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Author Topic: Data Rate Query  (Read 12967 times)

Jay

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Data Rate Query
« on: October 21, 2006, 01:26:05 PM »

Nice Forum and very informative site.

Just a little query.

A number of people quote a sustained sync speed of 8128 for example and refer to having a Data Rate of 8000.

The typical table relating sync speed to Data Rate, although I notice Kitz refers to it as IP Profile and not Data Rate, quotes an 'IP Profile' / Data Rate of 7150.

I find this reference to a Data Rate of 8000 somewhat confusing therefore.

This is in no way an academic point since I find it somewhat difficult to get all this clear in my mind, not least since my ISP, Plusnet, seem to provide your Stable Rate on their Portal, which Kitz seems to refer to as Data Rate.

In my case I have synced at not less than 7456 for a number of days.
BT's test site, which I'm amazed I got to work today, quotes an IP Profile of 6500 and Plusnet quote a 'Stable Rate' of 7000.

Any clarification would be most welcome.
« Last Edit: October 21, 2006, 01:37:48 PM by Jay »
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Jay

roseway

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Re: Data Rate Query
« Reply #1 on: October 21, 2006, 04:03:08 PM »

What PlusNet call the 'Stable rate' is simply a reference point which is used to determine your fault threshold rate (see the section 'Max stable rate' at http://www.kitz.co.uk/adsl/maxdsl2.htm ) and I imagine that the 'Data rate' you refer to is the same thing. It has no effect on the actual speed of your connection, and generally stays unchanged after the 10-day training period.

The bRAS profile, or IP profile, is a cap on your download speed which can change from time to time according to your sync speeds.

Eric
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Jay

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Re: Data Rate Query
« Reply #2 on: October 21, 2006, 05:08:13 PM »

Thanks Eric

The figure Plusnet quote, which Kitz refers to as Data Rate on the link you kindly provided, varies from time to time.
My MSR has never changed from 6816.

The main thrust of my post is that there are references by those on say 8128 sync, to having a Data Rate of 8000.

If they are on a Data rate of 8000 it does not correspond to the Data Rate quoted on the standard Tables available of sync speed/Data Rate.

The other way of looking at it is for me to ask what is my current Data Rate, where is it derived from and how.
« Last Edit: October 21, 2006, 05:16:17 PM by Jay »
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roseway

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Re: Data Rate Query
« Reply #3 on: October 21, 2006, 07:00:14 PM »

I don't really know the answer then, but I can only assume that a data rate of 8000 refers to the MSR, because as you say, the IP profile would be 7150.

Eric
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kitz

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Re: Data Rate Query
« Reply #4 on: October 23, 2006, 08:15:13 AM »

Hi and welcome

I must admit the introduction of the term IP rate by BT does seem to cause some confusion, and it was something I first queried myself during the beta testing phase of the new BTw Performance tester.
BT that seem to be introducing the difference names and terms without actually clarifying exactly what they are. :/

I'll try work through each one to the best of my knowledge...  If anyone finds out anything to the contrary then they are welcome to add their 2p.

Connection Speed (Sync Speed)

This is the rate at which your router connects (synchronises) to the exchange at.  This speed depends on various factors and local line conditions.  Obviously the better your line/nearer to the exchange you are the higher this will be. This figure can change each time you connect.


Maximum Stable Rate.

This is set during the first 10 days on MAX and is used to set your Fault Threshold Rate. This figure has no real relevance on the day to day running of your connection, and is perhaps something we can forget about and ignore, because once its set, there is little you can do about getting it changed anyhow.  More info on MSR.

bRAS Profile

The bRAS profile is a limitation of your speed at the RAS in an attempt to stop too much data travelling down the ATM backhaul and swamping the DSLAMs at the exchange, which apparently could cause packet loss.
Your bRAS profile is determined from your lowest sync speed over the 3 day period.
This is something only done by BT and doesn't occur on LLU.

Data Rate

The Data Rate should mirror your bRAS profile, which is rounded down to the nearest 500kbps.
BT send your ISP a delta report, which advises them of any changes in your bRAS profile.  BT state that the ISP should limit throughput in line with the bRAS profile and also any limitations on the account type - ie ensure that home Max accounts don't get more upstream than they should. 
Note: The ISP can also use this to limit any ISP related account types for example if an account is provided by Max, but they want to limit the account to 1Mb or 2Mb speeds.


IP rate

This seems to be the one that causes the most confusion right now.
This figure is supposed to be what BT estimate your maximum throughput (real) speed should be after overheads - if all conditions were perfect. This figure is only a guide as to what speeds you could expect to see.

Finally..

Plusnets "stable rate" page.

When BT first announced MAX, they advised ISPs that they would be introducing some limitations of throughput speeds and talked about Maximum Stable Rate.  They told the ISPs that there would be speed limitations that the ISPs would be required to implement.
Since PN were one of the max trialists, PN set up something so that their users could see this figure.
Unfortunately for them, at the time this was called a stable rate and they called the page stable rate.. but this actually became what is known as the data rate and should not be confused with the Maximum Stable Rate.  They removed reference to stable rate, but the fact remains that the word stable is still in the url which IMHO is what causes the confusion :/
The figure on that page should be your Data Rate.
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kitz

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Re: Data Rate Query
« Reply #5 on: October 23, 2006, 08:31:29 AM »

So how does this equate in the real world?
Perhaps if I put some figures in with my own connection it will all start to make sense hopefully.

~ Connection (Sync) Speed
Ive got a stable connection and have always synced (connected) at 8128 kbps

~ bRAS profile / Data Rate
Rounded down to the nearest 500.  8128 --> 8000 kbps
Data Rate confirmed as 8000 on the PN portal page.

~ IP Rate

Confirmed as 7150 as per the BT performance tester.
Remember this is a guide as to your maximum throughput speed after overheads. - an indication by BT as to what the maximum speed you could expect to see if your line conditions were perfect.


More on the IP rate / throughput speed

When I first got maxed I saw pretty good speeds, although things seem to have gone downhill a bit since more people have got max, and the exchanges are seeing more contention.
But a speeds I could get for quite a while was 7.09 Mbps (7260 kbps). 7.19Mbps (7362.56) was another common speed I hit during the wee small hours.

My conclusion is that the IP rate is simply a guide as to what speeds you could expect to see - in a similar way that on the old 512kbps connections it was said the max would be 480kbps.

Therefore IMHO the IP rate should be taken as a guide only - because it is possible when undertaking some speed tests that you could get more than the 7150 kbps particulary if overheads are taken into account.
7150kbps is NOT an overall limitation of what you may see when conducting speedtests, depending upon which tester you use.

eg

My best speed ever speed recorded on a speed test is 7.76 Mbps (7946 kbps).



Ive also screen caps such as this.. which show that its possible to get > 900 KB/Sec (7200 kbps) including overheads.  Therefore the 7150 figure cannot be something set in stone anywhere.??


Im also well aware of the impact of overheads..  but its almost impossible to know exactly what these are..  hence me sticking with the theory that the IPrate is a guideline figure only???

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Jay

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Re: Data Rate Query
« Reply #6 on: October 23, 2006, 01:35:36 PM »

Many thanks for your very detailed response which is much appreciated.

Part of the confusion to me is a Data Rate of 8000 being quoted for your steady sync of 8128, when the 'standard' tables giving sync speed to Data Rate quote 7150. Is everybody referring to Data Rate as the same concept or are people talking about slightly different things but calling them 'both' Data Rate.

Following a recent BT Fault which is now repaired my Profile etc has improved.

Using DMT I've dropped my Target SNM to 10 dB and my Profile has increased in two stages, which is probably correct.
Plusnet's Stable Rate has increased in two stages to its current value of 7000 for a sustained sync of 7456, and an IP Profile of 6500 per BT test.

If Plusnet's 'Stable Rate' is actually the Data Rate then based on the tables I would have thought it should be 6500.
On the basis that my Data Rate is my current Bras Profile rounded down from 7392 then no doubt its correct.
Plusnet of course assure me their systems have responded correctly to these recent changes.

« Last Edit: October 23, 2006, 02:05:28 PM by Jay »
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roseway

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Re: Data Rate Query
« Reply #7 on: October 23, 2006, 02:28:00 PM »

That's a terrific summary, Kitz. Perhaps you should copy your last two messages to a sticky, or incorporate them into your website.

Eric
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kitz

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Re: Data Rate Query
« Reply #8 on: October 23, 2006, 05:39:21 PM »

okay Im trying to get this cleared up once and for all.
Ive just asked for a woosh to be performed on my line and Ive been told that my bRAS profile is set at 8128 k

Other info available from WOOSH performed at 16:18 this afternoon is as follows;

Code: [Select]
Circuit In Sync
Loop Loss 7 dB
Margin 13dB
Errored Seconds 0
HEC Errors 0
Cell Count 403751989
Downstream xDSL Link Info Speed 8128 k

Downstream Line rate 8128
Downstream Line Rate Timestamp 28/04/2006 22.22.34
Profile Change Time 25/04/2006 09:13:29

Maximum Stable Rate 8128
Fault Threshold Rate 5689
Interleaved Auto

Top set of data is my current line rate (sync/ connection speed).

The middle set of data relates to my bRAS profile.
28/04/2006 is supposedly when my bRAS profile was was set. - - obviously because Ive always sync'd at 8128 this has never changed - but for people with less stable lines this figure and date will change.
25/04/2006 is the day I was maxed

Bottom set of data should hopefully be obvious.

-----

My data Rate is set from the BT delta report.. and rounded down to the nearest 500.
This figure will be based on the lowest sync speed over the past 3 days.

Data Rate Info as follows

Code: [Select]
Your current broadband speed is 8000 Kbps
This is the speed that the network supplier is telling us you should expect on your line.


Therefore the maximum speed I can ever achieve will be 8000 kbps including overheads.

My IP Rate/Profile  = 7150

Code: [Select]
IP profile for your line is - 7150 kbps
This is an estimate of the highest speed you will see under perfect conditions after allowing for overheads.
Confirmed as being a guideline only by a rep that I trust and is not known for BS.


---------
When I get chance Im gonna put all this info together..  but it will have to wait Im afraid until I can sit at the PC a bit longer.
Wanted to get this posted as I thought roseway (and a few others) may be interested.




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roseway

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Re: Data Rate Query
« Reply #9 on: October 23, 2006, 06:57:42 PM »

Thanks for that Kitz. So bRAS profile is not the same thing as IP profile, the latter being just an estimate. And your bRAS profile equals your sync rate, which equals your maximum stable rate. Some cherished beliefs are going out of the window. :-\

Eric
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Jay

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Re: Data Rate Query
« Reply #10 on: October 23, 2006, 07:31:04 PM »

Once again I appreciate the effort you have put in Kitz but at one level the issue of Data Rates is I would have thought very simple.

Plusnet, amongst many others quote:

Throughput Speed (Data Rate)
............................

Sync speed         Throughput speed

from 288kbps      up to 0.25Mbps
....................................................
....................................................
from 6816kbps    up to 6Mbps
7392kbps            up to 6.5Mbps
7968kbps            up to 7Mbps
8128kbps            up to 7.15Mbps

Yourself and no doubt many others syncing at 8128 confirm they have a Data Rate of 8000.

Plusnet state you have a Throughput Speed (Data Rate) of [up to] 7.15 Mbps.

Is there not a discrepancy here or are both statements correct.

Most tables I've seen do not refer to Throughput Speed but simply refer to Data Rate.
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Jay

kitz

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Re: Data Rate Query
« Reply #11 on: October 23, 2006, 08:14:05 PM »

Thanks for that Kitz. So bRAS profile is not the same thing as IP profile, the latter being just an estimate. And your bRAS profile equals your sync rate, which equals your maximum stable rate. Some cherished beliefs are going out of the window. :-\

Eric


Eric one of the things Ive always maintained is that this new IPrate/profile figure that seems to have raised its head fairly recently cant be the actual bRAS profile..  because Ive seen speeds (granted in the early days) that equate to more than 7150kbps. 
Screen caps of these are in one of my above posts.

I was one of the beta testers on the BT performance tester and the feedback I gave at the time was that the mention of the IP rate (7150) could cause some confusion.
I was told at the time, that this 7150 was simply an indication of what your maximum speed would likely be after overheads.

Roll back the clock further and this indeed seems to confirm what the likes of saffy was saying when it came to the maximum speeds we would likely see for each band of speeds when on max.
If we go back to the post here http://www.adslguide.org.uk/newsarchive.asp?item=2622

Quote
The BRAS rate limiting which sets the maximum IP rate your line can sustain
Then the list of IPrates are given.

Quote
To give an example from the table, if you have a downstream line sync speed of 768Kbps, the maximum throughput of data at the IP level will be 0.5Mbps,

We are now talking data throughput speeds again.. not something 500kbps less overheads.
The early days all mentioned expected throughput speed.

If we go back even further to the fixed products it took a sync speed of 576 kbps to be able to get a 512 kbps connection - and the theoretical max throughput after overheads was said to be in the region of 480kbps.


What I dont understand yet and what hasnt become clear..  is that obviously the IPrates go down in steps.. therefore it would seem obvious to me that the bRAS profile must also go down in certain steps too.

What are these steps?
What is this "round down to 500" that we have heard about (as per the Data Rate that the ISPs are supposed to set on their own equipment).

Could it be that the bRAS is simply the lowest sync speed.. and that the data rate (because that is rounded down).. is what causes the lower IP rates down across and through all the profiles.


Whilst its been interesting to see what happens when someone gets the full 8Mb.. it would also be interesting if someone who was on a different profile could get their ISP to perform a full xdsl woosh test and ask the ISP to forward the full report to them so that we could compare.
We would also need to know what Data Rate the ISP had set on their end too.

I'd ask my own ISP, but I think I may be pushing things a bit..  I took up someones time this afternoon asking the info I did.. and getting them to do me a woosh and forwarding it.  I think I may have been taking too much of a liberty to ask for them to perform one on someone elses connection (would this be against the DPA?).  :-\

Hope Im making sense, but Ive just taken some pretty strong painkillers which make my brain go a bit fuzzy for a while. :'(
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mr_chris

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Re: Data Rate Query
« Reply #12 on: October 23, 2006, 08:17:12 PM »

Just about to post this but kitz posted first... I'm posting anyway ;)

-----

I think you're looking too deep into this Jay :)

These terms are, at best, ambiguous, and at worst, very confusing.

Plusnet have confused the issue bigtime by calling that page "stable_rate" and referring to it as your data rate. It is NOT your exact data rate, it's your sync speed (ATM data rate, if you like) rounded down to the nearest 500kbps.

Data Rate and Throughput speed are one and the same thing. By themselves they don't refer to anything... sync speed? IP data? It doesn't make it clear.

The 8000 speed is only (as far as I know) quoted by Plusnet. They will use this figure to weight your traffic on their network so you get a fair slice of the bandwidth. It's simply your 8128kbps sync speed rounded down.

So we can pretty much discount this 8000 figure as simply a figure particular to Plusnet.

The 7150k figure is pretty much the maximum theoretical IP speed -- i.e. AFTER you take off the ~10% of ATM overheads, if you sync at 8128kbps. This is why it is known as your "IP Profile Speed" and is, as kitz says, simply a guideline figure, not set in stone. It's probably used to manage and prioritise your data through the BT network to ensure that you as a fast connection can't swamp the network for those less fortunate on lower speed connections!

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Chris

kitz

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Re: Data Rate Query
« Reply #13 on: October 23, 2006, 08:35:59 PM »

Hi Jay

Based on the information in the above posts..  it would seem that most of the information given in your post is actually correct.

The sync speed in the left column gives a throughput speed.
The throughput speed equates to the IPrate quoted by BT.

Throughput speed is what you can expect to see in real life after overheads.

Therefore it would seem to me that throughput speed is not what we know as data rate.
Data rate would appear to be the lowest sync speed rounded down to the nearest 500kbps

Throughput speed is the speed which we could expect to see on our connections after overheads.

If Plusnet set my data rate at 7150 (as indicated from the performance tester) then there would be no way that I could get speeds that I have done in the past.

If BT had set my bRAS profile to limit it to 7150..  then the maximum speeds I would ever see would be far nearer 6Mb than 7Mb. Therefore whatever it is that limits your speed on the RAS has to be higher than 7150.

I think that possibly the bit in blue that is incorrect is

>> Throughput Speed (Data Rate)

ie Throughput speed is NOT what we commonly know as the data rate


-------------
edit

chris has posted since I started this.. 
I think hes managed to explain it so much better than me.
« Last Edit: October 23, 2006, 08:37:45 PM by kitz »
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kitz

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Re: Data Rate Query
« Reply #14 on: October 23, 2006, 08:46:43 PM »

>> The 8000 speed is only (as far as I know) quoted by Plusnet.

Ive read somewhere chris (probably in one of the SINets).. that for an ISP to be able to provide MAX, they must have some way of controlling data throughput at their end too.

We know that BT send out delta reports to all IPStream ISPs.. Im sure Ive seen mention that Nilly do something similar to PN.
Zen must also do some sort of limiting their end too.. because they were able to limit their infamous max trialists to 2Mb.
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