Talk:Digital subscriber line

Can anyone add coverage over ADSL2, or ADSL2+?

I capitalized Ethernet. Ethernet is always capitalized. --imars 09:31, 22 Nov 2004 (UTC)

This page could use an explanation of the difference between fast channel and interleaved DSL. I don't know enough to write it myself. mvc 19:48, 8 August 2006 (UTC)

---

I cut this:

Some of the common "DSL Killers" are:

• Bridged taps
• Load coils
• "SLIC" boxes, or splitters, where copper capacity is increased by extending with multiple fibres. DSL can't travel over fibre, and most telephone companies choose not to offer fibre connections to residential customers.
• "DACS" boxes, where two baseband analog telephone lines are multiplexed over a single copper pair using ISDN-like technology to connect to the central office. Neither of the multiplexed lines is then usable for either DSL or ISDN service, as there is no metallic high-frequency path available. Where the central office connection is demultiplexed to analog connections, there is the added disadvantage that standard analog modem speeds are also reduced significantly.

As I'm not sure what its trying to say. You obviously need a continous copper line from CP to CO and I think this muddies the waters. Alex

I see that the titles Asymmetric Digital Subscriber Line, Integrated Services Digital Network, Asynchronous Transfer Mode, Asymmetric Digital Subscriber Line, and Digital Subscriber Line are all capitalized. These articles tend to have lots of incorrectly capitalized letters in the body of the article, and that makes me suspect that someone may have written them as capitals under the incorrect impression that the Wikipedia convention is to capitalize words in article titles? What is going on? Michael Hardy 21:23, 2 Aug 2004 (UTC)

dsl inventor

I am aware DSL technology started in Bell lab at around 1988. However, i can't see to find the guy behind the technology. A used google to try and look it up, but it looks like hundreds of people are claimimg dsl as their invention. This make it all the more important to find the real inventor and give credit to the right guy. I am aware that all inventions are progressive work and that Claude Shannon did most of the theoritical work, but then humans like personalizing achievement and hence the need of the guy who put things together and called it dsl. GITLIN, Richard claim to be one of them in this article [1] Anyone know the history behind this?

As a Practical Matter: How Fast Does It Go?

We're all looking for value and for that reason I've always gone for the cheapest DSL I could find knowing that TPC (The Phone Company...in what 60's movie was that used as a synonym for Big Brother) will always let you upgrade/increase speed/spend more money whenever you want as opposed to the opposite.

Plus, my line has always been fast enough for me, so why pay more?

Rather than give another speed test here, I'll give you a verbal/conceptual description of what throughput looks like on my setup, along with a detailed description of my setup. Until recently (1990ish to 2007) I have use my DSL only for heavy surfing. I've done major downloads (including full Linux setups) but generally only while I was away from the screen. That is I don't do major downloads while I'm trying to surf. I have a bottom rung fast machine (32 bit, 2GigHz, 1Gig memory, 200(?) 400(?) MHz Front side buss. ~4000 RPM ATA disks.) (Mid range would be faster hardware & wider buss (64bit), High range would be fastest hardware, widest buss, multiple processors.)

In all this remember: At max, the DSL is only 2/3 as fast as a 10Mb ethernet. There should be no delays. But an ethernet is like people hollering into a long tube. As long as they are having a Push to Talk style conversation, there will be no packet collisions and things will proceed at full speed. But once just 2 people begin to have a full duplex conversation, collisions (people hollering into the tube at the same time) cause things to slow down. Naturally, multiple conversations will only make things worse.

Speed has been satisfactory with this computer and 3-6 other computers on a 10Mb Ethernet system. Only one machine is generally surfing/downloading at once. The others are used as (remote control)terminals (bedside/other desks) and storage (I have about 500Gigs of disk space on line at home. I'm a pack rat. I still have all my CP/M (pre DOS) software on line. And until recently a PC XT running DOS 5.x all on the same Ethernet.) All this was first accomplished with 10/100 Ethernet cards using co-ax. Later (Year 2000ish) I bought some $10 hubs and plugged in some RJ (twisted pair) cards. In 2007 when I moved from a 3 bedroom condo to one room, I dumped the co-ax backbone and went to all twisted pair cards on one 10/100 hub. Ultimately my pre tweak net looked like this: Phone Line -> DSL Modem -> 3Com Router -> 3 Hubs (Kitchen, Office, Bedroom). The hub in the kitchen was where the phone line comes into my Condo and distributes to the rest of the house. The kitchen hub connects to a PC inserted into the phone line as a voice info system (voice mail, database querry) and begins the coax backbone to the rest of the condo. The coax runs to the office and bedroom hubs. There are 4-6 PCx wired to the office hub via RJ twisted pair. (fast workstation, medium speed file server, slow doc scanner and any other PCs for upgrade/repair.) The bedroom hub was twisted paired to a slow notebook for remote control of all the others. All the machines had remote control installed so I only needed 2-3 keyboards/screens to control them all.

Recently I moved in with some people who are still in the stone age. I've begun providing internet service for the household. Currently there are 3 of us. One does light surfing and music downloads. I and the 3rd gent have both recently begun online securities trading. The actual trading (entering orders) is not bandwidth intensive, but it does need to be EXTREMELY ROBUST AND RELIABLE. It is not unusual for a very modest Futures Contract position to move $100 per second so you really have to be sure that when you enter an order, it gets xmitted to the exchange floor and executed ASAP. You want to get in or out of the market NOW!!

The thing that takes bandwidth is the streaming quotes. During the day, the two of us will each, on separate machines, be watching a screen that shows the number of orders and the size of the orders (number of shares/contracts) at the market price and at the next 5 price increments above and below the market. In other words there are two machines looking at 33 numbers on the screen and those numbers are changing constantly. At the busiest times, these numbers might all change constantly every 1/4 of a second. That's just a description. Don't try to calculate anything from that.

When I first reconfigured the system for the other 2 users, on my system, the streaming quotes would stop for periods of time. The numbers would stop changing for periods from seconds to minutes to large fractions of an hour. If you can't get the futures prices, you can't trade, but fortunately I was using a simulated system and still trying to work out the kinks in my computer system and my trading abilities.

The second man's system would occasionally pause and give him some kind of message about net congestion. (Naturally, the guy never told me about this until I finished upgrading the system. He was probably afraid it was his fault and I would charge him for repairs. He's kind of a newbie. Sometimes he complains that his computer is not working properly and I have to go to his room and turn his keyboard right side up.) Fortunately he was trading options so he really only needs quotes hourly.

Anyway, just from long experience, I decided that my problems might very likely be due to network congestion and I needed to try and find out where the congestion might occur and what I might do about it. If the congestion was occuring within my system, I could fix that easily. It the congestion was external to my system, somewhere out on the net....well, I'd face that when I had to. Probably with tears.

My first idea was a line speed test. They are all over. Just Google. The problem is, line speed tests are meant to be run on an idle system. I did a few tests just to establish a bit of a baseline. Results were 600-630 Download, 130-138 upload.

Tiddling around with speed test got me to looking at any numbers or settings that might affect the operation of my LAN. There was one question which has always stood out in my mind which I've to this day never been able to answer. The question is: If, on a 1/100 LAN, one card alone is capable of only running at 10, do all the other 100 cards have to drop down and operate at the lower speed? I've never answered this question, but I have implemented a solution in case this is a problem. That later.

First of my solutions was to use my router status screens and the Windows Properties (My Computer/System Props/Hardware/NICs and Network Connections/Local Area Connections Props) screens to find out what speed my NIC cards are running at and make sure they are at the highest speed and Full Duplex wherever possible. Full Duplex vs Half Duplex is the difference between a regular telephone conversation and a 'Push to Talk' conversation.

My next solution, and the solution to the 'One card on my LAN is a 10speed and the rest are 100' problem was first, to analize the traffic flow for collisions and second, see that, as much as possible, all packets flowed into same speed or higher speed equipment.

Basically, while there are multiple computers on my net, there are really 3 users. The third user is basically a surfing nerd who does most of his work late in the evening. His other use is impossible to predict. The second user just streams quotes all day. Imagine someone watching video all day. I, user one, do heavy research surfing all day as I write and sometimes stream quotes. Nights and weekends I might watch a feature movie on line. Yes. The slowest, cheapest DSL and I can watch NetFlix movies.

My interim LAN looked like this: Phone Line -> DSL Modem -> 3Com Router -connection 1> My Hub and My machines.......... -connection 2> Wireless Router to 2 roommates machines.

I had already bought another router/wireless access point to allow service to my other roommates without stringing wires as I had at my Condo. However, I had some concerns about the visibility of my computers to my roommates. As they were on the same node with one computer each, they had to turn off file sharing so they could not see each other. Initially they could not see me as I was upstream, on the phone line side, of their router but I had to turn on file sharing so all my machines could see each other. The router act as a firewall as I am on the internet side, so I could not see my roommates machines, but if they learned the tricks of local TCP/IP addressing, they would be able to see my machines also. The router does not hide the internet side from the view of machines inside the node if you know how to use local (192.168.xxx.xxx) addressing. It is dificult and certainly beyond their talents, but that's not what you rely on to keep your net secure. Who know if they might have a geek friend over?

Plus the configuration above is still a modified One Node net. That means that everyone is still more or less hollering into one pipe as far as collisions are concerned. Worse yet, the way it was set up, their traffic would collide with my traffic, but by traffic would not collide with theirs, at least not on their segment of the node. Hubs pass all traffic in a node but routers only pass traffic destined for or passing through a node. My segment would share their traffic but their segment would not share my traffic.

My final configuration was: Phone Line -> DSL Modem -> 3Com Router -connection 1> wireless router #1 and My machines.......... -connection 2> Wireless Router #2 to 2 roommates machines. In addition, my fast workstation is RJ twisted paired to Router #1. My other 2-4 machines are connected to router #1 through a hub connected to #1. First, connecting my workstation to the router #1 should isolate it. #1 should only tx and rx packets destined for my workstation. All the rest of the traffic should be routed to the hub where my other machines reside, which are slower to begin with and have no critical traffic. Second, as I still don't use wireless on my side of the node, I needed more than the 4 wired ports available on router #1, hence the need for the hub.

My final configuration was:  Phone Line -> DSL Modem -> 3Com Router -connection 1> wireless router #1 and My machines..........  -connection 2> Wireless Router #2 to 2 roommates machines.  In addition, my fast workstation is RJ twisted paired to Router #1.  My other 2-4 machines are connected to router #1 through a hub connected to #1.  First, connecting my workstation to the router #1 should isolate it.  #1 should only tx and rx packets destined for my workstation.  All the rest of the traffic should be routed to the hub where my other machines reside, which are slower to begin with and have no critical traffic.  Second, as I still don't use wireless on my side of the node, I needed more than the 4 wired ports available on router #1, hence the need for the hub.

It worked!! There was a noticeable increase in the speed of high traffic tasks and the problem with my streaming quotes freezing has totally disappeared. Before, if my roommate was streaming quotes, I was aware of a visible delay in loading web pages. That has gone away also. And in addition to speed, I am now sure that the machines on the node served by Router #1 cannot see any of my files on my node served by Router #2. All that is left is to try a speed test during the day when my roommate is streaming quotes.

Finished half a dozen speed tests just now with the roommate's machine streaming quotes: avg download 585-609kbps, avg upload 295-316kbps. As you will recall, when I started, the results were 600-630 Download, 330-338 upload but those results reflect a totally quiet line. These results, plus the obvious speed increases of web page display seem to indicate to me that my LAN was being clogged by packet collisions before and now, even at maximum use, I still have about 75-80% of my bandwidth available. How much real use I get out of what's left depends on my ability to avoid packet collisions.

(1/27/08 to be continued. Should be finished in a day.)Tgdf (talk) 16:47, 17 January 2008 (UTC)

History

There should be more on the DSL History. Like how it was at one point intended to carry Video-On-Demand. linky

DSL history - sources?

The first paragraph on the DSL page makes some claims that I haven't heard elsewhere. Some sources are needed for it(news reports, historical studies, etc.). It's good writing, and interesting, but it needs to be sourced.

The paragraph: "Its origin dates back to 1988, when an engineer at Bell research lab deviced a way to carry digital signal over the unused frequency spectrum. This allows ordinary phone line to provide digital communication without blocking access to voice services. Bells management however were not enthusiastic about it as it was not as profitable as renting out a second line for those consumers who prefered to still have acess to the phone when dialing out. This however changed in the late 90s when cable companies started marketing broadband internet access. Realising that most consumers would prefer broadband over a second dial out line, Bell companies rushed out the DSL technology that they had been sitting on for the past decade as an attempt to slow broadband internet access uptake." - diff (Also posted on User talk:Wk muriithi) JesseW 19:48, 6 Apr 2005 (UTC)

wk muriithi replied on my talk page saying he got it from "Crafting and Executing strategy 14th edition by Arthur A. Thompson Jr.". If someone who has a copy could verify this, and add it as a footnote(use Wikipedia:Footnote3 style) that would be great. Thanks for replying, Wk! JesseW 05:34, 15 Apr 2005 (UTC)

DSL "modems"

I heard some claim that DSL modems aren't really modems. Is this just BS? - Omegatron 01:18, Apr 15, 2005 (UTC)

I'd say that's BS. The definition of a modem is something that takes data and modulates it onto an analog signal on one end and then demodulates it back to digital at the other end. What's called a DSL modem can be thought of as a whole bunch of dial-up modems working in parallel at different frequencies to get you a large pipe. I've just rewritten the "How it Works" section of the main article that explains it in some technical detail. --Blrfl Apr 17, 2005

I'd say it depends what you heard...these days most CP xDSL equipment is actuall a ROUTER, typically supporting NAT, and generally also a DHCP SERVER Xaosflux 05:42, 11 November 2005 (UTC)

From http://electronics.howstuffworks.com/vdsl.htm: 'Most residential customers call their DSL transceiver a DSL modem. The engineers at the telephone company or ISP call it an ATU-R, which stands for ADSL Transceiver Unit - Remote.' Even http://en.wikipedia.org/wiki/DSL_modem: 'To the end-user, it is functionally very similar to an analogue modem, however the underlying technology is substantially different.' Isn't DSL, by definition, digital and not analogue? The article itself doesn't make clear what part modulation plays, so maybe that is a place for improvement. 2006-05-19 03:25 UTC

Whether you call it analog or digital is a question of which half of the hair you just split gets picked up off the table. Ultimately, what ends up on your copper is an analog signal (several of them, actually) modulated to represent digital information. --Blrfl May 21, 2006

CarlosRibeiro 00:16, 22 October 2006 (UTC). Humm. At first I though that DSL modems were modems, end of it. But then I realized that the ADSL specifies both the line modulation method (DMT) and the layer 2 encapsulation (ATM). In this sense, an ADSL end user device would be a "modem" only if it presented a ATM interface for the customer connection, which clearly is not the case for any commercial unit commercially available since 1999. (In fact, I had in my hands an ADSL modem with a 25 Mbps ATM port in 1999 - since then, all ADSL 'modems' have Ethernet ports). In other words - even the simplest ADSL devices available today (as of 2006) are a little bit more than modems because they do layer 2 protocol conversion (encapsulating Ethernet inside ATM, as per RFC1483, etc.). So we have two options - calling them "ADSL transceivers" (as mentioned elsewhere; but that's still not entirely correct) or "ADSL bridges" (which I think is the best option).

Most widely used variety?

I wonder what variety of DSL is most commonly used? The only variety offered in my country is ADSL so I have no clue what is used in other countries. As I see it, ADSL is the most reliable variety, and hence the most common used. Can anyone comment on this? --Opiax 19:19, 25 Apr 2005 (UTC)

ADSL is by far the most common, but it's less an issue of reliability than one of giving the customers, most of whom receive far more than they send, high download speeds. With the exception of IDSL (which isn't really DSL; it's just a bonded pair of ISDN B channels), all of the flavors of DSL are pretty much the same from a technical standpoint. Two things differentiate them. First is the amount of spectrum above the baseband POTS signal. This is, effectively, a measure of the size of the pipe that carries all of your data in both directions. It's determined to a large extent by the basic technology in use (DSL, HDSL, VDSL) and the length and condition of the copper between you and the DSLAM. The second is whether the fractions devoted to the upstream and downstream channels are equal (for Symetric DSL or SDSL) or different (for Asymetric DSL or ADSL). As an example, my DSL line has a total of 4424 kbps available, and my ISP (Verizon) allocates 864 for upstream and leaves the remainder for upstream, giving me ADSL service. They could just as easily have allocated 2112 each way for SDSL or, if I had some special application where I needed it, 864 down and 3360 up for ADSL. --Blrfl 07:50, 16 May 2005 (UTC)

Actually, there IS a good technical reason for ADSL: at the customer end, the UPlink signal being transmitted by the modem is strong and the DOWNling signal being transmitted by the DSLAM is weak, whereas it's the other way around at the CO end. Crosstalk is much more likely to be an issue at the CO end, where local loops from a number of customers are physically close together. So the S/N is often better for DOWNLlink than for UPlink. It was good fortune that the average customer wants more speed downloading, hence ADSL made lemonade from this particular lemon.

External link

First external link is dead.

Internet Speed Calculator

There should be a calculator where you input a filesize and it outputs the time required to download/view that file on different internet speeds.

There are plenty online. -Omegatron 02:50, August 22, 2005 (UTC)

DSL Repeater

Can someone explain why there are no DSL repeaters to extend the range of DSL usage? Seems like it would be simple to have a line-powered repeater to regenerate the signal and extend the range.

See: http://en.wikipedia.org/wiki/Broadband_Internet_access#DSL_repeater Xaosflux 05:45, 11 November 2005 (UTC)

DSL repeaters do exist, such as those made by Charles Industries (HVDL products) and Versa Technology, and the now-defunct GoLong system by Symmetricom. These are digital systems requiring a relatively high voltage sourced either from the installation location, or from a separate copper wire pair dedicated to carrying power. GoLong failed because of several technical reasons. Charles Industries' HVDL product is moderately successful and suited for deployment on single lines. Ultimately there has to be a well-understood cost/reward relationship for any phone company to deploy equipment on single lines.

An approach better suited for mass deployment are Phylogy, Inc.'s TripleStream Line Conditioner products. TripleStream takes a different approach from the ones above, allowing for deployment of multiple lines with one truck roll. Phylogy uses an analog approach, power consumption is extremely low per line, providing the ability to power the unit directly from -48V POTS power without affecting normal POTS operation.

Phylogy also has ADSL2+ products and claim to provide a VDSL2 product in 2007.71.131.55.85 23:28, 15 January 2006 (UTC)SSD

PPPoE, PPPoA

The articles states:

Many DSL technologies implement an ATM layer over the low-level bitstream layer to enable the adaptation of a number of different technologies over the same link.

If I understand correctly, this is the ATM layer referred to in PPPoA, in which case it should read "ATM or Ethernet layer," seeing as PPPoE is more common in the US. Can someone verify this?

Scorpiuss 18:55, 14 December 2005 (UTC)

I believe that ATM is the transport over DSL whether PPPoA or PPPoE is used. These protocols are ways to establish point to point serial connections and refer to the interface that PPP talks to. In PPPoA, the PPP part happens in the modem which is ATM and is before encapsulation of Ethernet has occurred, hence the name I suppose. Snafflekid 22:11, 14 December 2005 (UTC)

Inventors of DSL

DSL was originally invented in 1988 by two Bellcore research managers: Charlie Judice and Ray Laane and by one marketing manager, Manny Kline, from NYNEX which is now part of Verizon. HDSL had already been developed as a technology replacement for T-1 carrier which was used by the telcos for provisioning DS1 service --- a full duplex service. It was our observation that the primary applications for a residential service (video-on-demand and internet access) did not require a high bit rate upstream signal. Furthermore, we understood that in order for a residential DSL service to make sence it had to work on one pair of wires. Within a day with the help of a Bellcore engineer, Joe Lechleider, we demonstrated that an asymetric service called ADSL was possible.

I translated the German HDSL article and linked it here, to DSL. Please revise and edit to fit American nomenclature. Justin 05:33, 22 June 2006 (UTC)

question from a dialup user : Distance Limitations

from the way this is worded, it seems that anyone with a phone line can use DSL.. i've been on 56k dialup since 1998, and i know virtually nothing about any form of high-speed internet. ? - Srrrrrrr 08:14, 5 January 2006 (UTC)

There's more to it than just having a phone line. Your telephone company has to (a) offer the service in the first place and (b) install special equipment in the central office nearest you that puts the service on your line. I'll take a look at the article to see if it needs tweaking to clarify that. --Blrfl Jan 13, 2006

A major reason many customers can not receive DSL is the distance from the customer to the phone company's central switching office (CO). All DSL signals lose strength and thus speed as the signal travels over thousands of feet of copper telephone wire. Many phone networks provide the facility for DSL to travel only 12,000 feet or so before the signal dies out completely. Customers within one mile of the CO could receive the maximum 8Mbps speed if the phone company allowed it but are usually capped at 1.5-3Mbps. The achievable speed decreases for customers further out from the CO.

For years now phone companies have installed equipment to provide DSL services to more customers, in the form of remote cabinets with environmentally-hardened DSLAMs and other products. As an example, SBC's Project Pronto cost billions of dollars but now provides a higher revenue stream due to new DSL customers who could not receive DSL prior to Pronto. 71.131.55.85 23:29, 15 January 2006 (UTC)SSD

The above user gives a good explanation of why exactly there is a distance limitation to DSL. Perhaps something to that effect should be included in the "Operation" section, as the explanation currently there is rather technical, which there is nothing wrong with, but it is also somewhat unclear. ("More usable channels equates to more available bandwidth, which is why distance and line quality are a factor.") 69.171.53.42 19:58, 16 February 2006 (UTC)SSD

Half duplex

I got the word from my ISPs tech support that all DSL was half duplex, so added this to the article. Usually I wouldn't trust such a source, but they've always been good. Anyhow, I could see this varying from country to country or over time, so if anybody has better information please revise.

ADSL is by definition full duplex, meaning data can be transmitted both ways at the same time. What your phone company may have tried to explain is ADSL is asymmetrical, meaning download speeds are much greater than upload speeds.

Active Phone Line Required?

Is an active telephone line required? I've heard varying views. It seems to me that you could use the phone line strictly as a data transmission line without having to have phone service. Do you have to have an active phone line? The only thing I could think of that might require one would be the routing of the signal, it might not be routed unless the line was active. Anyone know? --Littleman TAMU 20:58, 29 June 2006 (UTC)

The main thing I can think of that might require an active telephone line is a phone company that demands that you buy voice service from them if you're going to get an ADSL circuit from them. This is, I think, the most common reason why an active phone line would be required in the USA; phone companies don't want you getting Internet access from some other company, getting VoIP from your ISP or some third party, and only getting the low-level ADSL ATM transport from them. I know of no technical reason why an active phone line would be required. Guy Harris 20:22, 20 August 2006 (UTC)

Someone added info on naked DSL to the Operation section. That's what I was looking for. Littleman TAMU 20:22, 5 September 2006 (UTC)

Move stuff to the ADSL page?

Most of the stuff on this page appears to refer specifically to ADSL; should it be moved to the ADSL page, with this page just summarizing all Digital Subscriber Line technologies and pointing users to the ADSL page fairly quickly for the benefit of those users who are curious about their "DSL" connection? Guy Harris 20:20, 20 August 2006 (UTC)

DSL vs ADSL in common language usage

I need to know if the term DSL is commonly used in the USA to refer to ADSL (I know that ADSL is technically a type of DSL; this is a linguistic question). In Europe ADSL is called ADSL. A US technical friend of a colleague of mine swears that in the US, the term DSL is commonly used to mean (by default, I imagine) ADSL. Can anyone clear this up for me? If I say DSL in the states, will they assume I mean ADSL? Thanx. Ryancolm 07:39, 21 August 2006 (UTC)

Yes. In the US, DSL is normally understood to mean ADSL. The term xDSL is normally used when inclusively referring to all forms of DSL. ClairSamoht 08:28, 21 August 2006 (UTC)

That's cause of endless discussion... I believe that, as a encyclopaedia, Wikipedia should stand by the definition of DSL as the whole family of technologies, while keeping ADSL focused on the specific technology. I see no problem on the article about DSL telling people about the popular use of DSL, I don't mind, but for the sake of clarity, people should be redirected to the ADSL entry as soon as possible. Bear in mind that there's no "xDSL" entry on Wikipedia; adding one would do no good (except, perhaps, as a redirection to the DSL article). CarlosRibeiro 18:55, 5 November 2006 (UTC)

Also on the point of naming and common use. Do you think it's worth putting in a note about the confusion between DSL and cable. So many people I talk to think that DSL is cable and nothing to do with ADSL (they get that ADSL is over the phone line). They don't realise ADSL is a type of DSL and cable is just cable. I don't know if this confusion happens as much in the US but it happens here (UK) so much

They sound dumb.  ;-) Maybe I should take a picture of my DSL connection, which is just a plain-jane telephone line (not cable). - Theaveng (talk) 18:26, 20 November 2007 (UTC)

I think it would be extremely helpful to compare DSL and cable. DSL salespeople say that due to technology that DSL can guarantee a minimum speed whereas due to technology that cable cannot guarantte a minimum. It would help to state that explicitly, whatever the truth is. Another thing is that the DSL salespeople in the past have told me that I am too far from the office to get the slowest most economical speed and that I need to pay for faster speed to get DSL. That (seems to?) contradict what this article says so if that can be clarified that will help. Finally, some practical (less technical) explanation of extending DSL service would help. If DSL is now being offered at greater distances than a few years ago then it would help for there to be something explaining that, and hopefully it can be said in less technical terms than the article currently uses. —Preceding unsigned comment added by 76.87.181.194 (talk) 17:06, 11 December 2007 (UTC)

Current US Regulatory Situation?

The article states:

"When the FCC required ILECs to lease lines to DSL providers such as Earthlink, however, a move to shared-line DSL (also known as DSL over UNE) was made to avoid the need for custom installations."

My understanding is the FCC has recently removed this access requirement -- and the DSL market may be turning into local phone company monopolies?

An update on this subject is needed == and a dedicated section on the historical development of the DSL service business model (including the confusing issue of whether there is a distinction between the customer's DSL service provider and the ISP) would be very helpful.

The following discussion is an archived debate of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the debate was move. Andrewa 05:51, 6 October 2006 (UTC)

Requested move

Digital Subscriber Line → Digital subscriber line – One of Wikipedia's naming conventions is that second and subsequent words should be lowercase unless the term is a proper noun or is always or almost always capitalized. Digital subscriber line is not a proper noun, but it is frequently capitalized. However, I do not think that it is capitalized frequently enough to have the article's name be capitalized. I suspect that it is only capitalized at all because the acronym DSL is used so often. The letters in the acronym are capitalized, so people may think that the expanded version should be capitalized (see acronym and initialism), and people may also capitalize it to show where the letters in the acronym come from, as the first instance of the term is usually "Digital Subscriber Line (DSL)" and then it is referred to as DSL from then on. I have found many instances of digital subscriber line not being capitalized, including: Cisco Press, Webopedia, McGraw-Hill, Stanford Report (Stanford University), CNET, How Stuff Works and International Engineering Consortium. News organizations, which follow the rules of English to a greater extent than other organizations, frequently do not capitalize digital subscriber line. 9 out of 18 sites on the first two pages of the Google News search, at the time I am writing this, have DSL uncapitalized. 2 out of the 20 sites listed are not counted because the term is only given in a headline that capitalizes every important word and some non-important ones. I think that the capitalization of digital subscriber line is an error, as per acronym and initialism, and that Wikipedia should not repeat the mistake. Finally, it is confusing when Wikipedia chooses slightly/somewhat more popular usage over correct usage.

For consistency, I think that if the article is moved, articles which contain Digital Subscriber Line in their title should be renamed as well. — Kjkolb 11:37, 29 September 2006 (UTC)

Survey

Add "* Support" or "* Oppose" followed by a brief explanation, then sign your opinion with ~~~~

Discussion

Add any additional comments

The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Modem x Router x Gateway; Narrowband x Broadband; DSL x ADSL

CarlosRibeiro 17:46, 21 October 2006 (UTC). Three discussions into one revision:

• Modem x Router x Gateway - On the "equipment" section, I added some comments on the difference between modems, routers, and gateways. I though it was important given the previous discussion over the terms, and also given the way DSL is usually implemented.
• DSL x ADSL - Also on the "equipment" section, there were comments that applied only to ADSL, regarding splitters, etc. I thought it was better to move part of the comments there (explaining specifics of ADSL); but I retained some of the explanation there because it's important to understand in a generic sense.
• Narrowband x Broadband - The explanation wasn't technically correct; it confused narrowband x broadband with Shannon's limit. The best narrowband technology uses some of the same techniques that allowed DSL to get this far, specifially, multiple symbols per transition.

Redirects

Removed automatic redirect from DSL --Wavemaster447 00:37, 26 November 2006 (UTC)

No, you just removed the note that says "DSL redirects here" and points to the disambiguation page. If you really want to remove the redirect, redirect instead to the "DSL (disambiguation)" page, or request that "DSL (disambiguation)" be renamed to "DSL", if you think people looking for "DSL" should be sent to the disambiguation page rather than sent to the "Digital subscriber line" page. Guy Harris 01:07, 26 November 2006 (UTC)

1930s?

"However, in the 1930s techniques were developed for broadband communications that allowed the limit to be greatly pushed" <- is that date right? —Preceding unsigned comment added by 69.64.217.18 (talk • contribs)

I believe the blurb is referring to DMT, which was invented by John Cioffi in 1993. [2][3] So I'm betting it should say 1990s. - Keith D. Tyler ¶ (AMA) 20:17, 20 February 2007 (UTC)

It seems reasonable to suppose that was the intention, but it's all rather vague, given the ambiguity of the term "transmission line" and the failure to detail the relevance of the Shannon Limit. I mean, obviously a relation between bandwidth, noise and bit rate is most relevant when there's a bandwidth limit, and telephone wires are seldom pushed to any hard bandwidth limit, and Gaussian noise was not prominent among the problems that had to be overcome to achieve DSL. Hmm, the Shannon Limit would be highly relevant to the bandwidth article. I must look to see if it's there.

Arguing that the date is correct, we could point out that this was the time Groupband connections became available; see L-carrier which is where I ought to mention this development. Jim.henderson 21:26, 20 February 2007 (UTC)

U-R2

I've seen reference to 'U-R2' in the documentation for my ZyXEL ADSL Router, and wondered what it was. I did a quick google and the only page that came up was on the German Wikipedia. My German is practically non-existant but using Google Translation [4] I was able to judge that it is some variant of DSL. Presumably there must be some technical differences from 'vanilla' ADSL as used in the UK/USA or ZyXEL wouldn't bother to make seperate units for U-R2! Anyone know what this is, and care to add a section on it? Slothie 23:33, 8 February 2007 (UTC)

Title Name

I think the first letters in the title "Digital subscriber line" should be all capitalized, i.e. "Digital Subscriber Line". Is there any special reason for the small letters "s" and "l"? HkQwerty 20:19, 17 March 2007 (UTC)

See [5] for the standard Wiki style in this matter. As it happens, the term "Digital Subscriber Line" redirects to this article, so it shouldn't be a problem for anyone. Jim.henderson 22:36, 17 March 2007 (UTC)

I know it's case insensitive to search this article. I just don't understand why Asymmetric Digital Subscriber Line and Symmetric Digital Subscriber Line are all initial caps but this article is not. -- HkQwerty 17:06, 19 March 2007 (UTC)

Ah. There we go. We have an inconsistency. What you meant to ask is, is this article capitalised right, and the other two wrong, or vice versa? Reading the applicable section of Manual of Style, I think this one is correct and the other two are incorrect, but I'd like to hear arguments the other way before renaming anything. Jim.henderson 20:25, 19 March 2007 (UTC)

In this article DSL should be a name of a unique technology, not just a bunch of lines, right? I think it's a proper noun. -- HkQwerty 17:26, 21 March 2007 (UTC)

Proposed Change for Basic 'How it Works' Summary Section

I propose the following rewrite for the summary paragraph for clarity:

DSL connections work by splitting up the frequencies used in a single phone line into two 'bands'. The ISP data is carried over the high frequency band (25Khz and above) whereas the voice is carried over the lower frequency band (4Khz and below). The user typically installs a DSL filter on each of the phones connected to the same phone line as the DSL modem. The DSL filter filters out the high frequencies from the phone, so that the phone only sends or receives the lower frequencies (the human voice). This creates two completely independent 'bands', allowing the DSL modem and the phone to simultaneously use the same phone line without any interference from one to the other.

Loriculus 19:09, 2 July 2007 (UTC)

Yes, it looks like an improvement. Fairly minor suggestions:

• Rename the paragraph, too. It doesn't describe any part of how DSL works, except the use of different frequencies. This is not a criticism of the paragraph or of the intent; only of the title.
• Drop the DSL self link, and the repetitive linking of DSL filter and any others. Terms should be linked at first appearance, and perhaps at some repetitions in distant paragraphs.
• See ADSL for the fact that the spectrum is divided into three bands, not two. This is not to suggest that this article also should say so. There are reasons why articles that overlap should not go equally into detail.
• Oh, come to think of it, the third sentence perhaps overstates the obvious, and would be equally clear to newbies without the entire phrase "connected to the same phone line as the DSL modem. Jim.henderson 23:14, 2 July 2007 (UTC)

---

Thanks Jim. Here is a re-write based on your suggestions:

Title: Basics

DSL connections work by splitting up the frequencies used in a single phone line into two primary 'bands'. The ISP data is carried over the high frequency band (25Khz and above) whereas the voice is carried over the lower frequency band (4Khz and below). (See the ADSL article on how the high frequency band is sub-divided). The user typically installs a DSL filter on each of the phones. This filters out the high frequencies from the phone, so that the phone only sends or receives the lower frequencies (the human voice). This creates two completely independent 'bands', allowing the DSL modem and the phone to simultaneously use the same phone line without any interference from one to the other.

Loriculus 23:43, 2 July 2007 (UTC)

---

Recently, Phaniraj01 added this into the same section:

DSL uses PPPoA protocol between the CPE DSL modem/ router and the ISP.

However, PPPoA is just one of the protocols that are used by a DSL modem. So, it is not a correct statement. RFC1483 (or RFC2516) bridging/routing, RBE (Routed Bridge Encapsulation), PPPoA, PPPoE are common ones. I propose replacing it with this:

DSL uses a link layer protocol such as PPPoA, PPPoE, RFC1483 (or RFC2516) bridging/routing or RBE (Routed Bridge Encapsulation) between the CPE DSL modem/router and the ISP DSLAM.

Loriculus 18:36, 3 July 2007 (UTC)

I should have looked at the talk page before reverting that sentence on stylistic grounds. Anyway, now I inserted your text, but shortened it a bit and put in a title of my own of intermediate length. Feel free to re impose your own ideas, or to improve mine further. Jim.henderson 21:51, 4 July 2007 (UTC)

That looks good. Thanks Jim. Loriculus 16:40, 5 July 2007 (UTC)

How Much Faster is DSL compared to Dialup?

I came here hoping to find a definitive answer, because Verizon's claims make no sense ("21 times faster than 56.6K dialup"). My line is only 768 kbit/second. 768/56 == 13 which is nowhere near Verizon's claim. (It's even less when you consider 56K modems use compression to increase effective thoughput to ~150 kbps).) I'd like to find an actual study that's not biased by salesmanship. - Theaveng 17:37, 14 September 2007 (UTC)

Given that ADSL can run from 768Kb/s (or possibly even lower) to 6Mb/s (or possibly even higher), there isn't a single definitive answer to your question. I've gotten 1.5Mb/s; 1500/56 = 26. Guy Harris 21:33, 15 September 2007 (UTC)

When it comes to "Speed" Differences, it all depends on what DSL package you apply for, a lower costing package may seem less then the speed of dialup but you need to consider its still a broadband connection with an "Always On" connection that allows you to still use your phone to make or recieve calls The more expensive DSL packages can also give you up to and sometimes even more then 5Mb/s. I know my provider allows up to 18Mb/s downstream --MadFrenchie 19:43, 21 October 2007 (UTC)

I should have clarified I was talking about Verizon's claim about 768 Download connections. They claim 768 kbit/s is 21 times father than a ~50 kbit/s dialup, which doesn't fit the math. ' - Theaveng (talk) 18:24, 20 November 2007 (UTC)

Does DSL use V.42, V.44, or some other data compression?

My dialup modem uses V.44 to compress text 6-to-1 (effective throughput of 300 kbit/s) and executables like flash programs 3-to-1 (effective throughput of 150 kbit/s). Does DSL use a similar technology to squash data on the fly? - Theaveng (talk) 18:30, 20 November 2007 (UTC)

Not as far as I know, no. Perhaps in the old days when DSL was invented, logic to do such jobs at such speed was too expensive, or unimportant since files are usually small as in HTML texts, or already compressed such as pictures or self installing programs. 71.247.74.165 (talk) 18:05, 26 November 2007 (UTC)

Dsl user authentication

How does Dsl user authentication take place? Which device performs the per user authentication/billing? I think this point should be mentioned, it's important. —Preceding unsigned comment added by 203.220.146.76 (talk) 02:59, 8 January 2008 (UTC)