Missing 4Mb. 11.6Mb profile but tests only run at 7.6Mb.

[#1]

Hi there,
I have a puzzle regarding actual down load speeds (as tested) compared with sync and profile speeds.  I appear to be 4Mb missing.  Does anyone know what might account for this?
My sync speed is 13.258 Mb.  However download tests are always around 7.6Mb.  Given a line speed/IP Profile of 11.6Mb I am missing 4Mb.
I am performing the tests using a wired connection.  I have no complaint regarding the actual sync speed or IP Profile I’m just wondering where the rest of the capacity is.
From plusnet “High-speed Broadband” page:
Estimated line speed:
5Mb (This may vary between 4Mb and 8Mb) - Checked on 2011-10-10 14:50:03
Current line speed:
11.6 Mb

From BT Speed Tester:
Your DSL Connection Rate :13257 Kbps(DOWN-STREAM), 439 Kbps(UP-STREAM)
IP Profile for your line is - 11696 Kbps
Sample speed and line quality test results:
(Other tests give similar results at all times of day except overnight when I have no interest in testing)
Date Download Speed Upload Speed
Today 13:49 7705 kbps (963kB/s) 347 kbps (43.4kB/s)
Sunday 17:44 7653 kbps (957kB/s) 361 kbps (45.1kB/s)
Dec 25, 20:37 7258 kbps (907kB/s) 255 kbps (31.9kB/s)
Dec 22, 16:03 7657 kbps (957kB/s) 362 kbps (45.3kB/s)
[DSL Modem Stats]  (for an ADSL uptime of just over 5 days)
US Connection Rate: 439 DS Connection Rate: 13258
DS Line Attenuation: 29 DS Margin: 9
US Line Attenuation: 13 US Margin: 27
US Payload : 401127936 DS Payload: 3442928016
US Superframe Cnt : 42017662 DS Superframe Cnt: 42017662
US Transmit Power : 0 DS Transmit Power: 0
LOS errors: 0 SEF errors: 0
Errored Seconds: 6482 Severely Err Secs: 17
Frame mode: 0 Max Frame mode: 0
Trained Path: 0 US Peak Cell Rate: 1035
Trained Mode: 16 Selected Mode: 1
ATUC Vendor Code: 4946544E ATUC Revision: 2
Hybrid Selected: 1 Trellis: 1
Showtime Count: 2 DS Max Attainable Bit Rate: 13276 kbps
BitSwap: 1 US Max Attainable Bit Rate: 1108000 bps
Annex: AnxA psd_mask_qualifier: 0x0000
Power Management Status: L0 DS HLINSC: 0
US ACTPSD: -345 DS ACTPSD: -366
Total init. errors: 2 Total init. timeouts: 0
Showtime init. errors: 0 Showtime init. timeouts: 0
Last showtime init. errors: 1 Last showtime init. timeouts: 0
ATUC ghsVid:  b5 00 49 46 54 4e 71 be
T1413Vid: 00 00 T1413Rev: 00 VendorRev: 00
ATUR ghsVid:  b5 00 54 53 54 43 00 00
T1413Vid: 00 00 T1413Rev: 00 VendorRev: 00
[Upstream (TX) Interleave path]
CRC: 0 FEC: 0 NCD: 0
LCD: 0 HEC: 0
[Downstream (RX) Interleave path]
CRC: 0 FEC: 0 NCD: 0
LCD: 0 HEC: 0
[Upstream (TX) Fast path]
CRC: 0 FEC: 0 NCD: 0
LCD: 0            HEC: 0
[Downstream (RX) Fast path]
CRC: 9838 FEC: 0 NCD: 0
LCD: 0 HEC: 0
[ATM Stats]
[Upstream/TX]
Good Cell Cnt: 8356832
Idle Cell Cnt: 732416814
Tx Packets Dropped Count: 0
Tx Bad Packets Count: 39
[Downstream/RX)]
Good Cell Cnt: 71727667
Idle Cell Cnt: 789671509
Bad Hec Cell Cnt: 62077
Overflow Dropped Cell Cnt: 0
Rx Packets Dropped Count: 0
Rx Bad Packets Count: 0
Thanks in anticipation for any suggestions as to what is going on here.
Regards…Paul

[#2]

I've run some checks on your account and can't see anything obvious. I'd advise raising a fault, that way we can log this with our suppliers as a poor performance issue.

[#3]

To add to this.
Why is the reverse DNS for my connection showing as
92.78.125.91.rb4.adsl.brightview.com
The first part is not my current public IP though is if reversed.  But why brightview?
Regards...Paul

[#4]

Quote from: zetlandpaul

The first part is not my current public IP though is if reversed.  But why brightview?

Reversing the octet order in reverse DNS lookups is how the system works (explanation). If included in the PTR record returned the octets needn't be reversed but generally are.
IPs labelled as Brightview originated from the Madasafish brand which Plusnet now own. To maximise use of the scarce IPv4 addresses these ranges are used for all Plusnet customers now.
David