FTTC : annex A or B?

[#1]

My new router was defaulting to annex A - but I've found the speeds are low - should I be using annex B?
I've just changed the setting to B and it works but how long does it take for the system to respond?

[#2]

Annex A should work fine.
What sort of speeds are you seeing and what speeds are you expecting?

[#3]

Hi Chris,
When I first had FTTC installed I was getting just under 80meg on speedtest results (78Meg)
I've replaced the hardware because I thought the router was failing - lots of dropped connections reported in browser and applications.
The fritzbox shows me 44 down 17 up and speedtests are showing similar.
I did open a fault asking for a reset which I think happened this morning, but speeds no better.  I did a bit of googling and I found conflicting info about which annex should be used.  As I say I've just switched to annex B to see if it improves things.
I have vlan 101
vpi/vci 1/32
pppoE
Negotiated connection properties
Receive Direction Send Direction
Max. DSLAM throughput kbit/s 44000 17000
Min. DSLAM throughput kbit/s 22000 8000
Attainable data rate kbit/s 47080 14189
Current throughput kbit/s 43976 14152
Seamless rate adaptation off off

Latency fast fast
Impulse Noise Protection 0 0
G.inp off off

Signal-to-noise ratio dB 8 6
Bitswap on on
Line attenuation dB 17 3

Profile 17a
G.Vector off off

Carrier record B43 B43

[#4]

Max. DSLAM throughput  kbit/s  44000 is limiting your downstream sync (FTTC Profile band 22000 to 44000)
Attainable data rate  kbit/s  47080 suggests you can get a bit more (but nothing like 80Mb/s)
Signal-to-noise ratio  dB  8 confirms you can sync a bit faster (based on the normal FTTC target SNR of 6dB)
Line attenuation  dB  17 looks about right for the attainable rate above
I'm currently syncing at 63554 down (63800 Attainable) with a reported attenuation of 14dB.
I'd suggest a line test because if you previously got 78Mb/s on speedtests (suggesting 80Mb/s sync) then your attenuation may have increased somehow.  The best sync I ever saw on an unlocked Openreach Huawei modem was about 70Mb/s (so my F!B 7390 is maybe 10% lower sync than the HG612, some of which (maybe all of it) is likely due to increased cross-talk on my line as others have connected to the FTTc cabinet).

[#5]

thanks for the comment.
I know something must be wrong, but its working out what...  The annex a/b thing was something I found with a suggestion that it could limit connectivity.
I certainly had big problems with the old router which have now gone away, the question is what is the speed problem.
One thing that worries me is that the school next door had new wires installed recently and I'm wondering if they did something at my cables at the the time - we're all on the same pole.

[#6]

Quote from: toolateforaname

My new router was defaulting to annex A - but I've found the speeds are low - should I be using annex B? I've just changed the setting to B and it works but how long does it take for the system to respond?

FWIW, this is what is reported by the Huawei HG612 modem on my connection:-
xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 1
Last initialization procedure status: 0
Max: Upstream rate = 4421 Kbps, Downstream rate = 21072 Kbps
Bearer: 0, Upstream rate = 4516 Kbps, Downstream rate = 22271 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): 5.5 6.0
Attn(dB): 24.6 0.0
Pwr(dBm): 12.6 6.8

[#7]

Also using annex B
adsl info --stats
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    0
Last initialization procedure status:  0
Max:    Upstream rate = 30598 Kbps, Downstream rate = 89184 Kbps
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 79987 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            12.6
Attn(dB):        0.0            0.0
Pwr(dBm):        14.3            5.8
Does it not depend on the profile as to which PSD masks are in use?
ie

Quote

VDSL2 Profile8c - Annex A EU128 VDSL2 Profile17a - Annex B 998-M1x-A

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