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Distinguished Sage
Distinguished Sage
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Message 21 of 31

Re: FEC / CRC Errors & DLM

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@grantanyan

This is a BT Retail forum and has nothing to do with Vodaphone fibre, who have their own parameters.

Their forum is here https://forum.vodafone.co.uk/t5/Community/ct-p/vodafoneeforum

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Distinguished Sage
Distinguished Sage
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Message 22 of 31

Re: FEC / CRC Errors & DLM

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From the OPs first post.

"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."

As this is a BT Retail forum only, and Vodaphone use their own parameters, the information should be on the Vodaphone forum.

https://forum.vodafone.co.uk/t5/Community/ct-p/vodafoneeforum

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Beginner
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Message 23 of 31

Re: FEC / CRC Errors & DLM

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It seems that A, you're not reading the original post properly and understanding why the OP shared here in the first place, or B, you're being deliberately obtuse. I think I've made it clear that I'm suggesting the provider may be completely irrelevant in this case, and that this could be just as apt (and helpful) for BT Broadband users.
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Guru
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Message 24 of 31

Re: FEC / CRC Errors & DLM

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@grantanyanwrote:
It seems that A, you're not reading the original post properly and understanding why the OP shared here in the first place, or B, you're being deliberately obtuse. I think I've made it clear that I'm suggesting the provider may be completely irrelevant in this case, and that this could be just as apt (and helpful) for BT Broadband users.
Well, not really wanting to take sides, nor swing either way .... but Keith has a valid point. The way that Vodaphone run their fibre technology has little to bear on how BT run theirs ... apart from the basic concept of the transmission. Policy will be different, as will line and connection parameters, usage distribution and probably to some degree the type of equipment and line protocols used .... notwithstanding error correction handling and network balancing. Example, very few people actually realise their home line voltage drops below 230volts during peak usage ... neither do they complain, nor even know. What Keith is really saying is to get to that level of detail you require, it's no good to quote a problem with one supplier, and expect any real value to be conceded in the forums of another. It's a bit like asking the guard on an underground train in London, why the East Coast Mainline is seeing stoppages and lateness. 🙂
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Message 25 of 31

Re: FEC / CRC Errors & DLM

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The OP gave the title of their post as 'FEC / CRC Errors & DLM'. They elaborated, questioning whether there was a potential link between those reported errors, and a lower than expected sync speed.

I am suggesting that homeplugs may well be the cause of this pattern of errors. I saw a near identical pattern of numerous FEC errors (particularly excessive for uplink), with a bump in CRCs too, and can safely attribute this pattern to homeplugAV devices which were causing noise to travel back up in to the Openreach network, resulting in DLM kicking in. For me, within minutes of disconnecting them, the errors subsided. And, within a day or two sync speed was back up again. FWIW, my parents have (admittedly older) BT fibre equipment, and they saw a similar pattern when my brother gave them a couple of BT homeplugAV devices.

If you look into it, you'll find plenty more evidence, but not a great deal on the actual figures. These have been reported for many providers of VDSL, including BT. Apparently it's to do with the VDSL and homepglugAV common frequencies which, unfortunately for consumers, crossover. From my understanding, neither of these are provider (or their hardware) dependent. It is said that interference is caused by signals jumping from the electrical wiring (generated by the homeplug transmissions) to the phone wiring, particularly along longer parallel stretches.

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Message 26 of 31

Re: FEC / CRC Errors & DLM

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It's an interesting point about the homeplugs ... as you mention. I can't pretend to have that much knowledge at the scientific level to concur ... other than to say I use them myself on my cctv. Interestingly, I have one particular homeplug that is used for 2 cameras some forty yards from the house, and it has regular problems staying synced up with the other five I have connected to my home network. It's paired by code to the one next to my router, and that acts as a central to the others. Having said all that, it doesn't impact in any way on my routers broadband error correction at all, why would it, it's on the LAN side and not the WAN side ... where DLM would/could get involved. But to summarise, I don't discount homeplugs can cause problems ... but I'd doubt they impact upon the actions of DLM on the WAN side of the router. 

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Message 27 of 31

Re: FEC / CRC Errors & DLM

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FWIW, the issue is massively improved through the use of a properly filtered master socket, which much more effectively isolated the noise. I suffer from both an old master socket, and very unfortunate location of the socket itself, which is in the cupboard under the stairs and with no access to power, forcing the use of an extension socket elsewhere. I can only go by the numbers though: FEC upload errors in the hundreds of thousands within a couple of hours, as soon as the homeplugs were in use and transmitting data. When unplugged, the errors were completely non-existent. I tried it 2 or 3 times to be sure, over the course of a few weeks, so there was an undeniable link.

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Distinguished Sage
Distinguished Sage
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Message 28 of 31

Re: FEC / CRC Errors & DLM

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@RogerB wrote:

@grantanyanwrote:
It seems that A, you're not reading the original post properly and understanding why the OP shared here in the first place, or B, you're being deliberately obtuse. I think I've made it clear that I'm suggesting the provider may be completely irrelevant in this case, and that this could be just as apt (and helpful) for BT Broadband users.
Well, not really wanting to take sides, nor swing either way .... but Keith has a valid point. The way that Vodaphone run their fibre technology has little to bear on how BT run theirs ... apart from the basic concept of the transmission. Policy will be different, as will line and connection parameters, usage distribution and probably to some degree the type of equipment and line protocols used .... notwithstanding error correction handling and network balancing. Example, very few people actually realise their home line voltage drops below 230volts during peak usage ... neither do they complain, nor even know. What Keith is really saying is to get to that level of detail you require, it's no good to quote a problem with one supplier, and expect any real value to be conceded in the forums of another. It's a bit like asking the guard on an underground train in London, why the East Coast Mainline is seeing stoppages and lateness. 🙂

All ISPs (except Virgin) use the same DSLAM equipment in the green cabinet. There are only 3 different DLM profiles that can be set Speed, Standard or Stable.

Most ISPs use either speed or standard, BT uses speed, Vodafone uses standard. I.e BT lines will be more impacted by DLM taking action on errors than Vodafone.

Sorry to disagree Keith, but I think @grantanyan has a valid point.

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Beginner
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Message 29 of 31

Re: FEC / CRC Errors & DLM

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To add: I suppose the DLM might kick in as a result of the homeplug interference eventually causing the router to reboot/re-establish the link, which the DLM would see as regular disconnects / unrealiable line.

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Aspiring Contributor
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Message 30 of 31

Re: FEC / CRC Errors & DLM

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Just to update on this thread, I had exhausted all options with Vodafone by May of this year and switched to Plusnet. Apparently the high FEC errors on the upstream are a known issue with their routers affecting some customers. I do not use powerline adaptors/homeplugs and the router was connected to a brand new master socket. What was consistent about the errors is they would always stop for a few hours if I rebooted the router. They sent out two replacement routers which made no difference. In the end they decided it was a REIN issue in my property (seriously?) and they washed their hands. This is despite me switching off every device in my flat apart from the router, and still seeing the FECs in the billions.

Later a new problem had developed - high peak time latency, speed drops and packet loss between 7 & 10pm. This was reflected on a Thinkbroadband BQM which was mostly solid blocks of green & red during these hours. Vodafone made no effort to resolve the fault and refused to acknowledge their was one, other than the mysterious REIN issue in my property. After putting up with this new issue for two months, I switched.

The result? A constant sync speed of 40/10 (current uptime 3 weeks+ compared to only a couple of days with Vodafone) and a max attainable rate of 48/12 if I was on a higher tier.  Peak time contention issues went away immediately. I've had zero problems since. So my conclusion is that Vodafone are an awful ISP, their routers are flaky and their backhaul network is over capacity. The only other thing to note is that my Plusnet router syncs with a 4dB SNRm on the downstream as opposed to the Vodafone router which would always have a 6dB target, however I don't think this is the only reason for the dramatic increase in sync speed. Even with the lower SNRm the connection is evidently more stable reflected in the uptime.

To the poster(s) who moved this thread to The Lounge and marked a random post as a solution, I do feel that is quite petty and unecessary. I explained clearly my reasons for posting on this forum in my original post, the Vodafone forum is not nearly as populated and well established as this one, and the moderators had ample opportunity to move this thread at the time. And to the person who compared this to "asking the guard on an underground train in London, why the East Coast Mainline is seeing stoppages and lateness" that is ridiculous.

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