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This Section
Typically, poor or fluctuating speeds usually fall into one of 5 categories:
Section 1 - Software/Configuration Issues
Section 2 - Account provisioning is incorrect
Section 3 - Physical problems
Section 4 - Provisioning rates versus speed test websites
Section 5 - Many speed tests are not reliable


Important Recommendation: It is suggested that you use the Official BellSouth FastAccess Speed Test Website for your speed tests. It stays on BellSouth's network and eliminates some variables associated with other speed test sites. If you are using a wireless connection you must test with the computer hard wired via ethernet cable directly to the modem/router to eliminate the wireless connection from being at fault.

Section 1 - Software/Configuration Issues

Computers, modems, and routers must be configured and functioning correctly.
1. Make sure your computer(s) are tweaked correctly.
-FastAccess Lite (768/128) Tweak
-FastAccess Ultra (1472/256) Tweak
-FastAccess Xtreme (3000/384) Tweak
-FastAccess Xtreme (6000/512) Tweak

2. If you are using a third party router (wired or wireless) in conjunction with your modem remove it and connect directly to one PC and recheck your speeds. If your speeds increase and the router is suspect, make sure you have the newest firmware installed. If you are using a Linksys router in conjunction with the modem and getting poor speeds and intermittent connectivity check out this FAQ.

3. Make sure your PC is free of spyware, adware, viruses, or any applications that may be running in the background and using upload/download bandwidth. Even a small amount of upload traffic can drastically effect your download speeds.

4. Make sure your NIC and modem (or router) are negotiating a full-duplex (10Mb or more) connection. 10Mb half-duplex connections may create situations where you can not get full download speeds in the higher tier services. Check your modem event logs for connection information.

Section 2 - Account provisioning is incorrect

If you have just upgraded to a higher service tier your order may not be completed or there may be an issue with the order. To check your order status click here. Additionally, your modem may not be configured with the correct username or you may have been provisioned on the wrong service tier. If you are seeing speeds that are consistent with another speed tier (such as 768/128), verify that the proper username/password is configured on the modem. Your service level (speeds) may be assigned based on username. If you are absolutely sure the username is correct, contact BellSouth and have them verify your service provisioning.

Section 3 - Physical Problems

1. Make sure the DSL filters are installed properly, present on all devices, and functioning properly. This is probably the #1 reason for many speed related issues. The BellSouth supplied filters have two outputs, one for phones/faxes/etc and the for DSL. It is very important that all phones/faxes/etc have a filter installed. Filters can also go bad for various reasons so just because a filter is installed properly does not mean it is still functioning properly. To eliminate the filters as a cause of problem remove all filters and POTS devices from every jack in the home. Replace the filters and POTS devices one at a time and test the modem for any speed or stat changes. If your speeds drop off dramatically then replace that filter. Home alarms and satellite systems can also interfere with DSL. To troubleshoot, simply disconnect any line going to the alarm control module or satellite (even if you do not currently subscribe to the service) and check your speed and modem stats. If the alarm is causing issues you can install a special filter designed for alarms systems or call the alarm company for advice.
2. Pull your modem stats and event logs and save/print them while connected in your normal configuration before you make any changes or troubleshoot. Reference the guidelines within the modem stats FAQ to determine if your modem stats are good or not. If your stats and logs look good then you probably do not a physical problem and should look elsewhere. Best advice #1: After you have saved the previous logs, clear them and let the modem create new entries specifically for your testing. If your stats are poor you will have to do further troubleshooting by pulling your modem stats from the NID. Best advice #2: Run the test from the NID for as long as possible. You may have an intermittent issue that doesn't show up if you only check for a minute or two. If you are experiencing troubles at a specific time try and test at that time (if possible). Make sure you recheck the modem logs.
3. If your stats are much better at the NID, you have an issue within the house. Double check that the DSL filters are correctly installed and functioning. Bypass any surge protectors because some are incompatible with DSL and even if they are compatible, they may have gone bad. Completely disconnect or install a filter on any alarm system (even if you do not have active service). Eliminate any possible sources of EMI (Electromagnetic Interference) near the modem or the phone line. A simple hand held AM radio can also be used to track down noisy electrical problems. Tune the radio to a lower frequency so you hear only static. Pass the radio near the suspected device and if you hear a major change in the amount of static that device may be causing the problems. Check for loose connections and damaged wire if possible. You can eliminate the need to disconnect alarm systems and individual filters completely by installing a homerun. Customers who live in apartments can also install a homerun by using a specialized splitter.
4. If your modems stats are poor at the NID then it could be a local line issue or a bad modem. A call to BellSouth is in order. If they conclude the modem is bad they may replace it if it's still under warranty. If they conclude it is a local line issue they will troubleshoot further. BellSouth may or may not have the ability to fix your line issue. It may be easily fixed by a simple call or a local tech, but it may be a distance problem that is uncorrectable.

Section 4 - Provisioning rates versus Speed Tests

Your slow speeds may just be the way your line is provisioned and the speed test you use. Advertised DSL speeds are sometimes your "connection rate" or "data rate" not "download speed". Due to overhead and signaling it is not possible to download end-user data at actual advertised speeds. Depending on the type of service and whether you are served from a remote DSLAM or not you will have a minimum of roughly 12.5% overhead.

9.4% 5 byte overhead within 53 byte ATM cell
0.5% 8 byte PPPoE overhead
1.3% 20 byte IP overhead
1.3% 20 byte TCP overhead
12.5% Total Signal Overhead (minimum)

So a DSL customer with advertised speeds of 1472/256 will have a real world end user data speeds of roughly 1250/220 at best.

Section 5 - Many speed tests are not reliable

Most speed test websites have limited bandwidth or overall capacity that may erroneously provide poor speed results. It is suggested that you use the Official BellSouth FastAccess Speed Test Website for your speed tests. If you have good speeds from the BellSouth website but slow speeds from other sites you should not worry about it because the problem is their website...not your connection.

Andy Houtz DSL

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by Andy Houtz See Profile edited by FAQFixer See Profile
last modified: 2009-07-09 14:33:37