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B/W Usage Query.....

pawhe955
Grafter
Posts: 106
Registered: 31-07-2007

B/W Usage Query.....

Hi all,
I have an outstanding query with Plusnet at the moment regarding my recorded (VMBU) Internet Usage, as there appears to definitely be something wrong, but it’s not clear exactly what at the moment.
One of the most obvious "anomalies" seemed to be when I downloaded Windows7RC - all 2.36GBytes (size as quoted by MS before download; size as quoted by the download manager, during download, etc.). I started the download at 07:40, and at 08:00 (end of my Free Usage period), the MS initiated download manager, showed 69% done - being 1.63GBytes. It completed some time later, so I expected at least 2.36GBytes of data usage to be reported by VMBU for the day, with 1.63GBytes in the Free time. But VMBU reported 652MBytes "Free Usage", and 1.3GBytes "Paid-for usage" - total 1.95GBytes (up/down). Plusnet's provided hourly breakdown seems to show 616MBytes for the 07:00 hour, and an additional 1.2GBytes for the rest of the day (albeit only 362MBytes for the 08:00 hour) - total 1.6GBytes downloaded.....
I know that some download managers will use data compression over the wire - but we're talking about the download of a DVD ISO (which, now on my HD, is definitely 2,530,975,744 bytes, and which installed fine - so all data came down o.k.) - and anything with binary content (which I would have thought an ISO is a good example of) is usually less compressible than, for example, typical ‘data’ files. But this appears to suggest compressing to 40% of original size...
In a separate occurrence, I recently downloaded vista SP2 from Microsoft’s Downloads section of their support site, finishing way before the 08:00 "Free Usage" deadline. These "normal" MS downloads do not appear to invoke a download manager, like the one used for Windows7RC. Vista SP2 is over 300MBytes (365,230,920 bytes on disk); yet Plusnet's hourly analysis shows that 19MBytes was downloaded in the 07:00 hour, and 13MBytes in the 08:00 hour (and 422.76MBytes total for "Paid-for Usage").
Even this morning - I'd specifically waited to download MS's “Patch Tuesday” patches for a particular laptop, and had around 26MBytes reported as ready to download - did so before 08:00, then “disconnected” router’s connection to the Internet. “Netmeter” 'totals' reports over 27MBytes downloaded via the appropriate Network Interface on the laptop at 08:00. Turned the Internet back on at 11:18, and saw that VMBU reported 8MBytes of “Free usage” (as it still does now @ 15:00, well past the 2-hour catch up period).
Assuming that Plusnet's hourly statistics are accurate, can anyone offer an explanation for these figures?  Does this look like some form of line level data compression for anything from all Microsoft Download sites?  Does it seem possible to be getting over 50% compression on binary files..Huh
Any views on the suggestion of compression, or other advice, is welcome as I still feel that there’s something wrong with the recorded usage figures, specifically being worried that data isn’t being recorded correctly into the “Free usage” time...  (Next steps are to identify the best place, [e.g. somewhere other than MS] to download a specifically large and definitely known size of file from, before 08:00, and switch off Internet for 2 hours again, etc.).
Thanks,  pawhe
6 REPLIES
Community Veteran
Posts: 38,460
Thanks: 1,027
Fixes: 62
Registered: 15-06-2007

Re: B/W Usage Query.....

I saw the same effect when starting Vista 64 bit SP2 download in the late evening and running into the free period. A lot of the usage vanished
Community Veteran
Posts: 6,111
Thanks: 1
Registered: 05-04-2007

Re: B/W Usage Query.....

This happens when you download close to either 12am or 8am. Plusnet base their usage data on CBC reports that come from BT, but the reports aren't precisely aligned with the beginnings of hours, and they're also fairly infrequent - e.g. every 15 minutes. So, for example, if PN receive a report at 8:05am pertaining to the last fifteen minutes, they will discard all of the data used during that time, as they have no way of knowing exactly how much was off-peak and how much was peak.
Community Veteran
Posts: 26,627
Thanks: 860
Fixes: 10
Registered: 10-04-2007

Re: B/W Usage Query.....

Isn't it because the first usage report from one period to the next (i.e. just after midnight or 8am) is discarded because the system can't tell how much was before and how much was after the switch point?
Edit: Bah! Too slow typing!
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
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Community Veteran
Posts: 6,111
Thanks: 1
Registered: 05-04-2007

Re: B/W Usage Query.....

Snap. I win. Wink
pawhe955
Grafter
Posts: 106
Registered: 31-07-2007

Re: B/W Usage Query.....

Well, that all makes sense - thanks.
If my calculations are correct, then at my typical throughput of around 5.6Mbps, that's around 600MBytes that could disappear for a 15min period. That certainly accounts mathematically for a couple of the "anomalies" - although I'm still not sure about timing....  Whilst the Windows7RC download spanned the "Free Usage" and "Paid-for Usage" periods, I think the Vista SP download finished around 07:40, so nothing should have been discarded for that one. And very possibly the same sort of timing for the 27MBytes this morning. So I might take the time to test a large download well within the Free period, and see if it is all accounted for in there....
Thanks for the responses,
Community Veteran
Posts: 6,111
Thanks: 1
Registered: 05-04-2007

Re: B/W Usage Query.....

Occasionally a CBC report does go AWOL... I'm not entirely certain what happens in such a case (i.e. if the missing report's total is added to the next successful report), but either way it could explain larger sums of data going missing - if a missing report does get 'tied' to the next one, which crosses a peak/off-peak transition, then the combined total will be discarded as the single report won't tell PN when the data was used.