I am troubleshooting a poor DSL connection. Most mornings I am unable to receive any internet traffic.
The problem is always solved by restarting the DSL modem (and never solved by restarting the wireless router it is connected to). If I don't restart the modem, the problem is often solved on its own by the afternoon.
This problem has presented with both an ISP provided modem and a replacement modem of a different brand which I purchased.
How can I troubleshoot this problem?
Answer
How can I troubleshoot this problem?
You should quantify any issues by gathering the modem's transceiver statistics during the "normal" and "problem" times of the day. These numbers can be obtained by logging into the the modem's web pages using a PC's browser.
The salient statistics are the downstream and upstream numbers for:
- DSL speed in Kbits per second, is the performance number that is the typical end-user's primary concern. Some modems will try to maintain this rate even under adverse conditions, while others may auto-reduce this speed in order to minimize error rates.
- margin aka SNR (signal to noise ratio) is a measurement of signal quality, and the measurement most likely to fluctuate. A larger number is better.
- line attenuation is primarily a function of the wire length from the modem back to the telco's central office. This measurement should be rather stable and consistent. A smaller number is better
- transmit power is also closely related to the wire length, and should be rather stable.
Those are the basic statistics that should be displayed. If there is more than this, then record those numbers also. An ADSL modem issue will not be taken seriously without these numbers.
When the ADSL modem tries to establish a connection (after a power-on, reset or disconnection), it must perform a prescribed sequence with the DSLAM at the telco's central office. This sequence is referred to as "training", and involves preset signals, handshaking and negotiation to establish power levels, equalization and the all-important connection speeds. ADSL signals may span relatively long distances over low-quality wire (it's only small-gauge unshielded twisted-pair rather than coax), and thus suffer significant attenuation (reduction in signal level). The time-consuming training period is to configure the transmit and receive electronics at each end for fast but reliable (low error-rate) communication.
In the face of changing (i.e. deteriorating) line conditions, I've seen ADSL modems take different approaches. I've seen a modem try to "ride it out" by maintaining its configuration and speed in spite of increasing error rates. I've seen another modem that would compensate by reducing its speed as error rates increased; but the modem was very slow in restoring that lost speed. In most cases the simplest remedy for an ADSL modem after an error storm is to force it to retrain (e.g. power cycle or dis/re-connect).
Assuming that you do not have a dry line, also check the voice quality of the phone line. Over the years the static on my phone line increased to the point that even the service rep noticed it, and I had no problem in convincing them in fixing my ADSL issues. The diligent lineman conditioned my line by removing a bridged tap and also rerouted my line using a shorter (by 1000 feet) wire pair to the CO.
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