What would cause reducing upload speeds?

I've been with Zen for years without issues. I assume this would apply to any ISP but what can cause reducing upload speeds over time?

If I unplug the router from the BT socket the connection resets and it's showing the max speed on the Zen test page ie 40mb down and 8+ mbit up.

Leave it a few days and it's down to 40mbit down but only 2 or 3 mbit up.

Last week it was as bad as 24 mbit down and 1 mbit up.

Zen support don't seem to get there's an issue as they just do the test and it says 'everything is fine' but it clearly isn't as this same line was happily doing 6 to 7 mbit upload speeds for ages and it's gone stupid at some point and I noticed it only when the backup was running and I was doing other web browsing or streaming. It wasn't very good all of a sudden.

What can fault without registering a fault at Zen? There is only packet loss if the upload side is occupied ie when doing a back up for example. Then it happens. Otherwise it's not showing as anything than just slow and stuck at a new low max speed.

Any ideas on how to work out where the fault lies so I can at least say to them 'It's X what's broken'?

I’d start by replacing the router.

If it was the line, DLM would have kicked in, and wouldn’t spring back up so swiftly just by unplugging and then reconnecting the router.

Is the router connection speed (sync) dropping or just the throughput?

It's both. The Zen speed tests show the product speed I assume. When I do a speed test I generally get a proportion of that speed. So it often shows 40mb down so I generally get 36. 8 or 9mb up and I get 7 or 8. It remains roughly 10% off what the product speed is for download but the upload falls off.

I don't have a laptop to plug into the modem itself now.

Edited by serichards (Mon 07-Aug-23 09:48:18)

In reply to a post by Zarjaz:

I’d start by replacing the router.

If it was the line, DLM would have kicked in, and wouldn’t spring back up so swiftly just by unplugging and then reconnecting the router.

Interesting. I'm hoping Zen will realise this as I've told them twice now unplugging and plugging back in seems to just reset back to higher speeds.

Ran the speed test via Zen again. 40 mb down and 2.2 mb up. Yesterday it was 40mb down and 8mb up. It's just weird.

Edited by serichards (Mon 07-Aug-23 09:47:40)

Another option I could think of … something on your LAN side swamping the upload,

Unplug everything, disable wifi, then just use I single wired device for a few hours .. see how that goes

In reply to a post by serichards:

It's both. The Zen speed tests show the product speed I assume. When I do a speed test I generally get a proportion of that speed. So it often shows 40mb down so I generally get 36. 8 or 9mb up and I get 7 or 8. It remains roughly 10% off what the product speed is for download but the upload falls off.

I don't have a laptop to plug into the modem itself now.

Forgive me if I've got this wrong, but it's not clear from your answer if you have checked the synch speeds shown on the router, as you only talk of speed tests.

In reply to a post by Zarjaz:

Another option I could think of … something on your LAN side swamping the upload,

Unplug everything, disable wifi, then just use I single wired device for a few hours .. see how that goes

Not that. I can see on the Asus router page what the activity is like.

In reply to a post by burble:

In reply to a post by serichards:

It's both. The Zen speed tests show the product speed I assume. When I do a speed test I generally get a proportion of that speed. So it often shows 40mb down so I generally get 36. 8 or 9mb up and I get 7 or 8. It remains roughly 10% off what the product speed is for download but the upload falls off.

I don't have a laptop to plug into the modem itself now.

Forgive me if I've got this wrong, but it's not clear from your answer if you have checked the synch speeds shown on the router, as you only talk of speed tests.

I haven't done that as there is no easy way to do it. I'm assuming the Zen check is showing me the sync speed.

I can't interrogate the ADSL modem easily to find out what it thinks. The asus router plugged into the modem doesn't seem to have that information either that I can see.

Maybe if you post model of modem someone might know how to view it.

On the portal go to My Services, Broadband & SDSL, View Line Data

Hi there
I just fixed something like this for my mum, also with Zen and on FTTC 40/10, line running slow but Zen saying it was fine. Turned out to be a faulty faceplate, connecting to the master socket confirmed this as connection was fine. A new BT faceplate fixed it. Zen reset the profile and has been solid since.

In reply to a post by Black:

Hi there
I just fixed something like this for my mum, also with Zen and on FTTC 40/10, line running slow but Zen saying it was fine. Turned out to be a faulty faceplate, connecting to the master socket confirmed this as connection was fine. A new BT faceplate fixed it. Zen reset the profile and has been solid since.

Not sure on Zen, but with TT one of the first things they ask you to do is remove faceplate and use a plug in filter.

Agree with Burble’s post …. also, an iffy faceplate causing just loss of upstream speed ? Nah …

That's not on the new portal now. There's no useful data in it annoyingly.

Just gone into the old portal.

Found a load of info and it looks like the line is resetting and generally messing about regularly. Noticeably worse during July.

I thought the line speed and zen test speed were out of sync but I'm not so sure. It's only syncing now at the lower speed again.

Sodding connection dropped part way through this.

Modem is TG588V v2. Technicolour I think.

Can't use the broadband without the filter front plate as it means not having the phone line connected and internet doesn't work for some reason when you do that anyway.

Edited by serichards (Tue 08-Aug-23 14:43:44)

is the line completely resetting?

I'd do what Burble suggested for 24 to 48 hours and remove the face plate and use a microfilter in its place, as a test.

Have you access to a spare modem router?

In reply to a post by serichards:

In reply to a post by Zarjaz:

Another option I could think of … something on your LAN side swamping the upload,

Unplug everything, disable wifi, then just use I single wired device for a few hours .. see how that goes

Not that. I can see on the Asus router page what the activity is like.

Oh its an ASUS, that may be the problem. ASUS DSL routers are garbage and often have sync issues, which is frustrating as their plain ethernet routers are excellent.

Do you not have the router Zen provided with your connection to test this?

Wait, I see later you are using their router as a modem? That's not a good setup either as I do not believe their modem has a bridge mode though probably not the cause of your problem.

I'd definitely push to see if Zen will send you a newer router, I know its a free of charge if you sign a new contract, but worth pressing regardless as that modem (router) must be quite old now.

Edited by alexatkin (Tue 08-Aug-23 20:35:20)

I've found another microfilter so I have put that in the phone line to double screen it to see if that changes anything.

I can only use the test socket for more than an hour or two if I can still plug the landline in and have it working. Did try it without a microfilter as I hadn't found the one I've just found and that forced a reset. It can take anything between a few hours a day or two to step down the sync speed which is too long to be without the landline connected.

The asus is rarely troublesome as long as QOS isn't turned on. That seems to make it worse. It's a bit lean on memory by the look of it which won't help.

Checked sync speed from yesterday and it's still 8mb up so far with the new microfilter on the phone line connection.

It continues.

Reducing upload speed but with different dsl modem. Been given a fritzbox. Exactly the same issue. Download speed is the same. Upload speed starts at about 8mb then falls off over a number of days.

Different filters - no change. Test socket no change. Tried 3 different filters in different configurations and all exhibit the same behaviour.

Line is syncing at the full speed but the through put is reducing. Before it was changing sync speed in tandem. That's assuming the line stats info in the Zen page is accurate.

Lift and shift to new ties on the DSLAM would be my next step then.

Gave up with Zen in the end. Switched to AA as the ISP. No issues at all. Better download and upload and consistent speeds. 2 months of normal with everything else the same, including the Fritzbox Zen supplied.

I'm assuming either it's Zen's backend that was the problem or moving ISP has left the issue behind and it was some exchange hardware that was the problem?