Why does one person downloading kill the internet for the rest of the house?

5

We have 25 megs on the downstream and 2 megs on the upstream. When doing a speed test without anyone downloading (from Usenet, for example), we get the full download and upload.

However, if one person is downloading at max speed (let's say, 3 megs per second), it brings down the internet for the rest of the house, even though we have 25 megs on the download and only 3 are being utilized.

Why is this? Why does throttling it slightly fix this problem?

Thanks

John Smith

Posted 2013-01-27T20:25:28.273

Reputation: 53

1Wait… isn’t Usenet discussion groups? – kinokijuf – 2013-01-27T20:39:29.870

1@kinokijuf: Yeah you'd be surprised how much bandwidth large amounts of text takes up. – John Smith – 2013-01-27T20:51:24.210

3...especially if the text consists of base64 encoded binaries. – Dan is Fiddling by Firelight – 2013-01-28T01:39:35.993

Answers

5

It's the sneaky difference between megabits and megabytes that's killing you. Internet connections are typically rated in megaBITS (Mb), whereas downloads are measured in megaBYTES (MB). To convert between the two, divide by 8:

25Mb downstream / 8 megabits per megabyte = ~3 MB per second

Tanner Faulkner

Posted 2013-01-27T20:25:28.273

Reputation: 11 948

3And throttling it slightly fixes the problem because when you are at the absolute maximum bandwidth consumption, queues tend to be full, destroying latency for everyone. If you're even slightly below the maximum, the queues tend to be nearly empty, preserving latency. Maximum-bandwidth applications (like downloading with no limit) don't play nicely with latency-sensitive applications (like browsers). – David Schwartz – 2013-01-27T20:36:31.557

The exact formula: 25 * 1000 * 1000 / (8 * 1024 * 1024). The thing is that megabit is measured in powers of 10, but megabytes are usually measured in powers of 2. – Malcolm – 2013-01-28T01:46:39.290

@Malcolm: That's pretty close, but still not exact. The megabit measurements are line speeds, the megabyte measurements are useful data speeds. Some of the line speed has to carry address and control information. – David Schwartz – 2013-01-29T02:31:35.107

1@DavidSchwartz Yeah, but there are many layers in the network, and one protocol may require more traffic for headers than another, so it's quite hard to determine the exact bandwidth if we want take such subtle things into account. – Malcolm – 2013-01-29T03:02:08.583

Asked: 2013-01-27T20:25:28.273

Viewed: 443 times

Active: 2013-01-27T20:31:53.580