Inside the Numbers: Why DSL Speeds Vary

I recently made the move from an old 56 Kbps dial-up modem to a new high-speed DSL line. Using the Speed Test at DSL Reports, I was able to measure the speed of my DSL line’s upload and download rates. Currently, my download throughput speed averages between 975 Kbps and 1100 Kbps. My upload speed, however, averages only around 550 Kbps. Should there be this much of a difference between the upload and download ratings? Also, as fast as the download speed appears to be, I have noticed a small delay (about three- to-four seconds) before my Web browser loads a site. Do you have any idea what might be causing this delay or what I might do to circumvent it? Thanks.

This isn’t as much of a mystery as it might seem and is, in fact, perfectly normal. Basically, this condition is the result of the type of DSL service you are using. Just to be clear, let me emphasize this point: This has nothing to do with your ISP or DSL provider, but has everything to do with the type of DSL service you signed up for. Essentially, there are two types of DSL services available: SDSL and ADSL.

In a Symmetric Digital Subscriber Line (SDSL) data rates for upstream and downstream traffic are the same, hence the word symmetric in its name. This technology allows more data to be sent over existing copper telephone lines (POTS) and supports data rates up to 3 Mbps. SDSL works by sending digital pulses in the high-frequency area of telephone wires and cannot operate simultaneously with voice connections over the same wires.

A similar technology that supports different data rates for upstream and downstream data like you described is called an Asymmetric Digital Subscriber Line (ADSL). ADSL can support data transfer rates from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and from 16 to 640 Kbps when sending data (known as the upstream rate). It is also compatible with voice connections over the same wire. That’s why you can still use your telephone when it’s connected to a DSL line. This is the DSL service that most of the people in North America use today — particularly home users. Some small businesses might sign up for SDSL, but it is usually significantly more expensive.

In regards to your Web browser’s delay in loading pages, I wouldn’t worry about it. More than likely the lag time you are referring to is caused by one of the following:

  • The site you’re trying to visit is either too busy or is connected to a slower link
  • Perhaps your ISP’s DNS servers are having IP address resolution issues.
Unless the delay is really slow (around 15 seconds or more), I would just view this as normal Internet routing traffic and not bother putting anymore effort into thinking about it. Besides, considering the delays that you had with the dial-up line, I would consider a 3-to-4 second load time a bargain. I hope this helped explain things.

I have an HP Pavilion desktop computer running Windows XP Professional. For almost a year, I have been using the D-Link DWL-520+ PCI wireless card for network conductivity and, until recently, it’s been great. That was until I upgraded the system memory from 256MB to 512MB and had Windows Update download install the latest operating system patches from Microsoft’s Web site.

Since that day I have been getting the error message “(wireless) Card not Found” whenever I start the machine. Examining the Device Manager, I see an exclamation mark on the wireless adapter and when I look in properties it says, “This device cannot start (Code 10).” I have tried uninstalling the card and drivers and then reinstalling them, but this has not helped.

I even got so desperate that I attempted to contact D-Link’s technical support looking for assistance but all they could tell me was that this is a Microsoft problem. Now I’m not sure what to do to correct this situation and was hoping you might have some advice. Any help that you can give me would be much appreciated. Thank you!

I’ve had some bad experiences with D-Link’s technical support group myself, so I can definitely relate to your frustration. For starters, this is not solely a Microsoft problem. D-Link needs to accept some responsibility here, too.

My initial perception of the situation is that one or more of the patches that Microsoft installed as part of its update has created some type of incompatibility between the operating system and your previously functional wireless adapter. While it’s true that D-Link is not responsible for the adapter no longer working due to a Microsoft patch, it is still responsible to get its device driver updated to maintain compatibility with any changes Microsoft might have made to Windows — not leave you hanging out to dry.

That said, my first piece of advice is to download and install the latest version of the device driver currently available on D-Link’s Web site. You can find it here. Hopefully, this will work for you. However, you probably already tried this, so I’m going to assume it didn’t help.

Unfortunately, that doesn’t leave you with a whole lot of options. You might try relocating the PCI card to a different slot on your motherboard. Moving the card around sometimes lets Windows allocate different resources to the device and just might resolve the problem, providing that it’s a hardware issue. If it’s software-related, then this more than likely won’t do anything for you.

You could also try uninstalling the patches you downloaded, but ultimately it might be easier to redo the entire system. This will take some time to do, though, and requires you to first backup all of your data and track down the software that came with the PC so you will have hardware drivers you’ll need to reconfigure everything. The important thing to remember in this case is to not allow Windows Update to reinstall the patches that originally caused this problem.

The easiest and quickest solution I can suggest is to just replace your existing D-Link PCI adapter with a newer one. It doesn’t even need to be a PCI card. A USB one would work just fine. As a matter of fact, if you really want to keep it simple, you could just purchase a wireless bridge. A bridge just plugs into the Ethernet port on your PC in the same way you’d connect your PC to a wired router. The best part is that it’s completely self-contained and pre-configured. So as a result, there are no software or drivers for you to install on your PC. I actually use a Linksys WET54G at the office, and it’s great. Good performance, and it’s easily portable to other systems. It’s great for when I’m working on test systems. Nothing could be simpler.

In any case, I’m sorry for all of the difficulties you’ve encountered. I hope you find some of these suggestions useful. Best of luck.

Adapted from, part of the Network.

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