Adjusting the sync-time SNRM on ADSLx is a well-known technique, but the BT Wholesale and LLU DLMs on it is a very different beast from the SNRM on the Openreach DLM that Openreach controls.

The latter alters many other parameters when it adjusts SNRM, and the SIN specifically instructs that intervention to alter it is not allowed. Presumably because the overall setup is screwed up.

Capping by limiting the sync speed isn't specifically banned, but whether it is safe or not I don't know. Speed capping (with other adjustments) is what OR does to cap lines due to instability.

Wrt altering the HG612 upstream speed setting immediately after a sync, that is going to cause an immediate re-sync. Hmmm. Probably safe but not ideal when G.INP is active.

In reply to a post by RobertoS:

Adjusting the sync-time SNRM on ADSLx is a well-known technique, but the BT Wholesale and LLU DLMs on it is a very different beast from the SNRM on the Openreach DLM that Openreach controls.

The latter alters many other parameters when it adjusts SNRM, and the SIN specifically instructs that intervention to alter it is not allowed. Presumably because the overall setup is screwed up.

Yes, and setting the SNR on VDSL on a Broadcom modem won't do anything. Ironically, I noticed you can SNR directly on VDSL on the Draytek 130 which is a SIN498 modem, but that's not really the point on VDSL and as you say it's not allowed in OR SIN - and DLM did *NOT* like that so don't even try it even if you can.

In reply to a post by RobertoS:

Capping by limiting the sync speed isn't specifically banned, but whether it is safe or not I don't know. Speed capping (with other adjustments) is what OR does to cap lines due to instability.

By lowering the sync speed we're just influencing the training of the line between modem and DSLAM and thus the increased SNR is a 'side effect'. Like I said, by having your speed just a bit under the lowest DSL checker reported speed, the BT infrastructure seems to sync at 9dB instead of 6dB.

In reply to a post by RobertoS:

Wrt altering the HG612 upstream speed setting immediately after a sync, that is going to cause an immediate re-sync. Hmmm. Probably safe but not ideal when G.INP is active.

If you do do this, first disconnect the RJ11 phone line from the modem, then do any reconfiguration necessary on the modem, including setting the speed. Then only put the phone line back in the modem AFTER 30 minutes have passed. DLM ignores a sync event when there's been no activity in the prior 15 minute bin, so to make sure you surpass that 15 bin then you have to wait double the time. If you just resync the modem while connected, DLM will think it's an instability event and count on the MTBR (Mean Time Between Resyncs), which alongside the MTBE (Mean Time Between Errors - ES counts) is the exact thing DLM measures and decides how to impose countermeasures on the line.

Like I said, by having your speed just a bit under the lowest DSL checker reported speed, the BT infrastructure seems to sync at 9dB instead of 6dB.

What exactly do you mean by lowest DSL checker reported speed?
The lower estimate, or the observed speed from nearer the bottom of the page?

The default target SNRM is 6dB.

On a line that makes good use of the D3 downstream band each 1dB SNRM is worth roughly 3-4Mb.

On a line that makes no use of the D3 band each 1dB is worth less than 3dB, depending much of D1 and D2 are used.

Yes, and setting the SNR on VDSL on a Broadcom modem won't do anything. Ironically, I noticed you can SNR directly on VDSL on the Draytek 130 which is a SIN498 modem, but that's not really the point on VDSL and as you say it's not allowed in OR SIN - and DLM did *NOT* like that so don't even try it even if you can

The DLM doesn't give a hoot what the current SNRM is.
It sets a target SNRM and the DSLAM and modem try to sync at that.

DLM doesn't like the increased ES that can come with manually/artificially lowering the target SNRM.
Many users run with their lines on a manually tweaked SNRM just fine without DLM blinking an eye.

f you do do this, first disconnect the RJ11 phone line from the modem, then do any reconfiguration necessary on the modem, including setting the speed. Then only put the phone line back in the modem AFTER 30 minutes have passed. DLM ignores a sync event when there's been no activity in the prior 15 minute bin, so to make sure you surpass that 15 bin then you have to wait double the time. If you just resync the modem while connected, DLM will think it's an instability event and count on the MTBR (Mean Time Between Resyncs), which alongside the MTBE (Mean Time Between Errors - ES counts) is the exact thing DLM measures and decides how to impose countermeasures on the line.

Overkill.

While that is all correct the DLM allows up to 20 resyncs a day on the Speed policy and 10 resyncs a day on the Standard policy.
A recently temporal trial was testing lowering the Standard policy to 5 resyncs a day.

Still, never once have I ever seen DLM take action on a line for doing a resync or 2.
Keeping the modem offline for 30 minutes every time you need to resync once in a blue moon is wholly unnecessary.

Edited by j0hn83 (Mon 06-Apr-20 14:10:00)

Looks like DLM kicked off two resyncs today with a total further speed increase.

It also looks like I am on on low retx now as well.

1st Re-Sync

Status: Showtime
Retrain Reason: 1
Last initialization procedure status: 0
Max: Upstream rate = 22896 Kbps, Downstream rate = 59988 Kbps
Bearer: 0, Upstream rate = 14997 Kbps, Downstream rate = 28999 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 13.1 10.2
Attn(dB): 15.7 0.0
Pwr(dBm): 12.6 6.8
VDSL2 framing
Bearer 0
MSGc: -6 29
B: 228 31
M: 1 1
T: 0 64
R: 16 2
S: 0.2501 0.0678
L: 7838 4009
D: 2 1
I: 245 34
N: 245 34
Q: 2 0
V: 1 0

Bearer 0
INP: 47.00 0.00
INPRein: 0.00 0.00
delay: 0 0
PER: 0.00 7.62
OR: 0.01 36.70
AgR: 29102.34 15033.97

Bearer 1
INP: 2.50 0.00
INPRein: 2.50 0.00
delay: 0 0
PER: 16.06 0.01
OR: 47.81 0.01
AgR: 47.81 0.01

2nd about 10 mins later

xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 1
Last initialization procedure status: 0
Max: Upstream rate = 23091 Kbps, Downstream rate = 59561 Kbps
Bearer: 0, Upstream rate = 14997 Kbps, Downstream rate = 28999 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 13.3 10.4
Attn(dB): 15.7 0.0
Pwr(dBm): 12.6 6.8
VDSL2 framing
Bearer 0
MSGc: -6 29
B: 158 31
M: 1 1
T: 0 64
R: 16 2
S: 0.1742 0.0678
L: 8039 4009
D: 16 1
I: 175 34
N: 175 34
Q: 16 0
V: 7 0

Bearer 0
INP: 47.00 0.00
INPRein: 0.00 0.00
delay: 0 0
PER: 0.00 7.62
OR: 0.01 36.70
AgR: 29102.34 15033.97

Bearer 1
INP: 2.50 0.00
INPRein: 2.50 0.00
delay: 0 0
PER: 16.06 0.01
OR: 47.81 0.01
AgR: 47.81 0.01

I've now uppped my limits to the following

xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 1
Last initialization procedure status: 0
Max: Upstream rate = 23335 Kbps, Downstream rate = 59152 Kbps
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 35999 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 10.8 7.7
Attn(dB): 15.8 0.0
Pwr(dBm): 12.7 6.8

So all very postive progress, I just need to find the sweet spot now after it levels out.

In reply to a post by j0hn83:

What exactly do you mean by lowest DSL checker reported speed?

Low estimate of impacted speed. Mine is 56.6 and 15.1.

On a line that makes good use of the D3 downstream band each 1dB SNRM is worth roughly 3-4Mb.

On a line that makes no use of the D3 band each 1dB is worth less than 3dB, depending much of D1 and D2 are used.

Take a look at my stats in full if you like: Stats

The DLM doesn't give a hoot what the current SNRM is.
It sets a target SNRM and the DSLAM and modem try to sync at that.

I know it doesn't. Bearing in mind:
a) That I have 17.4dB of attenuation to deal with
b) My priorities are 1. Latency 2. Upstream and then only 3. Downstream

Means I regard FastPath as an SLA condition, and that battling with DLM to guarantee that it doesn't impose Interleaving is a big deal. Therefore, to keep ES's low enough to maintain Fastpath and to ensure there is sufficient SNR to keep the line stable, I needed to lower bandwidth, ergo DLM indirectly affected by SNR.

Overkill.

Good to know. However, even better would be to allow us to choose profiles based on our SLA priorities, and there's absolutely no reason DLM can't do this.

In reply to a post by zzing123:

b) My priorities are 1. Latency 2. Upstream and then only 3. Downstream

Means I regard FastPath as an SLA condition

The trouble with that is, it isn't!

It may be your priority, but I assume you are on a consumer level product at a consumer level price with a mass-market provider.

Is an SLA mentioned in the T & Cs for your contract?

Edited by RobertoS (Tue 07-Apr-20 19:55:49)

In reply to a post by RobertoS:

It may be your priority, but I assume you are on a consumer level product at a consumer level price with a mass-market provider.

Is an SLA mentioned in the T & Cs for your contract?

Unfortunately, no. Unless I'm very much mistaken, I don't believe such an SLA exists anywhere either... because I'd probably get it.

But I did say *I regard it as* such. I'm on a business line with SL3 at the moment with IDnet, but they're not delivering.

Thing is, there's such a wide gap between consumer lines at £30 and a leased line that starts at £250 for say 80-100mbps speeds, and there is quite a large market for quality products in between. My budget can stretch to about £125, and £1500/yr is a decent bit of wedge for internet access... so I'm willing to pay, but not excessively.

Problem is what do I get? G.Fast is available but can't do anything on my line since I'm too far away. FTTP isn't available here yet even under alt-net form. FTTPoD is a non starter while ECCs costs the same as a leased lines and there's no discount for the added contention and no SLAs. Virgin is also available, but service is even worse than FTTC for latency and quality. Their 'MIA' and 'DIA' products are equally a total waste of space since DOCSIS is the problem with them. Then there's EFM, which is too slow and *way* too expensive as it is now. EFM could be made viable if it wasn't 5x to 6x too expensive for what it is (essentially bonded VDSL with an SLA). In any case EFM is totally eclipsed by 'EoFTTC' (Ethernet over FTTC) which is VDSL with 1:1 contention and the same SLA as EFM for £75 (TTB) or £85 (BTW).

So really, my only option right now are either bonded broadband (no guarantees still, and offerings are too expensive for too little) and EoFTTC. But even with that, while I'll be able to call out an engineer every 7 hours for practically any reason, Openreach STILL won't guarantee performance!

So unless I'm very much mistaken, I don't know of any SLA offered on any product offers a decent quality line, that while pricier is not completely insanely so. Any suggestions?

Edited by zzing123 (Tue 07-Apr-20 23:21:39)