Big difference between actual download rate vs attainable

[#1]

Hi All,

I have a Draytek Vigor 166. Although it's been connected reliably (over 35 days), I can see my actual download and upload speeds differ by a large margin to the attainable rates. Anyone know the reason for the difference?

Before my last modem broke down I was getting consistently better download speeds than I am right now (70Mbps vs around 60Mbps now) so I wonder if this is the DLM being fussy now?

  ---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
   Running Mode            :      17A       State                : SHOWTIME
   DS Actual Rate          : 62470000 bps   US Actual Rate       : 19996000 bps
   DS Attainable Rate      : 76166225 bps   US Attainable Rate   : 28973000 bps
   DS Path Mode            :        Fast    US Path Mode         :        Fast 
   DS Interleave Depth     :        8       US Interleave Depth  :        1 
   NE Current Attenuation  :       16 dB    Cur SNR Margin       :        6  dB
   DS actual PSD           :    13. 1 dB    US actual PSD        :     6. 8  dB
   NE CRC Count            :      239       FE CRC Count         :     3427
   NE ES Count             :        0       FE  ES Count         :        0
   Xdsl Reset Times        :        0       Xdsl Link  Times     :        6
   ITU Version[0]          : 00000000       ITU Version[1]       : 00000000
   VDSL Firmware Version   : 12-3-2-3-0-5   [with Vectoring support] 
   Power Management Mode   : DSL_G997_PMS_L0 
   Test Mode               : DISABLE 
   nBandPlan               :        0 
  -------------------------------- ATU-C Info ---------------------------------
   Far Current Attenuation :        0 dB    Far SNR Margin       :       17  dB
   CO ITU Version[0]       : b5004244       CO ITU Version[1]    : 434da4a1
   DSLAM CHIPSET VENDOR    : < BDCM >

[#2]

@ally153 Can you post a screenshot of the 'Additional Diagnostic' - found after running https://speedtest.btwholesale.com/

[#3]

[#4]

Thanks for that - so your Plusnet profile is set to 71.05Mbps, and won't be the cause of restrictions, so something else is the cause.

Sorry for asking for more detail, but as your modem/router does not make it easy to find the information, one other (maybe) helpful report is:https://www.broadbandchecker.btwholesale.com/#/ADSL -obscure your phone number, though.

[#5]

It's fine, I appreciate the help

[#6]

OK - that tells us the speed to your test socket was ~ 65 (a week ago), but I have just noticed on the router details that your D/S SNR looks a little high - how far are are you from the green cabinet?

[#7]

I noticed the SNR margin had changed in my modem stats recently, which ties into what you're saying - not sure why the change happened. I'm less than 500m from the green cabinet.

Based from other forum posts from others that have Draytek devices, it looked to me that their actual & attainable speeds were very similar, which is in part what triggered me to post - I'm getting around about a 15Mbps gap between the two figures, so I assume this isn't the norm.

[#8]

What was the SNR margin previously? - to be honest, I may be misreading that as 'high' because I still tend to think in 'ADSL-mode'  - I understand from other more experienced members that a 'high' D/S SNR actually indicate you have more 'headroom', or leeway for errors &c.. A quick calculation says you should be seeing a speed of 63-65, based on the reported profile, do something is slightly awry. Unfortunately, I totally self-taught in this, and still learning - even after quite a long time.

[#9]

@ally153   It is your sync speed you should be comparing things to, not attainable - you are not getting your attainable speeds.

Your speed test is about right for your sync speed.

[#10]

@Mustrum I would have thought the sync should be a little higher, given the profile?

[#11]

@jab1  yes John, agreed, alas it is not. The BTW dsl checker also suggests it should be better, so back to basics, line noise, modem in the test socket, try another modem/router. Looking to see if attainable increases as I imagine the line may now be banded.

[#12]

Agree with your 'back to basics', @Mustrum , although looking at those results it doesn't - to me - appear banded.

[#13]

Thanks both of you for the input - I understand that the attainable rate doesn't tell me what I'm actually going to achieve in the real world - what I'm saying is they are miles apart.

I did the back to basics a month ago, I think that contributed in part with my issues - my SNR & d/l speeds suffered the more I swapped routers around, swapped cables, tried the test port etc. Think the DLM saw all the fiddling as a progressively worse connection. My hope was that leaving the connection alone would let the line recover. I could go the back to basics approach again - it has been 35 days, just been trying to avoid messing with my connection when I can.

I've heard the term banding before but what does it mean and when does it happen?

[#14]

@ally153 To answer your last question first: 'banding' is essentially a way of the DLM artificially restricting your speed to maintain stability - so it is possible that is what has happened, although the figures above don't actually suggest that - to me.

Having left it alone for over a month, I would expect DLM to progressively adjust things upwards - which doesn't appear to have happened, and unfortunately, on an FTTC connection, something PN can't do a lot to influence.

When did you last check the phone line for possible noise, as that could have a bearing on the situation?

[#15 · Accepted solution]

Cheers John, I figured you meant something like that.. Not had a chance to do much exploring tonight, but I did a quick power-reset on my modem - SNR margin looks better - also the actual & attainable rates are far more closely matched...

Will need to check later if the connection is behaving as well as the below suggests.

  ---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
   Running Mode            :      17A       State                : SHOWTIME
   DS Actual Rate          : 73078000 bps   US Actual Rate       : 19996000 bps
   DS Attainable Rate      : 77083990 bps   US Attainable Rate   : 30545000 bps
   DS Path Mode            :        Fast    US Path Mode         :        Fast 
   DS Interleave Depth     :        8       US Interleave Depth  :        1 
   NE Current Attenuation  :       14 dB    Cur SNR Margin       :        3  dB
   DS actual PSD           :    13. 0 dB    US actual PSD        :     6. 4  dB
   NE CRC Count            :        0       FE CRC Count         :        1
   NE ES Count             :        0       FE  ES Count         :        0
   Xdsl Reset Times        :        0       Xdsl Link  Times     :        1
   ITU Version[0]          : fe004452       ITU Version[1]       : 41590000
   VDSL Firmware Version   : 12-3-2-3-0-5   [with Vectoring support] 
   Power Management Mode   : DSL_G997_PMS_L0 
   Test Mode               : DISABLE 
   nBandPlan               :        0 
  -------------------------------- ATU-C Info ---------------------------------
   Far Current Attenuation :        0 dB    Far SNR Margin       :       15  dB
   CO ITU Version[0]       : b5004244       CO ITU Version[1]    : 434da4a1
   DSLAM CHIPSET VENDOR    : < BDCM >