WWW FAQs: I have DSL. Why did my connection suddenly get slow and unreliable?

2007-02-05: When a DSL connection is working properly, it is very fast. But when your connection to your provider is not quite good enough, DSL can become slow and unreliable. Sometimes your connection works at full speed. Sometimes it appears to work slowly. Sometimes you can only fetch part of a file. And sometimes it doesn't work at all, though you might still see a green DSL light on your DSL modem. This problem is called "intermittent sync."

What You Can Do About Intermittent Sync

If you suspect your DSL connection suffers from an intermittent sync problem, there are steps you can take to track down the cause. To avoid guesswork, follow this checklist.

1. Connect your DSL modem to the phone jack with a different phone cord! A bad phone cord can lead to a lot of wasted time. If your connection now works reliably, throw out the bad cord. It might work well enough for phone calls, but I guarantee there will come a day when you try to use that cord with a DSL modem again and repeat all of this hard work and frustration.

2. Shut off any radios (especially AM), stereo equipment, and other appliances in the house. Then test your DSL connection. If it works properly, turn on your appliances back on, one at a time, until you find the electrically noisy appliance. Then connect the DSL modem to a jack as far away from the noisy appliance as possible.

3. Connect your DSL modem to a different phone jack. Then test your Internet connection. If it works reliably, the phone jack you have been using is noisy or the wiring behind it is bad. Sometimes a jack is good enough for phone calls but not good enough for DSL. Use a jack that provides reliable service.

Still not working? The remaining steps are a little bit more complicated. But they will categorically rule out a problem within the house so that you can get your DSL ISP (the company you pay for DSL service) to take action on their end.

Following the remaining steps will momentarily interrupt your phone service, just like unplugging your phone would. Yes, I'll show you how to hook it back up again. Please don't do this when you are waiting for an important call.

Legal Note: these steps are OK to follow in the United States. If you live elsewhere, it might not be legal for you to access your own telephone network interface box. You follow these steps at your own risk.
4. Locate the box where your DSL/phone service comes into your house. This is called the "Telephone Network Interface." Often this box is on the front or back of the house. This is not your electrical service panel! Don't go anywhere near that! If it does not say "Telephone Network Interface" right on it, DO NOT TOUCH IT!

5. With a screwdriver, open the side of the box marked "Customer Access." Do not open the "Telco Access Only" side!

6. You will see ordinary-looking phone jacks. One of these will be hooked up for each phone line you currently have in the house.

7. Disconnect the plug for the line your DSL service is on. If you have only one phone line, the choice is obvious. If you have more than one, I'll show you how to figure out which is which in a moment.

8. With an ordinary phone cord that you know is good, plug an ordinary telephone into the jack you have just disconnected the house from. Pick up the receiver. You should hear a dialtone.

9. From a separate line, such as a cell phone, call the phone number associated with your DSL line. The phone you have connected to the line should ring. If not, you probably have multiple lines - hook this line back up to the house and try connecting the phone to another.

A few people have DSL on a separate line with no phone service on it. This is rare and offered mostly by specialists like Speakeasy.Net. If this is the case for you, then you will not hear a dialtone.

10. OK, we've identified the DSL line. Now we can test whether the intermittent sync problem is generated by something within the house. Hook up your DSL modem directly to the jack in the Telephone Network Interface and plug it in. Use a brand new phone cord to be sure the phone cord is not the problem. Then wait at least a minute. If you get a steady DSL light, hook up your computer to the DSL modem and check out your Internet access. Spend enough time online to make sure your connection operates reliably and at full speed.

11. Disconnect the DSL modem from the Telephone Network Interface and plug the house phone wiring back in to the jack.

12. Close up the Telephone Network Interface Customer Access panel.

13. Plug your phone back into a jack in your house (with a DSL filter) and verify that you have dialtone again.

14. Plug your DSL modem back into a jack in the house (never with a DSL filter).

15. If you had unreliable, slow DSL service when connected directly to the Telephone Network Interface, then the intermittent sync problem is your ISP's problem (the company you pay for DSL). Call their customer service. Patiently explain that you tested the DSL modem while connected directly to the Telephone Network Interface, so you know the problem is not in your house. You will have to be very patient and explain this more than once before they accept it. Eventually they will agree to do testing on their end. They may have to reset your connection. If the problem comes back, then they may have to decrease your DSL speed. If you are already at the slowest DSL speed, then reliable DSL service might not be possible in your house. This is usually because you are farther from the telephone company central office than anyone thought, or because the telephone company equipment between you and the central office is substandard. Consider switching to cable modem service, such as that provided by Comcast in most areas in the US.

16. If you had reliable, fast DSL service when connected directly to the Telephone Network Interface, the problem is inside your house. Go through steps 1-3 again, slowly and carefully. If you still can't find any jacks within the house that provide reliable service with all other appliances unplugged, then you probably have bad phone wiring in your house.

If you are not experienced with telephone wiring, you may be able to arrange for your phone company or DSL ISP's customer service to send someone out to upgrade the wiring, usually for a fee. Alternatively, an electrician can do it.

If you do have experience with phone wiring, you might be able to locate the point where the wiring from the Telephone Network Interface is "split" to hook up the various rooms in the house - usually somewhere in the baseement. Try attaching a jack here, before any splitting to wire individual rooms has been done. Then connect the DSL modem to it.

If service is reliable, then you just need to upgrade the wiring from this point... or, if you're lazy, just split off a pair for the DSL connection first, before wiring for any other jacks.

Of course, replacing a sloppy collection of daisy-chained, electrical-taped splits with a nice punchdown block from which every line "home-runs" all the way to the actual jack is a good way to ensure reliable service and easy maintenance in the future. For more information, see doing your own telephone wiring, a helpful article by Sean Crist.

"Can I improve my DSL speed with heavier-gauge wiring?"

No! Please don't do this. Never use anything other than standard-gauge twisted-pair phone wire - CAT4 or CAT5. (CAT5 is suitable for both telephone and Ethernet use.) Heavier-gauge wire may have the wrong impedance or fail to accommodate the high-frequency DSL signal.

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