cancel
Showing results for 
Search instead for 
Did you mean: 

VMBU accuracy - CS response: This doesn't sound plausible

kjaerligkatt
Grafter
Posts: 411
Registered: 02-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

As suggested by Mand, last Friday I submitted a ticket regarding my belief that the VMBU is overstating my broadband usage. I've explained that I’m using proper monitoring of the ADSL interface using SNMP to monitor all the traffic passing through my ADSL port. There is no other way into or out of my network for PlusNet traffic Wink My router is also handling and measuring the Ethernet packets – this is what routers do!!!

This is the response I received after providing full data logs:

Quote
Dear Mr Gardner,
This is easily explained as our software ellacoya measures all data that passes through from your connection, not just the IP, tcpip, UDP etc the ethernet packets are also measured & the packet over heads are the same size for every packet sent. This ethernet data is not usually recorded by data tranfer software unless it was to sit on our ethernet switches & be our ellacoya software.

So the difference is accounted from in the positioning & monitoring of the software. Our data is correct for you.

Regards,
xxxxxxxxxxx


I've also pointed out that before the new VMBU was introduced, the old one matched my logs almost exactly - the difference could easily be explained with overheads.

I analysed a 6 day period for end May/early June and there was some 500MB difference between what the VMBU claimed I had used, and what PRTG had logged, and 200MB of this was peak time. This is very significant, and will make a huge difference to anyone making full use of their monthly quotas.

What do others think? I know there have been other reports of similar discrepancies.

Why can we not get a response on the difference between the old VMBU and the new VMBU? There have been a number of posts listing differences between the two.

Why do PlusNet believe that my router is incapable of accurately measuring the Ethernet packets entering and leaving it – it has to process every packet correctly?

Take this comment:

Quote
This ethernet data is not usually recorded by data tranfer software unless it was to sit on our ethernet switches & be our ellacoya software.


This seems to entirely miss the point that my router is performing exactly the same function as their switches, and is therefore sitting on the data being passed between PlusNet and me.

I do not see the point of submitting tickets for problems like this if the only response forthcoming is ’our equipment is correct, yours has to be wrong’. Whilst there is no explanation as to the discrepancy between the figures reported by the old and VMBUs, it seems highly probably that there is something wrong at PlusNet’s end!

If you’re seeing similar discrepancies in your usage reports, why not post your results to this thread so that we can correlate results. For reference I’m on the Premier Option 1 product.

Regards, Neil
40 REPLIES
FooAtari
Grafter
Posts: 272
Registered: 30-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

I have just started to monitor my router using PRTG and noticed a 200mb difference yesteday. I'll get the eaxact figures later. but the VBMU was showing the higher figure. Which I didnt think was tooooo bad until I realised that would make four around 6GB per month! That quite a big difference between the VBMU and what PRTG records...
N/A

Re: VMBU accuracy - CS response: This doesn't sound plausib

Quote
Why can we not get a response on the difference between the old VMBU and the new VMBU? There have been a number of posts listing differences between the two.

I've had an ongoing ticket for a little while about this, as my usage jumped up hugely on the new VMBU compared to how it was previously and pushed me into Level 2 Management (BB+) - all with no big changes in internet habits, and no "intruders" into the network. A number of quotes from plus.net in my ticket regarding this:
Quote
3:19pm, Thursday 8th June 2006
I beleive a problem has been raised internally to deal with this issue - The summary totals are currently displaying incorrectly.

The daily totals however should be correct, and reflect your current usage accurately.

Quote
11:41am, Friday 9th June 2006
As my collegue stated we are currently investigating a problem with the vmbu, however your usage is correct overall

Quote
12:32pm, Friday 9th June 2006
the old VMBU will be incorrect as it is no longer used actively to monitor usage. the old VMBU has now been decommision and has not been reporting your usage correctly since you were change over to the new VMBU

Quote
1:06pm, Friday 9th June 2006
When Mandy stated "Regarding discrepancies between old and new VMBU, this is expected as they collect stats from different points, in addition old VMBU will represent peak entirely differently from the new VMBU.", This is what Agents Name is trying to get across but in different terminology. I hope this helps.

(The reference to Mandy in above quote, is to a forum post by Mand Beckett, and has therefore been left in as it's public)
Quote
4:12am, Saturday 10th June 2006
Contexts as to the VMBU tools are that the VMBU for old VMBU is collected from a different point in the network and that it doesn't accurately measure times anymore - it has been decomissioned and will not report accurate data anymore.

The new VMBU timescales are correct and will provide more indepth reporting going forward. That the times match to peaktime/offpeak and is more accurate representation of usage and allowances because of this.

Quote
2:15pm, Saturday 10th June 2006
We do not have access to the old vmbu data as this has been removed. The only reason it was still in place was due to some legacy systems problems, though it was not actually populated with accurate and up to date data. As such the data usage you saw on the old tool was incorrect and was not used for billing in any way

Quote
8:02am, Sunday 11th June 2006
The bandwidth usage is recorded in the same way on the new VMBU as the old. This has not changed.

Quote
1:55pm, Sunday 11th June 2006
From a customer point of view nothing has really changed. The usage still consists of the data you upload and download

There seem to be a few contradictions in their reply (in regards to the way data is collected) - sometimes its in different way, other times it's the same.
kjaerligkatt
Grafter
Posts: 411
Registered: 02-09-2007

Re: VMBU accuracy - CS response: This doesn't sound plausib

Quote

Quote
12:32pm, Friday 9th June 2006
the old VMBU will be incorrect as it is no longer used actively to monitor usage. the old VMBU has now been decommision and has not been reporting your usage correctly since you were change over to the new VMBU



Well, I've had PRTG running since Feb 4th, and so know how it correlated to the old VMBU when it was the only bandwidth reporting tool running.

Of course, if PlusNet have erased all their data, then they can't cross reference my figures!!!

--
Neil
kjaerligkatt
Grafter
Posts: 411
Registered: 02-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

Quote
Which I didnt think was tooooo bad until I realised that would make four around 6GB per month! That quite a big difference between the VBMU and what PRTG records...


It's best to think of it in percentage terms - what percentage is the VMBU adding to what PRTG logs. That will give you a better picture of what you're likely to see in absolute terms over a month, or a week. It adds up to quite frightening numbers Sad

--
Neil
N/A

VMBU accuracy - CS response: This doesn't sound plausible

Not sure if this helps but here's my router figures for this month vs new VMBU stats.

NOTE: Account Type - Business Option 2. All figures are MBs and router stats have been convered from binary to decimal (1000KB=1MB etc)

24th May, 10th, 11th June are big examples of where VMBU is totally wrong, the VMBU totals for this period are laughable and as I've said elsewhere, my router stats matched the old VMBU until plusnet removed my access to old VMBU last week....

Date        Off-Peak      Peak      Total

23-May-RT 55.870 213.928 269.798
-VMBU 57.520 219.990 277.510
24-May-RT 5848.845 70.722 5919.568
-VMBU 6.550 44.040 50.590
25-May-RT 499.580 125.801 625.381
-VMBU 64.030 127.510 191.540
26-May-RT 191.713 136.526 328.239
-VMBU 92.950 136.670 229.620
27-May-RT 1421.259 50.476 1471.735
-VMBU 1470.000 50.490 1520.490
28-May-RT 34.332 382.262 416.594
-VMBU 30.700 87.640 118.340
29-May-RT 49.722 97.264 146.986
-VMBU 42.950 86.690 129.640
30-May-RT 239.282 118.450 357.732
-VMBU 168.160 122.950 291.110
31-May-RT 769.246 98.243 867.489
-VMBU 27.720 97.710 125.430
01-Jun-RT 44.173 101.648 145.821
-VMBU 30.250 96.770 127.020
02-Jun-RT 57.140 592.389 649.529
-VMBU 31.550 130.660 162.210
03-Jun-RT 41.024 44.294 85.318
-VMBU 40.540 47.380 87.920
04-Jun-RT 75.229 163.977 239.206
-VMBU 80.870 24.270 105.140
05-Jun-RT 38.876 351.236 390.112
-VMBU 44.890 133.610 178.500
06-Jun-RT 60.003 60.745 120.748
-VMBU 65.730 78.800 144.530
07-Jun-RT 37.490 80.263 117.753
-VMBU 40.800 83.580 124.380
08-Jun-RT 17.828 62.013 79.840
-VMBU 19.750 66.450 86.200
09-Jun-RT 27.350 460.146 487.496
-VMBU 30.690 472.370 503.060
10-Jun-RT 2808.766 948.720 3757.486
-VMBU 201.890 65.450 267.340
11-Jun-RT 2995.098 163.681 3158.779
-VMBU 79.890 174.900 254.790
12-Jun-RT 166.753 425.581 592.335
-VMBU 173.030 438.440 611.470
13-Jun-RT 299.160 0.000 299.160
-VMBU 128.480 0.000 128.480

ROUTER TOT 15778.739 4748.365 20527.105
VMBU TOT 2928.940 2786.370 5715.310
FooAtari
Grafter
Posts: 272
Registered: 30-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

I finally got around to monitoring my router for a full 24 hours.

VBMU - 3.49
PRTG - 3.37

That doesnt look too bad, but thats still a difference of around 120mb I think, giving a total difference of around 4GB a month, which is quite a lot...

Edit

Yesterday wasnt to bad

VBMU 1.28
PRTG 1.23

So that about 50mb out.
kjaerligkatt
Grafter
Posts: 411
Registered: 02-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

Quote
Not sure if this helps but here's my router figures for this month vs new VMBU stats.


Sure, I think this is very interesting ;-) At least it shows that not everyone is claiming that the new VMBU is overstating their usage.

As reference, what router and bandwidth monitoring software are you using?

Regards, Neil
kjaerligkatt
Grafter
Posts: 411
Registered: 02-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

Quote
I finally got around to monitoring my router for a full 24 hours.

VBMU - 3.49
PRTG - 3.37

That doesnt look too bad, but thats still a difference of around 120mb I think, giving a total difference of around 4GB a month, which is quite a lot...

Edit

Yesterday wasnt to bad

VBMU 1.28
PRTG 1.23

So that about 50mb out.


These are about 4% out, which is the low end of what I see (anything between about 4% and 10% in 1 week at the beginning of June). To put this into perspective, as an example, it would mean that a Premier Option 1 customer would be throttled @ 9.6GB if your 2 days of figures are extrapolated. With the figures I've seen over a longer period, that throttling would begin @ 9.2GB.

It will be interesting to see what your figures are like over a longer period. Just to be sure, your figures do take a GB as being 1000*1000*1000?

--
Neil
N/A

VMBU accuracy - CS response: This doesn't sound plausible

Quote
As reference, what router and bandwidth monitoring software are you using?

The router is a Draytek Vigor 2800V and I have PRTG 5.2.0.582 Pro running on a server 24/7.

I asked for the old VMBU to be reinstated since it was working for me but it looks like we're stuck with the new one....
Quote
CSC Agent 6:42pm, Tuesday 13th June 2006
Dear Mr Moore,
The old VMBU system has been decomissioned due to the fact it is not compatible with future plans for the platform.

For some time now, the older VMBU has been reporting inaccuratly, as we no longer receive data on some part of our ADSL platform, whereas we do with others.

We are sorry you feel the platform is reporting inaccuratly for you, however as per our service status we are investigating incorrect usage being recorded for some customers.
FooAtari
Grafter
Posts: 272
Registered: 30-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

Quote
To put this into perspective, as an example, it would mean that a Premier Option 1 customer would be throttled @ 9.6GB if your 2 days of figures are extrapolated. With the figures I've seen over a longer period, that throttling would begin @ 9.2GB.


Thanks for that, but you kind of lost me a bit there... :?


Quote
It will be interesting to see what your figures are like over a longer period. Just to be sure, your figures do take a GB as being 1000*1000*1000?


Yep Smiley
kjaerligkatt
Grafter
Posts: 411
Registered: 02-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

Quote
Quote
As reference, what router and bandwidth monitoring software are you using?

The router is a Draytek Vigor 2800V and I have PRTG 5.2.0.582 Pro running on a server 24/7.


OK, a similar set up to me. Can't be accused of using 'noddy' equipment then ;-)

Quote
I asked for the old VMBU to be reinstated since it was working for me but it looks like we're stuck with the new one....

I can understand why they would want to stay with the new system. All I want is confidence that it's tracking usage correctly, and right now noone has given a plausible reason why people are seeing these descrepancies.

The ATM cells will be recombined by the router to reform the data packet, and the router counts the ATM cells passing into and out of it. I'm going to see if I can monitor the ATM cells passing into and out of the router.

Regards, Neil
N/A

VMBU accuracy - CS response: This doesn't sound plausible

Neil,

What will the cell count indicate, is it possible to calculate data throughput from the cell count?

ATM Statistics

TX Blocks: 17569850
RX Blocks: 188779463
Corrected Blocks : 156
Uncorrected Blocks: 5
Connected: 225hrs 40mins 51secs
kjaerligkatt
Grafter
Posts: 411
Registered: 02-09-2007

VMBU accuracy - CS response: This doesn't sound plausible

Quote
Neil,

What will the cell count indicate, is it possible to calculate data throughput from the cell count?


Without going into too much detail Wink for ADSL transmission, data frames (this is your data packet plus ADSL/TCP/Ethernet headers) are broken down into ATM cells for transmitting. ATM cells are a fixed size - 53 bytes. This is another overhead cost that you will lose from your bandwidth for data - there will be some padding due to the data frame not dividing exactly by 53, on top of the segmentation abd reassembly data.

The point is, the actual raw data transmitted across the ATM is this cell stream. This is the fundamental data block. There are no additional overheads to this. Each 53 byte packet leaves one end, and arrives at the other. Any retransmits will also be additional, counted, ATM cells. So, if you can count the ATM cells, you should have a 100% accurate reflection of the data being transfered to your router.

What I need to find out is how (if) it's possible to log the ATM cell Rx/Tx. I do not know exactly what this numbers are in the Vigor - and they are totals since the connection was established, anyway, so not very useful for daily comparisions.

Regards, Neil
N/A

VMBU accuracy - CS response: This doesn't sound plausible

Vigor supported OIDs can be found here but I don't see anything relating to cell tx/rx stats.

With my 2800V I had to add a .4 to the end of each to get a value returned in PRTG.