Mysterious slipping 40Mbps VDSL speeds

jonathanj

Member
Joined
Jul 20, 2015
Messages
14
Backstory
About 13 months ago I got 40Mbps VDSL, synced at 40Mbps, got 40Mbps speeds on speedtest (well ~38Mbps, but that's probably what one should expect), good SNR margins, practically never lost sync and all that good stuff.

About two weeks ago I noticed my speeds were really bad, speedtest said about 12Mbps but the line said it was syncing at 40Mbps. After messing around with my ISP to no avail, I tried changing the ethernet cable between my VDSL router and my PC and speeds roughly doubled to about 24Mbps. Good improvement but still a far cry from the 40Mbps I'm paying for (to Telkom and my ISP) and what the VDSL router is syncing at.

The last few days the sync has been intermittent and the sync speed has been slipping (40 -> 38 -> 36 -> 32), Telkom technicians say there's no detectable fault on the line, I've tried replacing the filter (with a spare one I had) but it didn't make a difference. There are 2 phone points in the house, one of which has two ports on it but I only have 2 filters plugged in.

Huh?
What is going on? :confused: Why after 13 months of a problem-free line do I suddenly have sync problems and slipping line speeds that Telkom technicians claim are not a result of the line? There have been zero changes to my setup for this time (apart from replacing the ethernet cable). The line at my previous place also did this, crept from 4Mbps to 1.5Mbps for apparently no reason. Unfortunately I don't have a spare VDSL router to try.

I'd really appreciate any suggestions or advice.

Stats from ZyXEL VMG1312-B10A:

Code:
============================================================================
    VDSL Training Status:   Showtime
                    Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a
            Traffic Type:   PTM Mode
             Link Uptime:   0 day: 0 hour: 20 minutes
============================================================================
       VDSL Port Details       Upstream         Downstream
               Line Rate:      3.124 Mbps       32.859 Mbps
    Actual Net Data Rate:      3.072 Mbps       32.763 Mbps
          Trellis Coding:         ON                ON
              SNR Margin:       18.1 dB           10.6 dB
            Actual Delay:          8 ms             16 ms
          Transmit Power:        5.7 dBm          14.5 dBm
           Receive Power:      -11.6 dBm          -3.9 dBm
              Actual INP:        4.0 symbols       7.0 symbols
       Total Attenuation:       17.3 dB           18.5 dB
Attainable Net Data Rate:      8.844 Mbps       51.026 Mbps
============================================================================
      VDSL Band Status    U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  6.6    47.1     N/A     N/A    17.7    47.9    74.9   
Signal Attenuation(dB):  6.6    47.2     N/A     N/A    17.5    47.7     N/A   
        SNR Margin(dB): 19.1    18.0     N/A     N/A    10.6    10.8     N/A   
   Transmit Power(dBm):- 5.1     5.3     N/A     N/A    13.5     7.8     N/A   
============================================================================
 

Sinbad

Honorary Master
Joined
Jun 5, 2006
Messages
77,440
Looks like, based on attainable rates, assia is making you its lil biyatch.
 

jonathanj

Member
Joined
Jul 20, 2015
Messages
14
Looks like, based on attainable rates, assia is making you its lil biyatch.

I just did some searching and reading about ASSIA on this forum, seems these are textbook ASSIA symptoms. Is the only way to get this resolved to beg Telkom to put me on an ASSIA exclusion list? :(
 

cavedog

Honorary Master
Joined
Oct 19, 2007
Messages
19,601
Have the same problem with my 40Mbps line. My limit is distance. 38.6Mbps max for 6.5dB SNR downstream. ASSIA kept on reducing it until it reached 30Mbps with 11dB SNR downstream.

Telkom forced it back but a week later same story.

I just downgraded it back to 20Mbps because it does not look like you can beat that thing.
 

Thor

Honorary Master
Joined
Jun 5, 2014
Messages
42,831
Give me the low down on this k@k thing.

Why is it forced on us, can't we be excluded by ASSIa
 

krustyrsa

Senior Member
Joined
Oct 16, 2015
Messages
626
Give me the low down on this k@k thing.

Why is it forced on us, can't we be excluded by ASSIa

Some have been added to the exclusion list, like myself. But it took nearly 3 months of fighting, You need valid proof that ASSIA is causing issues on your line, ASSIA kept dropping my speed on a daily basis and I had proof of it, TelkomZA aka Charl who is unfortunately not running the forum any more, helped me to be added to the list. More and more people will start complaining, MSAN's already installed will received new software updates with ASSIA ,telkom is rolling out new MSAN's 10 to 20 weekly . Those people will be added to ASSIA automatically..90% of all drops are fault related, the techs just don't pick it up, because not all of them know exactly how ASSIA works..Only tech support can see whats actually happening on your line, so you have to keep reporting it.
 

steel_dog

Senior Member
Joined
Jul 5, 2010
Messages
769
...because not all of them know exactly how ASSIA works..Only tech support can see whats actually happening on your line, so you have to keep reporting it.
... and Tech Support were in TOTAL denial. :(
My perfect 20mbps VDSL line in CPT was cruising at 20mbps down Local and 18mbps down from the US. Then following an exchange upgrade the freeking wheels fell off. I spent MONTHS trying to convince all involved that 4mbps down from the US... WAS.NOT.NORMAL!!!! Telkom disagreed and shared that 4mbps to 5mbps was all they got from their pipe in the PTA office. Yupppp...
At the end of the hundreds of burnt airtime minutes, tens of hours of proving the issue from my end, an inordinate number of hours fiddling and faffing from the other parties... the line... thankfully stabilized. It didn't get back to the performance prior to the "upgrade", however 4mbps improved to 16mbps (for some Intl. sites). Well this was until two weeks ago when I've been hit by mega latency issues from Hop 3. Others on Afrihost have been reporting the same.

So about getting on the ASSIA exclusion list... are you referring to being put onto FastPath? My line's still being managed by ASSIA - interleave depth is in the 700's.
 
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