Is my ISP throttling my connection?

October 24, 2011 7:50 PM

I'm in need of advice to determine why I never get close to the download speeds I'm paying for.

I'm trying to diagnose my internet connection and why I never get anywhere close to my advertised speeds. I'm paying for a 2MB download connection, but I only ever get 250k download speeds. I've checked my connection on various sites (e.g. Speedtest and Speakeasy) and they show that I am getting the 2MB download speed. I've also ran Namebench and DNSbench to see if those would help, but nothing. In a local forum on Topix, some users were complaining of poor speeds, while others were reporting consistent traffic. Am I missing something, or is my ISP throttling my speed? Any help is appreciated.

posted by medarby to technology (14 answers total)

are you wired or wirelessly connecting to the internet? if your speed tests say 2 megs, how do you know it's 250k? are you saying that torrenting caps at 250?
posted by nadawi at 7:53 PM on October 24, 2011

Megabits or megabytes? ISP speeds are given in megabits. Actual download that you see is usually given in megabytes. 1 megabit = 8 megabytes. Therefore a 2Mbit connection means that you will be able to download at 250kbytes max, which is what you're seeing.
posted by The Discredited Ape at 8:01 PM on October 24, 2011 [12 favorites]

Your approximate physical location and the URL of a site you're having problems with would be helpful. However, and I apologize for this if I'm wrong, but are you aware that a 2MB connection is 2 megabits/second, equal to, roughly 200 kilobits, as noted above? There's overhead, so you would not expect to achieve 250 kb/s in actual use.
posted by wnissen at 8:03 PM on October 24, 2011

Do you mean Mega bits or mega bytes?

If I'm not mistaken most ISPs label their packages as having "X" Mbps=Mega bits per second.

As for your speeds there are more than a few things that could be going on. A major limiting factor in download speeds is the server on the other end that you're connected to when downloading from a website. The distance to the server-where in the world it is in relation to you-plays a role, which is why you'll see your latency go up and your speeds drop when you pick a server far away when you do speed tests.

If you have cable remember that multiple households are on the same pipe. if you have a bunch of people in your neighborhood who all have cable internet you may very well see a performance hit.

As for throttling, I would be very surprised if your ISP wasn't at least throttling speeds by prioritizing what types of data get where when. If you're using bittorrent this would certainly be a reason why you're seeing a slow connection.

Also your modem can be a bottle neck, due to dodgy firmware or poor hardware design. If you're connected wirelessly to your router this can also be a potential bottleneck. My Fios modem/router needs to be rebooted at least once every week or two, because it will eventually slow all traffic to a crawl. Remember too that it is very likely that your ISP only guarantees a connection, and not if you are actually receiving the speeds you paid for in your plan.
posted by chosemerveilleux at 8:12 PM on October 24, 2011

The above answers are correct, but they both misstated their units. There are 8 bits in 1 byte. ISPs almost always advertise speeds in bits, whereas customers are usually interested in bytes.

2 megabits = 2 / 8 megabytes = 0.25 megabytes = 250 kilobytes

MB = megabytes, Mb = megabits

Unless you're absolutely sure you're paying for 2 MB/s, you're probably paying for 2 Mb/s, and thus seeing appropriate speeds.
posted by gilrain at 8:12 PM on October 24, 2011 [2 favorites]

Where are you downloading from? If you're taking your "real life" download speeds from a torrent program, or downloading from something like megaserver or rapidsearch where the speed is capped - you're likely not to get "full speed" since the source isn't able (or willing) to push that fast.

If, on the other hand, you're downloading from microsoft.com, a University server, or sourceforge, or something like that and the download speed on your browser is saying 250k, then that's another matter entirely.

Then again, if you're paying for a 2Mb connection, you're either somewhere remote or has horrible infrastructure or you're paying for very inexpensive internet. It's possible that your local infrastructure can't support even 2Mb, although your ISP is capable/willing to push that to you.

When you run Speedtest.net, have you tried it by selecting a server somewhere far away, as opposed to the closest location?
posted by porpoise at 8:13 PM on October 24, 2011

Oh, duh, stupid typo. I blame my dog. I said:

1 megabit = 8 megabytes

when what I meant to say was:

1 megabyte = 8 megabits

as gilrain correctly points out.
posted by The Discredited Ape at 8:39 PM on October 24, 2011

(From memory Speedtest.net shows results in Mb/s not MB/s, so you probably do have a 2Mb/s connection.)
posted by Xany at 8:51 PM on October 24, 2011

As a practical matter, most TCP/IP transactions have about 20% overhead, between packet encapsulation and checksums and higher-order protocols. My rule of thumb is actually that 10 bits of effective bandwidth equals 1 byte of transmission (plus about 2 bits of overhead). So if you have a 2 megabit/s link, then you're going to get somewhere around 200 kilobytes/s of data.
posted by Chocolate Pickle at 10:32 PM on October 24, 2011 [1 favorite]

I run into this bits v bytes misunderstanding about once a week. Working in IT, specialising in Data Storage, I talk BYTES per second. The Network guys all talk BITS per second. I do the same conversion at Chocolate Pickle, and estimate 10 bits of bandwidth gives about 1 byte of throughput.

Just a couple of weeks ago I had to correct this misunderstanding in a customer who wanted to run a load test on their 2M link to a remote office. I'm sure glad I cleared that up, since they wanted to pump 1MBps (about 10Mbps) down the 2Mbps link ...during business hours.
posted by Diag at 12:45 AM on October 25, 2011

Ditto bits vs bytes and 10 bits/sec ~ 1 byte/sec is a better conversion. If you still want to check the generic goodness of your ISP, Netalyzr is good at detecting some ISP and local network wonkyness.
posted by zengargoyle at 1:01 AM on October 25, 2011

Apart from the above, if you see perfunctory performance and you really can not figure it out:
- see if you are using the correct drivers for you network card (the ones for example delivered by Dell)
- check wireless interference (e.g. always test with an Ethernet cable direct into your router)
- test different browsers with your speedtest tools
- if you have fibre into the house, check if the bend in the local connection is not too tight (should be > 5 cm diameter)
- check if there is no dust in the fibre contacts
- do not place your router all too close to other hardware.
posted by Eltulipan at 1:35 AM on October 25, 2011

Yep, that's the answer. My ISP is advertising Mbps and not MBps. (As a side note, it would've been helpful if my ISP actually used the term megabits.) Speedtest and Speakeasy are both showing megabits. I hardly ever bittorrent; I'm mainly downloading from Steam, setting up games on my new laptop. Steam must by showing kilobytes, since that's where it only ever shows 250K.

Thanks for clearing up the confusion.
posted by medarby at 2:38 AM on October 25, 2011

Plus, don't forget to allow for LAN overhead also.

Plus most ISPs advertise an potential max speed. And it further complicates things with such amazing inventions as Comcast's precaching servers which offer quite a boost of speed at the beginning of long transfers, then a slowdown once you burn through the precached info.
posted by Samizdata at 1:12 PM on October 25, 2011