Internet Support: Solving An Unusual Bonded ADSL Problem

08. May 2012 Internet Support 1

Skyway West keeps a record of ADSL problems we have encountered over the years that were either stumpers or real mind benders. In this month’s blog post I would like to share one of those stories with you. For the record, this actually qualifies as both a stumper and a mind bender.

The client was fairly new to us when the problem arose. They were a larger client with multiple locations using one of Skyway West’s bonded internet solutions. It started out simply enough: standard install, no surprises, the service was set up and it just worked… or so it seemed.

A couple of months into the service we had a call from our client’s IT guy to say there appeared to be an issue at one of the locations. The overall speed of the bond was just not what was expected. Of course, being the diligent tech support person I am, I dug in and started examining the situation.

When looking at the separate connections there was nothing obvious that stuck out as an issue. Both services individually were running as fast as they were supposed to, but when bonded they just wouldn’t perform very well. No matter how hard I tried I just couldn’t find anything I could correct to make the issue go away until, that is, I compared the attenuation between the two services. What I found, interestingly enough, was a significant enough difference in attenuation so that one service couldn’t keep up with the other and data packets were having to be resent. This was what was slowing everything down when the lines were bonded.

A brief explanation of “attenuation” in the ADSL world. Attenuation simply means degradation of signal. Degradation happens when there are line issues or the cable ends are too far away from each other. When these issues appear the ISP (Internet Service Provider) will apply to the line something called SNR (Signal to Noise Ratio). This effectively increases the volume of the signal to attempt to overcome any degradation. If you would like to read further on the subject I can recommend these Wikipedia articles on Attenuation and on SNR.

So back to our story. Now that you understand a bit about attenuation here is our problem. Skyway West is providing a bonded service – in this case two ADSL services are bound together. Both services connect in the same building, in the same room, on the same panel, the inside wiring is the same length and the two ADSL routers are the same type. At the other end the cable lengths are the same and they two services connect to the same central office. So what’s wrong with this picture? Unfortunately, nothing was blatantly obvious. Why would the attenuation be different for both lines when they live right next to each other? We replaced the ADSL router – no change. We had the inside wiring checked – again no difference. We had the ADSL port changed – still no change. We asked to have the line from the Central Office to the building checked – the cable proved to test fine as well.

Well, at this point I was pretty stumped. Everything checked out but we clearly had an issue that was keeping these two services from acting as one. For all intents and purposes the line worked and was judged acceptable by itself. It just wouldn’t play nice when asked to work as part of a “team”. Why? Luckily, 2 days later, we got a break.

Whenever a building is newly constructed it is up to the local telephone company to drop a bundle of cable pairs to the demarcation point of that building (the panel where the lines come in to the building and where the lines inside meet). The more bundles and cable pairs you have coming in the more options you have when problems arise.

I sent another tech out to recheck the cable between the customer and the Central Office. Like the first tech they found no issues with the line. I then asked him to see if a new pair from the drop might help. The tech was kind enough to oblige and eureka!, on the second attempt we had equivalent attenuation on both lines. The speed increased to what it should be and we haven’t had a problem with the service since.

So what difference did the second cable pair make? Truth be told, we can only guess. In my opinion the most likely cause would be an inferior quality spot (or spots), somewhere along the cable. This would have an adverse affect on the signal getting through the line.

The whole process of troubleshooting this issue took approximately 48 hours, including delays while waiting for the field techs to be dispatched. We were fortunate that since the client had a bonded service they never completely lost their Internet service throughout the whole process. There was always one service up to keep them online.

I hope you enjoyed this month’s post. I have put together some interesting ideas for upcoming blogs – enough to last the rest of the year. So make sure you stay tuned. You don’t want to miss out on these: lots of good tidbits in store. I enjoy reading your comments and suggestions so please keep them coming into I’ll do my best to answer your questions right in my blog where I can. Regardless, you will always get an answer to any emails you send in. Until next month…


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