In reply to a post by Anonymous:

Hopefully someone on FTTC who gets a ping of around 8-9ms could check to see if it says the depth is 1 (D: 1).

I can take a look tonight - about 3 hours from now.

That would be great .

I use a draytek Vigor 2750n and so it reports the interleave by actual delay so I cannot tell what the d value is as I don't use the OR modem.

To get fastpath I didn't get the 80/20 upgrade and left it at 40/10 which then gives my line a noise margin in the 20's which means my line is extremely stable amd so the DLM granted me fastpath.

I wish there was a working way of adjusting the target SNR margin on the modem, e.g. instead of syncing with around 6dB I could specify to sync with around 15dB. I haven't discovered a mentioned and working way of this being done though, unlike ADSL, so I'm guessing it's not possible with VDSL at this time.

I've altered the noise margin on my Huawei and it was counter-productive. The behaviour of the sync's down and up was very strange, on three-six plays. (I forget exactly, but it was in that range). I decided I was better not messing.

It's also the case that in the latest Openreach documentation, which gives the specifications for modems' and modem/routers' behaviour when wires-only comes along, it specifically says:-

Note : It is the DLM system that sets the line profile, and this should not be interfered with by CPs/users setting rates, SNR margins etc. at the Modem.

That's the line profile by the way, not the IP Profile which comes along in the WBC DLM but not on Sky or TT.

Why would you want to sync FTTC at 15dB noise margin?

To try and encourage DLM to put me on fastpath (depth 1) as a result of minimal errors due to higher SNR. My depth is currently between 1100 to 1600, changes every few days typically.

The other future alternative I suppose is, when the contract has finished, choose a 40/10 package. Unfortunately that would mean losing the 20 upload, but by the time my contract finishes perhaps there will be more options .

Edited by Ixel (Thu 30-Aug-12 22:54:16)

In reply to a post by RobertoS:

I've altered the noise margin on my Huawei and it was counter-productive. The behaviour of the sync's down and up was very strange, on three-six plays. (I forget exactly, but it was in that range). I decided I was better not messing.

How did you achieve that Bob?

I have tried various "xdslcmd configure --snr" values with my HG612, but nothing seemed to change.

Now my connection has been repaired, I never see less than around 5.5dB SNRM. It usually hovers around 6.5dB to 6.9dB, so I would like to try it out at say 3dB.

My attainable rate is now always around 33Mb to 34Mb, but sync speed is always around a maximum of 28Mb (currently 28075 K with 6.5dB SNRM, so apparently not hard-cap banded by DLM).

DS Interleaving depth is around 450.
DS INP is at 3.00
DS delay isa at 8.00

I'm 12 hours later than promised, but here we are. I get 5-6ms to my first hop.

1 <1 ms <1 ms <1 ms 192.168.1.254
2 6 ms 5 ms 5 ms 217.32.147.97

# xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 33119 Kbps, Downstream rate = 88236 Kbps
Path: 0, Upstream rate = 20000 Kbps, Downstream rate = 79999 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 8.3 14.8
Attn(dB): 0.0 0.0
Pwr(dBm): 12.4 6.8
VDSL2 framing
Path 0
B: 239 237
M: 1 1
T: 23 45
R: 0 16
S: 0.0955 0.3782
L: 20107 5373
D: 1 1
I: 240 127
N: 240 254
Counters
Path 0
OHF: 115012215 3943928
OHFErr: 170658 796
RS: 0 4293740
RSCorr: 0 17195
RSUnCorr: 0 0

Path 0
HEC: 906477 0
OCD: 0 0
LCD: 0 0
Total Cells: 405528636 0
Data Cells: 531377316 0
Drop Cells: 0
Bit Errors: 0 0

ES: 50126 243
SES: 83 40
UAS: 17 17
AS: 7292543

Path 0
INP: 0.00 0.00
PER: 1.64 4.25
delay: 0.00 0.00
OR: 116.56 60.17

Bitswap: 521020 17724

These are the bits I said I was trying to sort out on my logs, but I got myself in a mess trying to make the log run on from the one I uploaded for you.

I can probably upload the area I was doing it, but I won't remember the --snr settings I used. IIRC the relative movement of the down/up sync's may be useful, but I think I concluded that they were inversely related.

I'll try to look again today or tomorrow. The differnce was very small compared to what we would expect, as you just said. Which is why I stopped messing.