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Author Topic: PCP Change - 20% Drop in FTTC Speed  (Read 676 times)

art37

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PCP Change - 20% Drop in FTTC Speed
« on: March 01, 2017, 12:40:43 PM »

I would be grateful for some advice. My FTTC line has been 100% stable at 85 Max down and 24 up for the past 2 years on an 80/20 profile. Over the past couple of months, BTOR has been installing a second PCP box. Last Friday, I walked past the site and three guys were working in the 2 PCP boxes and on an underground cable. When I got home, I found that my FTTC had suffered a brief disconnect and it was showing a DSL carrier but no internet connection. I walked back to the PCP and one of the guys offered to take a look. Twenty minurtes later, I got a call to say that he had reversed a jumper and everything should be OK. Yes and no - I got the internet connection back but at a max speed of 68Mbps with a downstream SNR of 4 and lots of errors.

This morning, I powered down my Fritz!Box. The FTTC speed has fallen to 66 but the downstream SNR has increased to 6. I have called Zen and they have run quote an invasive line test unquote and everything tests OK. They now want me to do the usual test from the Test Socket. I have 'no' for the moment as I have no reason to suspect that anything is wrong with my in house set up.

I am hoping now that the SNR has downstream increased to 6 that the profile will recover in  time. My connection is currently showing 66581/18507, Latency FAST/FAST, G.INP OFF, INP OFF, SNR 6/6, Bitswap ON/ON and Line Attenuation 13/13.

The error rate is beginning to fall. After 3 hours it is showing:

Fritz!Box      22ES 0 Many Errors(SES), CRC 0.12/min Last 15 Mins 1
Central Exc   14ES 10 Many Errors(SES), CRC 0.31/min  Last 15 Mins 0

Is there anything else that I should be doing/checking other than being patient?

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art37

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Re: PCP Change - 20% Drop in FTTC Speed
« Reply #1 on: March 14, 2017, 02:35:29 PM »

Update:

The change of PCP seems to have been completed. Since 1 March, my router log shows 44 disconnections/re-synchs: no further loss of synchronisation since the work was completed last Friday. I think that the contractors got rather fed up of people complaining about the loss of their broadband. They put it down to aluminium in the old PCP.

Not surprisingly, DLM has kicked in and I am now on a profile with max speeds of 67.4 down and 23.3 up (Profile 67.3/20). The max attainable downstream speed is still 20% below what my line was achieving a month ago (held steady for over 3 years). More worryingly, 10 days ago, my line started showing considerable packet loss on the TBB QM.

I confess that I am not sure how significant it is? No matter what I do in terms of turning things off, nothing changes.

[Moderator edited to fix the broken link.]

Further Update:

Thanks for fixing the broken link.

Well after 3 weeks of issues, I see that Zen has moved my line to their GEA backhaul overnight. DLM has been removed, and whilst my max attainable speed is still down by about 5Mbps, i am now on a 77/23 profile. Downstream SNR is 6 and Upstream 10. My BQM is still showing 40% packet loss and some single thread speed issues. It is a now a question of seeing how things settle down.
« Last Edit: March 15, 2017, 10:00:10 AM by art37 »
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Chrysalis

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Re: PCP Change - 20% Drop in FTTC Speed
« Reply #2 on: March 16, 2017, 11:16:34 PM »

there is no 77mbit profile, you may be confusing sync speed with profile's.

My speculation is at the moment with the new PCP installation they may have moved some cross tie connections around which effectively is reentering the crosstalk lottery and you may have lost out.

The packet loss report as a fault, clearly shouldnt be happening, but of course you should rule out the fritz box first as the fritz box "does" rate limit icmp by default. When I used my firztbox it caused packetloss on tbb ping tests until I adjusted the settings.
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art37

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Re: PCP Change - 20% Drop in FTTC Speed
« Reply #3 on: March 17, 2017, 10:08:34 AM »

there is no 77mbit profile, you may be confusing sync speed with profile's.

My speculation is at the moment with the new PCP installation they may have moved some cross tie connections around which effectively is reentering the crosstalk lottery and you may have lost out.

The packet loss report as a fault, clearly shouldnt be happening, but of course you should rule out the fritz box first as the fritz box "does" rate limit icmp by default. When I used my firztbox it caused packetloss on tbb ping tests until I adjusted the settings.


My current stats are:

                                                       Receive Direction             Send Direction
Max. DSLAM throughput   kbit/s   80000                             20000
Min. DSLAM throughput   kbit/s   128                                    128
Attainable throughput   kbit/s           77961                            25796
Current throughput   kbit/s           77961                            20000
Seamless rate adaptation             off                                    off
          
Latency      fast   fast
Impulse Noise Protection (INP)      0   0
G.INP      off   off
          
Signal-to-noise ratio   dB   5   9
Bitswap      on   on
Line attenuation   dB   13   12
          
Profile   17a      
G.Vector      off   off
          
Carrier record      A43   A43

Which settings did you adjust on the Fritz!Box to stop packet loss on BQM? It just appeared a couple of weeks ago: about two weeks after I installed firmware 6.80.

When I first set up my Fritz!Box 7390 on FTTC, I was getting 105Mbps max attainable downstream; how times have changed.
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Chrysalis

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Re: PCP Change - 20% Drop in FTTC Speed
« Reply #4 on: March 18, 2017, 12:42:05 AM »

Sorry I cannot remember the exact placing of it as I last used my fritzbox years ago, but its most likely to be in the firewall settings somewhere.

The stats you posted confirm you still on a open 80/20 profile.
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art37

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Re: PCP Change - 20% Drop in FTTC Speed
« Reply #5 on: March 19, 2017, 09:20:33 AM »

Sorry I cannot remember the exact placing of it as I last used my fritzbox years ago, but its most likely to be in the firewall settings somewhere.

The stats you posted confirm you still on a open 80/20 profile.

Thanks. Any idea how long an open profile will last on a GEA line?  I thought that it was only 2 days on WMBC? I have now been on my GEA line for 4 1/2 days.
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Chrysalis

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Re: PCP Change - 20% Drop in FTTC Speed
« Reply #6 on: March 19, 2017, 09:57:56 AM »

It will last forever if the line is stable.
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Sky Fiber Pro - Billion 8800NL bridge & PFSense BOX running PFSense 2.4 - ECI Cab

art37

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Re: PCP Change - 20% Drop in FTTC Speed
« Reply #7 on: March 19, 2017, 10:30:29 AM »

It will last forever if the line is stable.

Thanks - I didn't know that. My line is now very stable now that BTOR's guys have stopped grabbing handfuls of old wiring to find a particular line.
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