FTTC Downstream SNR

[#1]

@Gandalf if you are around it might make most sense for you to pick up on this one.

After a couple of years of speed issues and banding (FTTC 1km from the cabinet being banded at 27.4 or less), you made an adjustment to my connection at the end of July 2021 which resulted in my downstream target SNR being set to around 3 instead of 6 as previous.  I can't give you more info as I can't find the old ticket anymore, but we had this Community thread going here

This resulted in great stability from the beginning of August with sync speeds usually above 38 and at times topping 40.  See Fig.1 attached from 2nd November last year.  The line was actually stable at an SNR as low as 2.7 at times

This stability lasted for 6.5 months until 15th February when there was torrential rain for a day.  A DLM reset that night took the sync speed down to 33.4 and the SNR up to over 5.  Fig.2 attached.  Since then the SNR has steadily increased and the sync speed decreased until today the SNR is 6.2 and the sync speed is 32.8.  Fig 3. attached.  No banding that I can see as yet.

So, after 6.5 months of stability at the best download speeds I have ever experienced, things seem to be going awry once more.  Is it possible for the target SNR to be set to 3 once again?  And if so, please tell me what terminology I should use if I need to ask for this again 😊.

(Please don't switch the connection profile from standard/speed to stable as we have previously proven this only makes things worse)

Thanks,

Stuart

[#2]

Hi Stuart,

It's good to hear from you again and I'm sorry to see you're having speed issues.

I've tested your line and it's not showing any problems though I can see your speed has dropped and SNRM target increased.  We can't actually manually adjust the SNRM target for a fibre connection, so DLM would've done this by itself. 

Interestingly, your connection has in fact been on the "Stable" stability profile since July 2021 when we changed it. I can't see the order in the supplier systems due to how long ago it was, but judging from the notes on the ticket 216361295 and that previous forum thread, it looks like the change went through in the end, even after Adam tried to cancel it. 

The ticket 197244627 from 2019/2020 looks to be archived within our systems and not readily visible via your account. 

I've placed an order now to drop the stability profile down to "Standard/Speed" so hopefully your speed will pick back up. 

I'd recommend keeping an eye on it over the next week or so and let me know how it goes.

[#3]

@Gandalf after a week and one reboot the connection seems stable at an SNR of 6.7 and sync speed just under 32. So no real increase from the settings change you made last week. So I guess we leave it longer - and I'll get back to you should it get banded again.

Thanks, Stuart

[#4]

Hey @Junkman, thanks a lot for getting in touch and I'm sorry to see that your speeds have not gone up. I wonder whether this is caused by the L2TP profile ion the account. 

I've just reset it anyway, so if you can run another speed test in a couple of hours and let me know how you get on. 

[#5]

Thanks @adam945, but I have no idea what an L2TP profile is. Although my SNR and sync rate have both dropped since you reset it - after being stable for a few days. No point me trying a speed test, I know what the sync rate is.

Basically after a DLM reset following a problem late July last year, I had 7 months of stability at an SNR around 3 and a sync rate above 38. Until we had some torrential rain on 15/2. Immediately thereafter the SNR went back out to around 6 and the sync rate down to around 32. Where it has stayed. So I know its a copper infrastructure problem and that Openreach will do nothing about it. And as I understand it you can't trigger a DLM reset unless my connection gets banded again.

So as I said, suggest we leave it be and I'll get back to you if it does get banded. Note that banding took it down below 20 last spring and I was told there was nothing wrong with the line. So 32 is good but not as good as it has been.

Cheers, Stuart

[#6]

Adam's referring to a profile on your account which should always match the IP profile of the line. He's increased it to 37mbps, but unfortunately the changes wouldn't have done anything, because your sync rate is lower. 

I suspect the sync drop you've seen last night is unrelated, because changing this setting wouldn't affect the actual DSL connection. Also, it doesn't look like this change had caused the PPP session to drop so you would've had to manually disconnect/reconnect the session, or reboot your router, for the new profile to apply. 

I've pushed this profile back down to the correct level of around 31mbps. 

I agree with you, keep an eye on things and let us know how it goes.

Bring on FTTP! Incidentally, I've checked Openreach's site and there's sadly no signs of this being available in your area yet. 

Cheers

[#7]

@Gandalf thanks; I understand it better now.  But having had a stable sync rate above 38 from early August until mid Feb I have to question if pushing the L2TP profile back down will prevent me ever returning to that higher download speed?

[#8]

It won't do. The profile will automatically adjust to match the IP profile of the line which is 90 to 96% of your sync rate.

If your sync rate increases so will the IP profile as well as the "L2TP" profile our side. 

I've attached below a picture showing some of the profile changes on your account:

Where it says "Speed update by Delta Report" this means the system's automatically changed it to match the IP profile. 

[#9]

@Gandalf  thanks.  If those profile numbers should be matched by my IP profile, however, then they haven't been.  I have been taking occasional screenshots of my router stats, and the ones which correspond (or almost correspond) to the dates in that list are as follows:

Date           My sync speed    Your profile chart

11/08/21      35230                   27400

11/09/21      39641                   32800 (09/09)

15/09/21      38088                   33600

29/09/21      39189                   33600

20/10/21      38983                   35000 (21/10)

03/11/21      40120                   35000 (02/11)

19/12/21      40276                   35200 (18/12)

Indeed, I have been synced above 38000 solidly from 27/08/21 until 15/02/22 apart from a fall to 28 on 05/09/21 which was instantly cured by a router reboot.  My SNR fluctuating around 3 over this whole period.  These sync speeds have been reflected in the speed tests I have carried out over that time too, so they're definitely real.  But your column goes as low as 30400 and never goes above 35200 over this period.

So how do we explain sync and download speeds significantly higher than IP profile for a good few months?

Cheers, Stuart

[#10]

I think I've made things more confusing by sharing the data Happy to explain though. 

Delta reports can generally take 24-48 hours to come through after a sync speed changes, so it's hard to compare.

Also it's worth bearing in mind that those profiles aren't the IP profile, they're the profile in our systems (also called the "connection profile") which should match the IP profile, but they don't always for one reason or another.

As long as the connection profile is not set below the IP profile, I wouldn't worry about it. This type of profile is a legacy thing from the days of a bygone era when we used to traffic manage across our network. 

If it's set below then it can restrict your throughput, but only if you have a static IP (which you do). This is basically just due to the way static IPs work on our network that these route through different kit compared to dynamic IPs. 

Having a static IP and the connection profile in play doesn't mean that we traffic manage though. 

Cheers

[#11]

OK so not an issue then.  Having had great speeds and stability for a few months I'm just trying to be sure that nothing is currently holding it back.  Then when the infrastructure dries out again I might get back there.  So as I said, park it for now and I'll shout again if it gets banded.

Thanks again for your help, guys.

Stuart

[#12]

No problem Stuart. I love explaining the ins and outs of things. Sometimes that's my greatest weakness haha.

Sounds like a plan, let us know how things go.

Cheers