Mel
0
Since Sky upgraded my connection to ADSL2+, I've noticed that although my maximum sync speed seems to be capped, on first syncing the router still obtains a downstream noise margin of about 7db, when I'd expect to often see a DS noise margin a few db higher than that.
I've also noticed that the ADSLCTL command for tweaking the router's noise margin only works as I'd expect if I make a large increase in the target noise margin:-
Raising the target margin to about 12db (170%) will cause my router to sync at a lower rate, but making smaller changes than that to the target margin will result in the router syncing at the normal sync rate and results in changes in the adsl2 framing (and delay etc) instead.
stats with target margin set to 150% (10.5db) - I'd expect the sync rate to be lower than with the default 7db, but it isn't (the 'Max' rate has fallen though)
Target margin set to 75% (roughly 5.25db)
It's as if there's approx 5db held in reserve.
Maybe adslctl works differently for ADSL2+, but it looks to me that on a SKY LLU connection, a 7db noise margin no longer indicates that you are getting the fastest sync rate for your line!
I've also noticed that the ADSLCTL command for tweaking the router's noise margin only works as I'd expect if I make a large increase in the target noise margin:-
Raising the target margin to about 12db (170%) will cause my router to sync at a lower rate, but making smaller changes than that to the target margin will result in the router syncing at the normal sync rate and results in changes in the adsl2 framing (and delay etc) instead.
stats with target margin set to 150% (10.5db) - I'd expect the sync rate to be lower than with the default 7db, but it isn't (the 'Max' rate has fallen though)
Code:
Channel: FAST, Upstream rate = 796 Kbps, Downstream rate = 6142 Kbps
Link Power State: L0
Mode: ADSL2+
Channel: Fast
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 10.5 11.0
Attn(dB): 50.5 30.6
Pwr(dBm): 11.0 12.8
Max(Kbps): 7736 896
Rate (Kbps): 6142 796
G.dmt framing
K: 53(0) 25
R: 4 16
S: 1 8
D: 224 8
ADSL2 framing
MSGc: 72 68
B: 52 24
M: 1 8
T: 3 1
R: 4 16
S: 0.2743 7.7142
L: 1662 224
D: 224 8
Counters
SF: 6747 6298
SFErr: 0 1
RS: 1579020 55467
RSCorr: 7 0
RSUnCorr: 0 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 1567701 203297
Data Cells: 337 1312
Drop Cells: 0
Bit Errors: 0 0
ES: 718 1
SES: 0 0
UAS: 70 18
AS: 109
INP: 2.15 2.28
PER: 16.05 17.83
delay: 15.36 15.42
OR: 38.87 33.18
Target margin set to 75% (roughly 5.25db)
Code:
Channel: FAST, Upstream rate = 796 Kbps, Downstream rate = 6142 Kbps
Link Power State: L0
Mode: ADSL2+
Channel: Fast
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 5.8 11.5
Attn(dB): 50.5 30.7
Pwr(dBm): 11.5 12.8
Max(Kbps): 9384 896
Rate (Kbps): 6142 796
G.dmt framing
K: 27(0) 25
R: 10 16
S: 1 8
D: 128 8
ADSL2 framing
MSGc: 86 68
B: 26 24
M: 1 8
T: 5 1
R: 10 16
S: 0.1396 7.7142
L: 2120 224
D: 384 8
Counters
SF: 7620 7138
SFErr: 0 1
RS: 3505226 62864
RSCorr: 2813 0
RSUnCorr: 0 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 1773368 453765
Data Cells: 79 105
Drop Cells: 0
Bit Errors: 0 0
ES: 202 1
SES: 2 0
UAS: 65 21
AS: 122
INP: 7.24 2.28
PER: 16.05 17.83
delay: 13.40 15.42
OR: 45.83 33.18
It's as if there's approx 5db held in reserve.
Maybe adslctl works differently for ADSL2+, but it looks to me that on a SKY LLU connection, a 7db noise margin no longer indicates that you are getting the fastest sync rate for your line!
Last edited: