topic Re: Dodgy connection in Broadband

Dodgy connection

Fat_Leonard — Tue, 01 Mar 2022 23:58:36 GMT

I would be glad if someone could run a line test and let me know if there's a problem.

Download has gone from a norm of 3.5-4Mbps to <0.5Mbps and latency has become huge. A route trace shows <1ms to the router, but up to >1s for the next steps, and packet loss.

Nothing has moved inside the house. We use the only socket which is the test socket. Historical issues have been caused by wet joints on the poles down the valley, so I can imagine the recent wind and rain could have caused problems on the long journey back to the cabinet a mile or so away!

Taken just before posting this message:

My thanks for any help!

Re: Dodgy connection

jab1 — Wed, 02 Mar 2022 07:40:32 GMT

@Fat_Leonard Looking at those stats, I would go straight down the 'Report a Fault' route - https://faults.plus.net .

Re: Dodgy connection

Townman — Wed, 02 Mar 2022 09:05:39 GMT

Have you used a telephone handset to do a quiet line test - dial 17070?

Re: Dodgy connection

Fat_Leonard — Wed, 02 Mar 2022 10:58:50 GMT

Thank you both. Like an idiot I'd neglected the Quiet Line test. I'm now raising a fault (if the page loads!) as there was whirring and crackling on the QL.

Re: Dodgy connection

Fat_Leonard — Wed, 02 Mar 2022 11:41:47 GMT

Curiouser and curiouser. After running the 'phone troubleshooter' to report noise on the line, with broadband at a crawl, the troubleshooter timed out. This was expected as the router had lost connection and the troubleshooter warned of the possibility of line problems during the test.

It's just come back, and a speedtest shows a ping of 40ms and 3.71/0.8 Mbps down/up! I don't see how a line problem fixes itself...

Re: Dodgy connection

adamwalker — Wed, 02 Mar 2022 12:27:38 GMT

Hi @Fat_Leonard

I'm really sorry about the connection problems you're having. I've just been running some line tests on this side and we're not seeing signs of any obvious issues.

The fault ticket you raised had closed for some reason so I've re-opened that just now and have added an update advising of what we can do next: https://www.plus.net/wizard/?p=view_question&id=222453021

Re: Dodgy connection

Fat_Leonard — Wed, 02 Mar 2022 12:36:43 GMT

Thank you very much. I guess the timeout from the dropped connection interrupted the fault reporting process. It's tough when one's only means of reporting a fault is via the faulty object!

Current router status report is attached. The SNR margin and errors are somewhat out of whack compared to what I'm used to seeing but speedtest still reports ~35ms ping and >3.5Mbps download which is excellent!

Re: Dodgy connection

Townman — Wed, 02 Mar 2022 16:11:56 GMT

The act of testing a line can “fix” some issues (especially wet joints) for a short time. If that is what happened … it needs a proper fix which will be BT boots on the ground.

Re: Dodgy connection

Fat_Leonard — Wed, 09 Mar 2022 18:50:57 GMT

The connection has been OK since my last message, except for a dropout this evening. After rebooting from the router's admin webpages, this is the status since reconnection.

Re: Dodgy connection

Townman — Wed, 09 Mar 2022 22:38:19 GMT

Yup you’ve got a problem Huston!

That line looks banded - is there noise on the line?

Re: Dodgy connection

Fat_Leonard — Thu, 10 Mar 2022 00:16:06 GMT

I did a Quietline test during the Internet dropout and heard nothing. This evening playing games has been frustrated by fluctuating ping, often staying strangely stable at >300ms.

I understand automatic banding can be applied if the connection drops, perhaps that's what has happened. I'll consult the fault ticket.

Re: Dodgy connection

Gandalf — Thu, 10 Mar 2022 09:35:11 GMT

Hi there,

I'm really sorry to see you're still having issues.

I've also run a line test which isn't showing the cause for the problem, and your line's not banded, but I can see that the SNRM target has shot up to 12dB, which can generally cause latency issues, so I've brought it back down to 6dB.

I suspect we'll need to arrange an Openreach engineer visit to take a closer look, but from looking at the fault ticket, I believe you're looking at trying another router first which may be a good idea. I'll keep an eye on the ticket for you.

Let me know how it goes.

Re: Dodgy connection

Townman — Thu, 10 Mar 2022 10:43:05 GMT

Is the difference between being banded and having an elevated target SNRM semantics or expressly technical … but has the same consequence - a restricted speed?

Re: Dodgy connection

Gandalf — Thu, 10 Mar 2022 13:38:30 GMT

I think a bit of both.

Banding does raise the SNRM target, but if a line is chronically banded then it won't be removed by itself.

Re: Dodgy connection

Townman — Thu, 10 Mar 2022 14:29:14 GMT

Not sure if edification of confusion is emerging here.

Your comment suggests two different methods might be used to attempt to keep a line stable

Elevate the target SNRM (in 3dB increments) - and allow the sync speed to be whatever is attainable at resync
Band (constrain) the sync speed - and allow the SNRM to be whatever it is
1. non-chronic - if conditions improve the DLM will self adjust
2. chronic - banding remains in place until the ISP takes action - BT boots on the ground or a SNRM reset

Seems a tad confusing that an elevated SNRM is not "banding" but chronic banding needs a SNRM reset ... hence the question semantics or a real technical difference?

Colloquially a line with a stuck elevated target SNRM is effectively (chronically) speed banded as it is not going to go faster until the cause of the elevated SNRM is fixed (or just removed by a reset).

Re: Dodgy connection

Gandalf — Thu, 10 Mar 2022 17:10:45 GMT

Yeah the outcome to both are basically the same. Just different ways of achieving the same result.

Re: Dodgy connection

Fat_Leonard — Mon, 14 Mar 2022 17:59:08 GMT

Ahoy,

The latest news is that the connection had no change with the new router (a normal Plusnet one, unused before) so the connection still seemed OK, though I had the occasional reported in-game spike of >400ms, and once to 980ms. Mostly it was <100ms though, which is pretty normal when the connection is working well. Download speeds were reported as up to 5Mbps, which is about as good as it gets down here.

However, the router doesn't supply the same level of connection data as our TP-Link VR2800. After a total dropout yesterday I reconnected the TP-Link instead of rebooting the Plusnet router and have now got the following connection statistics since the TP-Link connected.

Re: Dodgy connection

bmc — Mon, 14 Mar 2022 18:41:26 GMT

@Fat_Leonard

Have you checked recently in case OpenReach have done any upgrades without letting locals know.

https://www.broadbandchecker.btwholesale.com/#/ADSL

Brian

Re: Dodgy connection

Gandalf — Tue, 15 Mar 2022 09:39:45 GMT

Ahoy matey!

Stats looking a lot better! Let's see if it holds like that.

Keep us posted on how it goes.

Re: Dodgy connection

Anywho — Fri, 18 Mar 2022 12:10:59 GMT

TL;DR - Lookup bufferbloat! "High SNRM can increase latency"? what? how?

Game lag spikes can be caused by other people using the internet - even web browsing can have a huge impact these days.

It's called bufferbloat (your buffers are full of traffic so the gaming packets get delayed in a queue).

Identifying this as the issue is as easy as ensuring the gaming device is the only device connected (preferably by wire/ethernet) and it is only running the game (no updates in background) and seeing if you still get lag spikes.

There are several tests that you can run that can give an indication of bufferbloat. The speedtest at DSL Reports is quite popular or even Fast.com (with settings).

One way to fix bufferbloat would be to open up your Plusnet Hub One (Homehub 5a) and install OpenWrt on it (https://openwrt.org/toh/bt/homehub_v5a) and then install SQM.

There are various other, less invasive/risky methods that could alleviate the problem... restricting bandwidth (up and down) on all individual devices, having a dedicated Wireless AP (with restricted internet bandwidth)... basically anything that reduces the buffering of data should help (the biggest bottleneck is usually the lowest bandwidth ie the modem in the upstream direction - interestingly, the amount of upstream bandwidth used just to acknowledge receipt of all of the downstream data received can use up a large percentage of the available upstream bandwidth - so, actually if you reduce your download speeds you may have more available upstream bandwidth).

Restricting downstream bandwidth usage from the modem side is a non-trivial task (the data received that puts you over your limit has already been sent [and there is even more on the line waiting to get to you!!] and used more bandwidth than you wanted!)

I'm just an enthusiast, I don't have all the answers and I am thoroughly confused how a high SNRM can increase latency (accept in large sustained downloads - obviously a download will take longer if the bandwidth is reduced by the high SNRM... but this is not what I would call latency) and interested to learn what @Gandalf meant by this?

But these issues plagued my household too. I fixed it with SQM.

Gaming usually only uses a very small amount of bandwidth (I'm talking 100-200 Kb/s [yes, kilobits] down... often less up) - but it is time sensitive... catchup TV using adaptive bitrate streaming algorithms will totally swamp your connection and make gaming impossible if you dont employ a proper QoS/queue management strategy.

Just giving your gaming PC highest priority for bandwidth in your standard router QoS settings is not a proper strategy and will not work if the high priority packets are just queued waiting to be processed/routed in a buffer; most routers will default to the FIFO queue strategy for traffic.

Routers with Active Queue Management can make priority routing work (they use the Linux traffic control [tc] function to shape the traffic). They will properly hold lower priority packets in a queue whilst letting higher priority packets (and often any small packets) through.

You can usually create your own classful qdiscs/schedulers and apply priority shaping on any router that allows access to the CLI - but it is not well documented functionality and can be tricky to get your head around. It is usually lost on router reset requiring it to be reapplied.