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[les-70]

  I have run with a speed limit for some time.  I have usually aimed for 9db snrm.  This gives me a reduction of crc's and es of about a factor of 3.  A speed drop raising the snrm from 6 to 9 would about 16mb/s at an initial 80mb/s attainable or about  8Mb/s with an attainable of about 40Mb/s. 

A capped speed will also avoid too high a sync occurring when noise or cross talk is low, this is important on my line which has wide variations in attainable when neighbours switch on and off.

Depending on your usual error rates a more moderate sync may suffice.  Why not just try 40 downstream for starters.  For upstream you can leave it at 20 and let it do its own thing.


 

[Ixel]

[xreyuk]

Thanks for the input guys.

I did have another thread when I was synced at about 43.2Mbps and SNRM was 6.9dB then, so I might try 42/42.5 first, and see how that goes.

As I say, I'll revisit this in a month, as I'll probably give my line some time with DLM at first before messing around with it.

My latest errors are in the first post at the top of this thread, and my first initial post with stats is here

Code: [Select]

# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 12087 Kbps, Downstream rate = 51204 Kbps
Bearer: 0, Upstream rate = 11999 Kbps, Downstream rate = 43225 Kbps

Discovery Phase (Initial) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3970)
Medley Phase (Final) Band Plan
US: (7,32) (871,1205) (1972,2644)
DS: (33,859) (1216,1961) (2793,3408)
  VDSL Port Details    Upstream    Downstream
Attainable Net Data Rate:      12087 kbps      51204 kbps
Actual Aggregate Tx Power:         7.0 dBm       12.6 dBm
====================================================================================
     VDSL Band Status U0 U1 U2 U3   U4 D1 D2 D3
  Line Attenuation(dB): 6.9 35.5 53.5    N/A    N/A 16.8 43.6 67.8
 Signal Attenuation(dB): 6.9 34.6 51.9    N/A    N/A 25.0 43.2 68.6
SNR Margin(dB): 6.0 6.1 6.1    N/A    N/A 6.9 6.9 6.9
TX Power(dBm): 0.0 -7.4 5.6    N/A    N/A 9.9 7.8 3.8
 # xdslcmd info --show
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 12080 Kbps, Downstream rate = 51204 Kbps
Bearer: 0, Upstream rate = 11999 Kbps, Downstream rate = 43225 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): 6.9 6.1
Attn(dB): 22.1 0.0
Pwr(dBm): 12.6 7.0
VDSL2 framing
Bearer 0
MSGc: 18 58
B: 51 237
M: 1 1
T: 64 33
R: 12 16
S: 0.0383 0.6297
L: 13376 3227
D: 845 1
I: 64 127
N: 64 254
Counters
Bearer 0
OHF: 28076340 186790
OHFErr: 99 86
RS: 2892472767 512583
RSCorr: 173669247 1238
RSUnCorr: 4616 0

Bearer 0
HEC: 1032 0
OCD: 37 0
LCD: 37 0
Total Cells: 1444066954 0
Data Cells: 5740135 0
Drop Cells: 0
Bit Errors: 0 0

ES: 27 90
SES: 0 0
UAS: 24 24
AS: 69050

Bearer 0
INP: 3.00 0.00
INPRein: 0.00 0.00
delay: 8 0
PER: 2.45 10.43
OR: 78.07 49.08
AgR: 43302.84 12047.83

Bitswap: 33243/33243 12011/12011



That sound like a good plan?

[NewtronStar]

I do hope you will keep us informed if you decide to go down the forced cap as all information is very welcome.

[burakkucat]

I do hope you will keep us informed if you decide to go down the forced cap as all information is very welcome.

The kuro neko echoes N*Star's statement. It is an interesting subject and one that was, to me, initially not at all obvious. 

[xreyuk]

I will do, I'll revive the threa

I do hope you will keep us informed if you decide to go down the forced cap as all information is very welcome.

Of course, I know everyone is trying to find ways to mess about with DLM

I'll revive the thread if I decide to down the route of capping

[les-70]

  If you cap at about 42 that will only give a small error reduction but when/if the interleaving is removed that cap at 42 would then have a snrm of about 9-10 and you may welll then stay on fast path.  A lower cap at about 36 should give a significant error reduction.  If you start with 36 and give it a chance to get to fast path you will be likely to keep on fast path if you then set to 42 after it has achieved fast path.

[xreyuk]

Thanks Les.

So you think I should go a bit lower, then when/if fast path is enabled, raise the sync speed slightly, but only to a level where we think fast path will stay enabled?

I also meant to ask, does this command need re-entering if the DSL goes down, or the router is rebooted? If so, is it worth me putting the command in DSLStats?

[les-70]

   Those would be my choices.  My cap to get a roughly 9db snrm corresponds to a sync almost identical to that which interleaving would give me.

   You only need reapply the cap if the modem does a full reboot as with a power off/on.  It is not needed again if just a resync occurs either though severe errors or the DLM.

   I had trouble with putting the command in dslstats - the trouble was almost certainly to do with coming out of standby when, on rare occasions dslstats mistakenly thought the sync to be down.  I disable vdsl in the gui so the command needed is e.g. xdslcmd configure --mod v  --maxDataRate 68040 20000 100000 where the --mod v enables vdsl. This approach ensures no sync occurs until the command is given.  I have not retried dslstats lately, you could try adding in a harmless command like xdslcmd info --linediag and then check whether you find any resulting output in the display or if you select it, the event log.  If you don't get any output after a few days it should be safe to use dslstats.  Out of interest I am going to do that myself.

[xreyuk]

My DSL stats will always be running on a server, so coming out of standby wouldn't be a problem, however, I may come back to this thread for some advice when I actually implement it .

[xreyuk]

[xreyuk]

I've decided to delay this for now. Looking at my stats, my max attainable upload has been dropping and dropping (I think as more people are coming on the cab, I saw them doing work the other day) and if I resync, I stand to lose 2-3Mbps of speed.

I'll update if I do bother doing this though

[NewtronStar]

[xreyuk]

So, after waiting to see if DLM would touch my line, I grew impatient, and also wanted to experiment a little.

I used the xdslcmd configure -maxDataRate command and it worked fine. However, since I've done it my error counts have literally gone through the roof and I don't know why.

Could just be coincidence but my SNRM went from 6dB to 7.9dB, so it should be more stable, but the error counts haven't just jumped a little, they've over tripled.

Any idea why?