Why is my internet connection so slow?
May 24, 2009 3:15 PM   Subscribe

How did my internet connection get 5x faster in 10 minutes?

I just chatted online with Comcast customer support. Before the chat, my download speeds were a paltry 0.2Mbps, but my upload speeds were 6Mbps (!!). Now, my DL speed is 1Mbps, which is much better, and my upload speed is 8Mbps. For me (and I'm sure a lot of other people), the internet just gets unusably slow a few times a month.


1. Why does the internet get slow so often? You'd think a major telecom company could at least guarantee faster-than-dialup speeds 99.99% of the time.
2. Why is my UL speed 8x faster than my DL speed?
3. What happened during my chat that made my connection 5x faster. The CS rep said she did a "hit" on my modem, and also tried resetting it. I also did a hardward reset on my modem, but I also tried that before contacting CS to no avail.

I'm just really curious about how internet speeds work, and what control telecom companies have for ensuring reliable speeds.

posted by mpls2 to Computers & Internet (8 answers total) 3 users marked this as a favorite
1. it's not the Internet, it's cable internet, specifically. You share your node with other people in your neighborhood. The more people using in your node, the slower it is. DSL is not shared.
2. ...
3. I noticed that Comcast bumped me up to 16mbps from 8mbps as some sort of promotion. Perhaps they did this to you, too? (screenshot of the email they sent me)
posted by nitsuj at 3:42 PM on May 24, 2009

I'm totally BSing here but the discrepency might be because of different frequencies on the cable connection for upload and download. If there's an issue (e.g. noise or excessive filtering) on the download channel, it would make it slower. There should be a way to diagnose this -- see if you can access the modem's diagnostics page.

Another option: I had issues with noise on my line (Cox cable), and the Cox guy hit some magic combination on the cable TV receiver to display statistics on the line signal quality. See if you can find something like this for Comcast (assuming you have cable TV).
posted by spiderskull at 4:01 PM on May 24, 2009

1. it's not the Internet, it's cable internet, specifically. You share your node with other people in your neighborhood. The more people using in your node, the slower it is. DSL is not shared.

I never bought this argument. Statistical multiplexing is statisitical multiplexing. Sure, DOCSIS is statistically multiplexed CSMA/CD at the access point, but DSL is statistically multiplexed at the DSLAM uplink, at the other side of the first hop. For a given uplink/downlink rate, the differentiator, if any, is the degree of oversubscription practiced by the DSL provider vs. the DOCSIS provider in your neighborhood.
posted by ZenMasterThis at 4:33 PM on May 24, 2009 [2 favorites]

DOCSIS modems (that is, cable modems) feature quality of service controls and varying service levels. You were likely on a modem config file that only allowed the low performance you were seeing.

They changed the way your modem was configured from their end. The person you spoke to must have configured your modem incorrectly again, which is why you're getting higher uploads than downloads. You'll probably need to call them again to get this resolved, although unplugging power to the modem and then reconnecting it may pull the correct config file.

While yes, cable is a shared network, it's rare for the network to be so burdened that you'll see such a decrease in performance. It has nothing to do with it in your case, and in 99% of the cases out there. People like to trump this up, but the reality of the situation is that any modern cable network is more limited by the fiber network connecting nodes than the coax network to the CMTS.
posted by Rendus at 4:38 PM on May 24, 2009 [4 favorites]

I'd say they've misconfigured your cable modem. Your download speed is far lower than their lowest tier, and your upload speed is very very high for Comcast. In fact, 8 down and 1 up is their standard performance tier in many markets (although mine switched to 12/2 about 5 months ago), so it seems exceptionally likely they got things reversed somehow. I'd call up and complain again.

This also might sound dumb to you, but this seems like such a strange problem to have that I'd double check you don't have upload/download reversed in whichever speed test you're using! How about you go run the test at speedtest.net and link us the result, so we can all just know for sure?
posted by floam at 5:14 PM on May 24, 2009

Yeah, having your upload rate higher than your down is highly unusual.
posted by sophist at 12:04 AM on May 25, 2009

Slow speeds can be three things:

- Too many people on your node, you would notice slowdowns mainly during prime time, upload and download would be slow
- Poor signal strength, you would notice erratic speeds, 'magic' fixes sometimes work from tech support where they turn up the amp that supplies your block/house/whatever.
- Finally, you could have had some wacky cable modem config that they reset. Every time you turn ot it, n your modem, it downloads its configuration file from a central cable company server. This holds the speed settings among other htings. This is how cable companies 'cap' you.

Connect to your cable modem's web page (usually, as a default), and look to see what your signal levels are. Compare them with something like this, and let us know what you think. While you're at it, see if the folks at www.dslreports.com can give you a hand, they've got really good support forums, sometimes with company reps to make things happen.
posted by Geckwoistmeinauto at 6:40 AM on May 25, 2009

my speed went up dramatically just by resetting tcp/ip
posted by canoehead at 6:36 PM on May 25, 2009 [1 favorite]

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