Infinity upgrade fail

Following on from my thread in the general forum HERE I spoke to a couple of guys on the BT community forum today HERE who have basically stated that it doesnt matter what the IP profile is on the upstream, you will only get what the BT wholesale checker states. Somebody convince me this isnt true??

You posted in the first link

3. My upload profile is 10Mbps but speedtests have never been above 6Mbps, is this normal?
...
Good news! We predict your download speed will now be 27Mb/s and your upload speed will now be 5Mb/s

So it wasn't true for you on 12 April.

To be fair, that post is not entirely accurate. The prediction was 5.7 up, which is almost exactly what I get.
Still doesnt explain the part about the profiling though.

Can anybody confirm this? It would certainly go some way to explaining my speed issues

In reply to a post by steadyeddie:

Can anybody confirm this? It would certainly go some way to explaining my speed issues

I would suggest this is not the case.

The availability checker says this for my line:

Our test also indicates that your line currently supports a fibre technology with an estimated WBC FTTC Broadband where consumers have received downstream line speed of 55.1Mbps and upstream line speed of 13.2Mbps.

This is what I actually get:

http://www.speedtest.net/result/1928298579.png

Although I do find that the upstream benchmarks much lower than this from certain speedtest sites. I suggest you try via the "London > Virtual Internet" server.

BTW these speeds are corroberated by what I can upload at via uTorrent, I hit just shy of 2MByte / Sec. Obviously I'm capping the hell out of that down to about 128KByte/sec but if I don't, that's what I get

http://www.speedtest.net/result/1928534079.png
The upload is scarily predictable!!

Edited by deleted (Wed 02-May-12 21:04:07)

I don't actually know the answer, but I think I may understand what they are on about.

My thoughts:
the backhaul back to their core network from the mini-DSLAM in the street via the exchange is all symmetric (i.e. same maximum speed up and down). However the VDSL service on customer lines is asymmetric.

The profiling is used to prevent an overwhelming amount of traffic hitting a given route.

e.g. you choose to download a massive file from a server on the internet somewhere that can happily serve that file at say 300Mbps+. All well and good - 300Mbps flies across the internet, over BT's core, down the backhaul to the DSLAM in your cabinet - at which point it hits a bottleneck as your downstream rate is a lot lower. The net result being buffering and/or discard of data by the DSLAM, in turn resulting in the dropped packets needing to be retransmitted again all the way from the server somewhere on the internet.

Not a very sensible thing to do as that would throw a stack of useless traffic over the backhaul to the cabinet which could unnecessarily lead to congestion as well as incurring the additional back scatter of upstream retransmit requests coming from you.

So the downstream data rate is limited so as not to bottleneck when it hits the VDSL segment. I presume this is applied at the BRAS so it relieves the unnecessary data from their on out i.e. the fibre feeding the exchanges and the fibre to the cabs.

Now think about the upstream - as far as BT are concerned - what need do they have to profile the data rate on that? You can only generate as much traffic as the VDSL segment can handle in the upstream direction which poses no risk to the onward upstream fibre capacity into the core.

To BRAS profile on the upstream would be plain stupid as by the time the data arrives there to be throttled it has already traversed the "narrowest" part of the network i.e. the fibre from cabinet to exchange. Upstream needs to be managed on the CPE (your router) which would be achieved by capping the VDSL synch rate in that direction or using capping on the VLAN (presuming the CPE is intelligent enough).

Basically what I believe they are saying is that they have no concerns about upstream congestion becoming an issue so they don't bother profiling it. Understandable really as downstream congestion is going to occur sooner on the symmetric backhaul, which will require the backhaul to be increased in size - adding more available upstream... and so on.

And yes - before anyone jumps in - I'm deliberately ignoring the ability (or otherwise depending on implementation) for the TCP stack to back off the transmit speed in either direction if required. It's a somewhat unreliable mechanism over the t'interweb.

GeeTee, I feel incredibly guilty, the time and effort that went into that post was totally wasted on me!!
I do think I understand the basics of what you are saying though, and thanks for taking the time to post it.
It will be interesting to hear what the BT technical bods have to say when (if) they ring me back.

Apologies - I got a bit carried away

Basically if my theory is correct then your upload data rate is only limited by the connection speed between your router and the street cabinet. Unfortunately you can't see what that is without somehow unlocking the Openreach modem.

I should probably go and read your other threads so I know what the actual issue is

The gist of my problem is that my upload profile was 10Mbps, then 20Mbps after the upgrade, but my achieved speed has never been more than 5.7Mbps, which is exactly what the BT checker predicted.

It may just be that due to the distance of your property from the cabinet (or possibly external influences such as electrical noise) that is the best that can be achieved on your line.

Might be worth asking the BT folks if they can tell you what speed your line is actually synchronised at with the cabinet DSLAM (as opposed to what the profile is set to or the BT checker estimates say).

If the line can only physically manage to synchronise at say 6Mbps then no amount of fettling the profile upwards is going to make any difference (if indeed it has any part to play at all as they seem to suggest).

I'd hope the BT Retail staff have access to this information to aid their diagnostics rather than it being held 'secret' by Openreach (part of the BT Group but operated entirely separately).

Your two posts triggered a thought, unfortunately not directly related to the question.

I can't remember seeing any BT speed test results for FTTC where the upstream IP Profile has not been either 10Mbps or 2Mbps. Neither however can I remember ever seeing an upstream IP Profile on ADSLx.

Bear in mind that on FTTC we have two overlapping DLMs .

Openreach have a "product setting" to cap the line speeds. I don't think they have IP Profiling within that. That DLM is the actual line controller, with (surmising) ISP-requested settings passed in from ...

... the BT Wholesale DLM, which I think applies a patch in its original downstreaming profile system. That takes the sync reported by Openreach and generates an IP Profile at around 97.69% of sync. (See Bald_Eagle1 posts). ADSL2+ sets it to 88.2%. IPSC (ex ADSL) appears to apply the original "up to 8Mbps" profile table.

(The BTW IP Profile has always done as you surmise - stop traffic too fast for the line arriving at the DSLAM).

Now I start guessing/proposing. It is highly likely that the BT Wholesale DLM contains fields for both downstream and upstream IP Profile, in case an upstream one was ever required. Pre-fibre, I suggest that was always filled with 448/832kbps for ADSL, and some unknown number for ADSL2+. (1.4/2.5Mbsp?).

To function on FTTC that upstream field needs a value. 2000/10000/(15000)/20000.

Discuss .

I don't have FTTC myself so I am speculating and extrapolating from knowledge gained over far too many years working in telco / ISP land.

Your explanation makes sense - the upstream profile figure may only exist because it 'must' e.g. it is a mandatory value in some underlying system or database, but is not actually used for anything so is just populated with the maximum upload speed dictated by the product specification. However, the actual governance of the upload is achieved using line synchronisation parameters e.g. the cabinet dslam caps the maximum upstream synch rate to 2Mbps, 10Mbps, 20Mbps etc. as per the product and then at synch time the line makes best efforts to achieve up to that speed.

With that in mind there would be absolutely no point doing any profiling further upstream, it would just be unnecessary configuration and management overhead on network devices upstream into the core.

So in the OP's case I suspect the best upstream synch speed the line can achieve is ~6Mbps - clearly in this circumstance changing the maximum allowed upstream synch from 10Mbps to 20Mbps on the DSLAM achieves nothing - the line is still just making best efforts. So actually when the BT Care folks suggest that referring to the Openreach checker estimate is more useful than referring to the IP profile. However, one sincerely hopes they have access to diagnostics tools that can tell them what the actual line synchronisation speeds are (along with the other useful stuff like SNR, attenuation, error measures etc.)

Yes, without explicitly saying so, I was agreeing with you and providing a plausible explanation of how the DLM programmers' moinds worked several years ago.

As for

However, one sincerely hopes they have access to diagnostics tools that can tell them what the actual line synchronisation speeds are (along with the other useful stuff like SNR, attenuation, error measures etc.)

and anything similar. Nope!

The estimates on the Wholesale checkers were produced by Moses. The attitude throughout the BT Group is that they are right, and no evidence to the contrary is accepted. The figures from engineers' test equipment is ignored. This has been the case for years.

We had a case the other day where a disgrunted user stuck on a 2Mbps upstream FTTC product, where it was obvious he could get more, was refused even at BT CEO level.
http://forums.thinkbroadband.com/bt/t/4114496-help-p...

I think it's unfair to pile the whole BT Group into one bag like that. From my experience there is still plenty of realistic boffinry going on regards improving testing, diagnostics and repair in dusty corners not just within the BT Group but also within the industry as whole.

I see two main reasons for the perceived decline in flexibility when it comes to this area. The rigid chinese walling of the various companies within BT Group (and within other large players in this industry) and the industry-wide desire to compete for custom purely on price-point alone.

I won't go on in a public forum, it could be detrimental to me

And no, I don't nor ever have worked for any part of the BT Group before anyone accuses me of astro-turfing.

The Group CEO Office should be able to cause action to be taken when Openreach engineer equipment reports a line is achieving upstream speeds 700% greater than a database says. Particularly when the upstream figure reported is consistent with the user's actual downstream and the estimates are consistent with each other.

Nothing to do with Chinese Walls. Simple common sense. Little technical understanding needed, and that should be easily obtained through a 3-minute internal phone call.

We are not talking about the high-tech areas. We are talking about obvious database errors, with no acceptance that they could be wrong, never mind there being no system facility to correct them.

In reply to a post by RobertoS:

I can't remember seeing any BT speed test results for FTTC where the upstream IP Profile has not been either 10Mbps or 2Mbps. Neither however can I remember ever seeing an upstream IP Profile on ADSLx.

Bear in mind that on FTTC we have two overlapping DLMs .

Openreach have a "product setting" to cap the line speeds. I don't think they have IP Profiling within that. That DLM is the actual line controller, with (surmising) ISP-requested settings passed in from ...

My results on speedtester.bt.com have always said 20mbps for the upload (except of course when I was on the 40/10 service). Downstream IP profile varies according to my downstream line speed, however nomatter what my upstream sync speed is, upstream IP profile has always remained at exactly 20.

I think the ideas proposed for why are correct as well - i.e. that there is no need for upstream profiling as the rate limiting hop of the line itself is already past by the time data reaches the profiler.

So while one can reasonably accurately deduce their downstream sync speed from their downstream IP profile, the upstream profile provides no such clues and there is no way whatsoever for a customer using the official equipment as provided to see their upstream sync speed.

It is certainly not the case that your upload will only be what the checker states, as the checker states I'll get 53/13 and this speedtest suggests otherwise.

What's more likely the case is nomatter what your IP profile states, your upstream will be the maximum your line can support up to the limit of the service you're paying for. In this case it just seems the checker was exceptionally accurate with its prediction.

Edited by deleted (Thu 03-May-12 03:01:57)

WOAH there tiger. I was simply trying to explain how the internal machinations go in the industry without elucidating.

If you want to rage by all means continue to hit [email protected]

The attitude throughout the BT Group is that they are right, and no evidence to the contrary is accepted.

I posed some questions in private, and response was similar, i.e. nothing wrong with products. It is the tester, or wireless, AV software or PC.

Hence why 'computer says no' became such a big catch phrase.

Proof that you are being fed bovine excrement ...

http://forums.thinkbroadband.com/bt/t/4120033-switch...

Not really relevant, this thread is about the upstream and that user gets no more upstream than the checker predicted.