Which term: Bandwidth, Throughput, Download Speed, Else?

June 4, 2009 3:30 PM

Throughput, download speed, bandwidth, or something else -- which of these am I trying to say? I can download a huge file, topping speeds of around 140 KB/s. Is 140 KB/s my maximum download speed? And isn't that speed the same for all information I can receive, or just file transfers?

I was trying to tell a friend that my DSL recently got bumped up in speed -- when I noticed that my previously-familiar download speed of 80 KB/s (kilobytes per second) is now suddenly in the 120-140 KB/s range, without a change in service plans. He tried to tell me that "download speed" isn't the right term, but couldn't offer an alternative or bother to explain the differences.

I'm from the 2400 baud modem era, and typically estimated my max bandwidth (my word) by the maximum apparent speed at which I could download a large file (a RAR for instance) the quickest, and assumed that's the maximum by which information of any kind could reach me. When I moved up to a 56,600 baud on dialup, I could pull down from 3.5KB/s to 4.5KB/s tops on a big file. Now with the DSL, I was getting 80KB/s, but now I'm getting 140 KB/s max download speeds. Is that my bandwidth, or download speed, or throughput, or what?

We play Halo 3 on XBL regularly, and he asserted that the communicating speed from x360 to XBL server is calculated differently than being governed by whatever limiter governs my 140 KB/s, but that doesn't make much sense to me. Hivemind, clear us both up!

posted by Quarter Pincher to computers & internet (16 answers total)

DSL is almost always really ADSL. The A stands for Asymmetric, meaning your download and upload speeds are different, download being faster. So your friend is right that the upload speed from the xbox to the server is unrelated and probably slower than 140 KB/s.

OTOH, I don't know why he wouldn't call the download speed the download speed.
posted by smackfu at 3:34 PM on June 4, 2009

Throughput, bandwidth, and download speed mean pretty much the same thing. Maybe throughput and download speed has the additional connotation of stuff-you-actually-care-about in the data stream, which excludes all the control information and framing.

In a modem-era brain, you can think of that minor difference being 2400 = bandwidth, but the parity bit steals some from download speed.

Your DSL is almost certainly "ADSL", and the "A" stands for "asymmetric", which means you can pack fewer things on the upstream train than on the downstream train. So, the communication from you to XBL (not XBL to you) is not the same as 140KB / sec.

(And, all the cool kids measure bandwidth in bits (b), not bytes (B). Probably because of that parity-bit or bit-robbing meaning, 8bits on the line != one byte of data out the end.)
posted by cmiller at 3:40 PM on June 4, 2009

Your friend could also be talking about latency, which is a big issue for games but not for downloads. Latency is the delay between when a packet is sent and received. It's independent of bandwidth.

For DSL, your latency to the Xbox server is probably in the 40-120ms range. Human reaction time is 20-30ms, so a player with high latency is at a real disadvantage against those with lower latencies.
posted by qxntpqbbbqxl at 3:48 PM on June 4, 2009

Yeah, I can only send around 30 KB/s.

For the bit-thinkers:
Top down-speed was 640 kbps (kilobits per second), now is 1120 kbps (or 1.12 mbps)
Top up-speed is unchanged, was and still 240 kbps.

The friend seemed to believe that "upload" and "download" only applied to files, such as up/downloading a shareware game and whatnot, and that the terms up/download limitations didn't apply to things like signing in to ICQ or Xbox Live data being exchanged.

On a side note, according to my provider (ATT) I was too far away from the station to get any of the higher plans, so I'm stuck with the lowest available option.
posted by Quarter Pincher at 3:51 PM on June 4, 2009

I'm aware of things like your ping (from years of IRC and playing Quake 1 multiplayer on dial-up) to the server (which is measured on the during-game score chart in Halo 3), but I was curious in regards specifically to whether the maximum "download" speed was the variable that could determine, say, your best possible ping, given ideal network conditions.
posted by Quarter Pincher at 3:56 PM on June 4, 2009

For very short, bursty transmissions, you may actually send or receive the data faster than what your connection is throttled at by your provider. So your friend is sort of right in a stupidly pedantic way.
posted by zsazsa at 4:02 PM on June 4, 2009 [1 favorite]

>Top down-speed was 640 kbps (kilobits per second), now is 1120 kbps (or 1.12 mbps)

What Im guessing happened is that your DSL plan is 1.54mbps down. In a lot of markets thats the cheapest plan. Your DSL modem negotiates the best speed it can considering how far you are from the central office switching station and how clean or dirty the lines are from your place to there.

It looks like something happened that allowed your modem to synch to a higher speed. Perhaps you removed a phone or answering machine that was interfering with the signal. Perhaps the phone company replaced some shoddy lines. Who knows. You can easily figure out your max bandwidth by doing a simple speed test.
posted by damn dirty ape at 4:06 PM on June 4, 2009

I think you're right and "download speed" is just fine. I don't like "throughput" because we often use it to mean "actions/time" and usually use it in database or transactional contexts rather than baseline networking.

So tell you friend to shut his duplex. You got a free download speed boost.
posted by chairface at 4:07 PM on June 4, 2009

The friend seemed to believe that "upload" and "download" only applied to files

Your friend is misinformed. Data is data, whether it's a file or an ICQ message.
posted by ook at 4:10 PM on June 4, 2009

140kb/sec would appear to be the highest speed you can receive information, or bandwidth. Run a speed test to a server physically close to your isp to get an idea of what you actual line speed is.

When playing Halo3 on XBL, what you care more about is lag or latency. That's the amount of time it takes for you to get data from your xbox to the server. The higher this is, the crappier your game feels, no matter what your bandwidth is. I've connected over a commercial satellite internet (don't ask), and bandwith wasn't too bad at 1.5mbit, but the latency was very high, 800millisec or more (I believe that was return). So I could download things at a half-decent speed, but playing games would have been futile, as anything that happened on my screen actually happened 1/2 a second ago on the server, and my reactions to those evens would happen almost a second later back on the server. That's bad in something like Halo3!
posted by defcom1 at 4:17 PM on June 4, 2009

(should have previewed!)
posted by defcom1 at 4:18 PM on June 4, 2009

"downstream bandwidth" is a good term for that.
posted by aubilenon at 4:43 PM on June 4, 2009

Yeah, the reason I gauged it only on large files was to make sure it would average out to something sensible -- because I do get a crazy high burst up front sometimes, or other times it slowly works up, and smaller files tend not to be quite so accurate for leveling off.
posted by Quarter Pincher at 4:53 PM on June 4, 2009

Also with ADSL, one thing worth remembering is that if you get 140KB/s downloading, if you start uploading (at the same time), and go inside the 90%-100% maximum upload speed, your download will drop considerably. You will generally want to try to cap any uploading you do to around 80%.
posted by lundman at 5:58 PM on June 4, 2009

140kb/sec would appear to be the highest speed you can receive information, or bandwidth.

Download speed and bandwidth are not necessarily equal.

If your download speed is limited by the available bandwidth of the path between you and the server, then the two are approximately equal.

However if your download speed is limited by the latency of the path, then the two won't be equal.

You can demonstrate this by running two simultaneous downloads. If the limiting factor is bandwidth, then the aggregate download speed will be ~140KB/s. If the aggregate speed is higher, then you're being limited by latency..

Note that generally the bandwidth between your ISP and whatever server you're talking to should be higher than the bandwidth of your own link, so your link to the ISP will limit total bandwidth - latency can be more variable however, depending on the hops to the server and the network load along the way, plus of course the load on the server itself. So to test the speed of your link, downloading something direct from your ISP will give the most repeatable results.
posted by HiroProtagonist at 8:19 PM on June 4, 2009

Also give the M-Lab tools NDT and NPAD a shot. They'll give you a much more nitty-gritty set of numbers that you can geek out over if necessary.
posted by Skorgu at 6:56 PM on June 5, 2009