What is the reason for the ADSL upload limit?

What is the reason for the ADSL upload limit? I'm thinking it must be an artificial limit imposed by the ISP's? The reason I'm asking is, my normal connection is around 5-6Mbps down and .6 up. However if I connect to my work via VPN I can as high as 1.8Mbps upload. Not complaining, just curious!

geek_smac, Jun 30, 4:00 pm

It isn't an artificial limit imposed by the ISP. It is a limitation of the adsl standard used and the amount of bandwidth dedicated in the standard to upstream traffic. The sync speed at which you are synchronised with DSL access multiplexor in exchange will be determined by line noise and distance from exchange apart from this bandwidth constraint.

geek_spyware, Jun 30, 4:25 pm

Since you seem to know what you're talking about there, spyware, why is it that I can't get voip at my local exchange and have to get a number with another town over?

geek_julieandcasper, Jun 30, 6:12 pm

Spyware SO following that logic, when I get 1+ mbps connected to the VPN, I am no longer using the adsl protocol?

geek_smac, Jun 30, 7:21 pm

Smac? What makes you think you're actually getting 1.8 up? What's your BB plan?

geek_badcam, Jun 30, 8:23 pm

Speeds As I said in my first post, my normal speeds are 6+ up and .6 down....so normal full speed ADSL. Those figures are against a local server on speedtest.net, not international. Doing the same test while connected to the VPN I get 1.5 or more up.

geek_smac, Jun 30, 8:31 pm

VPN - compression? It might be reporting faster than the actual traffic rate.. but the A in ADSL is async; they sacrifice bandwidth upstream to get max speed down.

geek_gblack, Jun 30, 9:31 pm

It's a balanced split between the UP & the DOWN Most average ppl want fast access for downloads so majority rules, fast down & slow up. In the grand scheme of things, theres only a FINITE amount of bandwidth available to be allocated.

geek_mrfxit, Jul 1, 8:56 am

The cheaper plans have capped uploads & the Pro plans have uncapped up & downloads. After that you have local & house wiring / exchange & general Isp loadings effecting the overall data speeds.

geek_mrfxit, Jul 1, 9:04 am

Anybody have any relevant comments?

geek_smac, Jul 1, 9:23 am

Apart from adding YOUR own computer software setup to take advantage of the available speed in YOUR area, in to the mix. .. . .. Then what the frick did I say above Stuart, that you didn't understand?

geek_mrfxit, Jul 1, 9:31 am

You don't just magically get a faster upload speed by connecting through a VPN. You are always going to be limited by the 600kbps upload that your DSL connects at. I believe the maximum theoretical upload speed for ADSL is 800kbps and 1mbps for ADSL2. The main reasons I can think that it is reporting that you're getting 1.8 through the VPN is either compression which has already been stated, or there is some sort of proxy running on the VPN and that is where speedtest.net is measuring the results from.

geek_rhys.m, Jul 1, 9:33 am

Mrfixit From what I can see you didn't have anything to say at all on why the speed would report (either real or otherwise) differently under the VPN.

geek_smac, Jul 1, 10:27 am

Whereas Rhys has. Could be onto something there...I believe I do see the outside world through a proxy. However if that were the case, I would also expect the download to report faster? (it's actually slower under the VPN than not).

geek_smac, Jul 1, 10:30 am

What connection is your work VPN on? Theres a whole lot of things which could be affecting the speeds. Its not a very definitive test. Theres too many variables and its not quite clear what your trying to test. Work up/down speed? Home up/down speed? Speed of VPN connection. In which case I don't think speedtest.net will give an indicative result for any of them.

geek_rhys.m, Jul 1, 10:55 am

It was more the comparison I was interested in, rather than the actual test result. I don't know enough about the actual set-up to give any more info really. Doesn't matter, just curious. I may test actuallt uploading some files later to see if I get a different result on and off the VPN.

geek_smac, Jul 1, 11:49 am