stuck on low rate again

[#1]

I'm trying to test different modems prior to an engineer visit, but my line has stuck at some safe, low level again - is this banded ? I was seeing 19-20M connects before.
[tt]
# adslctl info --show
adslctl: ADSL driver and PHY status
Status: Showtime  Channel: FAST, Upstream rate = 1203 Kbps, Downstream rate = 4543 Kbps
Link Power State: L0
Mode:                  ADSL2+
Channel:                Fast
Trellis:                ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):      18.8            6.6
Attn(dB):      23.0            11.0
Pwr(dBm):      0.0            12.1
Max(Kbps):      13488          1220
Rate (Kbps):    4543            1203
[/tt]
If so, can a Plusnetter please lift this ? I tried a Zyxel modem and it said that I was in 'DELT'  (dual-ended line test) mode. The other two modems don't show this info.
Wossat ?

[#2]

Over what period of time were you trying the routers? If you have repeated connections and disconnections in a fairly short space of time then the exchange can interpret this as an unstable line and so reduces the speed. The high SNR figure might imply this is what has happened. I'd suggest reconnecting no more than once per day if possible. Given a couple of days of stable connection your speeds should pick up again.
Sorry, I don't know what DELT is!

[#3]

A sync speed of 4543kbps almost certainly means the DLM has put you on the 2272-4544kbps banded profile. Plusnet staff will have to deal with that.
I suspect DELT mode is just a test mode used by the zyxel router on its way to syncing with the exchange. Have you ever seen "showtime", the running status for most routers, on the zyxel?

[#4]

@Denzil
I've been configuring the two different modems off line, swapping one in, leaving it 48hrs (min) and then swapping the third in and leaving that for a similar period of time. I haven't been changing modems more than once a day, so it isn't my fiddling that's caused the banding. I've also been careful to use the relevant telnet stop command prior to turning the power off !!
e.g. for a Broadcom 6348 (Linksys) this is [tt]'adslctl connection --down'[/tt] and for the Zyxel it is '[tt]wan adsl close[/tt]'
@spraxyt
DELT is part of one of the ITU standards that define ADSL, apparently. Which end is requesting the test mode seems unclear - some posts claim that DELT is CO-initiated and part of the multi-day training period and is diagnostic of being in this mode. Others claim it is part of the initial line training during power-on sync and always happens. Not sure I believe the latter claim - after all, a test mode is usually only required if the link is not performing properly.
As you say, it may just be an artefact of the Zyxel's GUI that it displays it and the other two modems don't.

[#5]

Hi disfroot,
The line was banded on the 18th, and from the graph below you can see why. Was it after this that you were trying the router?
Jojo

[#6]

@jojo

Hmm- I definitely tried to retrain the line yesterday (Thursday 23rd Jun) with an 'adslctl connection --down' followed by an
'adsl connection --up'. Why doesn't this event show up in the log that you have posted ?
I swapped out my Linksys WAG54GS for a Netgear DG384Gv3 on 16 Jun for a couple of days, then I swapped that out for a Zyxel P660HW-UK on Saturday evening, and then back to the Linksys for most of this week.
At any rate, I think I've proven to my satisfaction that there is nothing wrong with my original router, so I think I can take the expensive gamble of allowing a BT engineer to visit.  As you haven't lifted the banding, I can't do any more useful investigations at my end, e.g. here's the last 24hrs from the Linksys ( attached)
What do you think ?

[#7]

OK - now I get this from the faults team

"I’ve tested your line and can see that you’re staying connected to the internet. However there are some automatic settings on your line which are limiting the speed you’re able to get on the line."
it goes on to say that I'm on another 10 day training period, and, as far as I can see, the visit of an actual BT engineer to fix the fault that I originally reported on 14 May is now cancelled.
The faulty reasoning here needs to be pointed out. It is simply not correct to assume that the underlying fault has been rectified simply because my line hasn't been dropping for 3 days. The reason that my line has been stable for 3 days is that the line has been _banded_, operating at a massively conservative SNR for my line length.
So what happens now ? I have to put up with another 10 days of DLM flapping and sub-1M downstream like before the banding ?
The Plusnet faults resolution strategy seems essentially memoryless - I'm thinking Groundhog Day here.

[#8]

Hi disfroot,
Having done some checking on BTs systems I can see that the banding was applied on the 20th, however other systems are showing an LTB issue (lower threshold breach, i.e. sync speed too low). I'll put those details on the ticket and pass it back to the faults team for you, if you could add any further detail from what you're seeing that'd be helpful.
Sorry about that, and thanks,
ETA: Beg pardon, I can see you have done. I'll get the agent who reset the line to explain what's going on there for you and see if we can get it moving again.

[#9]

@matt
many thanks for unsticking this.  What does an LTB issue usually mean ? As you can see from today's graph, the DLM
tried an 18M connect last night and dumped it for a 1K2 30dB connect immediately afterward. Is that normal DLM operation ? That can't be described as a progressive back-off can it ?