Nope.

3db isn't the target margin by default.

6db still is, but DLM has the option now to reduce to 5, 4 or 3db if it thinks a line can handle it.

Lee beat me too it ...

If you read through your linked thread again, you'll see that *if* a line is stable DLM will attempt to lower SNR in 1db increments from the default 6, ensuring at each stage that the service stays stable.

Nowhere does it say that 3db is the new default.

In reply to a post by lee111s:

Nope.

3db isn't the target margin by default.

6db still is, but DLM has the option now to reduce to 5, 4 or 3db if it thinks a line can handle it.

the 6dB is not the default anymore as noted by Openreach's SIN document 498 which states that:

1.2.2 VDSL2 noise margins

Currently the default target downstream noise margin is set to 6dB. From March 2017 the target downstream noise margin shall be set to either 3, 4, 5 or 6dB

As you can see it says clearly that from March 2017 the default 6dB will change so that 6dB will no longer be the default.

I work on this stuff every day, 6 is the default, if it weren't, how come when I do a reset it reverts to 6 ??

In reply to a post by Zarjaz:

I work on this stuff every day, 6 is the default, if it weren't, how come when I do a reset it reverts to 6 ??

One of my neighbours had an issue last week and their line was reset and it went straight to 3, so I guess some areas haven't been fully updated yet as I believe the full the rollout will be done by the end of August.

If their line was reset and went straight to 3db, then either the reset didn't go through, or the issue causing the low SNR wasn't resolved.

Any how, us bickering isn't helpful to the OP at all.

I'm not bickering, just giving out up to date information regarding noise margin values, which is the topic of this thread and I wasn't the first person to mention about the 6dB.

Would everyone like some ice cream?

In reply to a post by robertcrowther:

I'm not bickering, just giving out up to date information regarding noise margin values, which is the topic of this thread and I wasn't the first person to mention about the 6dB.

Would everyone like some ice cream?

Zarjaz is an OR engineer. I think he knows what he's on about.

As he's rightly said, the DEFAULT is 6db.

When a circuit is first enabled, the target noise margin is 6db by default. IF DLM believes the line can handle a lower TARGET margin (by looking at error rates, retrains etc, it will attempt to reduce the target margin in 1db increments. That does not mean the default margin for VDSL2 circuits is 3db.

In reply to a post by lee111s:

Zarjaz is an OR engineer. I think he knows what he's on about.

As he's rightly said, the DEFAULT is 6db.

When a circuit is first enabled, the target noise margin is 6db by default. IF DLM believes the line can handle a lower TARGET margin (by looking at error rates, retrains etc, it will attempt to reduce the target margin in 1db increments. That does not mean the default margin for VDSL2 circuits is 3db

From what I've seen out in the field and by what other OR engineers have said is that existing connections will be going through the 5dB, then 4dB and finally 3dB steps, but new connections will be going straight to 3dB and if that's unstable then it will try a higher dB rate.

That's not my experience of it.

The lower target margins are simply an additional tool to DLM's belt in the battle between speed and stability.

3db is not the default target.

Edited by deleted (Mon 10-Jul-17 11:22:58)