topic Re: Severe Latency Issue in Broadband

Severe Latency Issue

silkster365 — Fri, 07 Aug 2026 09:40:04 GMT

Hi all,

I'm hoping someone can help me diagnose a problem that has appeared recently on my Plusnet FTTC connection. I've been with Plusnet for around five months and, until recently, the connection has been fine.

My normal download speed is only around 16–17Mbps because of my location, but that has always been the case and isn't really the problem. The issue is that web browsing has recently become very slow/intermittent, with pages sometimes hanging before loading.

I started testing latency to 1.1.1.1 and initially got some horrendous results. One 30-ping test averaged 728ms, with a maximum of 1018ms and some packet loss. Another averaged 897ms, reaching 1154ms.

Rebooting the Plusnet Hub Two initially restored the connection to around 12–15ms, but after roughly 10 minutes the very high latency returned.

I initially suspected my mesh Wi-Fi system. I therefore completely unplugged the mesh and connected directly to the Plusnet Hub. Ping to the Hub itself (192.168.1.254) is excellent: 1–4ms, 2ms average, 0% loss, so the local Wi-Fi connection to the Hub appears fine.

With the mesh completely disconnected, idle internet latency is also excellent at around 11–13ms. However, I've established that latency rises dramatically as soon as the internet connection is under load.

During a speed test, the download portion raises the ping from ~12ms to around 60–70ms. As soon as the upload test starts, it goes to 815ms, 1071ms and then request timeouts. I've also seen ordinary web browsing produce shorter spikes into the 200–470ms range.

This behaviour is definitely reproducible with the mesh system completely unplugged, so whatever is happening is not simply a mesh/Wi-Fi fault.

The Hub Two DSL statistics currently show:

Data rate: 3.085Mbps up / 18Mbps down
Maximum data rate: 3.085Mbps up / 19.392Mbps down
Noise margin: 6.0 / 7.3dB
Line attenuation: 11.2 / 27.1dB
Signal attenuation: 11.2 / 34.0dB

Speed tests normally give about 16–17Mbps download and somewhere between 0–2Mbps upload.

I realise that saturating a relatively small ~3Mbps upstream can cause bufferbloat, and the upload speed test itself is deliberately saturating the connection. What concerns me is that this has only become a noticeable problem recently after approximately five months of normal use, and even relatively ordinary activity can now sometimes cause substantial latency spikes.

One potentially relevant factor is that Openreach have recently been carrying out extensive FTTP installation work throughout the surrounding area. Our property is on a private lane and isn't currently getting FTTP, so we are still using the existing FTTC/copper service. I don't know whether work in nearby cabinets, chambers or ducts could have disturbed the existing copper line, but the timing made me wonder.

I'd particularly appreciate it if somebody could advise whether the 3.085Mbps upstream sync/maximum attainable rate looks reasonable for this line, and ideally whether Plusnet staff can check my historical upstream sync rates to see whether this has recently fallen.

I'm also interested in whether these results point more towards a line/DLM/profile problem, a Hub Two problem, severe bufferbloat that has always existed but is now being triggered more often, or possibly a physical copper-line issue following the recent Openreach work.

I've already submitted the issue to Plusnet, but I'd be grateful for any interpretation of the stats or suggestions for further tests. I'm happy to provide additional DSL information or run specific tests if useful.

Thanks.

Re: Severe Latency Issue

jab1 — Fri, 07 Aug 2026 09:55:05 GMT

@silkster365 Your D/S SNR looks a little high for your reported attenuation.

Does the the event log give any clues - DSL drops, or suchlike?

Re: Severe Latency Issue

silkster365 — Fri, 07 Aug 2026 11:06:15 GMT

Thanks John. I've attached/checked the WAN event log. The only explicit DSL Link Down / ERROR_NO_CARRIER entries I can see are from 27 Feb and 1 Mar; I don't appear to have had repeated DSL drops recently. Historical sync also seems quite consistent — upstream was generally 3200kbps in March, 3158 on 18 Jun, 3106 on 25 Jun, 3200 on 16 Jul, 2917 yesterday and 3085 this morning. Downstream has consistently been ~18000kbps. Downstream SNR was actually around 9.6–9.9dB in March and is 7.3dB now. Does that change your view of the SNR/attenuation figures?

Re: Severe Latency Issue

jab1 — Fri, 07 Aug 2026 11:13:21 GMT

@silkster365 Thanks for that event log. It concerns me a little that there are no corresponding 'DSL Down' entries, but I'm no networking expert.

Maybe @Dan_the_Van will have some thoughts?

Re: Severe Latency Issue

Dan_the_Van — Fri, 07 Aug 2026 12:17:57 GMT

@jab1

It concerns me a little that there are no corresponding 'DSL Down' entries

You only get the DSL Link down messages written to the event log if the router is powered on.

A restart or power off of the router does not record that event as the DSL Link wasn't down at that point.

Looking at the event log, which has had a category filtered applied so not All event are present.

@silkster365

Yes having a slow upload speed isn't really helpful for the modern world of the internet, devices with cloud saves/backups taking up the upload bandwidth.

The mesh system you have does it have a router mode with QoS/SQM settings? You could set the Hub Two to 'bridge mode' which makes it a modem only device, then you'll be able to take advantage of router functions.

Re: Severe Latency Issue

ExForce9 — Fri, 07 Aug 2026 12:30:02 GMT

@silkster365 wrote:

I'm hoping someone can help me diagnose a problem ...

Sigh !, where to start ?

@silkster365 wrote:

.... a problem that has appeared recently on my Plusnet FTTC connection

Are you -

really still on FTTC with a landline phone ?
on FTTC but without a phone attached ?
or upgraded to SoGEA (FTTC with the phone service deactivated) ?

How is your Plusnet router plugged into the BT landline ?

Is it plugged in to the BT master socket, or a via BT extension socket ?
Does the master socket have a DSL filtered faceplate, or is it a single phone socket with a dangly external DSL filter ?
Does you house have ANY phone extension wiring ?
How long is the cable between the phone socket and your router ?

@silkster365 wrote:

I've been with Plusnet for around five months and, until recently, the connection has been fine.

My normal download speed is only around 16–17Mbps because of my location, but that has always been the case and isn't really the problem. The issue is that web browsing has recently become very slow/intermittent, with pages sometimes hanging before loading.

Have you recently changed your mobile phone, or added a new device to your network, that is now doing cloud data backups ?

Apple iPhones and iPads are notorious for causing this type of issue, as they are designed expect the connection to not bufferbloat, and will grab as much bandwidth as possible to give the illusion of better performance (compared to Android alternatives).

Do you have something on your network that otherwise does a lot of uploading, such as CCTV cameras, or video sharing ?.

@silkster365 wrote:

I started testing latency to 1.1.1.1 and initially got some horrendous results. One 30-ping test averaged 728ms, with a maximum of 1018ms and some packet loss. Another averaged 897ms, reaching 1154ms.

Rebooting the Plusnet Hub Two initially restored the connection to around 12–15ms, but after roughly 10 minutes the very high latency returned.

That is typical Plusnet Hub Two behaviour, on a slow upload speed connection like yours, when something on your network is uploading continuously.

@silkster365 wrote:

With the mesh completely disconnected, idle internet latency is also excellent at around 11–13ms. However, I've established that latency rises dramatically as soon as the internet connection is under load.

What is the exact model of mesh system you have ?

Are you -

Using the Plusnet hub as a modem+router, and the mesh acting as wireless access points
Have you got the Plusnet hub in 'bridged VDSL modem' mode, and have the mesh in 'router' mode ?

I'm thinking as the Plusnet hub two doesn't have any anti-bufferbloat settings, that if your mesh supports 'router mode', then many mesh systems do have anti-bufferbloat settings - so you might be able to solve your problem by reconfiguring your mesh if it has some form of SQM, QoS, rate limiting, CAKE, fq_codel, etc.

@silkster365 wrote:

The Hub Two DSL statistics currently show:

Data rate: 3.085Mbps up / 18Mbps down
Maximum data rate: 3.085Mbps up / 19.392Mbps down
Noise margin: 6.0 / 7.3dB
Line attenuation: 11.2 / 27.1dB
Signal attenuation: 11.2 / 34.0dB

Speed tests normally give about 16–17Mbps download and somewhere between 0–2Mbps upload.

Those stats look OK for a long line.

Your FIRST move is to do EVERYTHING you can to optimise your home's internal phone wiring, get the router as close as possible to the master socket, and if necessary have the router's DSL port connected to the hidden 'TEST' socket behind the master socket faceplate. Minimising any noise or interference on your broadband connection, should improve your sync speeds, and reduce the bufferbloat.

@silkster365 wrote:

I realise that saturating a relatively small ~3Mbps upstream can cause bufferbloat, and the upload speed test itself is deliberately saturating the connection.

Yes, the Plusnet Hub Two often has this problem at those speeds.

Do you happen to have any other broadband routers (from previous broadband contracts) available to experiment with ?

@silkster365 wrote:

One potentially relevant factor is that Openreach have recently been carrying out extensive FTTP installation work throughout the surrounding area. ... ... I don't know whether work in nearby cabinets, chambers or ducts could have disturbed the existing copper line, but the timing made me wonder.

Maybe, but unlikely. If anything if the other customers in the surrounding area are moving from VDSL to full fibre, then the electrical crosstalk on your line should reduce (as their lines go quiet), and therefore your line should become less noisy and potentially faster.

@silkster365 wrote:

Our property is on a private lane and isn't currently getting FTTP, so we are still using the existing FTTC/copper service.

Have you checked whether you are in the connection area of any AltNet (non-Openreach) full fibre providers ?

If you let us know your postcode, then I could do a search for you to see if you have better options.

@silkster365 wrote:

I'd particularly appreciate it if somebody could advise whether the 3.085Mbps upstream sync/maximum attainable rate looks reasonable for this line

If you go to the BT Broadband Availability Checker , then enter your phone number or one of the other options, and get to the results table and explanatory text. Take a screenshot from the top of the purple table to the bottom of the screen but EXCLUDING your phone number or address at the top. Then post that image back to this forum topic.

@silkster365 wrote:

I'm also interested in whether these results point more towards a line/DLM/profile problem, a Hub Two problem, severe bufferbloat that has always existed but is now being triggered more often, or possibly a physical copper-line issue following the recent Openreach work.

Based on the information so far, something recently on your network has increased the background upload traffic, and has tipped the Plusnet Hub Two (which is particularly susceptible to this) to bufferbloat.

@silkster365 wrote:

I've already submitted the issue to Plusnet,

Well good luck with that, I've never seen any response from Plusnet front line support that indicates they understand what bufferbloat is or how to cure it, particularly since they removed traffic prioritisation in June 2017.

Plusnet Removes Broadband Internet Traffic Prioritisation

Going forwards -

Upgrade to full fibre if an AltNet network is available to you
otherwise, optimise your wiring around the BT master socket to give your VDSL modem the best connection
check whether your mesh can be configured to rate limit it's WAN connection to overcome bufferbloat
if there is still a problem, consider buying a 'gaming' router that supports some form of anti-bufferbloat SQM, QoS

Re: Severe Latency Issue

silkster365 — Fri, 07 Aug 2026 12:55:47 GMT

Thanks, this is useful.

I've run the BT Wholesale checker and attached the screenshot. It shows:

VDSL Range A: 20–30.8Mbps down / 3.8–5.6Mbps up
VDSL Range B: 17.8–30.2Mbps down / 3.6–5.5Mbps up

My Hub is currently synced at 18Mbps down / 3.085Mbps up, so downstream is close to the bottom of the impacted range and upstream is actually below the 3.6Mbps bottom estimate.

On the wiring side, the Hub Two is immediately next to the BT master socket with only the short DSL lead between them. The master socket itself was replaced with a brand new one by an engineer around 12 months ago. There isn't a long internal cable run between the master socket and router.

I'll check whether there is any remaining extension wiring connected to the master socket and can test from the hidden test socket if that would still be worthwhile.

The mesh is a TP-Link Deco AC1300 system. The Plusnet Hub Two is currently operating as modem/router and the Deco is explicitly set to Access Point mode, so QoS/routing on the Deco is currently disabled. I have not put the Hub into bridge mode.

I don't have CCTV cameras or any other device that I know to be continually uploading. Nothing significant has deliberately been added to the network recently, although I'll investigate cloud backups/sync in case something has changed without me realising.

One other potentially useful point is that the ~3Mbps upstream isn't completely new. Looking through the WAN event log, historical upstream sync has generally been around 3.1–3.2Mbps for several months. What is new is the severe latency/browsing problem.

FTTP unfortunately isn't a realistic option at present. We live on an unadopted/private road and the permissions required for Openreach to bring FTTP along it cannot currently be obtained. The BT checker also confirms FTTP is unavailable at the property.

Given the Wholesale estimate has a 3.6Mbps minimum even for an impacted VDSL line, does the current 3.085Mbps upstream suggest there is still some value in investigating the DSL side before I start reconfiguring the Deco/Hub for rate limiting?

If we do conclude it's predominantly Hub Two bufferbloat, I'd also be interested in what upstream cap you'd recommend starting with on this ~3Mbps connection.

Re: Severe Latency Issue

ExForce9 — Fri, 07 Aug 2026 14:30:51 GMT

@silkster365 wrote:

I'll check whether there is any remaining extension wiring connected to the master socket

Yes, that is a good start and easy to do.

You didn't answer the question, whether you still have a landline home phone plugged in ?

@silkster365 wrote:

... can test from the hidden test socket if that would still be worthwhile.

You might as well test it, because if the speed improves in the TEST socket, then you'll know there is something to fix.

@silkster365 wrote:

FTTP unfortunately isn't a realistic option at present. We live on an unadopted/private road and the permissions required for Openreach to bring FTTP along it cannot currently be obtained.

If you can't get permission for Openreach then it is also unlikely that you could get permission for an AltNet network to install new cables.

Have you investigated "FIXED WIRELESS" broadband (which is different to mobile data), as that can often provide higher speeds than you are getting now, and because it is wireless won't involve permissions for installing infrastructure along the public highway !

If you want to PM me your postcode, I can check for what fixed wireless is in your area (if any), without revealing on here where you live.

@silkster365 wrote:

Given the Wholesale estimate has a 3.6Mbps minimum even for an impacted VDSL line, does the current 3.085Mbps upstream suggest there is still some value in investigating the DSL side before I start reconfiguring the Deco/Hub for rate limiting?

It will be easier to optimise your VDSL connection in the configuration you currently have, so you might as well do that first.

@silkster365 wrote:

If we do conclude it's predominantly Hub Two bufferbloat, I'd also be interested in what upstream cap you'd recommend starting with on this ~3Mbps connection.

Once you have finished trying to optimise your DSL sync speeds, AND put the Plusnet Hub into 'bridged modem' mode,

use a bufferbloat optimisation tool such as https://www.waveform.com/tools/bufferbloat

If your Deco can bandwidth limit both upload and download, then start with say 5Mbps up, and 20Mbps down limits.

Repeatedly run the bufferbloat test, adjusting the Deco's upload limit by increasing/decreasing in 1Mbps steps until the test "Upload Active" result is less than +10ms, then repeat adjusting in 0.1Mbps steps until "Upload Active" is somewhere around +3 to +7ms.

Do the same for the download path, but aiming for "Download Active" to be in the range +5 to +15ms. You should check how much your download speed is lost at +5ms compared to +15ms, you can choose whether to compromise speed vs latency, or aim for the middle of the range with +10ms.

You might be disappointed to see rates 5 to 10% below previous speed test results, however your browsing should become much more responsive, lag problems disappear in video calls and mobile 'WiFi calling', you can do several things at the same time without buffering, and you actually gain some bandwidth back because your DSL link isn't having to process the previous volume of packet retransmissions caused by the bufferbloat that was causing data loss.

Re: Severe Latency Issue

silkster365 — Fri, 07 Aug 2026 15:48:07 GMT

Thanks again - useful info once more.

Re: the phone line - no we don't have a landline, its just the broadband coming in. Thanks also for the tip re: wireless broadband. Unfortunately I have checked that out and that's not available where we are either

I caught the fault again and ran a traceroute while it was happening. Local latency to the Hub is normal, but the huge delay appears immediately at the first hop beyond the Hub:

1 1ms 1ms 1ms 192.168.1.254

2 708ms 693ms 779ms 172.16.10.81

Subsequent hops remain around 700–1200ms all the way to 1.1.1.1.

At the same time, a 30-ping test to the Hub averaged 2ms with 0% loss, while 1.1.1.1 averaged 842ms with 3% loss. Resource Monitor showed the PC sending only ~18KB/s and the Deco app showed essentially no traffic from the other 14 connected clients.

This looks as though the latency is appearing on the WAN/DSL side rather than the local Wi-Fi network. Does this still look like normal Hub Two bufferbloat, given that there is no obvious upload load when the spontaneous fault occurs? It all seems so strange given service has been fine (if not mega fast!) for months, and in the past few weeks its basically unusable at times

Re: Severe Latency Issue

ExForce9 — Fri, 07 Aug 2026 17:09:24 GMT

Bufferbloat usually occurs on the slowest network link, which in your case is the DSL link between your FTTC cabinet and the modem in your Plusnet router. The increased latency shown by your traceroute occurs when either side of the slowest link is trying to output packets faster than the link can handle, this causes data packets to be dropped, which triggers automatic packet retransmission on the link, which reduces the available bandwidth to ordinary traffic, which increases the bufferbloat, which causes more packets to be lost, and the link exponentially collapses until either the sending end stops attempting to transmit, or you restart the modem to break the collapsed data link.

As your router is on your local LAN (which is faster than your DSL link) then pinging the router from your PC won't be subject to latency or packet loss, because this interaction doesn't reach where the bufferbloat is occurring. However pinging targets beyond your DSL link, ping packets will have to navigate both ways across the slowest link and suffer packet loss and transmission delays, therefore everything beyond your FTTC cabinet will be showing problems in the traceroute.

If you are keen to monitor your connection's latency and packet loss, before and after fiddling with the Deco's QoS, you could setup a (free) ThinkBroadband Broadband Quality Monitor to chart your connection 24/7, then post the 'live' chart on here for comments. Ideally having a Plusnet static WAN address is easiest to setup this BQM, but if you have a dynamic IP address then you should configure the router's DDNS setting and add the DDNS hostname in the ThinkBroadband settings - so that the Thinkbroadband server can follow your dynamic WAN IP address when it changes.

You could test for bufferbloat now by just running the https://www.waveform.com/tools/bufferbloat test.

For just browsing, email, and watching videos, a bufferbloat score of 'C' is acceptable if doing more than one internet thing

For interactive phone or video calls (such as 'zoom') then a score of 'B' should have minimal problems

If you are doing anything 'real time' like gaming or other collaborative interactions, aim for an 'A' score.

If you get to an 'A+' result, you are probably unnecessarily wasting connection speed just to achieve a bufferbloat high score.

In my opinion, if you get a bufferbloat score of 'D' or worse, then some sort of QoS is needed, with the aim to get at least a 'B' score, or ideally an 'A'.

Re: Severe Latency Issue

jab1 — Fri, 07 Aug 2026 17:21:49 GMT

@Dan_the_Van wrote:

@jab1

It concerns me a little that there are no corresponding 'DSL Down' entries

You only get the DSL Link down messages written to the event log if the router is powered on.

A restart or power off of the router does not record that event as the DSL Link wasn't down at that point.

Looking at the event log, which has had a category filtered applied so not All event are present.

I forgot there was a filter applied - wonder if the full log will be any more useful, providing of course that the Hub is powered up 24/7 as it should be?

Re: Severe Latency Issue

Dan_the_Van — Fri, 07 Aug 2026 18:09:40 GMT

@jab1

my thinking is it would not, as it looks like the issue is more likely the slow upload speed, which I suggested in my short post earlier.

@silkster365

This Hub Two page help identify which device uses the most upload.

Re: Severe Latency Issue

jab1 — Fri, 07 Aug 2026 18:08:11 GMT

Fair enough, @Dan_the_Van - it was just a thought, but as others are on he case...

Re: Severe Latency Issue

silkster365 — Fri, 07 Aug 2026 18:29:27 GMT

Thanks all. I’ve done some more testing and I think I can now rule out the Deco mesh and my iPhone or other devices as the sole cause.

It interesting to discover that an idle ping is continuously completely clean: 30/30 replies at 12–16ms, average 13ms.

However, as soon as I do some ordinary web browsing while running a continuous ping, latency immediately starts spiking again: 100–290ms repeatedly, with peaks of 374ms, 423ms and 453ms. Once browsing stops it drops back to ~12–15ms.

This fits the previous testing too. I have reproduced the problem with the Deco physically unplugged and connected directly to the Hub Two. During one bad episode the Hub itself was only ~2ms, while 1.1.1.1 was averaging ~842ms with 3% loss. Traceroute showed the large delay starting at the first hop beyond the Hub (172.16.10.81 at roughly 700ms+).

My DSL sync is currently around 18Mbps down / 3.085Mbps up. The BT Wholesale checker gives an impacted upstream estimate of 3.6–5.5Mbps, so my upstream is also below the bottom of that range.

At this point, would you agree this warrants Plusnet checking the DSL error stats/DLM and the PPP/access side, and perhaps trying a replacement Hub Two as a diagnostic? I’m reluctant to start changing the whole network topology or buying an SQM router until we know whether the Hub/line/session itself is behaving properly. it all just seems so odd!

Re: Severe Latency Issue

ExForce9 — Fri, 07 Aug 2026 19:40:40 GMT

@silkster365 wrote:

At this point, would you agree this warrants Plusnet checking the DSL error stats/DLM and the PPP/access side,

No, from your earlier modem stats, your line looks about right for the distance you are from the FTTC cabinet.

You have a latency problem due to low bandwidth, which doesn't have much to do with errors, PPP, etc.

@silkster365 wrote:

The Hub Two DSL statistics currently show:

Data rate: 3.085Mbps up / 18Mbps down
Maximum data rate: 3.085Mbps up / 19.392Mbps down
Noise margin: 6.0 / 7.3dB
Line attenuation: 11.2 / 27.1dB
Signal attenuation: 11.2 / 34.0dB

Speed tests normally give about 16–17Mbps download and somewhere between 0–2Mbps upload.

@silkster365 wrote:

... perhaps trying a replacement Hub Two as a diagnostic?

No, your existing Hub Two isn't showing any signs of being faulty (other than the design being prone to bufferbloat).

@silkster365 wrote:

My DSL sync is currently around 18Mbps down / 3.085Mbps up. The BT Wholesale checker gives an impacted upstream estimate of 3.6–5.5Mbps, so my upstream is also below the bottom of that range.

That is true, but you would need to at least double the upload speed to reduce bufferbloat, and that's never going to happen

@silkster365 wrote:

I’ve done some more testing and I think I can now rule out the Deco mesh

Why would you think it might be the Deco, when your own traceroute shows that it is bufferbloat on the VDSL link.

@silkster365 wrote:

I’m reluctant to start changing the whole network topology

It is hardly a big change, the physical layout stays the same, the wires stay the same, the modem is in the same place (but configured as a bridge), all you are doing is choosing to allow the Deco to perform the DNS, DHCP, NAT, and IPv4 routing, instead of the Plusnet Hub Two. That is maybe ten minutes of work, and a permanent improvement to your home network.

@silkster365 can you post here a screenshot of your bufferbloat test result

also post the 'live' chart URL to your ThinkBroadband Broadband Quality Monitor, so we can comment on your latency pattern