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 Introduction | Troubleshooting Procedure  | Init Strings  |  Handshakes  |  Access Numbers

Troubleshooting Procedure:

(I recommend printing this section out so you can read and refer to it while troubleshooting.)

You get a 56k connection, BUT - it seems slow. Possible causes: your connection is poor and are experiencing a high error rate, speedshifts, modem retrains, and possibly disconnections. Follow the 56k connection troubleshooting below. Also, check your throughput!

If you get an "unreliable" 56k connection - frequent disconnects, poor throughput, errors, retrains, etc:  You should check to see if there's a firmware/driver update for your modem. If you  follow the troubleshooting procedure below to call many V.90 servers, you may be able to find an access number or provider that gives you better connectivity. If you don't want to switch providers and there's no new firmware for your modem, you may be able to improve connectivity by Limiting Your Connect Speed. If you have a Lucent or 3Com modem, the modem diagnostic information can help you troubleshoot connectivity. See these resources: 

Lucent-based modem - LT firmware updates & diagnostic data
Firmware/driver updates for Rockwell/Conexant-based HCF Modems
Limiting Your Connect Speed
3Com Modem Diagnostic Data
Check Your Throughput
Interoperability Status

Checking Your Phone Line

It should also be noted that your ISP may change the firmware in its modems, or the telco may make a change in its facilities which may solve, or cause, unreliable 56k connections. In most cases you won't be notified of any of these kinds of changes; information on GTE and USWest facilities can be found - see my Links page. I believe that ISPs should have a page that shows their firmware updates - ask your ISP to post it!

If you don't get a 56k connection, you should determine whether you can get a connection to any 56k-enabled number using the steps below. Listen to your modem handshake - if you hear a "double" handshake, or if the speaker goes off and then comes back on before you get a CONNECT message, or if there is a LONG delay after the speaker goes off and you get a CONNECT message, the modems recognize each other as 56k but are unable to "understand" each other. When using dial-up-networking, this situation can be reported as "a failure to negotiate" or "the remote modem didn't answer".

1. Use a terminal program like Hyperterminal (it comes with Windows95/NT), Procomm, RapidCom, etc. (See: Setting up HyperTerminal to talk to your modem.) You want the program to access your modem. Give the modem the AT command and make sure you see the 'OK' come back. Now, give it the command to dial the service you are using : AT D#######. Wait for the connect message. What rate do you get? (Depending upon your access number, you may or may not get a text/login prompt from your service.) If you get a login prompt, go ahead and log in. If you don't get a login prompt, type some characters. In both cases, wait at least 30 seconds, then put the modem in command mode. ( +++ ). When you get the OK message, display your connection data. (On x2-type modems, use the AT I6 which will display information on the current data rates and error information; on Lucent Flex modems, the command is AT I11; on Rockwell modems, it is AT &V1) You can go back on-line (ATO), and repeat this several times (unless the server hangs up on you). Then hang up, and again examine your modem's connection data.

If you are connecting at a 56k rate, but have high error rates, retrains, speedshifts, or disconnection, go to step 2.

If you are connecting at a v.34+ rate, make sure you are using a 56k modem, and are calling the same protocol server modem (ie, Flex to Flex, x2 to x2, or V.90 to V.90) and go to step 2.

If the connection looks decent, proceed to step 3.

2. Find numbers for other ISPs in your area. Here is a list of toll-free numbers  as well as links to local access numbers for a variety of ISPs. Find as many numbers as you can. Follow the procedure in step 1 and call each one and note your results.

Find numbers that are toll and toll-free, both within your state and out-of-state for 56k access. Call these numbers using the procedure in step1 and note your results.

IF you get decent connections, or consistently better connections on toll or toll-free numbers than on local numbers, it is likely that there is an incompatibility with the levels commonly used on local telephone calls and the firmware in the modems, or RBS links are not being identified and compensated for in your modem's firmware. You will probably not be able to do anything until new firmware is released, or the telephone company makes an 'upgrade'. You should keep checking though, as firmware for the server modems you are calling is entirely different than the client firmware you are using, and there is no way for an ordinary user to know when new server firmware is released, and if it is implemented at the site(s) you are calling.

IF you do not get 56k connections to any of the numbers, it is likely that you have an impairment on your local line. It could be the equipment at the phone company office; you could be too far from your telco's switching office to permit 56k; you could be on a subscriber loop carrier (SLC) with an additional analog to digital conversion; you could be served with "pair gain" - a way for a telco to put 2 lines on 1 pair of wires, or you could have a bad line to the switching office. If you have a 3Com/USR modem, there is a fairly reliable way to determine if you have more than 1 analog-to-digital conversion. In most of these situations, there is nothing you can do (short of moving) to improve your connections unless the telco upgrades its facilities. However, if you are served by pair gain, and have 2 telephone lines, you could request the disconnection of 1 conditional upon pair gain being removed, or you might be able to get the phone company to serve you with separate pairs for each line. And, of course, if you have a really bad local loop to your switching office, the phone company may switch it. It is also possible that you have equipment at your location interfering with the modem - try unplugging ALL devices connected to the telephone line except for your modem and repeat the tests.

IF you get good 56k connections to some local numbers, but not others - the facilities used to serve the different providers (including the telephone network and the equipment and firmware at the ISP) may be the cause. If the bad connections all come from common central offices, it may point to the telephone network. If you get good and bad connections to providers located in the same central office, it may be differences in the ISPs equipment, firmware and setup. You may want to consider trying another ISP that looks like it will give you good connections. You may also want to contact your ISP to inquire into the type of equipment and firmware they are using - if you let them know you can't get a good connection with them, but can with their competitors which you are considering switching to, they might want to try and help you. Then again, they might not. At least you have a choice! You may also want to check my Interoperability Page.

3. Establish a normal dial-up networking connection to your ISP. After you complete your on-line session, run Hyperterminal and examine your connection information. (for 3Com modems: AT i6; for Lucent modems: AT i11; for Rockwell modems: AT &v1*) If there are a lot of errors, retrains, or a significant speed drop, you have an impairment as described above that didn't show up immediately. (Note - if the data is all blank or zero, the modem has been reset by your Dial-up networking; You need to prevent your modem from being reset.) Continue examining this data after each connect. If you find that you have both good and bad connections, there is probably a telephone network impairment, or your ISP might not have the same equipment/firmware serving all its modems. There's little you can do other than complain to both your ISP and the telephone company, and wait for new firmware to be released. If you have only bad connections, try the local and toll/toll-free procedure of step 2. If you have only good connections - but throughput it low, you probably have a "bad" ISP - overloaded. You may want to complain to them, or try another provider.

DEPENDING UPON THE RESULTS YOU GET, you may want to DISABLE 56k on your modem - and force it to connect at a v.34+ rate. With some of the problems described above, you will find that you actually achieve a better throughput with a 28.8 rate than a 56k rate. (If you can't play the 28.8k modem file on the Easy Throughput Check page with a 56k connection, you may have this problem.) You might also try disabling v.42 error correction (forcing MNP instead) - some combinations of modems and telephone facilities fail to operate reliably with v.42, but will operate with MNP. If you get a mix of "good" high-rate and "bad" low-rate connections, you may want to automatically Limit Your Connect Rates. In addition, some users find that their modem wants to connect at too high a rate - resulting in low throughput due to excessive errors. In this case, you can set a lower maximum speed for connection using the techniques discussed in Limit Your Connect Rates.

Modem Diagnostic Screens:

3Com modems give you the most complete information, and you can usually tell if your line has more than 1 a/d conversion. See 3Com Diagnostic Screens for the data and what it means.

Lucent modem I11 displays will tell you about errors, retrains, initial and final transmit and receive rates. See the LT Diagnostics.

Rockwell/Conexant hardware modems (ACF) give the least useful information (AT&V1); it will tell you the initial and final transmit and receive rates, but does not indicate errors or retrains. The "line quality" is of no value in troubleshooting. Rockwell/Conexant HCF and Soft56 modems give more information (AT#UG) - see HCF AT#UG.

If you have a Cirrus Logic chipset, see the Links page for the Cirrus guide from Jaton's website.

This is AT &v1 from a Rockwell (Zoom) modem:

at &v1

TERMINATION REASON.......... NONE
LAST TX rate................ 26400 BPS
HIGHEST TX rate............. 26400 BPS
LAST RX rate................ 42667 BPS
HIGHEST RX rate............. 42667 BPS

PROTOCOL.................... LAPM
COMPRESSION................. V42Bis
Line QUALITY................ 024
Rx LEVEL.................... 015
Highest Rx State............ 67
Highest TX State............ 67
EQM Sum..................... 00D8
Min Distance................ 0000
RBS Pattern................. 21
Rate Drop................... 01
Digital Loss................ 2D6A
Local Rtrn Count............ 00
Remote Rtrn Count........... 00
Flex fail

 

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