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Network Outages

Posted in General | Networking at Wednesday, 22 February 2006 23:00 W. Europe Standard Time

DSL ModemThis blog is hosted on a private server located in the lumber room of our apartment¹. Sites are served using a DSL link that's running at 3 Mbit/s downstream and 512 kbit/s upstream speed.

Two months ago we decided to upgrade to a new DSL2+ connection (DSL 16000) provided by Arcor. I ordered the upgrade on January 4th and today Arcor finally was able to switch speeds. I didn't expect any problems as the Arcor salesman (beware!) told me that the physical line is able to manage that speed. I expected the change to happen flawlessly like the last one. Alas, read how it took place:

As you know, DSL speed is limited by the distance from your telephone jack to the next network junction point set up by the telco company. Signals travelling from the router to the carrier's network and back are subject attenuation, which means they get weaker. A piece of hardware (DSL modem) is yet able to tell signals from noise if a certain signal-to-noise ratio is achieved. Attenuation is measured in Dezibel and has to be lower than 25 in our case. Arcor's technical support told me some minutes ago that this not the case for our line which has an attenuation of 27.25 dB.

The result of the bad line quality is that the internet connection remains up for about 20 minutes before Arcor disconnects us. I suspect this is due to numerous data errors they receive. The next login is only possible unless our server is restarted. Pretty neat! The tech folks at Arcor will bring us back online within 48 hours and the new DSL2+ connection will be downgraded to DSL 6000. This is not what I expected, especially since the upstream capabilities of DSL 16000 lie around 800 kbit/s as compared to DSL 6000's 640kbit/s.

Welcome to the world of DSL2+!

¹ I'm speaking of "us" here because I live in a shared appartment.

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