G.INP and latency

So i finally got my install finished, im at about 300m not sure exactly from the cabinet and just waiting to be activated (Im actually going onto ADSL first).

My concern with fiber is the lack of control over interleave, Im gonna see how my connection is on a fast ADSL profile first. After reading a lot of posts online I have found very few people have the 0 interleave vdsl profiles and that it seems to have been more common in the past before G.INP/Vectoring updates.

So I picked up a HG612 from eBay and when looking through firmware got to thinking if using a lower firmware which didnt support them may give better latency, has this been tried by anyone/is it worth trying? (Im on an Huawei cab).

FYI id rather a con of 30/10 with 0ms interleave than 80/20 with 8ms so the speed isnt really the concern, im approx 800-1000 from exchange for ADSL.

Thanks,

Dave

There is no such thing as interleaved depth zero. The number is the number of packets across which a real packet is spread. So a non-interleaved (fast path) line has interleave depth 1.

On Openreach fibre, (I prefer English to American ), you need to look at the Delay line, not the D: line. The same is also true on ADSLx in fact. The Delay line is the number if ms added to your raw latency by DLM.

The current unlocked firmware is G.INP capable. Earlier ones are not. G.INP is only activated on lines that would otherwise have interleaving depth in the hundreds or thousands and usually higher Delays. Get a firmware without it and you would be stuck with the high interleaving if Fast Path was not appropriate.

When G.INP is active on an interleaved FTTC line the normal interleaving depth is 8 but the Delay is zero.

With the HG612 and most other modems G.INP activation is easily spotted by the presence of Bearer 1. Which shows with zero sync but IIRC is 200bps. So rounded to 0kbps.

In reply to a post by davebruno:

So I picked up a HG612 from eBay and when looking through firmware got to thinking if using a lower firmware which didnt support them may give better latency, has this been tried by anyone/is it worth trying? (Im on an Huawei cab).

It isn't worth trying to avoid G.INP by using "old" firmware. You might trigger DLM to just leave you on an interleaved 8ms profile instead.

If G.INP is active, then you will be slightly interleaved. The depth will be 8 or 16, often, and the delay will be 0. That /actual/ interleaving delay is probably about 0.2ms

That's not unreasonable.

FYI id rather a con of 30/10 with 0ms interleave than 80/20 with 8ms so the speed isnt really the concern

IIRC, there are commands that can be issued on an unlocked HG612 that allow you to choose to cap your speed to something below the peak. You can use that to reduce your error rate if need be.

In the meantime, watch the ES (errored second) rate. Keeping that to the low hundreds per day, or less, is best.

In reply to a post by WWWombat:

IIRC, there are commands that can be issued on an unlocked HG612 that allow you to choose to cap your speed to something below the peak. You can use that to reduce your error rate if need be..

I think you may be right, but I can't remember. It is certainly possible on (at least the early) Fritzboxes.

In reply to a post by WWWombat:

In reply to a post by davebruno:

So I picked up a HG612 from eBay and when looking through firmware got to thinking if using a lower firmware which didnt support them may give better latency, has this been tried by anyone/is it worth trying? (Im on an Huawei cab).

It isn't worth trying to avoid G.INP by using "old" firmware. You might trigger DLM to just leave you on an interleaved 8ms profile instead.

If G.INP is active, then you will be slightly interleaved. The depth will be 8 or 16, often, and the delay will be 0. That /actual/ interleaving delay is probably about 0.2ms

That's not unreasonable.

FYI id rather a con of 30/10 with 0ms interleave than 80/20 with 8ms so the speed isnt really the concern

IIRC, there are commands that can be issued on an unlocked HG612 that allow you to choose to cap your speed to something below the peak. You can use that to reduce your error rate if need be.

In the meantime, watch the ES (errored second) rate. Keeping that to the low hundreds per day, or less, is best.

Wow think ive been quite short sighted with this then, so most people with fairly good lines would get like an 8 depth but 0 delay? I read the 8 and thought that was ms.. In that case am I even likely to gain anything from ADSL fast path?

Any idea what I can google to find more info on capping the speed to lower the ES? I cant seem to find much, will buy hardware if the openreach modem cant do it..

In reply to a post by davebruno:

Any idea what I can google to find more info on capping the speed to lower the ES? I cant seem to find much, will buy hardware if the openreach modem cant do it..

Take a look here -- http://forum.kitz.co.uk/index.php/topic,16427.0.html