Speed halved following line fault - line test request, please

[#1]

I reported a phone line fault on Monday 12/6/23 following a nearby lightning strike. I have a dial tone at the master socket but not on my extensions, which I have now disconnected.

My sync speed has dropped from about 55-58 Mb/sec to around half that. The Openreach engineer who attended on Monday this week fitted a new faceplate, and quoted the "7 day settling in period" to me when I questioned the sync speed, however I know that is not likely. A previous OR visit on Wednesday last week saw a van parked outside a couple of times, but although he apparently rang the doorbell it wasn't working and so I didn't get the chance to speak to him.

I have an alternative router I might try but before going to a considerable amount of trouble doing that, can I ask if a staff member could please run a test on my line to see if it is worth raising a VDSL fault rather that a phone line fault?

The line in to the property runs through trees, and previous issues have seen a bloke with a chainsaw going into the woods and trimming back branches.

[#2]

As likely as not the line needs resetting.  "7 day settling in period" is more BT Openreach myth.  If the line is banded chronically, it will never self right.

Can you please post your router stats.

Is the line quiet?  Dial 17070 option 2.

[#3]

Hi. I did the quiet line test and can't hear anything sinister on the line. Router is a Billion BiPac 8800 AXL, stats as follows:

xDSL
Mode	VDSL2
Traffic Type	PTM
Status	Up
Link Power State	L0
	Downstream	Upstream
Line Coding (Trellis)	On	On
SNR Margin (dB)	4.2	6.1
Attenuation (dB)	30.3	0.0
Output Power (dBm)	11.2	7.1
Attainable Rate (Kbps)	26097	9952
Rate (Kbps)	28965	9959
B (# of bytes in Mux Data Frame)	227	237
M (# of Mux Data Frames in an RS codeword)	1	1
T (# of Mux Data Frames in an OH sub-frame)	0	38
R (# of redundancy bytes in the RS codeword)	12	16
S (# of data symbols over which the RS code word spans)	0.2504	0.7591
L (# of bits transmitted in each data symbol)	7669	2677
D (interleaver depth)	4	1
I (interleaver block size in bytes)	240	127
N (RS codeword size)	240	254
Delay (msec)	0	0
INP (DMT symbol)	50.00	0.00

The attainable rate is lower than the actual downstream rate, and the SNRM at 4.2 suggests that there is no significant noise on the line, which is why I asked for a line test to see if a fault diagnosis could be made.

[#4]

I believe that attainable is based on 6dB noise margins. Your noise margin is lower hence slightly higher speed.

Attention looks rather high. Try running the fault bots - links below.

[#5]

@Jaggies  Those stats do not look good, the line isn't banded. that is capped at a low speed as the SNR margin is low. As @Townman says ( or intended to say ) the attenuation is pretty high so something is wrong with the copper line, you would never get 55Mbps sync with 30dB attenuation.

As for Openreach "engineers" who change faceplates and say the speed will increase then swiftly depart, just total incompetence. How about them doing some proper line tests.☹️

You have a line fault that needs further investigation.

[#6]

Thanks both.

I've changed to the Plusnet Hub 2 I hadn't taken out of the box before, and got an immediate improvement.

Connection status Connected
Connection type Fibre Broadband (VDSL)
Firmware version v0.05.03.07154-PN (Thu Jul 15 11:07:21 2021)
Serial number Redacted
Downstream sync speed 49.1 Mbps
Upstream sync speed 8.8 Mbps
Network uptime 0 days 0 Hours 7 Mins 46 Secs
System uptime 0 days 0 Hours 11 Mins 44 Secs
Broadband IP address Redacted
Default gateway 195.166.130.250
Primary DNS 212.159.13.51
Secondary DNS 212.159.13.52

Not quite the full previous speed, but much better. Unfortunately the attenuation and SNR margin are not shown so I can't compare those.

It only took 4 minutes for the TR-069 to connect me up, so it's now just a question of reconnecting my wireless devices. Pity you can't have separate SSIDs for the two wireless channels on this router, though.

The router must have sustained some damage when the lightning struck - it completely took out my Sam Knows "white" box, although I should reconnect that now everything is much improved. Even though the internet was working fine, albeit slowly, nothing connected to the Sam Knows box was connecting to the Internet, and my phone extensions stopped working. At least nothing else blew up..!

[#7]

On the Hub Two the SNR location is

Advanced Settings >Technical Log >Information 

HTH

[#8]

Thanks for that - never noticed it there...

Hmm... Export button doesn't work - gives a 404 not found error, so the following is just a straight copy/paste:

Data rate:8.83 Mbps / 49.101 Mbps

Maximum data rate:8.968 Mbps / 50.062 Mbps

Noise margin:6.7 / 6.4

Line attenuation:10.3 / 20.7

Signal attenuation:10.3 / -10.1

That last figure looks a bit odd...

I'll resync in the morning to see if that makes a difference.

[#9]

Stats look much better. DS attenuation is 10dB better which reflects in the somewhat higher speed.

If the line retains to 3dB SNRM you might see 55mbps again.

[#10]

@Jaggies  If we make the probable assumption that Openreach have not done anything to improve your line the wide difference in the stats from the Billion and the HH2 suggests that the Billion may have been damaged by the lightning strike.

Best to continue with the HUB2 for now and see if the speed improves.

[#11]

Thanks again for the replies. The connection has dropped a couple of times, but retains the 6dB SNR, and looking at my Thinkbroadband BQM the before and after suggest the router as the likely cause.

As I said, there was an Openreach engineer wandering about outside on the previous Wednesday, and it may well be he did something, however the fact that the Hub 2 has a better connection than the Billion router is worth persisting with, at least for now.

Prior to the fault, it was like this one from June 6th:

Below is the current one, so I'll keep an eye open for any potential issues, and watch for the SNR margin to lower. 

The ping spikes (yellow) were consistently higher with the Billion, and I have had it for a good few years, so it's probably time it was retired anyway...

[#12]

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@Jaggies wrote:

The connection has dropped a couple of times, but retains the 6dB SNR, and looking at my Thinkbroadband BQM the before and after suggest the router as the likely cause.

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The 6dB SNMR in isolation tells you nothing.  That figure is a MARGIN above the background noise.  When the line syncs it will do so at a speed which delivers a 6dB margin ... so generally it will always be 6dB around the reconnection after a drop ... but the speed might have changed.

The TBQM plots are more likely to be related to the use you were making of the connection at the time, rather than the router involved.  The messy one is very indicative of Sam Knows measuring activity and on-demand streaming.

[#13]

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@Jaggies wrote:

......I'll resync in the morning to see if that makes a difference.

---

If you want the best possible speed then just leave it alone, don't repeatedly reboot the hub to see if it reports a faster sync .

[#14]

@Jaggies 

In passing ...

"Even though the internet was working fine, albeit slowly, nothing connected to the Sam Knows box was connecting to the Internet"

Colourful snippets such as this (when included in fault descriptions) are pure gold, as they ensure that those offering advice have the full set of facts to consider.  In some scenarios it is possible that a Sam Knows Box is sitting quietly in the corner, unseen, unnoticed, hammering the internet ... whilst the user perceives poor speed performance on their key devices.

[#15]

Thanks once again for all the replies.

The SamKnows box is disconnected, the connection has been up for just short of 26 hours at Data rates of 8.3 Mbps up and 49.6 Mbps down. I'll continue to monitor, but happy enough for now.