DSL Speed Readings

Rozzy85 · 25 Mar 2009 at 18:39

For a while I've been noticing that my router displays the ADSL connection speed differently to what I actually get.

My ISP is Pipex and the router displayed the connection speed as 256kbps US/1024kbps DS which is what I signed up for. However, when Tiscali took them over quite a while ago things changed and the connection speed was reading differently displite no difference in actual speed. Whenever the router is restarted it'll read a different ADSL downstream connection speed everytime ranging from 1.5mbps to 3.5mbps. The upload increased to 448kbps and I do actually get that. I did a speedtest to show this:

http://www.speedtest.net/result/436837699.png

This starting happening around Feb last year and I initially thought that they may be testing my line for ADSL max or whatever it is. A year later and nothing has changed although it now only connects around 1.5mbps to 2.5mbps instead.

While this shouldn't really matter as I'm getting what I should, why is is connecting at a higher speed if I'm not even going to get that? It's also decreased my SNR to ~11db and increased the Line Attenuation to ~51. Why can't they just leave it at a fixed speed? I've logged onto my account on the Pipex website but it mentions nothing on any speed changes.

tolien · 25 Mar 2009 at 18:59

If you stayed connected at 3.5Mbps, it would increase towards that. Your SNR has dropped because your modem is now trying to sync as fast as it can.

Rozzy85 · 25 Mar 2009 at 22:26

So would that increase the risk of the connection dropping more often or have an effect on latency? I just don't understand why it would display as connected at around that speed while I only get the download speed of a 1mbps connection.

tolien · 25 Mar 2009 at 22:52

It shouldn't affect latency but a reduced SNR margin may make your connection more unstable.

It's like that because that's what the modem's connected at. If you're on the Tiscali LLU network your download speeds should follow your sync rate directly; if you're connected via BT Wholesale you'll be bound by an IP profile. In the latter case, as I said, your IP profile would rise if you stayed connected at a high enough sync rate.

Rabtech · 25 Mar 2009 at 23:11

tolien said:
If you're on the Tiscali LLU network your download speeds should follow your sync rate directly; if you're connected via BT Wholesale you'll be bound by an IP profile.

Thats best case scenario when Tiscali arent traffic managing or exchanges dont have enough backhaul to cope with the amount of customers or if IPStream when they cant be bothered getting more BT Centrals/segments to alleviate capacity issues.

Usually if your bandwidth is consistently 30% or less than your sync speeds then get onto them and raise a speed issue/complaint.

Rozzy85 · 25 Mar 2009 at 23:24

tolien said:
It's like that because that's what the modem's connected at. If you're on the Tiscali LLU network your download speeds should follow your sync rate directly; if you're connected via BT Wholesale you'll be bound by an IP profile. In the latter case, as I said, your IP profile would rise if you stayed connected at a high enough sync rate.

Oh, I see. So basically it's restricted to whatever BT see fit? I searched this in Google to find more about these "Profiles" and I found this.

http://www.kitz.co.uk/adsl/linestats.htm#fixed_rate_line

I'm guessing because my Line Attenuation will never go below 42 I'll be stuck on Profile 1000?

Rabtech · 25 Mar 2009 at 23:33

You can check your current ip profile (if applicable) at http://speedtester.bt.com/

Mattus · 26 Mar 2009 at 00:01

Are you signed up to a 1MB fixed-rate package? If so then you just need to change to an up-to-8MB connection to use your line to the greatest potential.

tolien · 26 Mar 2009 at 00:15

Oh, I see. So basically it's restricted to whatever BT see fit? I searched this in Google to find more about these "Profiles" and I found this.

You've got something totally different. The attenuation limits you've linked to are for fixed rate ADSL from BT Wholesale, you're on a rate adaptive product (whether it's from BTw or not). This gives the link between sync rate and IP profile step.

I'm guessing because my Line Attenuation will never go below 42 I'll be stuck on Profile 1000?

If your sync rate doesn't stay above 1440kbps (minimum for 1.5Mbps), yes.
The only useful conclusion you can draw from that part of Kitz's page is that because your attenuation is >42dB, you won't be able to order fixed rate 2Mbps. It's not going to "go below 42" unless the line is either made shorter or replaced with a material with a higher conductivity.

Rabtech said:
Thats best case scenario when Tiscali arent traffic managing or exchanges dont have enough backhaul to cope with the amount of customers or if IPStream when they cant be bothered getting more BT Centrals/segments to alleviate capacity issues.

Well yeah, but you're not going to see consistant throughput at a given level. That's why I said follow rather than match...

Rozzy85 · 26 Mar 2009 at 00:44

Correct me if I'm wrong, but If my connection remained synched at 1440kbps (going by your example), would that then mean my connection speed would eventually be changed to 1.5Mbps? Or is my Attenuation going to stop that ever happening despite it synching at this speed and remaining so for a long period of time?

Are you signed up to a 1MB fixed-rate package? If so then you just need to change to an up-to-8MB connection to use your line to the greatest potential.

I'm not sure. I believe when I signed up for it, it was, but since then Tiscali took Pipex over.

tolien · 26 Mar 2009 at 18:34

Yes, you'd wind up on the 1.5Mbps profile. Your attenuation is irrelevant here.

Rozzy85 · 26 Mar 2009 at 23:35

I'm sure my connection is stable around the ~2mbps mark as the router has remained connected for well over 72-hours at this speed before, or so it says in the logs. I guess it must drop connection at some points.

Oh well...