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Don't think these signal levels are good?

slcfam
I plan to stick around

6 person household, when the modem sees a lot of traffic (especially when a lot of upstream) we see packet loss and just general terribleness.

 

I suspected signal levels, so checked them out; seem bad to me?

 

IndexLock StatusFrequencySNRPower LevelModulation

Downstream
Channel Bonding Value
14
1
2
3
4
5
6
7
8
9
10
11
12
13
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
34
33
34
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
657 MHz
279 MHz
579 MHz
585 MHz
591 MHz
597 MHz
603 MHz
609 MHz
615 MHz
621 MHz
633 MHz
639 MHz
645 MHz
651 MHz
663 MHz
669 MHz
675 MHz
681 MHz
687 MHz
693 MHz
699 MHz
705 MHz
711 MHz
717 MHz
723 MHz
825 MHz
831 MHz
837 MHz
843 MHz
849 MHz
855 MHz
861 MHz
920 MHz
350000000
920000000
40.0 dB
40.1 dB
40.3 dB
40.3 dB
40.4 dB
40.6 dB
40.4 dB
40.5 dB
40.0 dB
40.2 dB
40.3 dB
39.9 dB
39.7 dB
40.0 dB
39.9 dB
40.1 dB
39.3 dB
40.1 dB
40.2 dB
40.5 dB
40.6 dB
40.9 dB
40.5 dB
40.5 dB
40.4 dB
39.9 dB
40.2 dB
40.2 dB
39.9 dB
39.7 dB
39.7 dB
39.4 dB
36.0 dB
39.6 dB
36.2 dB
1.0 dBmV
2.3 dBmV
2.1 dBmV
1.4 dBmV
1.3 dBmV
2.1 dBmV
1.8 dBmV
1.6 dBmV
1.4 dBmV
1.1 dBmV
2.1 dBmV
1.2 dBmV
0.6 dBmV
1.4 dBmV
0.1 dBmV
0.1 dBmV
0.6 dBmV
0.2 dBmV
0.1 dBmV
0.5 dBmV
0.5 dBmV
1.5 dBmV
0.8 dBmV
0.8 dBmV
1.3 dBmV
0.7 dBmV
0.2 dBmV
0.2 dBmV
0.8 dBmV
-1.4 dBmV
-1.5 dBmV
-1.8 dBmV
-2.7 dBmV
2.5 dBmV
-2.7 dBmV
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
OFDM
OFDM
OFDM
 

 

IndexLock StatusFrequencySymbol RatePower LevelModulationChannel Type

Upstream
Channel Bonding Value
1
2
3
4
5
Locked
Locked
Locked
Locked
Locked
21 MHz
25 MHz
32 MHz
38 MHz
42 MHz
2560
5120
5120
5120
0
37.3 dBmV
38.3 dBmV
38.3 dBmV
39.5 dBmV
37.2 dBmV
QAM
QAM
QAM
QAM
OFDMA
TDMA_AND_ATDMA
ATDMA
ATDMA
ATDMA
TDMA
 
 

 

Index 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
Unerrored Codewords 46005543 122758136 122766451 122771456 122776108 122781413 122787371 122792614 122797380 122803144 122808261 122812911 122818223 122823179 122827920 122834165 122840123 122845360 122850780 122855855 122861215 122866398 122871267 122876084 122881231 122885983 122890825 122896300 122901443 122901466 122905584 122906598 52591483 46005543
Correctable Codewords 44687852 3165 2 3 1 3 3 0 2 3 0 1 7 1 3 2 1 2 7 3 0 0 1 1 2 0 0 0 0 0 0 0 51912446 44687852
Uncorrectable Codewords 0 50 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5936 0

 

The uncorrectable codewords on channel 33 ... 5,963 ... was interesting.  Along with the -2.7, 2.5, -2.7 dB on OFDM channels.

 

Am I misunderstanding the data here?

 

Thanks for any info anyone can offer!

 

*Added Labels*

10 REPLIES 10

Re: Don't think these signal levels are good?

-G-
Resident Expert
Resident Expert

Here's an article on troubleshooting a slow or intermittent connection: https://communityforums.rogers.com/t5/Internet/Troubleshooting-a-Slow-or-Intermittent-Connection-Wir...

 

Your downstream signal levels don't look too bad.  Ideally, you want the SNR to be 38 dB or higher.  When they drop below 35 dB, that's when I start to see uncorrectable codewords errors.

 

On the Upstream side, your power levels are on the low side.  Ideally, they should be around 40 dBmV or slightly higher, and not any higher than 50 dBmV.  When your modem's transmit power levels are low, that is indicative that you do not need a high transmit power to communicate with the CMTS.  However, the connection is not quite as stable.  A tech can fix this by installing a Return Path Attenuator at the point of entry in your home, and this will cause your modem to transmit a slightly higher power level.

 

I would recommend that you send a private message to @CommunityHelps and ask them to perform a quick health check on your modem's connection.  They can also check to see whether there are any "area issues" affecting your neighbours as well, and they can also dispatch a tech to further troubleshoot your connection and bring your signal levels to within acceptable norms.

Re: Don't think these signal levels are good?

Datalink
Resident Expert
Resident Expert

Ok, I have a slightly different view of your signal levels.  The downstream signal levels and signal to noise ratios look ok.  You will typically see a high frequency roll-off above 750 Mhz if Rogers hasn't replaced the local tap with a higher frequency tap.  So, looking at the numbers, yup, it looks like there is a roll-off above 750 Mhz, but, it isn't terrible, and certainly within the range that the modem should handle without any issues. 

 

The upstream signal levels are ok.  Historically, on the Rogers network, the upstream QAM channels run in a 36 to 40 dBmV range.  Your upstream levels are in that range, so, their ok.  Personal opinion, adding a Return Path Attenuator isn't a great idea.  That results in higher upstream power levels, which remain in the cable until the upstream signal hits the Return Path Attenuator, at which point the signal levels drop back down to their original levels.  There isn't any gain to be had since the signal levels outbound to the neighbourhood node are the same, with or without the attenuator.  This might be an idea if your home happens to be a noisy RF environment, in which case you would end up running a higher signal level outbound, until the Return Path Attenuator, at which point that higher signal level and any additional noise are both dropped by the level specified by the attenuator.  The other case might be if the modem itself had real issues running at reduced signal levels below 36 dBmV, but, you're not in that situation.

 

The Cable Modem Termination System (CMTS) controls the connected modems and provides data services to those connected modems.  It commands the modems to increase or decrease the upstream signal levels, as required, to meet the signal levels required for arrival at the CMTS.  So, with or without the Return Path Attenuator, the CMTS will command the upstream signal level as required for the CMTS receive and decode purposes.  

 

I agree with @-G-, contact the moderators at @CommunityHelps to check the signal levels at the modem.  The OFDM signal levels as shown in the modem's user interface do not show the internal OFDM channel data that is available to the moderators and Level II techs.  So, its worth checking that out.  Same for the signal levels at the CMTS, which are not reported back to the modem.  The moderators can check those out to see if they are in fact, ok. 

 

Just to note, your downstream channels include two OFDM channels, which is a little unusual.  That is the future, two or more OFDM channels, but, I've wondered just how well the modems handle two OFDM channels.  This is just an anecdotal comment, but, I don't think I've seen signal levels with two OFDM channels where there wasn't some question regarding modem performance.  Not chucking spears here, just wondering aloud about this configuration.

 

You didn't indicate whether the 6 users were connecting via ethernet or wifi.  Can you expand on that, out of curiosity's sake.  

 

When all 6 are using the internet, is the modem running hot, or does it stay warm to the touch?  

Re: Don't think these signal levels are good?

-G-
Resident Expert
Resident Expert

@slcfam wrote:

6 person household, when the modem sees a lot of traffic (especially when a lot of upstream) we see packet loss and just general terribleness.


That's actually not entirely unexpected.  What, specifically, do you mean when you say "general terribleness"?

 

I have the Ignite 1.5 Gigabit cable Internet service.  My modem's signal levels are ideal and my connection is absolutely stable.  However, when I blast traffic upstream, my ping RTT to 8.8.8.8 will go from 15ms to 650ms.  I can also get packet loss, depending on how loaded my node is.

 

With multiple active users in a home, the available bandwidth should get shared evenly.  However, latency-sensitive applications could be severely impacted, especially when your gateway's connection to the Rogers network is saturated with both upstream and downstream traffic.

 

Re: @Datalink 's comments, I agree.  Your signal levels are still within norms.  However, if you are experiencing stability issues with your connection, you need to get Rogers to investigate.  Only they have access to the stats needed to fully assess the health of your connection.  I also would not recommend that you take any actions on your own to try to improve your connection; leave that to the Rogers field tech.

Re: Don't think these signal levels are good?

slcfam
I plan to stick around

Huge apologies for not replying sooner, you are all providing some great info, thanks for that.  Frankly, I didn't expect any replies - sorry about that.  (To be honest I must have missed the mail alerts saying there were replies.)

 

I've been through multiple in-house visits, Rogers swapped out the modem, tested all the cables at our location and everything passed, in the technician's eyes.  

 

I was still able to trip up the latency, and even force a disconnection, by simply downloading 4 linux ISOs at the same time; this reached a peak of about 120 megabits. It does seem to happen above 80ish megabit downloads consistently.  At least at that speed, the transfers are over quickly so the impact is reduced, hah.

 

I was able to demonstrate this to the tech when he was here last.  Right after the new modem was installed, even.

 

As for the questions posed;

 

6 users, each with cellphones, each with ethernet to PCs (or laptops, in two cases), I myself have about 3 desktops and 2 servers hooked up via wire as well.  Three or so firetv sticks.  All gigabit routers and switches set up in a segmented, security-based 'topography', channel congestion considerations made for wifi, as well as 5 or 2 ghz device priority based on proximity to WAP and, say, microwaves, etc.    But I digress...

 

Sounds like a lot, but when everyone is active, the connection is stable.  It's typically only when someone downloads a lot, quickly, (new games from Steam can be 50-100Gb these days, geez), that's when it has problems.

 

We've been at this house for 2 years without issue, without infrastructure change, without useage change, and issues just started happening earlier this year.

 

I'll have to push further with Rogers, as the tech has stopped communicating with me now.  (No, I'm not that annoying, I think he's just frustrated heh)

 

Again, thanks all for the info.

 

BTW, for context, been doing this for 40 years, anyone remember RogersWave?  <g>

 

PS: I did bypass all the house infrastructure and performed tests directly connected to the modem, there was no improvement - in that I was able to cause latency issues even with only one device using bandwidth.

 

73.

Re: Don't think these signal levels are good?

-G-
Resident Expert
Resident Expert

@slcfam wrote:

Sounds like a lot, but when everyone is active, the connection is stable.  It's typically only when someone downloads a lot, quickly, (new games from Steam can be 50-100Gb these days, geez), that's when it has problems.

 

We've been at this house for 2 years without issue, without infrastructure change, without useage change, and issues just started happening earlier this year.

 

I'll have to push further with Rogers, as the tech has stopped communicating with me now.  (No, I'm not that annoying, I think he's just frustrated heh)

 

PS: I did bypass all the house infrastructure and performed tests directly connected to the modem, there was no improvement - in that I was able to cause latency issues even with only one device using bandwidth.


The "problem" that you describe is actually expected behaviour.  Latency will always be a problem on DOCSIS networks.  There is also a need for the network to accommodate varying loads while also minimizing packet loss, and the easiest solution to this problem is to buffer traffic... and when traffic is transmitted onto the network faster than it can exit, the traffic backs up, delay is introduced, and variation in delay is what we call jitter, and when this becomes problematic, we call it bufferbloat.  Additional buffering in home network gear just compounds the problem.

 

Rogers has also been upgrading their DOCIS infrastructure, so that they can (in the short term) offer higher upload speeds and eventually offer even higher symmetric speeds with DOCSIS 4.0.  When Rogers upgraded my old analog fibre node with a new Casa DAA / R-PHY node and new routing infrastructure upstream, it negatively impacted performance and stability.  This is probably what caused you to notice performance problems all of a sudden.

 

Things are performing somewhat better for me now.  However, the future is uncertain given that Casa declared bankruptcy three weeks ago, has had its stock delisted, and will cease operations very soon, probably in a month from now, after it auctions off its cable business to Vecima, Technetix, or whoever end up being the highest bidder.

 

6 users, each with cellphones, each with ethernet to PCs (or laptops, in two cases), I myself have about 3 desktops and 2 servers hooked up via wire as well.  Three or so firetv sticks.  All gigabit routers and switches set up in a segmented, security-based 'topography', channel congestion considerations made for wifi, as well as 5 or 2 ghz device priority based on proximity to WAP and, say, microwaves, etc.    But I digress...


This YouTube video should explain why you are seeing the problems that you are seeing.

 

https://www.youtube.com/watch?v=LjJW_s5gQ9Y

 

There is really nothing that a Rogers tech can do to fix this, nor can you fix it by upgrading your Internet service to a higher speed tier; doing so might even make the problem worse.

 

Are you running totally on your own network gear, with your Ignite Gateway in Bridge Mode?

Re: Don't think these signal levels are good?

lethalsniper
I'm an enthusiast
How did you get the info I'm trying to see how mine are but I can't find it I have the ignite 7gen2 modem

Re: Don't think these signal levels are good?


@lethalsniper wrote:
How did you get the info I'm trying to see how mine are but I can't find it I have the ignite 7gen2 modem

What info?  The Downstream, Upstream and CM Error Codewords stats?

 

Log into your router with a web browser and go to "Gateway > Connection > Rogers Network"

Re: Don't think these signal levels are good?

slcfam
I plan to stick around

@-G- wrote:

The "problem" that you describe is actually expected behaviour.  Latency will always be a problem on DOCSIS networks. 

I'm surprised more people don't notice this issue, or maybe I'm not that surprised (too intermittent).  It can cause streaming to be interrupted and plays havok with online gaming (FPS games in particular).  Currently we have to plan Steam downloads (or any download lasting more than 30 seconds) so that others are not kicked out of gaming matches or the like... kind of sucks but at least doable.

 

and when this becomes problematic, we call it bufferbloat.  Additional buffering in home network gear just compounds the problem.

Yep, this was one of the first things I checked for, actually.  Finally forced me to find time to switch from dd-wrt to pfsense using proper ASICs, which was a nice side affect of troubleshooting.

 

Rogers has also been upgrading their DOCIS infrastructure, so that they can (in the short term) offer higher upload speeds and eventually offer even higher symmetric speeds with DOCSIS 4.0.  When Rogers upgraded my old analog fibre node with a new Casa DAA / R-PHY node and new routing infrastructure upstream, it negatively impacted performance and stability.  This is probably what caused you to notice performance problems all of a sudden.

This is what I was suspecting from the start.  Nice to hear some actual info to back it up.  I regularly check the routing and which internal servers my traffic goes through, sometimes you can just 'feel' the difference in flow.  At my old location (an apartment building) I helped identify a bad MDU, which took quite some time, but they did eventually switch me to the second one they had in the building.

 

Are you running totally on your own network gear, with your Ignite Gateway in Bridge Mode?

I run in bridge mode, however, for testing I did all configurations I could think of.  (This includes single user direct to modem, desktop, laptop, all manner of transfers - focusing more on downstream, however.  Granted there are negotiations for tcp/ip speed leveling etc, but that's regular overhead that I would expect to be negligible;  Especially for a single file transfer.)  During the techs' visits I would demonstrate the issue in bridged and gateway modes, via ethernet to port 4.

 

I appreciate you pointing me to the news about the DOCSIS uprgades, thank you!  Guess I'll wait and see what happens in the next few months.  Unfortunately Bell does not offer high speed in our neighbourhood (yet... fingers crossed.)  I usually have multi-homed internet, which, in the end is only Rogers and Bell of course.

 

End of rambling.

Re: Don't think these signal levels are good?

Interestingly, after reading your analysis, i removed the 9 dB Return Path Attenuator that a Rogers tech installed a few months ago. I was experiencing terrible unreliability of the internet. The connection was going down several times a day. I checked the data on the modem and saw lots of codeword errors. After I removed the attenuator, there were none. I have had no disconnections since. It makes me wonder why the tech installed it in the first place. He did that after I called about connection issues. He upgraded my modem and installed the attenuators.

Re: Don't think these signal levels are good?

57
Resident Expert
Resident Expert

@compster wrote: 1. ... After I removed the attenuator,...I have had no disconnections since.
2. It makes me wonder why the tech installed it in the first place. 

1. Great.  Good for you.

2. These are installed if the signal level is too high. Too high a signal can also cause issues.  You may wish to check your signals.

 

Just as an FYI, even simple devices can fail. I had a splitter go bad after only a couple of years.  Had TV signal issues that were solved with a replacement splitter....

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