ADSL Working Mechanism
ADSL Working Mechanism

Nepal Telecom has a lot of services, users and thus the problems. A lot of customers complain about the cellular network coverage, congestion and connection problem. NTC ADSL downtime problem is one of the biggest problem and headache. Two years ago “Hello Sarkar (1111)” had biggest complain on subject of Nepal Door Sanchar’s ADSL connection. Few weeks ago NTC was ordered to improve the service and increase the capability. Brabim Karki also wrote about his experience of this service in Annapurna Post daily. This time we had serious issue so we got there and talked with the officers to solve this out.

Experience: We have been using ADSL since many years as it is easy to get connection, pay the bill and other company don’t serve in our area. We had downtime for 3 Days and no body answered the phone so going there was final idea. When we went there and described the problem they reset our port bind and told to restart the router, but this didn’t solve the problem. Then we were told to bring the router, which we did and they finally said that it was their system fault. So it seems they are lacking behind system handling.

Down the Rabbits hole: Following the events we found that in my area only some were suffering such problem and some were still enjoying the internet. After rigorous inquiry we found that it was their DSLAM’s fault but the surprising thing was that they already knew the problem but were unable to fix it permanently. If you are also a NTC ADSL subscriber and everything is all right for example phone line, ADSL light is stable on router and you have checked router’s settings, tried restarting it than there are few things you should know.

How NTC ADSL service works?


Nepal Telecom’s ADSL service is simply internet served using PSTN or landline copper cable. To put it simply in front of you we will show you by listing the phases of the service.

  1. Nepal Telecom sends data in big optical fiber cables to exchanges.
  2. The fiber from exchange goes to specific areas.
  3. Each area have limited number of DSLAM
  4. The NTC ADSL DSLAM has a limit of actually 96 users.
  5. Router at your home helps to squeeze data from the phone line and you can use the internet.

What is DSLAM?

It stands for Digital Subscriber Line Access Multiplexer and is used in DSL systems. It helps to serve both voice and data over the PSTN lines. After a user requests ADSL subscription you phone line is disconnected from normal service and is connected with this new system which could send you both internet and voice service. It is fed by the telecom operators with high bandwidth cables like optical fiber so that the data can be distributed at required rate.

DSLAM Control Card
DSLAM Control Card


The common problem is no internet connection even while there is working ADSL system, slow internet even while there is no one on your local network, high latency and frequent down time. This all happens locally and in our case due to poorly managed DSLAM. The cluster of 96 people suffered this problem frequently but another group didn’t We found that the suffering were from DSLAM-2 and the others were from DSLAM-1. The problem was bad ventilation, lack of cooling and heating issues. The load caused the system to burn down too much. The control card would be useless and they needed time to fix it. This is why it takes about one or two days to fix this.

The heating of your DSLAM can also cause slower speeds and occasional service loss.Sometimes the problem is when the router hangs, settings are deleted, automatic resetting of router, unbalanced power supply to the device. NTC also has problems like disconnection of optical fiber feed, maintenance and upgrades. We still have hope that they will improve the service soon.

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