Fibre35 Isn't

[piston]

When moved onto Fibre35 (without being informed!) mid 2021 it worked fine: Sync. down/up: 35/8 Mbps. 

Suddenly, after 3-ish months, this dropped to 30/6 and stuck there. I have started trying to recover the promised 'guaranteed' delivery speed : connect modem to test socket, change: filters, cable to modem, Ethernet cable to computer... nothing makes the slightest difference.

TT website test tools reports:

'Speed to router 29Mbps' ('Poor' 'g/tee 35') then a later reports says 'line looks ok'?!

'We cannot recognise your modem or software...you may need to talk to our team' (it is a TT modem but old and clearly not tested by TT when I was switched to Fib.35). None of my other modems will work at all with FTC at all.

Looks to me like an DLM or exchange/cabinet kit disturbance-triggered issue (cabs at the end of my road seem to be opened up weekly by a variety of telco engineers) but there is no mechanism to flag the possibility. The 'Live Chat' button seems to do nothing (win7/win10 , 2different browsers) and 'contact us' links back to the start of the merry go round.

Is there any hope of salvation?

PS If it helps the Interleave level (2529) is way higher than I recall it being when Fib 35 happened out of the blue (but I wouldn't bet the farm on the  quality of my er... mmm...)

[piston]

No phone on system, test socket for connection, have changed all leads and filters to no effect, as per initial post. Speed just dropped one day (from sync. 35Mbps) and has stayed at that regardless.

Regards

P

[AllyM]

I would agree with what @ferguson says.

The high SNR margin on the upstream suggests that the line should be capable of a fair bit faster if it weren't hitting the 10Mbps Fibre35 limit. On the downstream the high SNR coupled with the very suspicious figure of 29999Kbps suggests the line has had a 30Mbps profile cap applied.

My parents had a similar issue not so long (although with a different ISP and I think theirs was capped at 35Mbps).

If it is a similar situation then the bad news I have is that in My parents' case, it was a matter of several weeks, rather than days, before the DLM released the cap.

[ferguson]

@martswain I would generally agree with what you said there, but in this case the exactness of the downstream rate suggests a fixed profile for some reason. There is often plenty of headroom in the SNR margin for a Fibre 35 connection. 

[martswain]

@piston and @Michelle-TalkTalk 

Those stats are abnormal, the Noise Safety Coefficients should be 6 dB on a "normal" FTTC line.

You should check for any extraneous noise on the phone line with all internal extensions disconnected, best done by removing the faceplate and connecting to the test socket, phone only at first, then plug in a microfilter and connect your handset and router and check again.

[Michelle-TalkTalk]

Morning,

I'm sorry to hear that there has been no change. Would you like us to send a replacement router for testing purposes to rule this out? We would also send a router returns bag so that one of the routers can be returned.

Thanks

[piston]

Hi Michelle,

Router on continuously over weekend; no significant change. I have pated some details in case this helps:

HG633
Hardware version: H.1.01
Software version: v2.00t
System up time: 4 days 16 hours 3 minutes 59 seconds

Upstream line rate (kbit/s): 9995
Downstream line rate (kbit/s): 29999
Upstream noise safety coefficient (dB): 15.8
Downstream noise safety coefficient (dB): 15.4
Upstream interleave depth: 1
Downstream interleave depth: 1897
Line standard: VDSL2
Upstream line attenuation (dB): 5.5
Downstream line attenuation (dB): 9.8
Upstream output power (dBm): 6.2
Downstream output power (dBm): 13.5
Channel type: Interleaved
DSL up-time: 3 days 8 hours 4 minutes 17 seconds

Given that TT simply upgraded my connection without notice and seemingly without being able to ID my router, is my router up to the job? Or, given that all was fast 'n' fine until suddenly dropping (and sticking) at 29999 has some kit at the exchange, local cab made a decision re my unknown router (it's a techno conspiracy I tell you...).

Regards P

PS What does 'guaranteed 35 Mbps' actually guarantee?

[Michelle-TalkTalk]

Hello,

Thanks for the update and please let us know if the sync speed does not improve over the weekend. If the router is switched off then we wouldn't be able to check the router firmware.

Thanks

[piston]

Morning Michelle

Thanks for the swift reply. Router remains in test socket and will be left on 24/7 now and over the weekend. Is being off overnight the reason why the TT test system could not identify my router model/software version?

Regards

P.

[Michelle-TalkTalk]

Morning,

I've run a test on the line now which hasn't detected a fault. Can I just confirm, is the router still connected to the test socket at the moment as it can take DLM 24-48hrs to make any changes to the speed if the connection remains stable?

Thanks

[Skynet_TX]

Hi @piston,

You may well be right that DLM has tweaked your settings, not sure what model of router you have, but if you can see a downstream noise margin or noise coefficient in the connection stats, what value is that showing ?

If you were syncing at 35 when all was working well, then that is less than the theoretical maximum of 40 for Fibre 35, so that likely means that 35 is the best speed you can get with the normal 'target' noise margin of 6dB. I just wondered if your noise margin was now showing higher than 6dB, as an increasing noise margin is one common indication that DLM has been tweaking things, although as you say, it can also tweak more subtle things like your interleaving.

The TalkTalk staff on this community will be able to help, they will hopefully be able to respond to this post tomorrow to check your line stats.