Packet Loss issue.
 

For the last couple of weeks I have been seeing signs of packet loss, there was apparently some maintenance work going on last night that I hoped would have solved it but unfortunately not. They appeared to be tinkering with upload channels as they were disappearing one by one.


https://www.cableforum.uk/images/local/2020/06/15.png

My power levels appear to be in check currently.

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID
1 298750000 -2.5 38 256 qam 21
2 138750000 -2.2 40 256 qam 1
3 146750000 -2 40 256 qam 2
4 154750000 -1.9 40 256 qam 3
5 162750000 -1.9 40 256 qam 4
6 170750000 -1.9 40 256 qam 5
7 178750000 -2.2 40 256 qam 6
8 186750000 -2.7 40 256 qam 7
9 194750000 -2.5 39 256 qam 8
10 202750000 -2.2 40 256 qam 9
11 210750000 -2.2 38 256 qam 10
12 218750000 -2.2 40 256 qam 11
13 226750000 -2.2 40 256 qam 12
14 234750000 -2.2 40 256 qam 13
15 242750000 -2.5 40 256 qam 14
16 250750000 -2.5 40 256 qam 15
17 258750000 -2.9 40 256 qam 16
18 266750000 -3 38 256 qam 17
19 274750000 -3.4 38 256 qam 18
20 282750000 -3 40 256 qam 19
21 290750000 -2.7 38 256 qam 20
22 306750000 -2.7 40 256 qam 22
23 314750000 -2.7 40 256 qam 23
24 322750000 -2.7 40 256 qam 24

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID
1 39399998 3.425 5120 64 qam 10
2 25800000 3.45 5120 64 qam 12
3 32599976 3.425 5120 64 qam 11
4 46200014 3.45 5120 64 qam 9

I have a 10dB Forward Path Attenuator that was fitted after issues leading to total outage last year, I was overseas at the time and had to try and help my mum with getting VM to understand that there was an issue.

I do find that when the weather is hot like the other week, my power levels drop to -7dBmV. This also showed a lot of errors in the log and Pre and Post RS errors were in the 10's of thousands per channel. Currently there's just a few pre RS and no post RS.

When the levels were that high I took the attenuator off and that caused them to jump to +7dBmV. Now I understand that heat makes them drop but dropping from the current -3 ish to -7 is perhaps a bit drastic?

Something is quite obviously up with the network here. Noise issues? Speeds seem fine for the most part, but upload does tail off to about half from time to time.

Re: Packet Loss issue.
 

If you're normally running at +7, a 6dB attenuator would be spot-on as -7 is too low.
~3dB change in hot weather sounds about right tbh.

Is it a standard attenuator or an 'Forward path Attenuator'? - As your tx looks quite low (although I don't believe 34dBmV would be an issue persay...

For that packet loss, you wanna be looking at the logs in particular, as you'll see the T3 and T4 errors crops up :)

Tom

Re: Packet Loss issue.
 

Hi Tom,

It is a forward path attenuator, I remember years ago we did have a 6dB one and at one point we were put on a wide band equalizer, I agree that a 6dB one would probably be better right now! It seems things just varied so much at different times that they had to come and change them for something else in their kit, We've been with VM for well over ten years now.

Power levels were around 0 this morning then by midday they were around -4, currently sitting at -3.7 to -5.0, upload was at 40 but now back at 34.5.

There hasn't been any T3/T4 errors today but there is still evidence of packet loss. There's also only a handfull of pre RS and 0 post RS currently.

One thing I have noticed is that the packet loss appears to be less on Saturday/Sunday if last weekend was anything to go by, this weekend seems to be following that pattern.

At the moment upload speed seems a little flaky again, was seeing a maximum of 7Mb/s earlier, maxing at 15 right now, generally it's 21Mb/s.

Quite an odd situation but not currently affecting me as much as it was the other week.

Re: Packet Loss issue.
 

Maybe try swapping it for one of these:-

https://www.ebay.co.uk/itm/Tratec-Fo...wAAOSwgFxezqIb

Re: Packet Loss issue.
 

Send me a private message and I'll pop one in the post for you, if you like (I've got tonnes lying around). Can't hurt :)

At least you can go back to them with perfect levels asking them to troubleshoot further!

Tom

Re: Packet Loss issue.
 

It crapped out this morning with a dropout and a bunch of T3 errors, RCS Partial Service and MDD Timeouts between 8 and 10.

Pre and Post RS are quite high since (I checked yesterday as my tbb graph was showing a lot of packet loss and there was no post RS) though it's not counting any higher right this moment.

Channel Locked Status RxMER (dB) Pre RS Errors Post RS Errors
1 Locked 38.6 502 3509
2 Locked 40.9 1738 6248
3 Locked 40.3 583 3787
4 Locked 40.9 518 3526
5 Locked 40.9 520 3770
6 Locked 40.3 497 3211
7 Locked 40.3 489 3504
8 Locked 40.9 463 3056
9 Locked 40.3 532 2793
10 Locked 40.3 544 2577
11 Locked 38.9 651 2479
12 Locked 40.3 480 3179
13 Locked 40.3 511 3095
14 Locked 40.3 509 3012
15 Locked 40.3 503 3040
16 Locked 40.3 497 3038
17 Locked 38.9 517 3104
18 Locked 38.9 552 3040
19 Locked 38.9 534 3000
20 Locked 40.9 551 2843
21 Locked 38.9 501 2765
22 Locked 40.3 500 3432
23 Locked 38.9 636 2000
24 Locked 38.9 623 1907

Power levels are between -0.4 and -2.4 right now, so not as low as they have been.

Thank you for the offer Tom but I will decline for the moment and see if there's any more issues, might have to contact them and see what's up, really should be re-contracting anyway as I feel we're paying 2x as much as the deals others are getting on 200Mb.

Re: Packet Loss issue.
 

I would give them a ring, it needs taking a look at

Re: Packet Loss issue.
 

It seems my issue is back, but in a different form this time. I thought I'd bump my old thread rather than make a new one for this purpose.

Still running on the 10dB FPA (as things eventually corrected with the last issues and them also doing some local works)

My power levels were edging on -7.5dBmV the other week, I took off the FPA and was up to around 7dBmV but I noticed yesterday that they had risen further to 9.5dBmV on the lowest frequency, but with the highest frequency being (up to) over 5dBmV less which if I am correct, is too large, most people seem to have like 2dBmV difference at most and that's how mine was before).

What I have also noticed is I am getting 1 - 2% packet loss throughout the day and that one of my upstream channels is rapidly flapping between 16, 32 and 64QAM constantly with some T3's.

I put the FPA back in place for the time being.

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID
1 402750000 -4.2 38 256 qam 30
2 202750000 0.2 40 256 qam 9
3 210750000 0 38 256 qam 10
4 218750000 -0.2 40 256 qam 11
5 226750000 -0.2 38 256 qam 12
6 234750000 -0.4 40 256 qam 13
7 242750000 -0.7 38 256 qam 14
8 250750000 -0.9 40 256 qam 15
9 258750000 -1.2 40 256 qam 16
10 266750000 -1.5 40 256 qam 17
11 274750000 -1.9 38 256 qam 18
12 282750000 -1.7 40 256 qam 19
13 290750000 -1.7 38 256 qam 20
14 298750000 -1.5 38 256 qam 21
15 306750000 -1.7 40 256 qam 22
16 314750000 -2 38 256 qam 23
17 322750000 -2 38 256 qam 24
18 330750000 -2 38 256 qam 25
19 370750000 -3.2 38 256 qam 26
20 378750000 -3.2 38 256 qam 27
21 386750000 -3.7 38 256 qam 28
22 394750000 -3.7 38 256 qam 29
23 410750000 -4.5 38 256 qam 31
24 418750000 -4.7 38 256 qam 32

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID
1 39400000 39 5120 64 qam 10
2 25800000 39.5 5120 32 qam 12
3 32599971 39.5 5120 64 qam 11
4 46200000 39 5120 64 qam 9

Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts
1 ATDMA 0 0 0 0
2 ATDMA 0 0 2 0
3 ATDMA 0 0 0 0
4 ATDMA 0 0 0 0

I tried my Hub 3 in normal mode after resetting the other week and on the VM broadband checker it said that there is an issue affecting broadband due to noise on the line coming into the property. When it is in modem mode the checker says they noticed improvements that can be made to WiFi and to call them (probably to try and sell those crappy boosters), but that masks the other issue relating to noise!

Here is the downstream before I put the 10dB FPA back:
https://www.cableforum.uk/images/local/2020/12/17.png

TBB Graph showing the packet loss throughout the day. I could assume this is related to the upstream noise?
https://www.cableforum.uk/images/local/2020/12/18.png

Re: Packet Loss issue.
 

I am sure somebody will correct me if I am wrong but I am sure the downstream spec is -7 to +10. That being said, a 10db fpa seems a bit excessive and is taking you from one extreme to the other and I would be tempted to go with an 6db fpa and see if that improves things.

https://www.amazon.co.uk/Forward-Pat...t-items&sr=1-1


Where do you live btw?

Re: Packet Loss issue.
 

Yeah -7 is way 'outta whack' - That 10dB isn't helping.

In the summer (when the copper's warmed up) - You'll see the signals change by ~3dB.

A 6dB attenuator would be perfect as per Maximus and hold you in good stead for any weather differential :)

Tom

Re: Packet Loss issue.
 

I believe FPA’s shouldn’t be used anymore, due to the filtering on them. You would need a wideband attenuator. The reasoning being FLD5W-65-860-FPA-6

The 65 is 65mhz, which is where the return path spectrum currently ends. Going forward this will be increased. The 860 is 860mhz is where the max this attenuator will go on the forward path spectrum.

Using FPAs just means that certain frequencies will be totally cut off when they are launched, meaning technician visits will be needed

Re: Packet Loss issue.
 

Can you provide a link for what he needs please so we know for the future

Re: Packet Loss issue.
 

I would only recommend using equipment provided by VM. And the £13/14 being charged for the FPA seems excessive. I haven’t worked on CPE for years so not sure of the sensitivities of the kit nowadays, but if he has a 10db FPA on there I would just take it off and see how he goes

Re: Packet Loss issue.
 

lol of course you do. Maybe you can arrange for a tech visit to give him one.

he has and it swings the other way and has the same problem. 10db is too much hence why I recommended the 6

It is but it is the only one I could find and well worth the price imho if it fixes the problem. These days everything seems to be forward path equalisers and not attenuators and I am not sure if they'll make things better or worse

Re: Packet Loss issue.
 

I *could* do, but I don't believe this is levels-related. I've been PMing the OP, and I'm awaiting more info.