DSL Data rates at office versus home

March 31, 2005 2:08 PM

I've never completely understood why my work's Internet connection, which is supposedly "3 megabit DSL", seems so much faster, shared amongst many more users, than my home's "3 megabit DSL". What am I missing here?
posted by Big Fat Tycoon to technology (9 comments total)

One possibility is that oftentimes home connections are throttled at the ISP. So although it may be capable of 3.0 speeds it isn't doing it. dslreports.com have speed tests to tell you the range you're really in.
posted by petebest at 2:12 PM on March 31, 2005

It could also be a contention issue. I have the same speed DSL at work and home, but my home connection has a contention ratio of 20:1. That is, 20 people share that bandwidth with me. Theoretically (although it doesn't happen this way) my home connection could be 20 times slower. This Broadband FAQ mini-article explains it better than I could.

Other things to consider. It may seem slower because your PC isn't as good as the work one. You may have some kind of malware installed on your PC which is stealing bandwidth.
posted by seanyboy at 2:17 PM on March 31, 2005

The connection at work probably has a higher upstream than your home DSL, which may be limited to 128 or 256 kbps. Upstream speed signifigantly affects both downstream speed (throughput) and responsiveness (latency) when there is contention such as downloading multiple things, or uploading and downloading simultaneously.
posted by zsazsa at 2:29 PM on March 31, 2005

You might have SDSL at work, which provides 3 Mb/s in both directions. Home DSL is usually RADSL (RA = "rate adaptive, asynchronous") which, as the name implies, is 3 Mb/s down and a fraction of that up.

The reason this might show up as a big difference is that TCP connections (which comprise the majority of Internet use) require bidirectional traffic (data is acknowledged by the recipient [your PC]). With SDSL, the upstream is usually not a bottleneck. It can very easily be a bottleneck in (R)ADSL.

Also, what petebest said.

Finally, if your work has a caching web proxy, you might notice a speed difference due to the fact that frequently-accessed pages are served locally by the proxy instead of going out to the DSL connection.
posted by aberrant at 2:34 PM on March 31, 2005

Going with the limited upstream idea, you will notice horrendous speed losses if you are uploading near your upload speed cap. This means if you are using filesharing software, you have to limit your filesharing upload rate to something somewhat less than your DSL upload cap.
posted by TheOnlyCoolTim at 3:03 PM on March 31, 2005

Isn't DSL also distance sensitive? If your work is closer to the CLEC than your home, your speed at home will naturally be slower.

I could be wrong about that, but back in the day when I worked for an ISP and DSL was in early adoption phase we had to explain this to people all the time.
posted by FlamingBore at 3:23 PM on March 31, 2005

I'd suggest that while you both have 3 Mbps connections to the exchange, the other thing that matters is the pipe out of the exchange to the rest of the internet, which is shared between you and other customers, and isn't wide enough to give you all 3 Mbps at the same time. I'd imagine with business DSL they hook you up to a less busy one.

The other thing is latency - the time between your computer sending data and it getting a response. Some provider's equipment seems to add a lot to this delay (I've seen up to one second), meaning the time between you clicking a bookmark and the page appearing is noticably greater, and it has nothing to do with bandwidth.
posted by cillit bang at 3:39 PM on March 31, 2005

The router at your work connection may prioritize outgoing ACK packets, which will allow inbound connections to continue to work well even when the outbound connection is nearly saturated. Similarly, the ISP at work may do the same for ACKs inbound to your work network, which will help outbound connections work well even when inbound is nearly saturated. They may not offer this feature on a home-grade DSL plan. And as others have said, the outbound pipe is likely faster at work, possibly even matching the inbound pipe, which will have all sorts of performance implications.
posted by kindall at 3:46 PM on March 31, 2005

There are quite a few different possibilities for the cause of speed difference, most of which have already been named. Another possibility would be the difference in wiring between the two locations, equipment differences, OS, or network topologies. Distance is also definitely a factor. The biggest cause of speed issues I've seen has been wiring, and EM interference. Heck I had one customer whose DSL would lose sync when the street lights outside of his house would turn on. You can try a home run line straight from your CPE (the gray or white box on your house where your service comes in), that could possibly improve your speed. You may also want to try removing all the phones in your house from the phone lines, especially if you have an older handset, or 2.4Ghz phone.
posted by jackofsaxons at 6:08 AM on April 1, 2005