Kevin, excellent follow-up and a great example of how informed customer engagement accelerates troubleshooting.

Downstream Signal Level Correction
Your +15 dBmV downstream levels were at the edge of DOCSIS spec (-15 to +15 dBmV). The technician’s two 4-way splitters in series provide approximately 14 dB of attenuation (~7 dB each), bringing you down to around +1 dBmV—right in the optimal range.

The TV-Data Filter Removal
Those legacy filter traps can introduce impedance mismatches and micro-reflections that degrade MER on OFDM channels. Modern DOCSIS 3.1 plants perform better without unnecessary passive devices in the signal path.

The Real Value: Headend Monitoring
The supervisor escalation for proactive modem monitoring is the most critical outcome. Intermittent upstream issues are nearly impossible to catch during a point-in-time truck roll. CMTS-side monitoring over days or weeks dramatically increases the likelihood of catching T3/T4 timeouts, partial service events, and FEC spikes that correlate with plant problems.

Your continued logging combined with their headend monitoring creates the two-sided visibility needed to isolate intermittent issues.

For Other Readers
Kevin’s experience shows that presenting organized, technically-grounded observations fundamentally changes the support interaction. Technicians respond well to customers who articulate symptoms with data rather than frustration.

Thanks for sharing this resolution, Kevin.

Great addition Maria, this is indeed a common point of confusion. Let me expand on this for your colleagues:

Context: What Are IUC 12 and IUC 13?
Interval Usage Codes (IUCs) define the type of transmission opportunity being granted in the upstream MAP messages. IUC 12 and IUC 13 are specifically designated as Data Profile grants for OFDMA upstream channels (Type 5).

Why Type 5 Channels Only?
Type 5 upstream channels are OFDMA (Orthogonal Frequency Division Multiple Access) channels introduced in DOCSIS 3.1. Unlike legacy ATDMA/TDMA channels (Types 1-4), OFDMA supports:

• Multiple data profiles (modulation/coding schemes) per channel
• Per-minislot profile assignment for fine-grained link adaptation
• Higher spectral efficiency through adaptive bit-loading

IUC 12 and IUC 13 provide the CMTS with additional grant mechanisms to direct CMs to use specific data profiles optimized for their channel conditions.

Relationship to Multiple Transmit Channel Mode (MTCM)
As the spec notes, operation uses MTCM. This means:

1. CMs can be bonded across multiple upstream channels
2. The CMTS scheduler must coordinate grants across channels
3. IUC 12/13 grants allow profile-specific scheduling within the OFDMA framework

Again, thanks for pointing out the needed context.
-Brady

7.2.1.3.11 Data Profiles IUC12 and IUC13 Ies
These Ies are only applicable to Type 5 Upstream Channels. The CMTS uses Data Profiles IUC12 and IUC13 Ies to
grant bandwidth to CMs assigned to IUC12 or IUC13 respectively. Operation on a Type 5 upstream channel uses
Multiple Transmit Channel Mode.

This is from the docsis 4.0 specs

A quick update, Brady:

Thank you, first and foremost, for the very detailed response and explanations! (Much more than I was expecting, and glad it seemed to also verify how I was interpreting the results of my measurements.) I packaged up our exchange and forwarded that information to my cable ISPs regional customer service email address. This was on Tuesday evening. The next morning I was notified by text and email of an appointment that was set for this morning (Thursday) with a tech coming to my house to do their typical start-at-the-customer’s-house tech visit. (Apparently customer service thought my support request sufficiently important to jump me ahead immediately to next-day service.)

I spent about 90 minutes with this tech as he checked out my drop at the top, at the side of the house, and at the cable modem with his Viavi metering device. While the line checked out good at all three places (so no need to put in a new drop line and verifying that he was not finding issues in the house), he did remove a TV-data-only filter trap from my NID box (as apparently as of November, my ISP is no longer installing these and in fact techs are supposed to remove any that they find in the field, which meant that he also removed two other such traps from my neighbor’s line up at the tap when he was testing there). He also decided he must deal with the high +15 dBmV values on my downstream signals that I am receiving. Apparently my ISP has not for several years used inline attenuation traps, so instead he built a 14 dBmV trap using two 4-way splitters, which now sits in my NID box.

More importantly, possibly, is that I had this entire time to ask questions and describe to him my means of logging my modems behaviors, and what you suspect, for these intermittent issues (which he was never going to see during his visit). I explained that all that was in the email that I have submitted to customer care. He seemed to understand and also believe all that I explaining, and indicated that he was submitting a request as well to his supervisor (which it looked he did using his work phone while he was on the call) to monitor my modem. He also encouraged me to continue with my monitoring for a while and to feel free to contact them again if I am still seeing the same issues.

I do hope that upper levels of support do follow-up on my support ticket and look to find mine and other intermittent issues.

Again, thank you for your patience and willingness on two occasions now these past few months to interact with me and continue your teaching even to a user like me! I look forward to continue to follow your blog and videos.

Kevin Anderson

Hi Kevin,

Your description and excellent documentation point to an intermittent upstream impairment on the HFC network that is causing dynamic changes in your modem’s transmit power and brief service instability. This behavior matches several scenarios outlined in SCTE-280 and SCTE-294 regarding return path issues.

Based on your information, the root causes could include:
1. Ingress Noise Bursts
SCTE-280 describes that ingress, especially impulse noise or bursty ingress from intermittent sources (like electrical devices, faulty house wiring, or nearby RF sources), can cause sudden, short-lived upstream signal degradation SCTE-280, page 20.
When this happens, your modem sees a higher noise floor and temporarily increases its upstream transmit power to maintain communication with the CMTS, resulting in the spikes you observe.
2. Micro-Reflections or Standing Waves
SCTE-280 also identifies that micro-reflections from impedance mismatches can cause unstable upstream conditions, particularly if they worsen intermittently due to environmental changes (temperature shifts affecting connectors or cables) SCTE-280, page 73.
Given you are connected near the end of a distribution line and possibly a tap labeled “17N,” this adds risk for standing waves or impedance mismatch issues.
3. Common Path Distortion (CPD)
SCTE-294 explains that CPD can behave intermittently and worsen with vibrations, temperature, or mechanical stress on cable plant elements like taps, connectors, or corroded hardware SCTE-294, page 42.
CPD can cause brief noise bursts and lead to a momentary need for your modem to boost transmit power and retry ranging, resulting in T3 timeouts.
4. Dynamic Range Window (DRW) Violations
SCTE-294 outlines that the DRW is designed to ensure modems operate within a specified transmit power window relative to the CMTS nominal receive level SCTE-294, page 51.
Your modem event log indicating RNG-RSP CCAP Commanded Power in Excess of DRW and T3 timeouts strongly suggests that for brief periods, the modem has to increase transmit power beyond acceptable margins due to a temporary RF degradation — perfectly matching the symptoms of impulse ingress, CPD, or standing waves.
5. Environmental or Field-Induced Noise
Because the phenomenon is highly intermittent (sometimes not happening for hours), it is likely tied to external conditions rather than a permanent fault within your home wiring.
Sources could include utility power devices, mobile transmitters, poorly shielded neighboring equipment, or fluctuating network plant issues.

⸻

Final Analysis:
• The sharp upward spikes in upstream transmit power, brief DRW violations, occasional T3 errors, and return to normal operation are classic signatures of intermittent upstream noise or CPD.
• Given your upstream power is normally low (25–30 dBmV, healthy) and DS signals are hot (+15 dBmV), it suggests a reasonably clean baseline — thus temporary ingress or CPD on the shared line is most likely.
• Other subscribers on your tap could be impacted too, especially if the tap has a degraded port or corrosion issue.
• The errors (especially uncorrectable ones) on the OFDM PLC also support the idea of intermittent RF disruption because OFDM subcarriers are highly sensitive to noise across a broad frequency band SCTE-294, page 51.

⸻

Recommendations:
• Monitor when these events occur — sometimes environmental patterns like temperature (sun heating a tap) or evening loads may help narrow down the trigger.
• Contact your ISP with your logs and explain that the symptoms match potential intermittent ingress or CPD near your tap or line extender.
• Request field maintenance to inspect your tap (17N) and possibly replace connectors or hardware around your drop or the end-of-line equipment.
• If possible, request the ISP to perform a spectrum capture or upstream triggered spectrum analysis (UTSC) at your node or tap SCTE-294, page 50, which can precisely detect ingress events.

⸻

You have done outstanding monitoring and diagnosis on your own — far better than most end users and even many technicians!

-Brady

This is your “end user” (not in the industry) who emailed you in February to ask a question (in response to a different video blog post) about removing an attenuator I had installed on my otherwise simple internet-only cable install to try to see if that would help remove errors I am getting. I did remove that trap on your advice, plus also added just recently some software that allows me to grab regular connection information from my Motorola DOCSIS 3.1 cable modem to compare against my cable modem’s event log to try to better understand what is happening. What the information appears to suggesting to me is prompting this question to you.

What I have discovered that I can actually go several hours in the row with no issues (as in no added correctable or uncorrectable errors by my DS SC-QAM channels or single DS OFDM channel). Then suddenly I’ll get a whole bunch of DS errors, after which a moment later everything be back to normal and continue to hum along again just fine. But what now clearly stands out (by more modem data captured every 15 seconds) that over about a minute or slight longer time period, my US SC-QAM and OFDMA will suddenly jump upwards by 10 to 15 DB, with half the time a DRW violation being recorded with possibly a single T3 error, and then all power levels go back down to where they were before.

I captured two good logs of event this happening this afternoon. So my question to you, and particularly Ron with his RF background (and I too am a licensed amateur radio operator), is what exactly on the HFC network would suddenly cause such short-term, and very intermittent “spike” (either directed or responsive) in my modem’s US power increase and then disappear again, and not possibly to appear again for ten minutes or sometimes another hour or more later? I also should note that my drop is connected to a low-value four-tap at the end of a distribution line (where I think the tap has a 17N or similar label on it) so my DS is somewhat “hot” (starting at around 15 dBmV and varying down from there) and my US power levels are low, starting at typically around 25 dBmV and 29-30 at this time of the year in eastern Iowa.

Below is an example of what I am trying to describe, giving you first my cable modem log for the time period in question and then my capture of the two US channels power levels plus the OFDM DS power level and uncorrectable error count every 15 or so seconds. I should also add that my CM is a Motorola MN8600 running what appears to be 2019 firmware that my ISP supplies, which unfortunately includes loss of user access to the built-in spectrum analyzer. I should also point out that my OFDM downstream channel has its PLC at 351 MHz and appears to be 192 MHz wide (although I do not know if 25 or 50 subchannel width), and there are 16 SC-QAM DS channels starting at 165 MHz up to just below the bottom of the OFDMA edge. And the two US channels include an OFDMA indicated with 6.0 MHz as its indicated frequency (32000K symbol/sec rate) and one SC-QAM channel with 35.8 MHz as its frequency (5120K symbol/sec rate), in support of my 500 Mbps stated service level. My ISP also has some sort of data-only trap installed on the grounding block within the NID on the side of my house.

—> Modem Event Log:

15:16:38


Fri Apr 18 2025 Warning (5) RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
15:16:39
Fri Apr 18 2025 Critical (3) Started Unicast Maintenance Ranging – No Response received – T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
15:16:48
Fri Apr 18 2025 Warning (5) RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
15:16:58
Fri Apr 18 2025 Warning (5) RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
15:16:58
Fri Apr 18 2025 Warning (5) Dynamic Range Window violation

——–> Corresponding modem characteristics captured at the same time span:

Fri Apr 18 03:16:04 PM CDT 2025
moto_downstream_channel_power_dbmv{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 11.4
moto_downstream_channel_uncorrected_total{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 27089
moto_upstream_channel_power_dbmv{channel=”1″,channel_id=”1″,modulation=”SC-QAM”} 30.5
moto_upstream_channel_power_dbmv{channel=”2″,channel_id=”7″,modulation=”OFDMA”} 27.5

Fri Apr 18 03:16:19 PM CDT 2025
moto_downstream_channel_power_dbmv{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 12.2
moto_downstream_channel_uncorrected_total{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 27089
moto_upstream_channel_power_dbmv{channel=”1″,channel_id=”1″,modulation=”SC-QAM”} 34
moto_upstream_channel_power_dbmv{channel=”2″,channel_id=”7″,modulation=”OFDMA”} 27.5

Fri Apr 18 03:16:34 PM CDT 2025
moto_downstream_channel_power_dbmv{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 13
moto_downstream_channel_uncorrected_total{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 27089
moto_upstream_channel_power_dbmv{channel=”1″,channel_id=”1″,modulation=”SC-QAM”} 34
moto_upstream_channel_power_dbmv{channel=”2″,channel_id=”7″,modulation=”OFDMA”} 27.5

Fri Apr 18 03:16:49 PM CDT 2025
moto_downstream_channel_power_dbmv{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 11.5
moto_downstream_channel_uncorrected_total{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 35852
moto_upstream_channel_power_dbmv{channel=”1″,channel_id=”1″,modulation=”SC-QAM”} 42.3
moto_upstream_channel_power_dbmv{channel=”2″,channel_id=”7″,modulation=”OFDMA”} 27

Fri Apr 18 03:17:04 PM CDT 2025
moto_downstream_channel_power_dbmv{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 11.5
moto_downstream_channel_uncorrected_total{channel=”17″,channel_id=”159″,modulation=”OFDM PLC”} 35852
moto_upstream_channel_power_dbmv{channel=”1″,channel_id=”1″,modulation=”SC-QAM”} 31.5
moto_upstream_channel_power_dbmv{channel=”2″,channel_id=”7″,modulation=”OFDMA”} 27

————————— End

Any ideas come to mind of what is happening? What can created such a short-term US power fluctuation being needed or measured? I’ve tested everything I can think of within my house, so expect this is out on the HFC network and therefore should be affecting some number of other users.

I have not yet contacted my ISP yet, as my service keeps humming away except for this blips that sometime causes the video streaming for my wife to briefly “spin” for twenty seconds or so. And I am aware of only one time for when when when my service dropped into partial mode with the loss of one of my US channels, as otherwise I manage to keep both the SC-QAM and OFDMA channel active.

I look forward to any enlightenment you can provide as I keep waiting for my ISP’s PMA/PMN procedures to discover and fix. In the meantime, the upward climbing upcorrectables do bother me, both that they exist at all and thankfully that they seem to be intermittent (although potentially at multiple increments each day and many of the hours of the day).

Regards,
Kevin Anderson

Hi Kevin,

Thanks for reaching out and for following my content over the years—I appreciate your dedication to understanding and optimizing your setup.

To address your question about DRW (Dynamic Range Window) errors:
1. How DRW is Measured:
• The DRW is evaluated across all upstream channels that your modem is locked onto, both SC-QAM and OFDMA. The modem compares power levels across these channels to ensure they stay within a reasonable range of each other.
2. Impact of Power Differences:
• If there’s a significant power-level difference between the SC-QAM and OFDMA channels, the CMTS may command power adjustments, which can trigger the errors you’re seeing.
• The issue isn’t necessarily due to the way the modem firmware interprets the OFDMA power level in raw form (34 dBmV vs. an equivalent of 40 dBmV at 6.4 MHz). Instead, it’s about how the CMTS expects power levels to align across channels in the bonding group.
• Since you mentioned that these adjustments seem to correlate with temperature changes and wind, this suggests a possible issue with your drop cable or aerial plant (especially in a climate like Iowa’s). If this isn’t being caused by in-home wiring, you’ll likely need Mediacom to inspect and possibly replace your drop to stabilize these variations.
3. Attenuation at the Modem:
• I recommend removing the attenuator at the modem. While it lowers your downstream power, it doesn’t actually improve upstream performance because proper padding needs to be done at the tap, not at the modem.
• The CMTS dictates upstream power levels dynamically, so an attenuator at the modem simply forces your modem to transmit at a higher level without truly improving the signal quality.
• If your modem is stable and performing well overall, further adjustments might not be necessary. However, if you’re seeing degraded performance or significant signal fluctuation, Mediacom should check your drop.

If you notice quality-of-experience issues—such as intermittent service, higher packet loss, or speed fluctuations—definitely push for a drop inspection. Otherwise, if your modem is holding a stable connection, you might be okay leaving things as they are.

Let me know if you have any other questions!

Best,
Brady

I am an end-user (not working for my ISP) who is trying to understand and make “clean” my end of the network. I am also a ham radio operator, and so know more than the typical end user. And as background, I live in Iowa, and so a climate that involves seasonal temperature changes, and including (in the winter right now) temperatures that can get quite cold, with my ISP being largely an aerial distribution in my neighborhood.

My DOCSIS 3.1 cable modem (MB8600) has for upstream one OFDMA channel and one SC-QAM channel, both below a “standard” low-split system cutoff, with the OFDMA at the bottom and the SC-QAM just above, as my ISP (Mediacom) appears not to have raised to mid- or high-split yet. I also have a single a single downstream OFDM channel (PLC at I recall 351 Mhz) and 16 256QAM channels in the space below the OFDM channel (down to channel 1 with a center frequency of 165 MHz if I remember correct, as I am emailing from work). I have a 10 dB attenuator on my line just ahead of cable modem, which I put there, and my line out to the ISP service line is clear of any splitters. (The 10 dB attenuator was to make up for what previously a four-way splitter, followed by a two-way splitter (as I used to have TV service as well, but now am data only), that originally for “ahead” of the cable modem.) My DS power levels are generally in the 6 to 9 dB range with the attenuator, with the upstream OFDMA typically reporting around 34 dBmV (which I presume is the 1.6 MHz bandwidth value), with the SC-QAM channel typically around 38 to 40 dBmV. My modem has always remained in full service, with downstream SNRs typically 42 to 44 with this setup, nor has it ever gone off-line, failed to connect up, or want to reboot on its own. In other words, I feel like I have a “clean” and reasonably configured set up for what I can control.

My question is this – if the cable modem is periodically recording type 3 DRW errors (“RNG-RSP Commanded Power in Excess of 6 dB Below Value Corresponding to top of Dynamic Range Window”), and occasionally with those a DRW violation error message, is this likely the OFDMA channel that is being compared to arrive at this error? And could it be simply because the firmware is looking at the “raw” OFDMA power level being a value of 34.0 dBmV, and not taking in account that it is really an equivalent of 40 dBmV when the value is converted for a 6.4 MHz bandwidth, a power level very close to the same as that with the neighboring SC-QAM channel in the same bonding group?

The reason I ask is because I have also noticed that for the most part, each time the CMTS-CCAP is commanding changes in power levels for the upstream (and the above RNG-RSP errors get record), this also seems to coincide to when I also see another whole batch of errors (both corrected and uncorrected) show up for the downstream channels (particularly the 256QAM channels). Otherwise, when I reset my modem, I can actually go a long time into a day (and occasionally multiple days) when the the CMTS-CCAP is not commanding power-level changes and all I see for “error” messages are every 10-minutes adjustments to the upstream profile. It seems to be with weather temperature changes and windy conditions when most of the power-adjustment commands are issued.

I am trying to interpret all of this, both to knowing whether I still have issues that I can attend to versus something I need to call Mediacom about (such as checking for the need for a new drop line. And whether I should try further adjustments, such as add 3 more dB to my attenuator (as I separate 3, 6, and 10 dB attenuators I can daisy-chain). Or just leave well-enough alone, since my system otherwise works reasonably well.

You advice would be welcome. I have watched many of your monthly videos, and have read your material for much longer (at least 8 years now) as I try to understand the technology I use and do my part of clean my operations clean.

Thanks for the fun comment!

We had a internal discussion about CER and CCER and stumbled upon this topic on your site.
Thanks for all the effort you are putting into the socials

your formule is:
correctable codewords = corrected codewords/total codewords*100
The calculation on this website is
correctable codewords = 760804 /13861878 *100

In our opinion this should be
correctable codewords = 760804 /(13861878+760804+47090 ) *100

As the total is 13861878 good 760804 corrected 47090 uncorrectable = 14669772 in total

Or do we miss the point somewhere.

Regrads
Bram and Ronald

Hi Artem,

You can use a DOCSIS protocol analyzer made by Averna

They are expensive, but they will do what you are looking for.

Awesome Greg, thanks for the feedback!

Thank you Sarah!

Hi Don,

The SBG 6900-AC modem is relatively new in modem lifespan terms. Your modem is getting a lot of T3 timeouts (see https://www.youtube.com/watch?v=LjieCgQ6Ji0 for more on T3 timeouts). Once you get 15 timeouts in a row your modem will go offline. It should recover gracefully, but there is a bug in your modem’s code which is preventing that. Eventually your modem will get upgraded code to resolve it, but I don’t know a timeframe for that.

In the mean time, verify your in-home wiring is not the issue, per my video. Once you eliminate that, escalate the issue to your ISP or try a different modem. Those are your options.

Hi Ariel,

Great to hear from you.

I cover this exact question in this article: https://volpefirm.com/docsis-3-0-partial-service/

This is also a very common condition where your cable modem has RF signal, a hand-held meter shows the signal as good from an SNR/MER and power standpoint, but still the modem will not use the channel. So what happens? The technician will replace the modem, but still partial mode exists. But why? Every-time we find that the root cause is always micro-reflections or group delay which are not discoverable by a test meter. So what is the solution? Well, we have had this conversation before – it is PNM. PNM gives you visibility into hidden impairments like micro-reflections and group delay.

You can create new TCS groups in the CMTS so that the modem will bond to 2 channels or even 1 channel. This will make your modem no longer show up as partial-mode, however your subscriber will now have slower upstream speeds. This is not a good solution for obvious reasons.

My recommendation is to use NimbleThis PNM. We have many good partners as well and would love to help you. 🙂

Take care and hope we can one day help you Ariel.

Status – Event Log
The table below contains the log of events that the SBG6900-AC has detected. This log can be important to the service provider to help diagnose and correct problems, if any should occur.

Time Priority Description
Time Not Established Notice (6) Honoring MDD; IP provisioning mode = IPv6
Time Not Established Notice (6) WiFi Interface [wl1] set to Channel 149 (Side-Band Channel:N/A) – Reason:INIT
Time Not Established Notice (6) WiFi Interface [wl0] set to Channel 11 (Side-Band Channel:N/A) – Reason:INIT
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Tue Oct 20 01:37:55 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received – T4 time out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Tue Oct 20 01:33:35 2020 Critical (3) Started Unicast Maintenance Ranging – No Response received – T3 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Tue Oct 20 01:33:30 2020 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Tue Oct 20 01:33:30 2020 Critical (3) Unicast Maintenance Ranging attempted – No response – Retries exhausted;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Tue Oct 20 01:33:30 2020 Critical (3) Started Unicast Maintenance Ranging – No Response received – T3 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Tue Oct 20 01:33:06 2020 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 3;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Tue Oct 20 01:33:06 2020 Critical (3) Unicast Maintenance Ranging attempted – No response – Retries exhausted;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Tue Oct 20 01:33:06 2020 Critical (3) Started Unicast Maintenance Ranging – No Response received – T3 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Sun Oct 18 17:37:20 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received – T4 time out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Sun Oct 18 17:33:00 2020 Critical (3) Started Unicast Maintenance Ranging – No Response received – T3 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Sun Oct 18 17:32:55 2020 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Sun Oct 18 17:32:55 2020 Critical (3) Unicast Maintenance Ranging attempted – No response – Retries exhausted;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Sun Oct 18 17:32:55 2020 Critical (3) Started Unicast Maintenance Ranging – No Response received – T3 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Sun Oct 18 17:32:34 2020 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 3;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Sun Oct 18 17:32:34 2020 Critical (3) Unicast Maintenance Ranging attempted – No response – Retries exhausted;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Sun Oct 18 17:32:34 2020 Critical (3) Started Unicast Maintenance Ranging – No Response received – T3 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) SYNC Timing Synchronization failure – Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No UCDs Received – Timeout;;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) SYNC Timing Synchronization failure – Failed to acquire QAM/QPSK symbol timing;;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No UCDs Received – Timeout;;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No UCDs Received – Timeout;;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No UCDs Received – Timeout;;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Time Not Established Critical (3) No Maintenance Broadcasts for Ranging opportunities received – T2 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.0;CM-VER=3.0;
Time Not Established Critical (3) No Ranging Response received – T3 time-out
Sat Oct 17 19:39:26 2020 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received – T4 time out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;
Sat Oct 17 19:35:05 2020 Critical (3) Started Unicast Maintenance Ranging – No Response received – T3 time-out;CM-MAC=20:3d:66:8b:1a:a9;CMTS-MAC=00:01:5c:76:ae:68;CM-QOS=1.1;CM-VER=3.0;

Thank you for your nice comments. Just a correction to your comment though, Brady graduated from PSU and also JHU. PSU all the way though.

Which Tools I can use to check does CMTS sends UCD message to the modem or not?

Hi Natarajan,

The cable modem is a layer 2 device (OSI Model) and does not inspect any user traffic. Therefore, it does not know DNS traffic from from email. So no, there is no priority given to it and has no idea what DNS traffic is.

Hi Harald,

Blog post and video is up on your question here: http://volpefirm.com/do-t3-timeouts-impact-my-service/

Hope you enjoy.

Hi Harald, thanks for the question, it’s good. We are going to write a blog post on it. It’s a long answer. However, if you cannot wait we do cover T3 timeouts with channel bonding in this video http://volpefirm.com/docsis-3-0-upstream-downstream-channel-bonding/. Thank you for the great question!

Hi Ron, thanks for coming to the site. Send us an email info@volpefirm.com, we need the cable operators name, business address etc. I recently found some. So if I find them again, sure thing.

Any chance that you might be able to send me one of these posters if you have any available. My coworker used to have one at my previous role and would like to have one of my own.

We do have an episode where we discuss Low Latency. http://volpefirm.com/angacom-fdx-r-phy-and-big-data/ We actually believe we discuss it a couple of other times as well, but that might be actual conversations we had and not on air. 😉

Edited – actually we did discuss it http://volpefirm.com/r-phy-orchestration-arris-cisco-brady-volpe/ and a couple of other times. Just search on it.

Are you interested in something more specific?

Hi Irfan,

Thanks for reading and the question. Your question was selected to be part of our podcast. You can watch or listen here. http://volpefirm.com/docsis-cmts-best-practices-recommendations/

Thanks or your interest.
Mia

Hi Manuel,

Thanks for reading and the question. Your question was selected to be part of our podcast. You can watch or listen here. http://volpefirm.com/docsis-cmts-best-practices-recommendations/

Thanks or your interest.
Mia

Hi Jerry,

Thanks for reading and the question. Your question was selected to be part of our podcast. You can watch or listen here. http://volpefirm.com/docsis-cmts-best-practices-recommendations/

Thanks or your interest.
Mia

Hi Heather,

Thanks for your question. It was selected to be a podcast question in episode 25. You can either watch or listen to the answer here. http://volpefirm.com/docsis-cmts-suggestions-best-practices-recommendations/

Thanks for reading!

Mia

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 17 615000000 Hz 3.1 dBmV 41.1 dB 3635 890
2 Locked QAM256 1 519000000 Hz 4.6 dBmV 42.4 dB 3745 1180
3 Locked QAM256 2 525000000 Hz 4.5 dBmV 42.3 dB 3935 1014
4 Locked QAM256 3 531000000 Hz 4.5 dBmV 42.3 dB 3957 1070
5 Locked QAM256 4 537000000 Hz 4.4 dBmV 42.1 dB 3660 1109
6 Locked QAM256 5 543000000 Hz 4.3 dBmV 42.0 dB 3790 1285
7 Locked QAM256 6 549000000 Hz 4.2 dBmV 42.1 dB 3415 1575
8 Locked QAM256 7 555000000 Hz 4.1 dBmV 42.0 dB 3300 971
9 Locked QAM256 8 561000000 Hz 4.1 dBmV 42.0 dB 106 133
10 Locked QAM256 9 567000000 Hz 3.9 dBmV 41.9 dB 115 142
11 Locked QAM256 10 573000000 Hz 3.7 dBmV 41.7 dB 132 112
12 Locked QAM256 11 579000000 Hz 3.4 dBmV 41.6 dB 90 140
13 Locked QAM256 12 585000000 Hz 3.1 dBmV 41.3 dB 117 128
14 Locked QAM256 13 591000000 Hz 3.1 dBmV 41.3 dB 116 146
15 Locked QAM256 14 597000000 Hz 3.3 dBmV 41.4 dB 112 181
16 Locked QAM256 15 603000000 Hz 3.2 dBmV 41.4 dB 104 126
17 Locked QAM256 16 609000000 Hz 2.9 dBmV 41.9 dB 0 0
18 Locked QAM256 18 621000000 Hz 2.7 dBmV 41.4 dB 0 0
19 Locked QAM256 19 627000000 Hz 2.7 dBmV 41.4 dB 0 0
20 Locked QAM256 20 633000000 Hz 3.0 dBmV 41.8 dB 0 0
21 Locked QAM256 21 639000000 Hz 3.1 dBmV 41.4 dB 0 0
22 Locked QAM256 22 645000000 Hz 3.3 dBmV 41.8 dB 0 0
23 Locked QAM256 23 651000000 Hz 3.1 dBmV 41.4 dB 0 0
24 Locked QAM256 24 657000000 Hz 2.9 dBmV 41.3 dB 0 0

Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 81 5120 Ksym/sec 36400000 Hz 48.0 dBmV
2 Locked ATDMA 82 5120 Ksym/sec 29500000 Hz 42.5 dBmV
3 Locked ATDMA 83 5120 Ksym/sec 22600000 Hz 47.5 dBmV
4 Locked ATDMA 84 5120 Ksym/sec 15700000 Hz 45.5 dBmV
5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

Do you see anything glaring in the above status? These errors are driving my family and I crazy.

Could you recommend acceptable Upstream Codeword error ratio, correctable ratio, uncorrectable ratio?

1. per cable modem
2. per upstream channel

Thanks
Jerry

Great post.

I am doing some research around manpower (and any costs otherwise) involved in provisioning in a DOCSIS. I see the flow but would like to understand how many people are involved, and how long the tasks take – for anything that isn’t automated.

Any information is highly appreciated.

Best,
Antony

Hi Matthew,

Yes, absolutely. This is a huge opportunity for PNM remote spectral monitoring.

-Brady

Hi Ariel,

Great to hear from you!

The ideal upstream transmit power for any cable modem is between 40 to 50 dBmV (100 dBuV to 110 dBuV). This keeps your modem’s upstream signal out of the noise floor (at 40 dBmV), but far enough below max transmit (50 dBmV). This is a standard best practice across many MSOs around the world.

For cable modem receive levels (input to the modem on the downstream) the ideal is 0 dBmV (60 dBuV). This is the optimal input for all cable modem chipsets. Each cable operator has a window they allow installers to deviate, such as +/- 5 dB, +/- 10 dB and even +/- 15 dB. My recommendation is really work hard to not have any modems running outside of -10 dBmV to +10 dBmV (50 dBuV to 70 dBuV). Once you start to get outside of this window you will run into either low MER at the modem (-10 dBmV) or you can overdrive the input of the modem (+15 dBmV).

Hope this helps.

-Brady

For DOCSIS 2.X and DOCSIS 3.0 cable modems, which values for RX Power, Tx Power and US SNR are recommended to ensure that CM is working in the acceptable levels.

Thanks

Ariel Mendoza

I am at my wits end. I have been getting T3 time out errors for 2 months and this has been affecting my gaming and most things requiring a stable live connection. Here is an exact message I have been getting.

No Ranging Response received – T3 time-out;CM-MAC=f0:f2:49:93:7d:60;CMTS-MAC=00:17:10:91:0c:11;CM-QOS=1.1;CM-VER=3.0;

My service provider says they have checked myine and all signals up and down look good.

Do you have any suggestions as to what I can tell them. I have read posts on this same issue from other customers. I think they know what it is but not willing to fix it.

Thank you

I have a few Questions

If those nodes vary from 42 to 35 dB in SNR and the cable modems don’t have any substantial flaps and the UP MER is over 35
According to my experience I shouldn’t have any problems.
I think I don’t but some people say that my SNR should be flat with no variation

Other question
Which are the limits on variation in SNR as long as you don’t fall in the threshold

First comcast suggested it was a backlevel (End of Life) modem problem…. But now I’ve tested with three different model modems and see the same problem. DPC3000, SB6141 and now CM820A.

I see continual timeouts T3 and T4 every 30 seconds in the modem logs.
Today, tech over phone suggested removing a splitter.
When I do that, no more timeouts – But I still don’t think all upstream are working because
status message shows “—-” empty instead of real numbers for power and upstream symbol rates.

Tech will make a home visit on Wednesday…
Advice?
Thanks!

I guess that answers my first question 🙂 . But i wanted to understand what are the prerequisites for this ? IP Network ?? RF. What are the main areas for orientation towards this material ?

Thanks
Bharat C P

Your articles are simply awesome. However i have a favor to ask of you. Do we have any reference guide/book on DOCSIS. I understand that DOCSIS 1.0 may be shelved , however i still want to know about it. It is something like 802.11b/g/a nobody uses them (almost) , however for a beginner it is better he starts from the source to appreciate the enhancements made in 802.11n/ac . I tried reading the SCTE specification from Cable labs completely lost, even at the basics there is not table like

Modulation , Channel Width , range etc etc Especially for upstream in DOCSIS 1 and 2 , see the confusion lies in Upstream channel width frequency, DOCSIS 3.0 and 3.1 are well documented but DOCSIS 1 and 2 i cannot seem to get a clear picture on the numbers. Kindly help.

Thanks
Bharat C P

Glad to hear it got resolved for you!

Thank you for your reply. The problem was solved by my ISP operator, bonding upstream channels.

Best regards,
Dan.

There are a lot of elements to a cable plant and your point is well taken. Thanks for the comments!

Hi Lior, Yes, 2 separate subnets.

Ta
Cabs

Hi Daniel,

Sorry TLV this isn’t in our bailiwick. I tried around but all I can say is good luck to you.

Hi Kevin,

According to the experts it Should “appear” flat and in line with rest of chs on your plant at the input to the laser.

Hi Dan,

I asked about this and you need scm ver from CMTS perspective to see what is happening. Levels would be first thing to check and verify. If single US is only using 42 dBmV, then levels should not be an issue unless freq specific issue from your house, then could be low US EMR for the other chs.

Hi Sam,

9e-7 means 9 errors out of 10,000,000 Even 1% error would be 1 out 100. SO, you see, this is < .000001 %.

Hi Kevin,

2-ch US bonding using 64-QAM maxes out at 54 dBmV, so it may be an US level issue.

Hi Widiyatmika,

JJD suggests – D3.0 depends on modulation and chs transmitting. It’s ~ 23 dBmV, but I would suggest having modems Tx between 42-48 dBmV with a median of 45 if possible.

Hi Cabs,

It’s called PNM –Proactive Network Maintenance because it is being proactive and not reactive, Pre-eq is “masking” issues on the plant keeping the end subscriber happy. But, it’s up to the cable company to be proactive to track how hard this pre-eq is working to fix issues that could potentially get worse and then affect the customer later. The cable plant does not heal itself.

There are so many times in history where people were skeptical of a new technology and now a days we cannot image living without it or going back to how it used to be. Thanks for the feedback!

Hi ZJ,

I suspect this is one of the options like Option 82 or 144 for emta, etc. – JJD

Hi Ed,

Running near the diplex rolloff can be an issue for that US ch’s MER readings especially for 64-QAM and wider chs like 6.4 MHz. Also worse when running through long amplifier cascades because of the cumulative effect of group delay. Easiest fix is lower the freq or activate pre-eq (equalization-coefficient. Or run narrower ch like 3.2 MHz or lower amplifier cascade. FP laser has nothing to do with the grp delay issue associated with diplex filter edge. With that said, FP lasers have much lower dynamic range vs DFB lasers and can be overdriven much easier and cause non-linear mixing from laser clipping. Digital reverse lasers are even better and also the new architectures coming soon called remote phy will get rid of analog lasers altogether. The optical receiver is a PIN diode or avalanche diode. I think you are using the term receiver to mean the node, but not sure. – JJD

Hi Carlos,

It is more cosmetic than anything, It may be good to see if the CM has a new firmware version available. I have seen where the CM reports proper time offset on the first US it ranges on, then it seems to double on the other USs and is cosmetic. You might want to consider watching or listening to our podcasts on these topics as well. Good luck to you.

Hi Usman, The general consensus is the question is too vague to answer. You might want to brush up on the manual to help this along a bit. Good Luck

Hi Flavio, here is the input from JJD. If it’s not an US signal level issue, it could be a timing issue. I have seen where sometimes the MAP advance is too aggressive and the modem goes to US bonding partial mode. What does scm ver display? All 4 USs should report STA.

Hi JC, thanks for the comments. It really just depends. CMs report issues all the time. We recommend you work it out with your ISP. Really you should have good service all the time with maybe an intermittent issue in a blue moon. I would say every cable operator we have worked with really wants you to have a positive and quality experience. So they will want to fix your problem too. Good Luck

Hi Kosai, I sent you a direct message with Devisor contact information. Good Luck. Mia

Im new to Docsis and i find this website with most of the information

Please share the below poster
DOCSIS 3.0 Cable Modem Registration with T3 & T4 Timeouts Poster

poster available online is blur and i can not read it

Please share

Knowing that it is impossible to have perfect connections 100% of the time… just trying to understand a bit more than just signal level being in spec, as an end user in diagnosing trends before calling in for what may be a momentary issue.

Hi George,

Will you be at SCTE EXPO? Who do you work for?

Thanks,
Mia

Hi Pradeep,

Will you be at SCTE EXPO? Who do you work for?

Thanks,
Mia

Oi,

Obrigado pelo feedback. Atualmente temos apenas oferecê-lo em Inglês / com legendas em inglês . Se o YouTube oferece uma Inglês para Portuguese que seria ótimo. Se você está interessado nos subtítulos em inglês , clique em CC na parte inferior direita da tela.

Obrigado!

Gostaria de assistir esta podcast com legenda em português do Brasil.

Grato,

http://www.docsis.org/node/7645

Hi Asaf,

The general rule of thumb is each time you double the number of channels your RF max transmit power will decrease by 3 dB. This is based on the formula of 10*log(2). So you can apply this to the rest of the channels for your remaining bonding groups.

-Brady

Hi Greg,

Great to hear from you. Thanks for pointing out the error. It has been corrected.

-Brady

By the way, during the presentation a discussion happens at approx. 25mins.

John remarks that blacker pictures mean more power because the visual modulation is negative.

Actually the visual modulation could have been positive ie it could have been white pictures requiring more power.

The reason why the visual modulation is negative, is that because this is an AM signal, it is sensitive to AM noise, such as electrical. Making the modulation negative, means that noise introduced during the transmission process, appear as black spots which are much less perceptible.

Say hi to Ron & John from Andy now living in South Africa!

i came from Germany and would send my collegue Mr. Schwegmann to get two Posters from you.
It is OK?

Regards,
Oliver

Can you please help me to get this poster?

Thanks,
Pradeep Deshpande

Hi Irene,

It is a Gray coding scheme for all modulation formats in DOCSIS. See https://en.wikipedia.org/wiki/Gray_code for more information on why the Gray code schema is used. In general it helps reduce error between adjacent symbols.

-Brady

I’m playing with 24×8 cable modem.

for 4 channel bonding group the spec is specifing the numbers at the table below.

Constellation Pmax (dBmV) TDMA
1US BG 2US BG 4US BG
QPSK 61 58 55
16-QAM 58 55 52
32-QAM 57 54 51
64-QAM 57 54 51

does someone know what are the numbers for 5,6,7,8 bonding groups?

Hi Parvez,

If you have a CMTS and Ethernet drop from an ISP you can connect the drop to the CMTS with either copper or fiber. The next step is to activate the GigabitEthernet port of the CMTS and then assign it an IP address and subnet provided to you by your ISP.

-Brady

Hi Bryan,

Catch Hangout on April 8th and well cover this question.

-Brady

Hi Matt,

I’ll be at ANGACOM in Cologne Germany in June. Hope to see you.

-Brady

16 Primary Capable DOCSIS 3.0 channels vs 8 Primary Capable & 8 Non-primary capable.

Assuming a fair amount of modems (500 modems), would there be a throughput/performance savings when limiting Docsis messaging to the first 8 Downstreams?

Thanks in advance!

The local CATV provider gave a line from their CO and I need to integrate that like pass through integrating Internet with the CATV.

Will you please tell me the concept of DEPI tunnel Between RF gateway and 3G60 card of cisco 10k . What actually the DEPI tunnel do ? Also Share the information about the fiber nodes .I have query about How many fiber node we can configure on single upstream connector .?

Hi Michael, Thanks for letting us know. It should work now.

Hi Rohit,

MAP (Media Access Protocol) is the communications protocol between he CMTS and CM that allocates time slots for cable modems to transmit data on the upstream in a Time Division Multiple Access (TMDA) system. Each modem must transmit within their own time slot. The MAP messages from the CMTS tells the cable modem when they are permitted to transmit data without colliding with another modem.

-Brady

What is Media access protocol (MAP)? Is it same as media access control(MAC)?

I have a question how we can channel high speed internet data when there is down stream rf channel bonding happening.

Honestly your god of catv. your tutorials really helped me to understand the idea of CMTS and DOCSIS 3.0.
I have a question related to IP Bonding in CMTS from Internet side, how it is done? if there is a telephonic data how it is separated at CMT side. last but not least does CMTS auto tests and make connectivity between all cmt’s or there are some technical tests involved. If it does what are those? are they situation based tests.

Cheers 🙂

Hi Sergey,

Yes, it is very common to do 4 or 8 DS channel bonding on the MC20x20 cards. Also upstream channel bonding is very common. This is in the I-CMTS configuration. Same for the 5×20 cards, but I generally recommend the MC20x20 cards over the MC5x20 cards because performance in the MC20x20 cards is far superior over the 5×20 for a number of reasons.

-Brady

Hi Ken,

Great question to ask before moving to D3.0. DOCSIS 3.0 modems will only go as far down as 111 MHz with some down to 108 MHz. So you will need to keep your DOCSIS channels above 111 MHz recommended.

-Brady

i want to know why we are used two down stream D0 & D1 in cisco ubr 7225 CMTS.

uBR10012#show cable modem 2C:AB:A4:09:B4:6C ph
MAC Address I/F Sid USPwr USMER Timing DSPwr DSMER Mode DOCSIS
(dBmV) (SNR) Offset (dBmV) (SNR) Prov
(dB) (dB)
2cab.a409.b46c C5/0/1/U4 7445 49.00 35.18 5228 2.20 39.00 atdma* 1.1
2cab.a409.b46c C5/0/1/U5 7445 49.00 33.61 2742 2.20 39.00 atdma* 1.1

Thanks

Could you help me to understand – is it possible to have DOCSIS 3 DS and US bonding on the uBR10k with 20x20v linecards and 5×20 licensed channels (I-CMTS mode). So we have only 20×20 linecards and 1 DS freq. on each card DS connector. All DS from each card combined.

Thank you!

WBR,
Sergey TArasevich.

regards

What are station maintenance bursts?
Why should they have a low modulation (QPSK,…) to maintain the CM online?

Best regards

thank you.

What are the expected PNM capabilities for the remote PHY? Are they same as what have been specified for the CMTS as in section 9 of PHY3.1 spec? For example, R-UEPI didn’t specify pseudowires for downstream symbol capture and upstream histogram, does this mean these PNM functions are not required for remote PHY?

Another question is where are the pre-D3.1 PNM functions specified, e.g. 24-tap pre-EQ, spectrum analysis, channel response, impulse noise, etc?

Hi Phil,

We covered your question in our G+HOA / podcast. http://volpefirm.com/operationalchallenges/

Thanks,
Mia

could I know what is the minimum power level that modem should transmit ? what is the factors that involve ?

Hi Nikesh,

Your question was answered in our podcast. http://volpefirm.com/operationalchallenges/

Thanks,
Mia

Thanks

I am a bit confuse in the concept, still trying to figure out

I read the CER should be 9E-7 and when we do the calculation here I can see that about 7% of the data, I am not sure maybe I am making a wrong concept can you please help me clear the concept

Thanks
Sam Wills

Please i would like to know what coding scheme was used to generate the 64 qam signal.

We know the starting power for D3.0 CM initial ranging is 23 dBmV. What is the CM starting power for D3.1 O-INIT-RNG-REQ message?

Thanks!

I have the following problem with a docsis 3.0 modem: randomly it `lose` 1 or 2 / 4 upstream channels (connecting on the modem interface 192.168.100.1 I see 0dBmV on one or two up channels, the other ul/dl channels have ~ 42dBmV) and on the ISP site it apears blocked, at home it has all 4 sync leds on and internet blinking. The MTA is offline too, the led is off and the thelephone has no tone. I call the ISP and they changed 3 modems by now, remake the connections, changed the splitter but no result. Can you please tell me what verifications can be done further to solve the problem?

Thanks!

I have a query . we installed new cisco10k cmts . The problem is that Few of the modems on the cmts getting the 50 mbps speed but the 0mbps download speed .
we checked the snr and power related parameters but all parameter are fine . We all getting the loss when ping the modems from the cmts . Please advice why speed is getting download as 50mbps and upload as 0mbps.

cmts 10k#ping 10.112.62.126 r 200

Type escape sequence to abort.
Sending 200, 100-byte ICMP Echos to 10.112.62.126, timeout is 2 seconds:
!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!.!!!!.!.!!!.!!!!!!!!!!!!
!!!!!!!!!!!.!!!.!!!!!!!!.!!!!!!!!!!!.!!!!!.!!!!!!!!!!!!!!!!!
Success rate is 94 percent (189/200), round-trip min/avg/max = 4/9/40 ms

cmts 10K#snr712
US phy MER(SNR)_estimate for good packets – 15.5941 dB
US phy MER(SNR)_estimate for good packets – 16.3475 dB
US phy MER(SNR)_estimate for good packets – 18.6444 dB
US phy MER(SNR)_estimate for good packets – 18.2092 dB
cmts10K#

Pune-10K#shcm mac address
D
MAC Address IP Address I/F MAC Prim RxPwr Timing Num I
State Sid (dBmv) Offset CPE P
affnn,mdfnsd, 10.112.62.126 C7/1/2/UB w-online 653 0.00 2247 1 N

Hi John,

you can never take a specific measurement in time and assume accuracy. There are too many variables. It’s best to have a start point and an end point to do delta readings in a specific time period.

Hi Matthew,

The problem with RFoG (DPON) is the ONU will turn on for any energy whether it’s DOCSIS or not. Issues could be uncorr FEC not from OBI, but optical link misconfig/wrong levels/setup. Other issue is lasers turn on from any energy (CB, noise, docsis, STB, impulse noise, etc). Not much we can do about it. I know our own ONU has a squelch feature to turn off the laser if on continuously more than about 20 msec and logarithmically increases that turn off when it happens more often. It is difficult to pinpoint a bad house in an RFoG environment since the noise (if low enough) will not activate the ONU/laser and you would not “see” it in the HE. PNM’s base feature was to look at pre-eq info which is not the same as noise viewing. Maybe using new CMs with US ingress viewing would be fastest and easiest way to identify the culprits.

Hi Mariah,

The cable modem has not received any periodic Upstream Channel Descriptor (UCD) messages from the CMTS within the timeout period. This error message is DOCSIS event message is U01.0, Upstream Channel Descriptor. Should get this message once every 200 msec.

Hi Maria,

CMST setting; (Cisco CMTS default is cont ranging on failure to allow it to come back automatically). Some customers have turned this off.; US MER is still bad; time offsets are out of whack and or map advance is too aggressive. Also, this question was discussed in our last G+HOA. You can either watch the video or listen to the podcast here http://volpefirm.com/cablelabs-interop-docsis-3-1-channel-bonding/

Hi Meghan,

It would be good to see the state of the modem where it gets stuck, such as init(d) init(o), etc.

Thanks,
Mia

Hi Mike,

We will be supporting our parters at their booths as needed. However, Brady will be presenting at SCTE EXPO again this year and also will be speaking at the BTR Breakfast. http://volpefirm.com/btr-tech-breakfast-docsis-3-1-revisited/ or Wednesday, October 14, 10:45-11:45 am DOCSIS® Proactive Network Maintenance: Getting Ahead Of The Game

Will Volpe have a booth or will you be at another vendors booth this year?

I sent you a private email.

let me know what is the command to verify whether the emta is failing because of registration in the cmts or dhcp offer or request done by emta.

What are the primary reasons if the US partial mode do not go back to UB after some recovery?

Hi Ervinbegu,

You make some great points and there is a lot of debate among cable operators as well as vendors on DOCSIS 3.1. Many say why not just go fiber to the home, while others recognize that extending the live of the invested coaxial infrastructure has significant merits. DOCSIS 3.1 does not require any changes to the outside plant – this is optional if you want to really experience the full potential of DOCSIS 3.1.

You could drop a DOCSIS 3.1 CMTS and cable modem into you existing plant and see significantly increased downstream and upstream spectral efficiencies without any plant changes due to OFDM and the LDPC error correction. This is one big reason major cable operators are looking to invest in D3.1 to extend the life span of their existing HFC plants with minimal investment in the near term. Further the built-in testing capabilities of D3.1 are quite powerful – this is the PNM applications.

Longer term cable operators will likely need to change the split (85 MHz or 200 MHz returns), which means a lot more investment. This does bring up the question of “when does more fiber make sense?” I think that question will be dependent on a case-by-case analysis.

What do you as readers think about DOCSIS 3.1 vs. PON architectures?

Hi Kadamnikesh,

I edited your post to obscure the MAC addresses. I recommend this in general as you never know what someone may do with the MAC address information when posted publicly. As a general rule to anyone reading this its a good recommendation to not post full MAC addresses.

As to your question, we often see issues with CPE devices not sending or accepting DHCP messages correctly. Depending on your DHCP server you may be able to capture the error messages there and diagnose the issue. If not, I recommend that you go back to the basics of DHCP troubleshooting which means capture the DHCP discover and reply messages either on the CMTS in debug mode or using Wireshark with port mirroring. Capture both a successful DHCP discover and offer message and a failed discover and offer message. Compare the two for what is different and you will usually see what is wrong. Often times you can modify the DHCP server to rectify the situation and get the offending CPE device to get an IP address. However sometimes the CPE device will require a firmware update or need replaced.

-Brady

Hi Meghanathan,

There are many possible issues that are preventing your modems from passing TFTP. We recommend that you work with your modem vendor as the TG series and gateways often require specific MIBs to be loaded into the config file in order for them to come online.

-Brady

Hi Bob,

The recommended best practices for upstream transmit power from cable modems is 40-50 dBmV. The low of 40 dBmV keeps your modems out of the noise floor and therefore improves upstream SNR (MER). Keeping modem below 50 dBmV will ensure that when you are doing upstream channel bonding that you don’t run out of transmit power. As you read in the article on “Why are my DOCSIS 3.0 cable modems transmitting at 52.2 dBmV?” you are aware that max Tx power drops as modulation increases and the number of bonded channels increases. While you may not be doing 4x channel bonding today it is likely that you will sometime in the future. So now is the time to start grooming your plant to get modem Tx levels in line rather than when you want to add those extra upstream bonded channels.

-Brady

Home, home on what range?

Thank you.

This issue is only with gateway devices rest other CM and emta devices are working fine. Please let us know what could be the issue..

thanx for your valuable help . i have a query that we have CASA c3200 cmts ,when the netgear wifi router is connected to the modems it is working fine ,but when the d-link wifi router connected to modem it is not assigning the ip to wifi router i.e the wifi router(d-link) is not binding .
please suggest me to rectify this problem.

casa_CMTS#
casa_CMTS#shcm fc4a.e90c.xxxx cpe
CPE IP Address Method CPE MAC Address CM IP Address CM MAC Address
0.0.0.0 dhcp 3c1e.0494.xxx 10.116.0.120 fc4a.e90c.xxxx

HI,

Your questions was answered during the podcast. Please see here http://volpefirm.com/cablelabs-f2f-and-acta-along-with-other-topics/

Hi,

Same technique since every US ch for D3.0 US bonding still does independent station maintenance and treated independently. But, keep mind that max TX level; for 4-ch US bonding using 64-QAM is only 51 dBmV, so modems could max out quicker. US balancing is still fundamentally based on unity gain. Once balance, CM levels can be changed by just manipulating padding in the HE. Also see http://volpefirm.com/cablelabs-f2f-and-acta-along-with-other-topics/

Hi Gopal,

Simple spectrum analyzer, Nimble This, CBT, new Brcm US analyzer feature in new modems. Also see http://volpefirm.com/cablelabs-f2f-and-acta-along-with-other-topics/

Hi Vijay,

Can you be more detailed in describing your issue?

Hi,

Too many modems with ! (maxed out) can create more entries in the Flaplist for power adjusts and also more maintenance on the CMTS since the CMTS can go into fast-polling mode whenever a SM, 3-way handshake, is not successful.

I still think an easy, low cost fix for the low end of the bell curve is at least an in-line EQ pivoting at 1 or 1.2 GHz and all the way to 5 MHz. This could “help” 11, 8, and 4 dB taps where most of the noise comes from since less attenuation from house to amplifier through these taps. EQ without step-attenuation also has minimal grp delay issues or no need to be changed out when, and if, diplex filter split changes are decided upon.

Another by-product of letting CMs transmit low is the propensity to ramp up during outages and potentially cause laser clipping or even exceed isolation is the HE and show up as ranging on US ports you didn’t think were possible. Also, don’t disregard “babbling” modems.

In regards to settop boxes utilizing CMs (DSG) for signaling and located deeper in the house, we have proposed DOCSIS restricted load balance groups and other “Steering “ methods to have those devices use a ”quarantine” US ch like 1.6 MHz at QPSK or 16-QAM to achieve higher output and not take up much spectrum and can be placed in the low band. (1.6 compared to 6.4 MHz ch width will be 6 dB better CNR). QPSK vs 64-QAM will have ~ 10-12 dB more robustness.

One more option is installing modems with new Cablelabs ECR for Ext US transmit power in location where needed.
Padding at the tap makes the most sense to drop potential noise from drop and house.

Also see http://volpefirm.com/cablelabs-f2f-and-acta-along-with-other-topics/

Hi Asian,

dhcp process is “dora”. discover, offer, request, and acknowledge. we have init(d), init(io), init(dr) and init(i) to indicate those 4 states of registration.

In regards to US states, this means down with ranging enabled. Any state other than STA is bad and mode will be marked /p for US bonding partial mode.

Also see: http://volpefirm.com/cablelabs-f2f-and-acta-along-with-other-topics/

Hi Jairo,

No. Max US pwr is based on modulation of the a-long burst. But, the US power level setting range on the CMTS US port IS based on the ch width. Also see: http://volpefirm.com/cablelabs-f2f-and-acta-along-with-other-topics/

Please re-phrase. If talking Ds and interleaving, than default of 32:4, with 4 other options available. If talking US interleave, I recommend dynamic when using freqs < 20 MHz to help with impulse noise issues. It is not on by default. Also see: http://volpefirm.com/cablelabs-f2f-and-acta-along-with-other-topics/

A 3.2 MHz wide ch will always “appear” 3 dB higher than the 6.4 MHz wide chs. Another cause could be, where are you doing the test? The CMTS wants 0, but because of rolloff, etc, the chs could be higher at the higher US freq to overcome the roll-off farther towards the CMTS. Please read some of the other replies for further answers. Also see: http://volpefirm.com/cablelabs-f2f-and-acta-along-with-other-topics/

Up in the white north we have some ftth & ftts implementations and are using rfog to the suites. We currently have some tier two tools we utilize to see noise in our cable plant, and I have seen noise in all-fiber buildings (presumably some form of light interference getting into the fiber? or the noise is so high it passes past the onu?) Do you forsee any possible way to utilize docsis 3.1 and pnm to help track down the source of these disturbances too?

Hi Lashone,

Sorry, we don’t email them out. If you or someone in your organization attends SCTE EXPO we will have some on hand when we are there. Brady will be presenting at EXPO again this year.

Thanks,
Mia

I’m a network engineer, and new to Docsis technology. I would love if you would email me a poster please…

Thank you

When considering metrics via SNMP would you suggest capturing each instance of a given metric or just capture the one instance and use that for the overall measurement? Performing statistical analysis on each instance will be a very thorough approach but I’m not sure that the added complexity is really necessary. Your thoughts?

i have a question regarding the partial mode of cable modem,. what are the causes behind the CM goes in the partial mode . and how to rectify this problem ?

Cheers
Ganesh

Hi Ajoy,

Sorry I don’t believe it does but we are in Cable not Satellite TV.

Thanks

Hi Edwin,

This is a more detailed answer. You might also try http://volpefirm.com/load-balancing-continued-episode-8/

Hi Raul,

If you attend ANGACOM or SCTE come find us. I give them out at the trade shows.

Hi David,

DS FEC CW is 6/128 for Annex B and 16/204 for Annex A (Euro-DOCSIS)

Trellis coding is 1/15 for 64-QAM and 1/20 for 256-QAM. I think this is just for Annex B.

US FEC overhead is based on the mod profile and is 2*T per CW. We shoot for ~ 7% overhead; 9T bytes for 232B CW = 2*9/(2*9+232) = 7%

Also see http://volpefirm.com/load-balancing-continued-episode-8/

Hi Ahmed,

Good topic but more detailed. Also see http://volpefirm.com/load-balancing-continued-episode-8/

Hi Toni,

CMs in mtc-mode (US bonding) will report their US Tx level and I would trust that. CMs not in US bonding or D2.0 will only show US Tx level on the CMTS if remote query is set up. It’s hard to trust this not knowing when and if it has updated. You could be seeing an old reading.

If the CMs are truly transmitting 10 dB higher, then it sounds like added attenuation either external to the CMTS to inside, which could be a bad gain stage, which could lead to CM Tx issues and/or MER issues and could be a hardware issue requiring an RMA. Keep in moind that the 20×20 card can do US freq stacking on even ports. This means, if intending to do 2 US freqs per service area, you could feed the cable to US conn 0, assign 2 US chs ‘freqs to conn 0 and now US conn 1 would be “dead”. If US2 above is on conn 2, you could assign to conn 3 and see if any difference. Every 2 adjacent connectors on the 5×20 and 20×20 cards share an internal Broadcom chip.

http://volpefirm.com/load-balancing-continued-episode-8/

Hi Shanker,

MER and uncorr FEC. Also see http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Jason,

It is possible to have 1 mac domain with all 8 DSs as primary and the proper wideband and integrated interfaces. It’s a bit more detailed. LOL on the last part. Also see http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Mauro,

FM band is 88 to 108, so 111 is just outside the FM band. DOCSIS restricted load balance groups can be used to “steer” devices based on tags. Those tags can be DOCSIS version, modem capability, etc. You could tag based on D3.0 and force them to use specific DS freqs. You may be able to make multiple fiber node configs to indicate these different scenarios and the modem can resolve the ambiguity. Also see http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Nelson,

Sh cab hop threshold will give a column of corr and uncorr FEC in a 1 sec update %. We say < 1% uncorr FEC is acceptable. Corr FEC is subjective and some would say < 5%, but I have seen it at 50% and still not create uncorr. What’s the question? Don’t use > 450 MHz for DS freqs till the entire service group is upgraded. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Prabha,

Each flow has its own setting, so the UGS is guaranteed in the scheduler and does not “eat” into your BE flow of 40 Mbps. Voip is a drop in the bucket compared to 40 Mbps! Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Michael,

You are correct, it should have said 152 no-diff 64. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi David,

Mixed mode would be mod profile 124 or some variant of 1xx. I don’t recommend odd constellations like 32-QAM. With that said, 32 = 2^5 power leading to 5 bits per symbol * 2.56 Msym/sec = 12.8 Mbps raw, which is ~ 11 Mbps usable-aggregate. Per-CM US speed has many more variables to overcome. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Kevin,

A 3.2 MHz wide ch will always “appear” 3 dB higher than the 6.4 MHz wide chs. Another cause could be, where are you doing the test? The CMTS wants 0, but because of rolloff, etc, the chs could be higher at the higher US freq to overcome the roll-off farther towards the CMTS. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Keshav,

You can have a modem complete registration, but the operational state could be online(d), reject(pk), reject (c), etc. So, it completed registration with the CMTS, but it still may not be operational. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Charlie,

If you are talking about US and “usable” rate, then that would be ~ 27*8 = 216 Mbps. If talking about DS, then it would be closer to 36*8 = 288 Mbps. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Armol,

The low MER is probably group delay related. I would suggest activating pre-eq with cable up an equalization-coefficient. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Prasad,

Too deep to go into here. First step is always look at physical layer. US and DS MER readings, levels, corr/uncorr FEC, etc. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Hi Scott,
The “*” symbol next to online state is added by DDTS “CSCtj59842” to display the modems that fail bpi-plus-policy. The DDTS Description says: “When modems fail the bpi-plus-policy, the modems come online(pt) but are blocked from sending l3 traffic using a per-device ACL. There is currently no easy way to see which modems are affected so a new symbol was added to show the modems that failed the bpi-plus-policy.”
No network access could also be online(d) where cm file disabled network access. Also check out http://volpefirm.com/intx-the-internet-television-expo-review/

Thanks

Hi Mike,

Thanks for writing in.

Are you attending SCTE EXPO this year in NO? If so Brady will be again presenting and I will bring some posters with me and save a couple for you.

Thanks,
Mia

Could I get a couple of the 3.0 posters?, I attended the demo with Brady at SCTE last year and purchased PNM management and US Analyzer through our provisioning partner Momentum for all of our CMTS’s. We were one of there first deployments of the Momentum PNM.

I am Vijay from India. i installed Cisco 10 K CMTS and having approx 20K online subscribers. now i am facing binding issue. SNR is from 23 to 26 dB in majority us ports. i am having 7 US cards in CMTS. pl suggest changes to resolve this problem.
Vijay Vadnere
+919822054008
vijuv20001@gmail.com
India
Pune

Where can I find helpful information that will teach me all the possible TLV meanings when building CM configs? I would like a better understanding in configs for MTA, PW, and basic CM’s.
I am a little familiar with Packet Ace, but the help files are lacking any helpful information — and there seems to be a lot of TLV’s.

Any help is appreciated.

Daniel

Im new to Docsis and i find this website with most of the information

Please share the below poster
DOCSIS 3.0 Cable Modem Registration with T3 & T4 Timeouts Poster

poster available online is blur and i can not read it

Please share

Can you please shed some light why all the DOCSIS engineers like to have an US power of around 45-48dBmV? I heard from many peaople that a “low” transmit power (like 30-40dBmV) can cause problems but I don’t se how. The whole point of US ranging is to make the colser (less attenuated) modems to transmit with less Tx power, and the modems further away to transmit with higher Tx power, to get a balanced signal level on the Amps (and eventually the CMTS’s) upstream port.

I even heard that some technicians put uplink attenuators to modems that transmits with less than 40dBmV. That sounds ridiculous, because the modem will transmit exactly that much higher what the added attenuation is.

So if you can share your professional opinion about this ever lasting topic, many of us would be aprreciate it 🙂

Thank you!

* IM = waiting for initial maintenance
* SM = waiting for station maintenance
* Cont = continuous ranging (ranging miss or adjustment is needed)
* STA = station maintenance
* DR = down & recovery with extended ranging opportunities
* DT = down due to timeout, and no recovery
* DI = down due to interface shutdown

UBR10k-PRE4(config-if)#do scm 0880.39e6.7300 ver | i Rang|Up
Extended Upstream Transmit Power : 0dB
Upstream Channel : US0 US1 US2 US3
Ranging Status : dr sta sta sta

Is there any relationship between the Max TxPower and the Upstream channel bandwidth (3.2MHz, 6.4MHz)?

Thanks.

Thank you for the great feedback!

Nice explanation regarding DOCSIS 3.0, as I am a new to this technology, I need some information regarding, if there is particular modem is offline ( when we see them using show cable modem) or any interface issue or any issue related to frequency lab lab laa…, then how to do some real time trouble shoot , so can we identify the particular error, and how to fix it.

please provide some real time examples, which will be more helpfull

Thanks,
Prasad

Hi Roger,

Thanks for your interest. We are currently only giving them out to current customers and at Trade shows. We will be at SCTE EXPO 2015. If you have a colleague that is attending have them look us up. Brady will be presenting. I’ll be happy to give them one.

Tanks,
Mia

Hi Dalai,

Thank you for your interest. I’m currently limiting them to customers and trade shows. If you or any of your colleagues ever go to ANGACOM or SCTE EXPO 2015 let me know. I’ll be happy to pass one along to them.

Thanks,
Mia

I’ve asked that someone who does work for you all to send you a poster. He has some extra. I think.

Hi Darrin,

I’ll be going to SCTE EXPO 2015. Have one of your colleagues look us up. Brady will be presenting. I’ll be happy to give one to them to give to you. We have such a limited amount I don’t mail them out anymore.

Thanks,
Mia

Hi Sebastian,

Since this network belongs to the operator your best option is to work with the Cable Operator until you are happy with your service. Even if you have an approved modem, check with the manufacturer to see if it’s up to date on it’s firmware. From my experience most operators truly want their customers to be happy so keep working with them. Good Luck.

Mia

Thanks

In cable modem I want to know the difference between registration complete and operational state(online).

Could you please provide the details.

thanks,

Keshav.

Any chance that you might be able to send me one of these posters if you have any available?
I don’t get the opportunity to attend any of the trade shows.

Thank you!

There’s some great answers on this thread and I’m hoping you might share your expertise to help me troubleshoot an issue.I’m an internet only subscriber with TWC. I’m located in Brooklyn and am paying for 50/5, maximum available at my house is 300+. There’s no splitters installed, coax runs straight to my ubee DDM3521 modem. I own this modem and checked that it’s TWC approved before buying it.

For three months (since I signed up with TWC), I’ve been having the same issue everyday. At the same time every day, the downlink speed drops to 1 Mbit/s and stays pegged until I powercycle the modem. The uplink is never affected and remains at a constant 5 Mbit/s. TWC blames my modem and wants to shove one of their leased modems down my throat.

The log is full of “No Ranging Response received – T3 time-out” and “Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received – T4 time out” errors. I’m also getting “TCS Partial Service;CMTS-MAC=00:17:10:88:39:96;CM-QOS=1.1;CM-VER=3.0;”. Upload channel 4 seems to be dead altogether, even the technician’s meter only showed three available channels. Channel four has 126 T3 and 1293 T3 timeouts listed. The technician said that this was “normal behavior”.

Does any of this make sense to you?

Thanks so much,
Sebastian

I have one question,

In your updated version of the modulation profiles, you wrote these two lines :

cable modulation-profile 224 a-short 6 76 6 22 64qam scrambler 152 no-diff 152 shortened qpsk1 0 2048
cable modulation-profile 224 a-long 9 232 0 22 64qam scrambler 152 no-diff 152 shortened qpsk1 0 2048

Is the “152 no-diff 152” a typo?
Should it be “152 no-diff 64” ?

Greetings!
I’d like to understand a specific behavior in DOCSIS networks.
I have a 40 Mbps Max Sus Rate configured for my primary US SF. Now, if a dynamic service flow for voice comes up with 150kbps Max Sus Rate, would the CMTS ensure that the Cable Modem overall gets 40 Mbps Upstream or would it be 40 Mbps + 150kbps(VoIP)? If the latter is true(I believe that this is true), how do I ensure that only 40 Mbps cap is given to US for the DOCSIS 3.0 Cable Modem such that any service flow that comes up uses up from the cap?

Thanks

How can I determine or calculate the Error Rates per Upstream? and what could be the acceptable Symbol Error rate?
We are currently in Docsis 2 and still using the old system 450MHz on our existing HFC netwrok but now we are gradually replacing the old amplifiers (450Mhz) with new Amplifiers (1Ghz).

Appreciate your advise on this

Thanks!

Hi Sam,

Yes, you are correct. You are sharing the upstream and downstream with your neighbor. It is common that during peak traffic hours cable modem speeds could slow down if there are too many users on a DOCSIS 1.1 network.

-Brady

Hi Jairo,

The modems use the full upstream channel when they transmit. The reason you only see a small sliver on the spectrum analyzer is because the spectrum analyzer uses a sweep technology. When displaying the RF spectrum the analyzer sweeps through all points of the upstream. As it is sweeping (i.e. scanning across all RF frequencies) it will only capture some of the RF energy that the modem is transmitting because the modem burst is very short. If the spectrum analyzer sweep time is 20 msec and the modem burst is 20 micro-seconds, then you will only every capture small portions of the cable modem burst. That is why you must put the spectrum analyzer in max hold to eventually build the full modem haystack.

One thing you can do is ping the modem very fast with large amounts of data – or you can run multiple speed tests from the modem in order to generate a lot of upstream data. This will cause the modem to generate more upstream traffic and increase the probability that you will capture the upstream bursts using a spectrum analyzer.

-Brady

Hi Ricardo,

You have a valid point. When NATing on the CMTS you really cannot open specific ports for individual users without opening the ports for all users. Again I don’t recommend NATing for many reasons, but unfortunately some small operators are forced to use NATing because they only have one public IP address.

-Brady

Hi Jay,

I must apologize, but there is a lot of info in these log files, but the real details are actually in the CMTS. That is where the troubleshooting begins. I am not really able to be of much help from the data provided.

-Brady

Hi Mauro,

Using UGS (Unsolicited Grant Service) for a video camera is possible, but may not be the ideal scenario. USG was intended for voice and video communications where real-time delivery of UDP traffic was essential with minimal delay and jitter. Your scenario is a bit different if I understand it correctly. You are using an IP camera likely for video surveillance and not two-way communication. In this case I would recommend setting up a static flow in the modem’s config file just for this camera’s IP source and destination along with its port. This will be way easier than trying to dynamically bring up a USG flow, which requires PacketCable. Static flows are fairly simple to implement. And as you have stated you do need the best effort flow first for standard traffic and then a second flow for the IP camera.

-Brady

Hi Mauro,

You are correct, the second article you reference, (http://volpefirm.com/docsis_timout_descriptions/), has a more concise explanation of T3 / T4 timeouts. I need to go back to this article and clean it up. Thanks for pointing out the inconsistency.

-Brady

Hi Ben,

Over utilization on CMTSs is a very common problem. I would not recommend adding a second C3 to the mix as there are many issues you will face, such as splitting subnets, having modems register between two downstreams, etc. Depending on the number of subs you have I would recommend two options. First consider going with a CMTS that supports multiple DOCSIS 2.0 line cards. This gives you some future expansion. Second, if you really want to future proof yourself, now is the time to consider investing in a DOCSIS 3.0 CMTS. There are many options. The question you need to ask yourself is how often do you want to upgrade your CMTS? Is this something you to be doing on a yearly or bi-yearly basis? Or do you want to upgrade the CMTS with something that lasts you for the next 3-5 years?

-Brady

I work in a MSO and we use private IPv4 for cablemodems and (yet) public IPv4 for CPEs. Now I’m studying how to modify the DHCP and all the other necessary stuff to get IPv6 provisioning for CPEs (because off course is getting more and more difficult to us get new IPv4 public networks). But until today I never thought of using IPv6 for cablemodems. So, is there any significant advantage in doing this?

PD: DOCSIS 2.0 cablemodems supports IPv6? Our cast majority of cablemodems are DOCSIS 2.0.

Thanls a lot and best regards, Mauro.

T3 and T4 timeouts occur during station maintenance and do provide insight to the health of a DOCSIS plant as well as diagnostics. The counters themselves are in the DOCSIS cable modems and start and stop at the beginning and end of the station maintenance process. The CMTS sends a MAP message to the cable modem instructing it to send a RNG-REQ to the CMTS, so the CMTS knows the message is coming. Once the cable modem transmits the RNG-REQ it starts an internal counter. If the cable modem does not receive a RNG-RSP in 200 msec it flags a T3 timeout. One can assume if the CMTS did not send the RNG-RSP it most likely did not receive the RNG-REQ due to upstream impairments, therefore T3 timeouts usually indicate upstream impairment.

When the CMTS does not receive the RNG-RSP it will send a new MAP for another RNG-REQ. If again the RNG-RSP is not received another T3 timeout will be generated. Once a certain number of T3 timeouts or time is exceeded (typically about 15 T3 timeouts, but this is vendor-based), the cable modem will be forced to re-register and a T4 timeout error will be logged. A T4 timeout can indicate an upstream that is not passing traffic or even possible downstream problems. But most often a T4 timeout occurs when the MAP message for a RNG-REQ is lost in the downstream, which indicates potential downstream issues.

But, in another article (http://volpefirm.com/docsis_timout_descriptions/) reads:

T3 Timeout ( Ranging Request Retries Exhausted )

Explanation: The cable modem has sent 16 Ranging Request (RNG-REQ) messages without receiving a Ranging Response (RNG-RSP) message in reply from the CMTS. The cable modem is therefore resetting its cable interface and restarting the registration process. This typically is caused by noise on the upstream that causes the loss of MAC-layer messages. Noise could also raise the signal-to-noise ratio (SNR) on the upstream to a point where the cable modem’s power level is insufficient to transmit any messages. If the cable modem cannot raise its upstream transmit power level to a level that allows successful communication within the maximum timeout period, it resets its cable interface and restarts the registration process. This error message is DOCSIS event message is R03.0, Ranging Request.
T4 Timeout ( Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received )

Explanation: The cable modem did not received a station maintenance opportunity in which to transmit a Ranging Request (RNG-REQ) message within the T4 timeout period (30 to 35 seconds). The cable modem is resetting its cable interface and restarting the registration process. Typically, this indicates an occasional, temporary loss of service, but if the problem persists, check for possible service outages or maintenance activity on this particular headend system. This error message is DOCSIS event message is R04.0, Ranging Request.

I think the last is the correct, but I haven’t checked the DOCSIS documentation yet. So, could you please clarify these concepts?

Thanks a lot and best regards!

Mauro.

I haven an IP camera connected to a cable-modem (DOCSIS 2.0). The camera sends video data to a static IP and port (server that store the video). Initially, with the US channel configured with 3.2 Mhz wide and QPSK the quality was awful, lot of delay and freezes. It’s important to note that the US channel it was not congested.

Later, I configured the US channel in 6.4 MHz QPSK and now the quality was great (the IP camera is limited to 2 Mbps bitrate), almost no delay and no freezes.

Later, because we need more US speed (because the number of users has increased), I change the channel to 6.4 MHz 16QAM and everything works great. I even tested configure the IP camera on 4Mbps and it works fine too.

In this scenario it seem that I have nothing to do (the camera works fine), but I have been tried time ago to configure a cable modem with UGS service flow but I did not succeed. Tell me please if I’m wrong, but in this case I first need to configure at least one service flow with best effort and then one with UGS and their respective classifier (based on destination IP and port). Is this ok? Do you recommend UGS in this case? Is best to configure a best effort SF with max priority and reserved CBR insted of use UGS?

Thanks a lot in advance and again, thanks for such an excellent information on DOCSIS related.

Mauro.

Apologies, some information was missing from my prior question…

I have been using the NETGEAR CMD31T for a little over a year now and things have been going fine until I moved to a new apartment (within the same complex) two months ago. When my technician installed my cable modem, he put a FAM-3 attenuator. I never had an attenuator before and never had any disruptions in service that ultimately ended in me needing one. When I moved to my new place, the cable tech told me that he needed to put one in order to boost my signal and ensure I don’t have any internet drops. After living in my new place for nearly two months, I had no problems. Then almost on a daily basis for the past week, I would get dropped. The only recourse was to turn on/off the modem after I get disconnected. I didn’t know we could look at event logs until recently. Maybe you could help translate this jargon for a computer illiterate like myself?

I’ve read on various forums that I should leave the attenuator alone; while others say remove it. Out of desperation, I removed the attenuator two days ago, and things have been normal and fine ever since. I’m a bit surprised, but I’m not holding my breath.

Did I do the right thing? Do you see anything in my event log that would worry you?

Here is additional info I obtained AFTER I removed the attenuator:

Startup Procedure
Acquire Downstream Channel: 819000000 Hz, Locked
Connectivity State: OK, Operational
Boot State: OK, Operational
Configuration File: Complete
Security: Enabled, BPI+

Downstream Channel 0
Lock Status: Locked
Modulation: 256 QAM
Channel ID: 1
Symbol rate: 5360537
Downstream Frequency: 819000000 Hz
Downstream Power: 1.9787 dBmV
SNR: 37.0927 dBmV
Correctables: 14
Uncorrectables: 642

Downstream Channel 1
Lock Status: Locked
Modulation: 256 QAM
Channel ID: 2
Symbol rate: 5360537
Downstream Frequency: 813000000 Hz
Downstream Power: 2.6244 dBmV
SNR: 37.0927 dBmV
Correctables: 0
Uncorrectables: 520

Downstream Channel 2
Lock Status: Locked
Modulation: 256 QAM
Channel ID: 3
Symbol rate: 5360537
Downstream Frequency: 825000000 Hz
Downstream Power: 1.1022 dBmV
SNR: 37.0927 dBmV
Correctables: 13
Uncorrectables: 644

Downstream Channel 3
Lock Status: Locked
Modulation: 256 QAM
Channel ID: 4
Symbol rate: 5360537
Downstream Frequency: 831000000 Hz
Downstream Power: 2.0204 dBmV
SNR: 37.3560 dBmV
Correctables: 13
Uncorrectables: 648

Upstream Channel 0
Lock Status: Locked
Modulation: 64QAM
Channel ID: 1
Symbol rate: 5120 Ksym/sec
Upstream Frequency: 36300000 Hz
Upstream Power: 30.5000 dBmV

Upstream Channel 1
Lock Status: Locked
Modulation: 64QAM
Channel ID: 2
Symbol rate: 5120 Ksym/sec
Upstream Frequency: 29800000 Hz
Upstream Power: 32.0000 dBmV

Upstream Channel 2
Lock Status: Locked
Modulation: 64QAM
Channel ID: 3
Symbol rate: 5120 Ksym/sec
Upstream Frequency: 23300000 Hz
Upstream Power 32.0000 dBmV

Upstream Channel 3
Lock Status: Locked
Modulation: 64QAM
Channel ID: 4
Symbol rate: 2560 Ksym/sec
Upstream Frequency: 18400000 Hz
Upstream Power: 30.5000 dBmV

Your help would be greatly appreciated.

-Jay

I have been using the NETGEAR CMD31T for a little over a year now and things have been going fine until I moved to a new apartment (within the same complex) two months ago. When my technician installed my cable modem, he put a FAM-3 attenuator. I never had an attenuator before and never had any disruptions in service that ultimately ended in me needing one. When I moved to my new place, the cable tech told me that he needed to put one in order to boost my signal and ensure I don’t have any internet drops. After living in my new place for nearly two months, I had no problems. Then almost on a daily basis for the past week, I would get dropped. The only recourse was to turn on/off the modem after I get disconnected. I didn’t know we could look at event logs until recently. Maybe you could help translate this jargon for a computer illiterate like myself?

I’ve read on various forums that I should leave the attenuator alone; while others say remove it. Out of desperation, I removed the attenuator two days ago, and things have been normal and fine ever since. I’m a bit surprised, but I’m not holding my breath.

Did I do the right thing? Do you see anything in my event log that would worry you?

Here is additional info I obtained AFTER I removed the attenuator:

Downstream Power: 2.1140 dBmV
SNR: 37.3560 dBmV
Correctables: 13
Uncorrectables: 648

Upstream Channel 0
Lock Status: Locked
Modulation: 64QAM
Channel ID: 1
Symbol rate: 5120 Ksym/sec
Upstream Frequency: 36300000 Hz
Upstream Power: 30.5000 dBmV

Upstream Channel 1
Lock Status: Locked
Modulation: 64QAM
Channel ID: 2
Symbol rate: 5120 Ksym/sec
Upstream Frequency: 29800000 Hz
Upstream Power: 32.0000 dBmV

Upstream Channel 2
Lock Status: Locked
Modulation: 64QAM
Channel ID: 3
Symbol rate: 5120 Ksym/sec
Upstream Frequency: 23300000 Hz
Upstream Power 32.0000 dBmV

Upstream Channel 3
Lock Status: Locked
Modulation: 64QAM
Channel ID: 4
Symbol rate: 2560 Ksym/sec
Upstream Frequency: 18400000 Hz
Upstream Power: 30.5000 dBmV

Your help would be greatly appreciated.

-Jay

thanks in advance.

I would like to ask a small question. Me and my neighbor’s cable modem is running at the same frequency levels and is on docsis 1.1
Does this mean that we are sharing the same channel. Consider the following example.

The ISP is having a 200mbps uplink at their router level. A CMTS is connected to the router and CMTS provides communication to 100 cable modems on same signal frequency ( like 270mhz for down stream and 27 for upstream). So what I feel is the 100 cable modems are sharing a maximum available data rate of 42mbps (downstream)and the modems may face slow internet if the total bandwidth required at any stage is more than 42mbps. ( Like 20 cable modem trying to access 4mbps streaming video at the same time)

Am I correct?

I have all of the downstream ports configured in C1/0 with 4 upstreams. I only set up one fiber-node with 4 upstreams and 8 downstreams. I have tried a few things so far but eventually had to take Integrated 1/1 downstreams out of the fiber node so the modem would come online. I am able to do this because we are not utilizing our system until our WAN is upgraded. I believe the solution is playing around with the load-balance excludes but we’ll have to see.

As soon as you think you have everything figured out you are working overtime again because the unknowns slap you in the face!

As a followup question, I was wandering how my STB (which is both for cable TV and an internet router/modem) will be able to communicate with a VOD server, for example. Is it possible that my STB has 2 DOCSIS IP interface, a public one for the internet, and a private subnet for communicating with the internal VOD servers of my cable provider?

Thanks again.

Thanks in advance.

Dalai

Hi Lior,

It is typical for cable modems to get an IP address that is from a private subnet (RFC1918), such as the 10.x.x.x, 172.x.x.x and 192.x.x.x space. In the article you referenced you were seeing a cable modem getting a DHCP IP address and not a PC (CPE) getting an IP address.

Generally all CPE devices, such as PCs and routers attached to the cable modem, would get public IPs. However, back to your question, this is not exactly required. There are times where smaller cable operators may have a limited number of public IP addresses. In these cases we have the ability to assign one IP address to the CMTS. Then we NAT (Network Address Translate) all of the cable modems behind the CMTS. The CMTS acts like your home router, assigning private IP addresses to cable modems and then translate public traffic to the private IP space.

Why don’t we do this all of the time? Because it takes up more processing resources on the CMTS. So as long as the system is small and there is sufficient CPU and memory on the CMTS everything works fine. We find this works great for apartments, RF parks and small communities. But we would not recommend it for a large city.

-Brady

Hi Jeff,

There are a lot of variables to check. Are you using a diplex filter vs. a splitter? Is your padding correct (is your modem transmitting at 40-50 dBmV and receiving at -10 to +10 dBmV)? Is your downstream MER >33 dB is your upstream MER >30 dB? Are your micro-reflections >-25? Turn on pre-equalization.

Those are just some things to verify, many other things can cause your T3’s including CMTS over-utilization.

-Brady

Hi John,

Thanks for reading!

CMTS physical ports and QAM channels do have an association provided that the QAM channels originate from the CMTS (QAM channels originating from an eQAM – edge QAM are a different story). To see how these are associated simple walk the ifDesc on the CMTS and you can see the QAM channels the way they are are described on the CMTS.

For example:

snmpwalk -v 2c -c public 10.x.x.x ifDesc
IF-MIB::ifDescr.1 = STRING: FastEthernet1/0
IF-MIB::ifDescr.2 = STRING: GigabitEthernet0/1
IF-MIB::ifDescr.3 = STRING: GigabitEthernet0/2
IF-MIB::ifDescr.4 = STRING: GigabitEthernet0/3
IF-MIB::ifDescr.5 = STRING: Cable3/0
IF-MIB::ifDescr.6 = STRING: Cable3/1
IF-MIB::ifDescr.7 = STRING: Cable4/0
IF-MIB::ifDescr.8 = STRING: Cable4/1
IF-MIB::ifDescr.9 = STRING: Cable5/0
IF-MIB::ifDescr.10 = STRING: Cable5/1
IF-MIB::ifDescr.11 = STRING: Cable6/0
IF-MIB::ifDescr.12 = STRING: Cable6/1
IF-MIB::ifDescr.13 = STRING: Cable3/0-upstream0
IF-MIB::ifDescr.14 = STRING: Cable3/0-upstream1
IF-MIB::ifDescr.15 = STRING: Cable3/0-upstream2

What you are seeing is names of each port for the downstream and upstream QAM channels. From here it would be helpful to have a full MIB browser to dig more deeply into the these specific ports.

-Brady ]]> https://volpefirm.com/cable-modem-registration-a-second-look/#comment-676 Sat, 27 Dec 2014 02:41:25 +0000 http://volpefirm.com/?p=3023#comment-676 Wow Brady,

Nice job! Recently had issues with my old Docsis 2.0 modem and replaced it with a Docsys 3.0 device. I had no idea all these transactions were going on on startup. Assume having 8 downstream channels open will greatly increase available bandwidth over previous gen. Fascinating stuff…thanks!

Hi Agad, Your question was answered in the following podcast http://volpefirm.com/load-balancing-continued-episode-8/. Thanks, Mia

Abraham what is the full Mac Address of your cable modem and the Max Market that you subscribe too.

My background is IP/Networking – new to cable so I’m learning something new here and am very grateful for your posts. I’ve read through your tutorials and one concept which is not yet clear to me is the physical – logical association between CMTS physical ports, QAM channels, and subsequently the modems. Essentially, after a modem becomes registered, I’d like to be able to determine the topology of an HFC network by querying the CMTS & modems (via SNMP). Can you shed some light on this physical-logical association?

Thanks so much

Regards

-John

Hi Abraham,

This is an item that you will need to work out with your ISP. It’s best that you call your ISP and try to work with them on the issue. I’m sure they want you to be a happy customer.

I’m a Time Warner Cable subscriber and am experiencing a strange issue where my modem will just suddenly reboot. Looking at the logs, I’m seeing numerous T3 timeout messages on my Zoom5431J that say the following:

Wed Dec 17 05:25:10 2014 Error (4) Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=fc:4a:…
Wed Dec 17 05:25:10 2014 Warning (5) DHCP WARNING – Non-critical field invalid in response ;CM-MAC…
Wed Dec 17 05:25:01 2014 Critical (3) Started Unicast Maintenance Ranging – No Response received – …
Wed Dec 17 05:24:56 2014 Critical (3) No Ranging Response received – T3 time-out;CM-MAC=fc:4a:e9:00…
Wed Dec 17 05:24:43 2014 Critical (3) Received Response to Broadcast Maintenance Request, But no Un…

My old modem (Motorola Surfboard) would log both T3 & T4 Timeouts like:

Cable Modem Reboot due to T4 timeout ;CM-MAC=**:**:**:**:**:de;CMTS-MAC=**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received – T4 timeout;

I’m fairly certain we started experiencing this issue after they silently upgraded everyone’s internet to 100/200/300 mbps (up from 16mbps for me). I have already tried purchasing a new modem and connecting a computer directly to the modem and am still experiencing this issue. About 30-50 times a day, probably more, it will just timeout and reboot, leaving me without internet for 20 seconds to a minute and terminating any live connections. I’ve had numerous techs out here and on support and none of them seem to be able to shed any light on the situation 🙁 … Maybe you can help.

Any experience with such an issue or thoughts on what I can tell TWC to understand and fix the problem would be tremendous! (assuming it’s their fault of course 🙂 )

Thanks,
Abraham

PS. I read the article but didn’t understand it well enough to help me with my problem :p

Do you know how to split the upstream by 2-way splitter? Those 2 ways will connect with 2 different optical receiver ports. So, I don’t split the upstream from the inside of CMTS. But I’d like to split the upstream from the cable. Because I have tried it and failed.

I’m sorry for my bad grammar. Thank you 🙂

Hi Larry,

We do not email them out. We have a limited number left and hand them out at trade shows or to customers now. If you attend a trade show be sure to look us up.

Hi Raul,

We have a limited number left and hand them out at trade shows or to customers now. If you attend a trade show be sure to look us up.

Hi Shawn,

We have a limited number left and hand them out at trade shows or to customers now. If you attend a trade show be sure to look us up.

Hi Brian,

We do not email them out.

We have a limited number left and usually only hand them out to customers or individuals at trade shows.

I have been reading your topics from this site with interest, and I was struggeling with a question where we would make Partial Service more visible to the operators. We are using SNMP based systems and I am looking for any DOCSIS standard MIBs that would provide visibility for Upstream and Downstream Partial Service conditions.
For Upstream I have figured out a solution, where I can retrieve the UpstreamRangingStatus using the following MIB:

docsIf3CmtsCmUsStatusRangingStatus 1.3.6.1.4.1.4491.2.1.20.1.4.1.12

Modems that provide any other status then success (4) will be marked with Partial Service.
I would like to have a similar solution for Downstream, where we could observe these modems and get an overview of modems with Partial Service in the Downstream direction. It would be even better if it is possible to get an overview of Channels that are deleted from the DBG?

Kind regards,

Edwin Heuser

Hi Scott,

I believe I did send you posters two years ago. Probably four. Did you change jobs?

Thanks,
Mia

Thanks

xxxx.xxxx.xx6f C6/0/1/U0 104 42.75 36.08 1134 9.70 42.20 atdma* 1.1
xxxx.xxxx.xx6f C6/0/1/U1 104 42.75 36.12 1134 9.70 42.20 atdma* 1.1
xxxx.xxxx.xx6f C6/0/1/U2 104 52.00 36.12 1134 9.70 42.20 atdma* 1.1
xxxx.xxxx.xx6f C6/0/1/U3 104 43.25 36.12 1135 9.70 42.20 atdma* 1.1
xxxx.xxxx.xx73 C6/0/1/U0 108 36.50 31.53 1020 5.60 44.50 atdma* 1.1
xxxx.xxxx.xx73 C6/0/1/U1 108 36.00 36.12 1020 5.60 44.50 atdma* 1.1
xxxx.xxxx.xx73 C6/0/1/U2 108 47.25 36.12 1020 5.60 44.50 atdma* 1.1
xxxx.xxxx.xx73 C6/0/1/U3 108 37.00 36.12 1020 5.60 44.50 atdma* 1.1
xxxx.xxxx.xxcb C6/0/1/U0 148 51.50 36.12 1008 – 4.80 42.50 atdma* 1.1
xxxx.xxxx.xxcb C6/0/1/U1 148 51.50 36.12 1008 – 4.80 42.50 atdma* 1.1
xxxx.xxxx.xxcb C6/0/1/U2 148 52.00 31.32 1008 – 4.80 42.50 atdma* 1.1
xxxx.xxxx.xxcb C6/0/1/U3 148 52.00 36.12 1008 – 4.80 42.50 atdma* 1.1

We had 4 nodes connected on this port. Now only 2 and other two nodes cleared out of this problem when moved to different port. I have replaced _all_ connectors&cables between 20x20card and fibre receiver’s. Also I hard rebooted the whole 20×20 card with no help.

There are no error reports by any customers and all the modems seems to work fine, but every U2 has ~10dB higher transmit lvl in this port. Last modem on sample list has transmit levels on max, so basically it would want 62 dBmV for U2. SNR is still 31.32 which is somewhat acceptable.. Our CMTS has been set +12 dBmV.

We had before same problem on other linecard but our hands in full of job we decided to shut down the upstream channel which wanted to be 10dB higher and we have had no problems. Idea was to return to this problem when we have time but now to same problem occur on the other linecard causes some concerns.. Do you have any ideas how we should proceed?

Thanks,
Toni

Hi Tenrai,

There are a lot of factors in a cable plant. As a subscriber you are not privy to all the inner workings of your ISP. If you are having issues with your service please contact your ISP to resolve your service complaints and or concerns.

Hi Bobi,

Your question was answered during the G+Hangout. You can watch it here or download it on iTunes. http://volpefirm.com/load-balancing-docsis-3-1-episode-7/

Thanks,
Mia

Hi Willy,

Your question was addressed in the G+Hangout which you can watch here or download on iTunes. http://volpefirm.com/load-balancing-docsis-3-1-episode-7/

Thanks,
Mia

Hi Marc,

The question was answered during the G+Hangout. You can watch it here or download the podcast on iTunes. http://volpefirm.com/load-balancing-docsis-3-1-episode-7/

Thanks,
Mia

Thanks,

Sam

Larry,

Your email bounced. Please check it and make sure it’s valid.

Thanks,
Mia

Sorry we do not offer the PDF

could you please release the PDF version of this poster would kinda be nice.

thanks.

Does the following make sense?
Reed Solomon FEC, 7 bits = 1 RS symbol, and 128 RS symbols = 1 RS codeword?
ITU-J.83 Annex B indicates Reed-Solomon FEC with a 128/122 code

122 * 7 bits = 854bits (mpeg/docsis/tcp ip over head/Trellis coding ~ 20%) = 683 bits / 8 =
~85 bytes per Downstream keyword?

seems much lower than US?

Thanks
David

This is a great site. Thanks for all the info.

I’m having a provisioning issue where the CM sometimes get’s online sometimes doesn’t. It fails while in ranging, the log shows “TCC Acquisition failed : TCS_FAILED_ON_ALL_US”.

Any idea on might be causing this?

Best Regards
Willy

Hi Peter,

We did stop by the Averna booth and got to look at the equipment. Sorry they didn’t let us take a picture and it’s not production ready yet. So once they come out with a production unit hopefully we can swing by their Atlanta office and get a demo of the unit. We will keep you posted.

Alles Gute,
Mia

My cable modem wouldn’t sync, I called my ISP (Worldcall.pk), they said everything was fine at their end. I checked the main drop cable and splitter. Everything was fine. Confused.

I later remembered, my ISP recently did something to their amplifiers, I knew they had upgraded to Docsis 3.0 connected the cable modem directly To the drop cable. Modem synced; I checked levels upstream power level jumped from 47dbmv to 58dbmv … Previously, modem would become unstable at >55dbmv hence the need of -9db cut off splitter. Now upstream levels are at 61dbmv and modem is still stable! How is this possible?

Now modem wouldn’t sync if upstream power is <57dbmv this is a Docsis 2.0 modem. My question is can the CTMS instruct the cable modem to boost upstream power levels? I keep reading that closers to 60dbmv modems upstream gets drowned in the noise; how is it that it's working fine at 61dbmv?

Thanks

Hi Rajeev,

PAPR (peak-to-average power ratio) in OFDM is a consideration in DOCSIS 3.1. However until we get actual hardware we won’t know how much internal calibration the chipset vendors have done for us. So this is certainly a factor we will be looking at. We are optimistic that a lot of the correction will be done. What is more of a concern is the impact of PAPR on return path lasers and even forward path amplifiers. Even worse is PAPR in the low cost in-home amplifiers that many homeowners purchase. These likely will not be able to handle the extra peak power from OFDM signals.

-Brady

Hi Liangzhou,

You can set the priority QoS in the config file, but it depends on the config file editor. There is a free one from Excentis (search my blog and you’ll find a link). You can also use UGS for the video stream service if all packet sizes will be the same (assuming its UDP and CBR traffic). However this is always fairly complicated to setup. You will need to have a constant destination port and IP, say of your video content server.

This is rather involved project and much more than I can include in a comment.

Good luck.

-Brady

Hi Joe,

Great to hear from you again. I will reply offline as

-Brady

Thank you for the informative article – You provide a tremendous service to the community, and it is much appreciated!

We have some Cisco 3010 modems which appear to be misbehaving – They will range, come online, everything will appear to be fine (modem is pingable, subscriber can pass data) and about 90 seconds later, the modem stops passing data. Behind the scenes, when I run a debug cable mac-address [modem] and debug cable dhcp on the uBR10K, I see that the modem cycles through the DHCP process about 10 times … Odd. When I issue a show cable modem verbose, I am presented with “CM Initialization Reason : TCS_FAILED_ON_ALL_US”

Based on your article, it would appear that the modem has gone into partial service, however, if it is failing on ALL upstreams, am I correct in saying that there is no way it could transmit on the cable network?

Interestingly, the CM continues to show online after it makes it’s initial registration. Though it will no longer pass any data. I am thinking it may be a firmware issue, as I can plug in an identical modem running DPC3010-v302r12901-110516a-COX..2.3.0_R1..185933. and it works fine. The misbehaving CM I have been able to isolate is running dpc3010-v302r12901-091119a..2.3.0_R1..185933.

Have you seen this in your travels? It is causing our service desk and field techs a great deal of consternation …

Thank you as always!

Joe in Okinawa

Hi QD, thank for the Table of Contents. Please note that you can also find a similar table of contents in the upper right hand corner or by going to Blog

But your ToC maybe specific to your needs.

-Brady