Are broadband speed tests accurate?

[Lyris]

My Virgin Media "20mb" connection gives me measurements of about 7.8-9mb on www.speedtest.net and www.updn.co.uk.

When I call Virgin for support, they sometimes recommend UPDN.co.uk to me, other times they say those sites are not accurate and shouldn't be trusted and that there's no problem. They have me download a file from gamefiles.virginmedia.net then tell me the reported speeds are fine.

Are they lying?

Connection is wired, of course.

[Strolls]

"It depends".

What speed to you get from gamefiles.virginmedia.net? The speed in meg may not be obvious, as you need to convert your computers displayed speed in kilobytes per second into megabits per second (I think).

If you get 20meg from gamefiles.virginmedia.net, then it's a matter of debate whether you should get 20meg from anywhere else. There are always going to be some sites that are slow, because the site's server is slow.

In the ideal world Virgin should give you 20megs to anywhere in the UK - some people will demand that you have a "right" to this, but in reality there will always be contention issues whichever ISP you're with, and I don't know that any ISP will give you much better.

The best thing you can do is check on other sites - such as http://forums.thinkbroadband.com/ - and see what other people are claiming. I'm on about 3meg, but I'm on old ADSL, not ADSL2, and I'm pretty happy with that lower speed, really.

I should add that around here I would consider 7.8-9mb to be very good indeed - I've never seen more than about 6meg on any of my customers connections. But then my customers aren't hardcore internet users or computer geeks (so won't be paying extra for top-speed internet connections), we don't have cable around here and the phone lines aren't ideal for ADSL.

[smouty]

I've found speedtest to be accurate. It matches what speed I can download at from fast sites - microsoft.com etc.

Try different times of day to see if your speed is due to contention.

[AlonzoUK]

When determining download speeds, you have to factor in latency (ping round trip response time), TCP window size and bandwidth available.

If you know the latency and what your line speed should be then you can tweak your TCP window size to maxmize your throughput - you would typically only do this though if you plan to download files from that site regularly. Theres plenty of web sites which provide information on how to do this.

[Ian(not Ian)]

Contention my arse. Throttling more like, Virgin admit to doing this at 'peak' times.

[smouty]

Oh yeah. Being on Be I'd forgotten about that

[Ian(not Ian)]

I'm wondering what Be is?

[Ian(not Ian)]

.....and you shouldn't have gone to Specsavers lol