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[leonroy]

I have a G.Fast connection with Zen Internet. I get 300Mbps down and approx 47 Mbps up.

It has an odd problem where the upload speed gets slower and slower until it hits about 0.5Mbps whereupon I power cycle the modem and it goes back up again. Download speeds seems to be totally unaffected.

It does this both with a Huawei MT992 modem and with a Draytek Vigor 166 modem.

Stats look like so currently after a power cycle:

Code: [Select]

DrayTek> vdsl status
  --------------------------- ATU-R Info (hw: annex A, f/w: annex X) -----------
   Running Mode            :   G.fast       State                : SHOWTIME
   DS Actual Rate          :329582000 bps   US Actual Rate       : 49926000 bps
   DS Attainable Rate      :457798000 bps   US Attainable Rate   : 85988000 bps
   DS Path Mode            :        Fast    US Path Mode         :        Fast
   DS Interleave Depth     :        0       US Interleave Depth  :        0
   NE Current Attenuation  :      127 dB    Cur SNR Margin       :        9  dB
   DS actual PSD           :     0. 0 dB    US actual PSD        :    -1.-1  dB
   NE Rcvd Cells           :        0       NE Xmitted Cells     :        0
   NE CRC Count            :        0       FE CRC Count         :        0
   NE ES Count             :        0       FE  ES Count         :        0
   Xdsl Reset Times        :        0       Xdsl Link  Times     :        1
   ITU Version[0]          : fe004452       ITU Version[1]       : 41590000
   ADSL Firmware Version   : 12-3-2-3-0-5
   Power Management Mode   : DSL_G997_PMS_L0
   Test Mode               : DISABLE
  -------------------------------- ATU-C Info ---------------------------------
   Far Current Attenuation :      127 dB    Far SNR Margin       :       13  dB
   CO ITU Version[0]       : b5004244       CO ITU Version[1]    : 434dc190
   DSLAM CHIPSET VENDOR    : < BDCM >

I'm running the latest 4.2.3 firmware on the Draytek. Any suggestions on what might be causing the slowdown to upload speeds?

[re0]

Just to confirm, is it the upstream sync. rate or the upload (throughput) speed that is affected?

Could you post the full stats of when it happens again if it is the sync rate?

[kitz]

The thing that immediately springs to mind with the symptoms as described is bit-swap not working correctly.   But I think that if same happens on both the Huawei and Draytek modems, then that rules that out.    On reflection re0 raises a valid point, as if it also happens using the Openreach supplied Huawei without any stats, then it could be throughput as opposed to sync.

G.Fast is supposed to use SRA.  So will lower sync speed on the fly, but tends to need a full resync to get any increase in speed.