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[WWWombat]

The IP profile is something artificially implemented by BT wholesale to rate limit traffic to each line as it is something BT have long believed necessary on their services.  It is separate to the natural overhead of the connection protocol which is PPPoE for BTw based FTTC services.

That was true in the days of ADSLmax, with the stepped nature of the IP profile, exacerbated by the slow restoration time - both aspects were indeed artificial. And delays incurred within Plusnet will have further exacerbated problems.

But the artificialness went away with the immediate updates in both 21CN and FTTC, with the values reflecting real overheads.

Unfortunately, delays still occur within Plusnet, making issues appear there still. Added to the fact that they (appear to) leave room for their QoS prioritisation work.

But, overall, the modern IP Profile is no longer the artificial tool it once was.

After all, your line can indeed only cope with a certain rate. If more data has to be sent, it can only ever be handled in one of two ways - queued (causing bufferbloat and jitter) or dropped (the right answer, for TCP).

[ejs]

Thanks I'll take the higher throughput reading of 67920 Kbps
67920 / 72089 X 100 = 94.21% a we bit shy of 96% by 2%

This is why I thought about factoring in the TCP and IP layer overheads, to get a value comparable to the IP Profile. I wouldn't expect a speedtest result to be exactly on the IP Profile value. Assuming a MTU of 1492 and the usual 20 byte TCP and 20 byte IP header:

67920/72089 × 1492/1452 × 100 = 96.81%

[ejs]

My feeling those ratio's will start to drop off once the Exchange has reached it's limit with broadband users the next stage is to reduce the throughput slightly for each user a way to alleviate congestion at the exchange.

It may even come under the contention ratio rule but this time it's not the ISP it's the Exchange  which may need upgrading because of over demand.

This is all hypothetical of course

Were you thinking of the IP Profile being deliberately reduced if the exchange is congested? I don't think that's likely to happen. SIN 498 does mention downstream prioritisation rates, of 30 and 15 Mb, for the up to 80 and 40 Mb products respectively, or your line speed if it's lower than the downstream prioritisation rate. I thought all ISPs and the broadband infrastructure in general tends to rely on not everyone using their full line speed at the same time. However, I do think that as people's line speeds get faster, it'll become more likely that people won't always get the full e.g. 330 Mbps at all times, and it won't be considered a fault so long as it's above some other, lower speed.

[S.Stephenson]

For G.Fast at 330mbps, didn't they say for every line there will be 80mbps of back haul?

[ejs]

I don't know about the back haul (to where?). BT STIN 518 does mention 80 Mbps as this "downstream prioritisation rate". Reading a little further into that STIN, the downstream prioritisation rate sounds like it works by allocating everyone 80Mb each that's prioritised above every line's next 250Mb, but I don't think it implies a dedicated 80Mb for each line.

[NewtronStar]

Thanks ejs tbh I am grasping at straws here my line used to show the 96.8% ratio that was three years ago and have not bothered to check it until a few weeks ago and it's now either 91.1% - 92.6% depending on the sync rate 33000 - 39000 Kbps.

I am not to bothered with the loss of throughput 2-4Mbps just trying to find out the reason why this could have happened as most users on FTTC it's 96.8%

[burakkucat]

That's interesting. So the BRAS is told the sync speed. I wonder where and how is the IP Profile is calculated?

Hmm . . . I think you will find some relevant information on a page of the main site --

• http://www.kitz.co.uk/adsl/IPprofile.htm#RAP
• http://www.kitz.co.uk/adsl/IPprofile.htm#IP_profile_calculated

Granted that was written in the era of 20CN technology but I am fairly certain that the overall concept is still correct.

[NewtronStar]

Do you think I have a stuck bRAS ?

If you suspect a stuck bRAS on your line then you will have to contact your ISP asking them to get BTw to clear a stuck bRAS profile fault.

[tbailey2]

Ho him. @ns switched to a different modem, so no longer appears in the drop down list of users - I can't see any graphs at all. 

Use the Range option, that lists all users who have uploaded in the past three months rather than in past 48 hours.

[NewtronStar]

Sorry I have been moving between modems to see if the ratio would go back to 96.8% but no luck

I am fairly certain this happened two years ago when looking at speedstest results it was always way lower than expected from the current sync rate.

Just thought this was normal for my line.

[Dray]

There seems to be a suggestion that MTU is involved in the calculation somehow

[NewtronStar]

There seems to be a suggestion that MTU is involved in the calculation somehow

It would be nice if someone could explain the MTU in words we can understand and do that in layman's terms unless it's all cut & paste stuff and they don't even understand without having to use google 

 

[WWWombat]

Ho him. @ns switched to a different modem, so no longer appears in the drop down list of users - I can't see any graphs at all. 

Use the Range option, that lists all users who have uploaded in the past three months rather than in past 48 hours.

I'll go check that shortly, ta.

[d2d4j]

Hi

I'm not sure if this explains easily to layman terms but

MTU. Is maximum transmission unit

Now to try to explain it in layman terms, look at it like currency conversion for monies for holiday

You have 100 pound sterling and need euro for holiday, a bank converting the money would not give you the 100% value, so you might only get 96% of value, which this analogy translate to your MTU, and the overhead of connections (ppp etc...) say your MTU IS 1492, but including overhead is 1500, then it reduces your 1492 accordingly

I hope that makes sense as I'm tired but could be wrong or give bad analogy

Many thanks

John 

[WWWombat]

That's interesting. So the BRAS is told the sync speed. I wonder where and how is the IP Profile is calculated?

Hmm . . . I think you will find some relevant information on a page of the main site --

• http://www.kitz.co.uk/adsl/IPprofile.htm#RAP
• http://www.kitz.co.uk/adsl/IPprofile.htm#IP_profile_calculated

Granted that was written in the era of 20CN technology but I am fairly certain that the overall concept is still correct.

Can you humour me briefly, and confirm exactly how the FTTC IP profile calculation is formulated? What is it that makes 96.8% an appropriate adjustment?

The recent mentions of MTU is making me think...