Kitz Forum
Broadband Related => FTTC and FTTP Issues => Topic started by: cbdeakin on December 10, 2019, 03:27:30 PM
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I noticed that when downloading files, my speed drops down to about nearly half, from ~50mbps down to ~27mbps. This generally only happens every 1-2 minutes (usually) for a few seconds, but sometimes the speed drops multiple times.
Is this likely to be caused by the homeplugs in my home? There's one connected to the router and several others around the house. The homeplug next to the router has VDSL - powerline avoidance mode on (I forget the exact name), which limits it to SISO speeds.
I noticed that when I enable bandwidth control on my router and select DSL for the connection type, it limites the speed to about 40mbps, but the speed is fairly constant (between 42-38mbps). If I choose VDSL instead, the max download speed is higher, but it drops every couple of minutes.
Does selecting the DSL connection type somehow limit the FTTC connection to DSL frequencies only? And therefore, avoid the well known problems between powerline and VDSL?
Does this speed dropping sound familiar to anyone with homeplugs?
Is it possible to prevent the homeplug frequencies from interfering with VDSL?
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Router & modem downstairs in master socket, homeplug 600Mbps plugged in to same 6-gang extension lead as HG612 modem and ZyXEL VMG1312-B10D, homeplug 600Mbps upstairs in office (on different ring main) to 1gbps switch, PC plugged in to switch. Also two 200Mbps homeplugs linked to 600MBps homeplugs.
Recent speed test result from PC:
(https://www.thinkbroadband.com/_assets/speedtest/button/1575291574820754955.png) (https://www.thinkbroadband.com/speedtest/results.html?test=1575291574820754955)
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And you should be getting close to 80mbps, correct? The latency seems a little high too, but maybe thats unrelated.
Does the switch have any effect at all?
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The homeplugs do affect the latency (directly wired to the router it's well below 20), but that's the only issue I actually see.
I've used a switch for years and never seen any effect - I did upgrade from 100Mbps to 1Gbps when I got VDSL.
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And you should be getting close to 80mbps, correct? The latency seems a little high too, but maybe thats unrelated.
Does the switch have any effect at all?
what type of vdsl filter do you have, dangly microfilter or master socket nte5 mk type?
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Yes. Get rid of them.
Prepare to install Cat6 cable instead...
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I noticed that when downloading files, my speed drops down to about nearly half, from ~50mbps down to ~27mbps. This generally only happens every 1-2 minutes (usually) for a few seconds, but sometimes the speed drops multiple times.
So just to be clear, is it the case that your data throughput drops temporarily, rather than a reduction your dsl sync rate?
One possibility then would be that it is a problem with the source from which you are downloading, unable to provide the data as fast as your broadband connection is allowing you to consume it.
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I have experienced dropped VDSL connections while using home plugs. ADSL was unaffected, same Huawei modem used for both, same router.
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I'm considering just using EE 4G with a router instead.
Presumably, a 4G router would be unaffected by homeplugs / powerline?
I might even be able to get higher speeds than VDSL where I live, since the sync rates are limited by the shittyness of ECI VDSL cabinets, lack of G.INP and distance from the cab.
I doubt I would be able to persuade my family to stop using homeplugs, even though they get disconnections every day or so (I've been using Wi-FI instead).
My dad might be willing to install ethernet cabling by drilling some holes around the home, but this will have to wait a few months.
It would be ideal if I could confirm this problem is caused by powerline interference. Does anyone know of a way of to monitor the VDSL signal in realtime and check for interference?
Or, is there a reliable way to filter out any powerline noise from the VDSL signal?
Note - The VDSL connection does not drop. The download speed falls every couple of minutes by a varying amount, I've been tested it by downloading 1gb files from here:
https://www.thinkbroadband.com/download
It has been happening more consistently today and it still happens when I use bandwidth control to limit bandwidth to other PCs in the LAN. Also, if I limit download bandwidth on my own PC to 10 / 20mbps, the same drop in throughput occurs.
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There's a guy here (link - https://community.virginmedia.com/t5/Networking-and-WiFi/TP-Link-PA9020P-ethernet-powerline-kit-speed-REDUCED-when-I/td-p/3768109/page/7)
who had his Virgin Media internet speed cut from 350mbps to 170mbps when using homeplugs. He somehow fixed it by using an Archer C9 router in between his homeplug and Virgin modem.
The chipset the Archer C9 uses is: Broadcom BCM4709. I wonder if there is something different about this chipset that prevents or blocks interference?
This seems odd to me as a 350mbps connection would use DOCSIS / hybrid fibre rather than VDSL (please correct me if I'm wrong). Maybe powerline adapters overlap with these frequencies also?
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I'm considering just using EE 4G with a router instead.
Presumably, a 4G router would be unaffected by homeplugs / powerline?
If you think the speed dropping from the homeplugs is bad, don't even think about going 4G.
VDSL is infinitely more reliable than 4G unless you are very very fortunate in your area. Latency is never going to be as good either, even with a perfect 4G signal.
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Could the drop in download speed be related to varying SNR margin (caused by powerline interferance)? I noticed that it often drops from 6.1 to 6.0 during downloads. It drops at other times to but I need to monitor more to see by how much.
If the problem is related to SNR or SNR margin, I wonder if setting the SNR margin higher could help? I think there are modems that allow this.
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You may just be observing perfectly normal flow control that kicks in transiently during transfer of large amounts of data.
Is the elapsed time for the downloads of these large files broadly consistent with your DSL connection speed? Or alternatively, does the TBB speed test roughly match up to expectations?
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I noticed that the Downstream and Upstream Max Rate often changes a small amount every few seconds too.
The SNR margin also varies when the line is idle. Also, the SNR remains at 6.1 (downloading via WI-FI or not) on the modem at night when the homeplugs are presumably idle.
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The SNRM fluctuates up and down all day long.
It can go up/down 0.1dB multiple times a minute.
Such small variations are of no concern.
Same goes for the max attainable rate.
My homeplugs didn't affect my SNRM at all but they sent my FEC rate through the roof.
I always advise against their use.
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I see a lot of Upstream packet errors (> 4 billion) after the router is reset. Sometimes it happens throughout the day too. If I reset the intergrated modem only, the error counter usually shows 0 upstream and downstream errors.
I wonder if this is related to homeplugs interfering with the VDSL frequencies?
Is there really no way to weaken or block the interference? What about connecting each homeplug to an extension lead or surge protector with a low pass filter?
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If we convert that error counter to hex, 4294967294 becomes FFFFFFFE.
That’s far too interesting a bit pattern to be a count of the actual number of errors. I’d therefor suggest it might just be a quirk of the software that is displaying it, and that it certainly does not mean there’s been 4 billion upstream errors. :)
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Homeplugs triggered banding on an old VDSL line of mine.
Anything other than the most basic ones are big noise generators for VDSL.
Check the options on it. Might have a mode specifically avoiding the VDSL frequencies - the ones I was using did. Came at the expense of a bunch of performance, though.
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Thanks. I will check the frequencies on the older homeplugs, they seemed to work well enough for Internet use in my house if I recall correctly. Do you mean HomePlug AV 200mbps? Or do you mean older models than that (non AV homeplugs)?
I tried the PLC - VDSL frequency interference avoidance mode but it didn't resolve the issue. AFAIK, all this does it set the homeplug to work in SISO mode.
I also tried connecting the AV 1200 mbps homeplug next to my router to a surge protector with an RFI filter inbuilt. EDIT - I'm still getting brief throughput drops of upto 60% on the downstream, which is consistant with performance drops studied in academic technical reports.
I wish there was a way to restrict / choose what frequencies they operate on.
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The VDSL frequency avoidance is broken, then.
The whole point of the functionality is, as it says, for them to not transmit on VDSL frequencies.
Is it possible perhaps to get the homeplugs a few metres away from the VDSL modem and cables by putting them in a distant socket and connecting via an Ethernet cable?
Should help.
https://forum.kitz.co.uk/index.php/topic,18651.0.html
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I also tried connecting the AV 1200 mbps homeplug next to my router to a surge protector with an RFI filter inbuilt.
What about connecting each homeplug to an extension lead or surge protector with a low pass filter?
If you mean you connected the homeplugs to the mains through a mains extension with surge protection or low pass filter then that could be the cause of any problems you are experiencing as it will most likely cause errors in the comms between home plugs. Home plugs need clear and uninhibited connection to the mains in order to work.
Tbh, whilst home plugs do sometimes/often cause problems, nothing you have said in this thread convinces me that they are causing a problem on this occasion.
I’m still not clear what is actually worrying you. An occasional blip in network activity, during data transfer, does not in itself prove there is a problem with the DSL connection, providing overall data throughput is as expected. Your connection appears stable, your SNR margin sounds stable, and the only error counter you have posted is clearly not an actual error counter (see reply #16).
I don’t think you’ve yet posted the results of an actual speed test, such as TBB?
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From my limited dealing with HomePlugs of various makes have always found that they won't work through any form of surge protector/filter adaptor, always had to connect directly to the ring main.
May have been just my particular combination of HomePlug's/Filter-Surge Protector's ?
Early days, I have used HomePlugs when on ADSL-2 service and after migration to VDSL-2, perhaps I've been lucky but never had any issues with noise as monitored by RouterStats & DSLStats.
Currently don't use any HomePlugs as I've had the time to run quite an extensive, hard wired LAN system, not too difficult in a timber framed bungalow, obviously this is the way to go if at all possible and will always be superior to HomePlugs or Wi-Fi.
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The VDSL frequency avoidance is broken, then.
The whole point of the functionality is, as it says, for them to not transmit on VDSL frequencies.
Is it possible perhaps to get the homeplugs a few metres away from the VDSL modem and cables by putting them in a distant socket and connecting via an Ethernet cable?
Should help.
https://forum.kitz.co.uk/index.php/topic,18651.0.html
Good advice, thanks. I recently asked my dad if I could move the homeplug to another socket but he's quite concerned about the aesthetics of the hall, where the master socket is located. I could try this on a temporary basis to see if it fixes the problem, as it's very easy to test.
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If you mean you connected the homeplugs to the mains through a mains extension with surge protection or low pass filter then that could be the cause of any problems you are experiencing as it will most likely cause errors in the comms between home plugs. Home plugs need clear and uninhibited connection to the mains in order to work.
I only added a surge protector recently as a test. Before, the homeplug was plugged directly into a power socket. It doesn't seem to have effected the performance, as far as I can tell it has made no difference.
Basically, I need to connection to remain stable at around 40mbps or higher. Newer streaming services like Google Stadia can use upto this amount and suffer if there are drops in bandwidth.
Here's an example of the issue while downloading a game via the Epic Game Launcher (the throughput is dropping approx. the same amount as test file downloads on thinkbroadband.com) :
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Problems caused by home plugs would be reflected in DSL error counters and probably dips in SNRM or, if extreme, in DSL connection drops.
In my experience a blip in a throughput graph is not necessarily indicative of a problem, providing that overall throughput remains adequate.
Blips may of course imply errors and retransmissions but they can also be caused by normal flow control procedures applied by the protocols, or if some other activity is competing with the file download for network bandwidth, or if some other activity is competing for disk or CPU access within the destination PC. If you’re using WiFi for the test then that’s another thing that might cause throughput blips.
Remember too that, depending on sampling rate, the graph may make the blips look worse than they are. Streaming services usually employ buffering that will survive blips, as long as they are short.
I’m not defending home plugs, they have a terrible reputation and I’m sure it’s justified. But in your case, if eliminating the home plugs is a big upheaval then I’m not yet convinced that doing so would eliminate these blips.
You did say earlier that you were getting disconnections every day or so. Is it worth expanding on that, as it might be more indicative of a DSL problem?
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Tbh, whilst home plugs do sometimes/often cause problems, nothing you have said in this thread convinces me that they are causing a problem on this occasion.
+1
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IF the homeplugs were messing up the VDSL I think you'd be seeing far more issues than the occasional blip in download throughput.
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The homeplugs don't transmit at the same power all the time. They go into lower power mode when traffic is minimal and increase power and, hence, bitrate, throughput and interference level, when they need to.
Bursts of errors when connection is under load, manifesting as throughput drops, would be an indicator of these issues.
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The homeplugs don't transmit at the same power all the time. They go into lower power mode when traffic is minimal and increase power and, hence, bitrate, throughput and interference level, when they need to.
Bursts of errors when connection is under load, manifesting as throughput drops, would be an indicator of these issues.
Yes but when maintaining a large file download of constant data rate for duration of a few minutes or more, if interference were occurring, I’d expect to see a corresponding dip in SNRM, for roughly the duration of the download.
It’s a while since I looked at DSL protocols but isn’t the SNRM that is shown by the router calculated by an algorithm comparing current BER with some reference BER (that reference being regarded as zero margin)? If so, it’s hard to see how BER could increase without SNRM dropping.
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I've just tried downloading the 1GB test file from TBB and monitoring the stats while it was in progress. The download was running at over 8MBps (around 65Mbps), during the down load there were a couple of brief drops of SNRM from 6.6 to 6.5, but I see similar drops when not downloading. My homeplug is within 2ft of the HG612 modem.
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Yes but when maintaining a large file download of constant data rate for duration of a few minutes or more, if interference were occurring, I’d expect to see a corresponding dip in SNRM, for roughly the duration of the download.
It’s a while since I looked at DSL protocols but isn’t the SNRM that is shown by the router calculated by an algorithm comparing current BER with some reference BER (that reference being regarded as zero margin)? If so, it’s hard to see how BER could increase without SNRM dropping.
I can't say I've seen comments here about how SNRM held up, though if it were only certain frequencies being impacted you're at the mercy of how it's being calculated.
You mentioned flow control earlier. A properly working TCP connection should not show abrupt drops in throughput once ramped up given modern TCP stacks.
The throughput should show a tiny sawtooth effect that is imperceptible. A big drop indicates congestion control kicking in - a different issue and one indicative of a possible fault.
Packet loss would trigger congestion control, not flow control.
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Since the frequencies used overlap, how exactly do VDSL2 and powerline frequencies co-exist without dropping connections entirely? Do they operate on different channels??
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All your neighbours with FTTC/VDSL2 are also using those exact same frequencies.
As are radio stations across the country.
They all simply create additional noise.
I used 2 different types of Homeplugs for about a year with a Youview box upstairs while running DSLStats at the same time.
They only ever had an effect when data was being transmitted.
They had no impact on SNRM.
They sent FEC numbers through the roof.
They caused no disconnections and no ES.
My brother had a set of TP-Link AV1000's and had a very different experience.
They frequently caused his line to drop sync, resulting in banding.
When in use they sent ES numbers through the roof.
I've seen so many cases of these being an issue with VDSL that I strongly recommend people either use wi-fi extenders or run proper Ethernet wiring around the home.
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I can't say I've seen comments here about how SNRM held up, though if it were only certain frequencies being impacted you're at the mercy of how it's being calculated.
You mentioned flow control earlier. A properly working TCP connection should not show abrupt drops in throughput once ramped up given modern TCP stacks.
The throughput should show a tiny sawtooth effect that is imperceptible. A big drop indicates congestion control kicking in - a different issue and one indicative of a possible fault.
Packet loss would trigger congestion control, not flow control.
Congestion control is about avoiding flooding the network with data it won’t be able to handle, not necessarioy related to DSL error rates.
Flow control occurs when the receiver is unable to accept the data at the rate it is being presented. If for example, the receiver simply unplugs a local ethernet cable, then the incoming data will be buffered up to a point but when the buffers are full, flow control will kick in to tell the sender to stop transmitting, and the connection will fall silent.
Error recovery is a different process to either of these, but can also cause a glitch. That’s the scenario that would be attributable to home plug interference.
@cbdeakin, I think you said you are running this test over WiFi. Have you tried to negotiate an agreeable time with other occupants to temporarily disconnect all home plugs, and run the same test in those circumstances?
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For me simple answer. Never had a problem. However my VDSL frequencies are very limited due AL cable. Only get D1 and limited U2.
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I've just done another 1GB download monitoring errors - and there was indeed a significant increase:
CRC per sample shot up from 0 to 1
FEC errors rocketed up to 8 per minute
N.B. DSLstats and the download both running on the same PC over the tplink 600Mbps homeplugs.
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According to this post on Reddit:
https://www.reddit.com/r/HomeNetworking/comments/9wjm2v/vdsl_settings_on_devolo_powerline_adapters/
Devolo dLAN 1200 Powerline adapters have a few VDSL coexistence modes, such as "VDSL Profile 17a", "VSDL Profile 35b" and "SISO mode".
I'm thinking that the 'VDSL Profile 17a' option would probably prevent a powerline adapter from using VDSL2 profile 17a spectrum (~0 - 17.6MHz), used in the UK.
Has anyone tried these settings, found in the Develo Cockpit software? Did it help with your VDSL throughput / performance?
Also, which Develo Powerline adapter models have these option available? Or are you aware of an alternative powerline adapter with a similar feature?
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Flow control occurs when the receiver is unable to accept the data at the rate it is being presented. If for example, the receiver simply unplugs a local ethernet cable, then the incoming data will be buffered up to a point but when the buffers are full, flow control will kick in to tell the sender to stop transmitting, and the connection will fall silent.
Nope. In TCP, which was the context, flow control is end to end. Issues with intermediate network nodes would trigger congestion control.
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Nope. In TCP, which was the context, flow control is end to end. Issues with intermediate network nodes would trigger congestion control.
In a word, ‘nonsense’.
Edit, apols, not nonsense. It was late. :)
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In a word, ‘nonsense’.
You're confusing Ethernet flow control, pause frames under congestion conditions, with the layer 4 sliding window flow control of TCP, which has to be done between endpoints of the flow as they're the ones involved in window exchange.
Entirely different things, same name.
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Apols, in the case of pulling an ethernet cable, it is congestion control that kicks in. My example of pulling an ethernet cable was the wrong example. :-[
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Phew. Given I work with this stuff on a daily basis I was worried for a minute there. Handing my notice in out of shame over Christmas didn't appeal! :lol:
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Embarrassing thing is, I wrote protocol stacks for a living once upon a time. I think mine worked alright at the time, honest. ::)
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According to this post on Reddit:
https://www.reddit.com/r/HomeNetworking/comments/9wjm2v/vdsl_settings_on_devolo_powerline_adapters/
Devolo dLAN 1200 Powerline adapters have a few VDSL coexistence modes, such as "VDSL Profile 17a", "VSDL Profile 35b" and "SISO mode".
I'm thinking that the 'VDSL Profile 17a' option would probably prevent a powerline adapter from using VDSL2 profile 17a spectrum (~0 - 17.6MHz), used in the UK.
Has anyone tried these settings, found in the Develo Cockpit software? Did it help with your VDSL throughput / performance?
Also, which Develo Powerline adapter models have these option available? Or are you aware of an alternative powerline adapter with a similar feature?
Any thoughts about this? Is this likely to fix (avoid) interference caused by powerlines to VDSL?
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It might help.
Surely cheaper to hard wire with cat6 or use quality WiFi extenders than buying expensive Devolo Powerline adapters.
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I'm wondering if just 1 develo homeplug set to '17a profile' would work next to the router + BT master socket, or if I would need to replace all of them. As you say, replacing all of them wouldn't be cheap, and I think my family are mostly ok with the homeplugs we have (but they get fed up with occasional disconnections).
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Just start running some cables in dude... it is the best way forward.
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What is the best way sideways though :D
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I'd be inclined to say crabby :P
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I did some tweaking to my WIFI, such as setting to 20mhz, enabling LDPC (error correction) and Cyclic Delay Diversity (on the router) and that stabalised downloads on Epic game store at 49-52 mbps, but only when homeplugs upstairs are turned off. I think the performance is a lot better with multi connection downloads too ( I don't think most downloads are).
I still get some drops with multi threaded downloads when all homeplugs are on, but its not that bad.
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Its possible depending on your wiring and the homeplugs used there will be no impact. However I dont suggest using them. Choose between ethernet or wifi, modern wifi standards should be fast enough now days.
My sister had a ADSL2+ line which was god like, and it was synced at something like 4meg, when the homeplugs were unplugged it synced at the full speed and a tiny fraction of errors.
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Yes, they absolutely destroyed my FTTC line.
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I thought I'd add my observations based on using various Devolo powerline adapters.
With ADSL2+, no major impact of Devolo adapters on such lines.
VDSL2:
- Devolo dLAN 1200 (HomePlug AV2 standard) - major impact on the quality of the line, resulting in errors and potential disconnections, regardless of SISO/MIMO profiles (17a)
- Devolo Magic 1 (g.hn standard) - no impact on the quality of the line, plus there's an option of integration with Fritzboxes via the TR064 protocol (impact tested *without* integration). The newer g.hn standard stops powerline adapters from using overlapping frequencies, especially if there's interference, and also to use higher frequencies. As far as I know, there's a limited number of routers that can offer this integration with Devolo plugs.
- Devolo Magic 2 and Mesh WiFi, i.e. the plugs that use the new g.hn standard can do that.
The following resources may help forum members in case they encounter problems. Please note that every set up is different and you may be in a fortunate position not to have any impact of dLAN 1200 on your VDSL line because of the way your set up works:
https://www.devolo.de/ratgeber/vdsl-dim
https://www.devolo.co.uk/about-devolo/press/en-devolo-optimises-the-interaction-between-vdsl-and-powerline-communication
https://www.allnet.de/en/allnet-brand/produkte/pointopoint/ghn-lan-over-2-wire-and-coaxial/
https://homegridforum.org/wp-content/uploads/2018/09/hKg8.pdf