Acceptable Range of Speeds.Have the always been so wide?

[#1]

First of all, I have to say that PlusNet are in the middle of progressing this problem with BT. However, it has brought something  to my attention:
When I first joined PlusNet, I was predicted to get 4Mbps down, and lo and behold, I got 4Mbps down - sometimes up to 5Mbps. Recently, performance has bombed. I've just used the BT speed checker and the result was 2.65Mbps. However, I note that it also quotes that the acceptable range of speeds for my connection is 1.2 to 4Mbps, with an IPProfile of 3.27Mbps Therefore, they "were unable to find a fault with the line". Have acceptable line speeds always been so wide? I don't remember it being quoted when I first took out a contract. I was considering going to fibre, but if the acceptable speed range can start so far below the expected speed, then I'm not sure it's worth the cost.
Thanks in advance.

[#2]

The "acceptable range" can be even worse on fibre:

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For your connection, the acceptable range of speeds is 12 Mbps-69.2 Mbps

They always range from 12Mbps to your IP profile.
Having said that, I have found actual speeds to be far more consistent than they ever were on ADSL.

[#3]

Your line has something called a Fault Threshold Rate which is 70% of the lowest sync rate achieved during your 10-day training period.  Any speed less than that is deemed to be a "fault".  The "acceptible range of speeds" reported by the BT speed test is based on your current IP Profile and so is absolutely meaningless.

[#4]

Hi NickAndShell,
Looks like we're pushing to get an engineer out to replace the old master socket so hopefully that should improve things for you, though as above the acceptable speeds can be across a fairly wide range. I hope this doesn't put you off fibre totally, from what I've seen both on here and with friends/colleagues with fibre has been far more positive than negative.
We'll update your ticket with the engineer request times as soon as we're able to, hope that happens soon and sorts it all for you.

[#5]

Thanks all for the responses. Hopefully a master socket upgrade will improve things.
Best Regards,
nickandshell

[#6]

Well, this is going nowhere. Apparently, no-one wants to listen to the fact that my connection has degraded. It's within BT's acceptable limits so it is, according to Plusnet support (and this has incensed me), "Fine". "Fine", it isn't. I've just upgraded to Extra, and the confirmation email states:
'Estimated speed 5 Mbps'
Yes, we all know that's estimated, but I used to get close to the above speed, and now don't. Never mind, it's crept up to 3.3Mb and it's withing the rediculously wide range that is acceptable, so it's "Fine". 0/10 from me, and I'll be looking around when my contract expires. You'd think signing up with a BT company would count for something. I guess not.

[#7]

If you are a BT Broadband customer in the same situation you will be steered towards a home visit from an engineer who charges £90 for the first hour and £30 for each subsequent half hour with no guarantee they can do anything for you.  BT seem to be trying to make money by taking a more hard-line attitude to broadband faults.  Perhaps this is reflected in BT no longer being willing to do work for Plusnet (or other ISPs) that they might once have done.  Hence, I presume, Plusnet's inability to get you a new master socket fitted.

[#8]

Quote from: ReedRichards

Your line has something called a Fault Threshold Rate which is 70% of the lowest sync rate achieved during your 10-day training period.

Er, 80%, unless something's changed recently.

[#9]

Quote from: Jameseh

The FTR is set during the first 10 days. It is 70% of the MSR (Maximum Stable Rate) which is the lowest speed at which you sync during the training period. Syncing at beneath the FTR gives us the ability to raise an EPP (End user Poor Performance) fault to BT Wholesale. Of course your line stats are still useful for diagnosing problems as well as seeing if your speeds are below those given in the BT availability checker.

[#10]

Hi there,
I'm sorry about this but unfortunately if there isn't a fault found and the line is within our suppliers' acceptable limits then there's nothing we can do to get an engineer out.
I have tested the line from a phone faults point of view in case there was noise there and we could get an engineer out that way, but unfortunately there were no issues seen there either.
I'm afraid all we can do at the moment is leave things as they are and jump on it if a fault does manifest itself, but until then I'm sorry to say we're stuck where we are.

[#11]

Quote from: ReedRichards

Quote from: Jameseh The FTR is set during the first 10 days. It is 70% of the MSR (Maximum Stable Rate) which is the lowest speed at which you sync during the training period.

Interesting. I haven't checked mine for a year or so, but it's always been 80%.
Googling "maximum stable rate" on "site:community.plus.net" throws up a few posts with quoted MSR and FTR figures, all at 80%. Here's one from July -

Quote

Maximum Stable Rate (KBPS): 2016 Fault Threshold Rate (KBPS): 1612

http://community.plus.net/forum/index.php/topic,105981.msg904467.html#msg904467

[#12]

For some reason I can't seem to edit the above post - so, just to add -
I believe the rate was once 70%, as quoted in para 6.2 of BT Wholesale's 'Broadband Max Myths and Legends' PDF -
https://www.btwholesale.com/shared/document/Products/Broadband/IPStream/dsl_max_myths_legends_issue1...
I'm sure that a previous version of the PN help page https://portal.plus.net/support/broadband/speed_guide/broadband_terminology.shtml#dlm mentioned it. I can find no mention now on any PN help pages.

[#13]

I am only parroting what Jameseh of Plusnet Staff told me; you would think he should know.

[#14]

Yes, I would. 

[#15]

Doing a bit of digging I found this https://www.btwholesale.com/shared/document/Application/Orders_and_Faults/Best_Practice_Guides/Fault... updated 2007 but is for ADSLMax not 21CN

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Should be used on a Broadband Max circuit when the line speed (downstream line rate) drops at least 30% below the stated (pre determined) minimum acceptable level (maximum stable rate). This is known as the fault threshold rate.

For 21CN this http://support.zen.co.uk/kb/KnowledgebaseArticle.aspx?ArticleID=10537 states

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Fault Threshold Rate:  The fault threshold rate (or FTR) is 80% of the MSR.  If the line rate drops below the FTR for more than 8 hours in a week period it is considered a fault and a low threshold breach fault can be raised.

So it looks as though the fault threshold rate calculation changed between 20CN and 21CN