember correctly) was unable to get DSL from anyone. Because of a patch-job that Bell Atlantic woudn't fix, Covad didn't have access to, and Flashcom... well, Flashcom didn't seem to be able to find it's butt with both hands, so they responded by opening three new accounts.
However, our tale of woe had a happy ending. Before Bell Atlandic owned up to the fiber thing, Covad came and installed a modem, and the thing couldn't find a link. So they came and installed it again, this time drilling more holes in our walls and breaking the phone patch box so that we didn't have a landline for a week. When the whole thing finally turned out to be impossible, we called Covad to give them their modem back. Covad told us that the modem belonged to Flashcom (which didn't sound right, since Covad was in charge of the actual installation). Flashcom told us that it belonged to ConcentricDSL. Concentric had no idea who the hell we were, so we started over with Covad, and repeated the cycle. After getting the runnaround again, we put it up on eBay, got $200 for it, and treated outselves to a nice dinner.
--
In spite of the suggestions and all the tests that I have made, I have not cavato a spider from the hole.
I work in Verizons DSL division and honestly, you're probably stuck. If there is fiber anywhere on the line between your home and CO, no DSL. They're not going to run new lines, but they *MIGHT* switch you to an all copper pair if you manage to talk to the right people and there is one available. I've had it done for a few customers before, it's a right pain in the butt though. What people don't really know is that VOL (Verizon Online) is *NOT*, I repeat, *NOT* Verizon the phone company. They are two separate entities. Therefore, when we (VOL) try to get the phone company to switch a customer to a new copper pair, well, we have to jump through hoops, do a dance and pray to the BroadBand Gods. Depending one where you live this may be an option(If you're in NY, forget about it). The only problem is finding someone within Verizons mass of idiots that knows how to do so, and to be honest, it's worse then finding a needle in a hay-stack(I'm Mr. Pessimist today). Your best bet is to maybe do what I did and get cable. Best of luck.
plop
Not totaly true. Lucent make the DSLMAX boxes. They simply take a fiber, or ethernet, or ATM line, and supply it to upwards 64 coper lines. My Apartment complex uses these boxes. They take a fiber link from the CO, and supply each apartment with DSL service. works quite well because the coper link is only about 50 feet.
This broad spectral band transmission technology you speak of is what in electrical engineering they call "broadband". As opposed to putting a purely digital voltage level on your line, called "baseband" - that's what your network card uses hence "10base*" or "100base*". The problem with baseband is that attenuation scrubs the signal in pretty short order - however the circuitry for baseband is pretty simple. Not so with broadband, open up your DSL modem, I gaurantee you'll see at least one high performance DSP and a whole lot of RF shielding. It's a lot of work to take the wacky signal on your DSL line and convert it to 1's and 0's.
Now to create the broad spectrum of signal on a copper wire is fairly easy. We take fancy electronics and jiggle electrons on the line and the resulting wave travels down the wire - slowly degrading as it encounters impurities in the copper, bridge taps, and so on.
Now the analog of all this to fiber doesn't quite work. There is no reason you couldn't transmit a broad spectral signal over fiber, it is just difficult to generate the different frequencies of light quickly. What we can do is toggle on and off a particular frequency of light really fast. So what is done with fiber is we put an led at one end and it gets turned on and off millions of times a second and we put a detector at the other end. This is sort of baseband style transmission over fiber. Of course the fiber itself can handle transmission of more than just the one frequency given off by the single LED, but there are cost effectiveness issues in there affecting how complicated to make your emitter/detector pairs.
As for the voice and compression issues you mentioned... It really isn't that complicated. The cutoff for your telephone is about 4KHz. The telephone company generally samples everything down to 56kbps of digital data - that's what their switching equipment handles. Ever notice that old ISDN was 56kbps per channel and old T1 was 24 channels of 56kbps? Well, there is a reason for all that. It's all 64kbps now, but I digress. The phone company does a straight digital sampling down to 56kbps on your voice and then passes you through a bandpass filter to remove the artifacts when it puts your voice back together. This is why if you listen to one of those call in radio shows the person on the phone always sounds bad. Audio fidelity on telephones isn't good and there really isn't much difference in talking with someone across the street or across the country anymore. They don't need a supercomputer to compress your voice.
Education is a better safeguard of liberty than a standing army.
Edward Everett (1794 - 1865)
The converter between copper and fiber focuses on the relatively narrow spectrum that voice communications are in and discards DSL as mere noise, thus not sending it over the fiber. The two solutions are to move the CO (not gonna happen), or by a converter with a greater range (also not going to happen - at least anytime soon). Look for a flavor of DSL known as G.lite - I think it fits into the range of the converters and will run over fiber.
So you're a karma whore, eh? For the right price, I'll be a karma pimp...
SIG: HUP
Still, the effect is you get DSL at your premises which is of course what he wants. I have to assume that some phone companies have been using these among other tricks to get DSL to people. The area of DSL coverage in Tucson that Qwest provides has increased dramatically since they started offering it and often people who were before told they couldn't have it, have been able to get it now.