Moved: DSL-N16 Packet Loss Hi guys. I’ve been having packet loss issues on the upstream part of my FTTC (VDSL2) line, in the UK. I can test this by looking at the amount of...

[UK Sentinel]

Good idea

In a completely sane world, madness is the only freedom (J.G.Ballard).

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[Betatester548]

So, a BT engineer showed up today, due to a query sent to my ISP. They decided to randomly send an engineer to our house, who had a look at the master socket and replaced the front plate. He did a line test after this, his device said ‘line fault’ a couple of times.

There was another engineer outside who did some work on the cabinet, which was apparently not where I thought it would be, at the bottom of my street, but maybe a bit closer.

I asked the engineer who did the work on our master socket if they’d improved the line (I asked if the SNR had been improved), he said yes. They looked like they were going so didn’t ask them anymore questions.

Interestingly, even though the line was reset, there is still interleaving on the line.

Then I checked the line, but same line stats (attenuation and SNR graph the same), and Mlab’s test is still reporting 0.5% packet loss or more on the line.

It looks like the BT broadband engineer just reset the line at the cabinet (line stats reset and SNR margin now at 6DB), wonder if I can find out what was actually done.

 

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[UK Sentinel]

BT engineer may come back to cabinet at a later time if there was a fault they could not fix at the time.

If DSL profile has been reset, you need to leave whatever modem you are using currently plugged in for at least 7 days so the DSLAM can evaluate your line signal etc.

good news Engineer turned up and I guess ISP may have notes on what BT OPENreach engineer reported after a day or so 👍

In a completely sane world, madness is the only freedom (J.G.Ballard).

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[Betatester548]

Yeah, nice of them to arrange a visit (should be with no charge I think).

I also think my line may be packet loss free now :)

I tried it at 1080p in stadia with no packet loss for 11 minutes. Will try it for longer periods, but suspect its fine now.

I noticed that the power output has  increased on both the downstream and upstream, according to my router. By about 1dbm for both. I’m unsure if this indicates they made any changes or, if this is related to the line DLM being reset.

Lots of FEC errors reported when I telnet to the router, but maybe these don’t matter?

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[UK Sentinel]

CRC are bad, FEC to a point, are less of a worry  ;)

In a completely sane world, madness is the only freedom (J.G.Ballard).

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[Betatester548]

156 upstream CRC errors in 3 hours 30 mins. I suppose the line needs to settle again, but hasn’t effected the performance.

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[UK Sentinel]

Betatester548 wrote:

156 upstream CRC errors in 3 hours 30 mins. I suppose the line needs to settle again, but hasn’t effected the performance.

Be patient

In a completely sane world, madness is the only freedom (J.G.Ballard).

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[Betatester548]

Indeed I will, I know it’s important not to fiddle with stuff that already appears to be working quite well.

There’s also the possibility that that upstream SNR strength has been boosted (I’ve no way to to check as my upstream SNR isn’t plotted on my Asus router. It might explain why I’m not getting packet loss on Stadia now, at least at 1080p.

 

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[Betatester548]

0.001% packet loss on Stadia now after 20 mins, it’s looking good. That miniscule amount of packet loss was probably caused by local network congestion.

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[Betatester548]

I have a question about packet loss, do CRC errors lead to packet loss?

Or are these errored packets discarded by the router, before this happens (resulting in a slightly reduced bit rate).

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[UK Sentinel]

FYI:

CRC errors occur during transmission of a DSL packet and are not recoverable at the receiving end, so the packet is dropped by the router, another packet is then resent as requested by the router (usually).

High CRC can cause packet-loss, due to resends etc, as well as how the modem handles CRC etc.

Telephone usage (not VoIP) can also cause high CRC, ?

In a completely sane world, madness is the only freedom (J.G.Ballard).

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[Betatester548]

Hi, is it normal for a router to discard packets?

I’ve been checking this with this telnet command on my router:

tcapi show Info_Adsl

The number of ‘outDiscards’ on my router has gone up a lot since I started uploading a large 10GB file to Google Drive.

Its going up by hundreds every minute, but generally only when files are being uploaded.

Note – I also noticed that there are just over 2 billion FEC downstream errors after about 2 days connection uptime.

 

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[Grisu]

Some FEC are ok as they will be corrected in the modem, but if they are lets say >1000 a minute you should work on it.

CRC are troublesome as they need retransmission.

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[UK Sentinel]

Betatester548 wrote:

Hi, is it normal for a router to discard packets?

A few is normal, but not desirable as this means the packet has to be resent which can be an issue for gaming / VoIP etc.

2 billion FEC is a tad high, I realise FEC are correctable, but that’s a lot of corrections.

Alas, the DSL-N16 does not handle bad/noisy lines well, hence if the stats worry you, then you need to consider using a Broadcom or simular chipset based DSL modem/Router ?

• DSL-AX82U
• Draytek 130 Modem > Router of your choice
• Fritz!Box 7530 AX etc.

 

In a completely sane world, madness is the only freedom (J.G.Ballard).

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[Betatester548]

The difficult part to work out is, if it my line that is causing the ‘outDiscards’ when uploading files, or, is it the Asus DSL-N16 router?

I tried enabling bitswap, but my router still reports packets being discarded.

I wonder if it has anything to do with firmware?

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