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Message 1 of 31

FEC / CRC Errors & DLM

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Hi all, I'm not currently a BT customer myself but family members are and I've posted on their behalf previously.  I've decided to post on here because the audience is greater than my ISP's forum and I feel I've a better chance of getting responses. Mods: please feel free to move the thread if I've posted in the wrong section.

 

Anyway, I took out Vodafone Fibre 38 last month and my minimum speed guarantee was 37Mb. The people in the flat below me have BT Infinity and get 55mb+ speeds. The distance to the fibre cabinet is less than 200m. So for the 1st day my sync speed was 40/10 and my actual speeds reflected this. After 24 hours the DLM kicked in and dropped me down to about 28/7. It also put interleaving on high and my pings were in the 30s, also spiking to 100ms+ frequently. After having several Openreach engineers out fixing various line faults, the DLM was reset yesterday and I'm back up to 40/9.9 with interleaving on low.

 

I've had a look at the router stats and the error counters after just 14 hours of uptime (since the engineer left) are as follows:

Indicator name Downstream Upstream
FEC Corrections1966337113
CRC Error1472818

 

Before the line faults were fixed, the upstream FEC corrections would shoot up into the billions within a few hours, however the CRC errors are a lot higher now than they were previously - despite the high FEC corrections the upstream CRC errors were about 300 per day. The figures are increasing steadily and weren't clocked up in one go when the router was reset.

 

What I would like to know is are these figures acceptable and are they going to cause DLM to reduce the speed again and/or put interleaving back on high? As far as I can tell the connection seems fine but I'm worried about the high number of these errors, particularly on the upstream and I won't be happy if DLM throttles my speed again.

 

Thanks in advance.

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Message 2 of 31

Re: FEC / CRC Errors & DLM

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Was the router rebooted while the eng. was there or just resynced?

 

The downstream errors look low. Upstream errors are usually insignificant.

 

Have a look @ Kitz: Stats - Errors .

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Message 3 of 31

Re: FEC / CRC Errors & DLM

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Thanks for your reply, the router was rebooted just before the engineer left, but the errors have been clocking up gradually since then. Upstream CRC errors have increased by around 35% since posting this thread. I'm not too concerned about them currently, especially as the BQM looks a lot better than before, but I'm worried that the DLM is about to throttle the speeds back down and increase interleaving.

 

The page you linked to explains "many CRC errors in a short period of time will show a noticeable reduction in throughput speed" but doesn't specify just how many errors in a specific timeframe would be considered problematic, unless I'm missing something?

 

Here are my router stats @ 16hrs uptime if that's helpful. From my research it appears the line attenuation is quite high for the relatively short distance to the cabinet.

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Message 4 of 31

Re: FEC / CRC Errors & DLM

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You are getting the top of Voda Fibre 38, 40/10 Meg. The NMs seem low for a line hitting its caps, possibly as it is near its max capability.

 

What does BT Broadband Availability Checker estimate for your phone number? Post just the whole table and the line above it, blanking out your phone number. If it doesn't recognise your phone number, use the Address Checker, not the Postcode Checker.

 

I never heard anyone give a quantitative measure of error rates but have heard it said that up to 1M FECs Down per day is bearable. I just go by Error Seconds (ES), which you don't have, using my own rule-of-thumb of 1 ES every 3 mins. on Interleaved is OK.

 

It's surprising that you have high errors on Up as being slower than Down this is not usually so much exercised.

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Message 5 of 31

Re: FEC / CRC Errors & DLM

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Hi again, thanks for your reply!

 

Unfortunately over the weekend the speeds have deteriorated again as I feared they would. I'm now syncing at 31.0/8.7 with interleaving on high. It'll probably drop to around 28/7 next week. Here are the router stats for the last 24hrs uptime - the FECs are increasing by around 10,000 every second and, as requested, here's the BT Broadband Availability Checker table. As the handback threshold is 35Mb for the downstream (last engineer said this figure was 27Mb, was he lying?), will my ISP be able to get another engineer out if necessary?

 

Really getting fed up with this now, no-one at Openreach seems to be concerned despite all my neighbours getting 50Mb+ speeds.

 

Any ideas?

 

Thanks again

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Message 6 of 31

Re: FEC / CRC Errors & DLM

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You don't have a contract with OR; it's with Voda. Go back to Voda & complain they are not meeting their minimum speed guarantee of 37 Meg. 

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Message 7 of 31

Re: FEC / CRC Errors & DLM

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Thanks, I know it's the ISP who deals with OR but I was just making the point that when the engineers come out they don't seem bothered that everyone else on the street is getting significantly better speeds than I am.

 

Voda did actually give me the option of leaving, but I assume I'm going to have the same issues whoever I go with (no VM cable here) and I do believe that it's not beyond the realms of possibility to get similar speeds to the neighbours in the downstairs flat that use the same telephone lines from the same cabinets & exchange. In fairness to Voda, they have little control over what OR do or don't do to fix a fault and so it's OR I'm unhappy with for not taking this seriously.

 

I'll update this thread with a final outcome whenever that may be.

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Message 8 of 31

Re: FEC / CRC Errors & DLM

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What does the BT Checker give for your neighbours' addys? Maybe it's faster than yours for some reason we don't know. Are they on the same cab?

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Message 9 of 31

Re: FEC / CRC Errors & DLM

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Don't know their landline telephone number but yes, they're definitely on the same cab and their telephone line comes from the same telegraph pole as mine. Come to think of it, no-one's checked the connections at the pole, though it is covered by an overgrown tree.

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Message 10 of 31

Re: FEC / CRC Errors & DLM

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No, I mean by using the Address Checker (don't use the Postcode Checker).

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