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1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

Frequent Visitor

1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

Comcast installed new service they labeled “Gigabit FTTH” (with XB6 Gateways) in our community of 1,100 homes.

The install was finished about 2.5 months ago, I have personally been running the service for a month in my home.

 

  • Most of our community has voiced concerns this new “Gigabit” service is slower than their former “Blast” service (30 - 150 Mbps previously).
  • More than half of our community’s XB6 gateways are re-syncing 3+ times a day, causing about 8+ minutes downtime multiple times per day.

 

I’ve worked for MSO’s (many years ago), and I realize you need something more specific:

 

Comcast techs (and supervisors) have worked on many homes in our development. No issues have bee found, no fixes implemented.

 

Knowing this field very well, I’ve asked many of these techs (and supervisors) related questions, not one of them is familiar, or educated in our community’s unique build.

 

Some background on our unusual build:

 

· Comcast installed an HPON/RFoG network, not true FTTH

· RF Only (no PON Pass-through) @5-42 Mhz Upstream, still using old ~500 Mhz band Down

· From the Headend to SDU, it looks something like this:

Plant <-fiber-> EDFA <-fiber-> 5x Nodes (Arris HPON passive splitters) <-fiber-> CPE (less than 250 HHP’s per node)

· For the CPE:

<-fiber from HPON -> Arris HPON RFoG SDU ONU #CP8051U (RF Only) <- RG6 Coax -> 6 DB Attenuator <> XB6 Gateway

 

To Answer the Forum Prerequisites:

 

Make and model of your modem

Arris TG3482G (aka XB6) + external fan (to assure no issues with heat)

 - HW Version: 9

 - BOOT Version: 0.1.9.430478

 - Download Version: 7.1.0.53 (updated April 26th 2018, previously at 2.0.2.209)

Make and model of your router

For diagnostic purposes, I’ve run the XB6 as a gateway and in Bridge-Mode.

In Bridge-Mode, Router: Ubiquiti EdgeRouter ER8-Pro, 8 Gbps 650k PPS speed)

Have you contacted Comcast / Tech Visit

Multiple tech visits for most people in our community. No resolution.

Signal Reset / Verified Provisioning Tier, many times with many community members

Modem light behavior when issues occur

             Complete Headend Re-sync Process (8+ minutes down, identical to signal reset pattern)

Modem Error Logs

Absolutely nothing (not one single row) in my system logs relating to signal (login, settings change, nothing else)

Keep in mind that in our topology, the ONU connects the XB6, making this a very short/clean signal, high SNR, no errors, etc.

 

My Own Personal Experience with Service

I have adequate equipment in my house (8 Gbps router, Enterprise 10 GbE + 1 GbE Switch)

I also have AT&T Gigabit Fiber Service (true FTTH)

I previously had Comcast Blast 150 (on former fiber-deep HFC, ran perfect, approx 190 Mbps Downstream 24x7)

AT&T Fiber runs 930-940 Mbps Down, 920-938 Mbps Up (typically) 24x7. Real-world DSL-Reports Speedtest & CDN’s, always over 800 Mbps

Comcast Gigabit runs 100-300 Mbps DS, 42 Mbps UStream. Real-World downloads on high-capacity CDN's within 20ms and one peer-point, less than 180 Mbps

I only use Internet. No TV’s, No Splitters, No exposed F-Connectors

 

Because AT&T runs 930+ Mbps (14 months now, tested 24x7), it should be clear the issue is not inside the premise

No security/anti-virus/proxy software is running on test systems

Tested with XB6 as gateway (modem+router) (and) as Bridge-Mode with external router

From my modem to Comcast’s Ookla Server in Miami, runs 9ms consistently.

 

Speed Test Summary (conducted all hours, including 2am-to-7am)

· 11ms by speedtest.xfinity.com           500-600 Mbps Down,           42 Mbps Upstream

· 50ms avg by dslreports                    350-500 Mbps Down,           42 Mbps Upstream

· 9ms to Miami-Comcast Ookla           190 to 266 Mbps Down,           32-42 Mbps Upstream

· 14ms to Miami-Ookla server           140 to 170 Mbps,                     32-42 Mbps Upstream

· Bufferbloat                                         30ms Down,                     150-200ms Upstream

Real-World File Downloads

· Geographically Multi-Homed Servers on Gigabit Uplinks           300 to 580 Mbps

· Peered with Comcast                                                            170 to 460 Mbps

· Optimized, Distributed CDN Content (Google Drive, etc)          80 Mbps Max

· Uploads to AWS, Azure, Google Drive (closest geo)                    28 Mbps Max

 

 

Signal Levels and Modulation, Pasted directly from XB6 (Arris TG3482G)

 

Downstream

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Index

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

Lock Status

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Frequency

513 Hhz

459 Hhz

465 Hhz

471 Hhz

477 Hhz

483 Hhz

489 Hhz

495 Hhz

507 Hhz

519 Hhz

525 Hhz

531 Hhz

537 Hhz

543 Hhz

549 Hhz

555 Hhz

SNR

40.366

40.366

40.946

40.366

40.366

40.366

40.366

40.366

40.366

40.366

40.946

40.946

40.366

40.366

40.366

40.366

Power Level

17.700

17.700

17.500

17.400

17.500

17.600

17.700

17.700

17.600

17.800

17.800

18.000

18.100

18.200

18.300

18.200

Modulation

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

 

Downstream

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Index

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

Lock Status

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Locked

Frequency

561 Hhz

567 Hhz

573 Hhz

579 Hhz

585 Hhz

591 Hhz

597 Hhz

603 Hhz

609 Hhz

615 Hhz

621 Hhz

627 Hhz

639 Hhz

645 Hhz

651 Hhz

657 Hhz

SNR

40.946

40.946

40.366

40.366

40.366

40.366

40.366

38.983

38.983

38.605

38.983

38.983

38.983

38.605

38.605

38.983

Power Level

18.200

18.400

18.300

18.500

18.500

18.400

18.400

18.500

18.400

18.400

18.500

18.400

18.200

18.100

18.000

17.900

Modulation

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

QAM256

 

Upstream

 

 

 

Index

1

2

3

Lock Status

ACTIVE

ACTIVE

ACTIVE

Frequency

29.4 Hhz

23 Hhz

35.8 Hhz

Symbol Rate

5120 KSym/sec

5120 KSym/sec

5120 KSym/sec

Power Level

35.771

35.771

36.271

Modulation

64QAM

64QAM

64QAM

Channel Type

US_TYPE_STDMA

US_TYPE_STDMA

US_TYPE_STDMA

 

 

Relating to the Signal Stats:

  • I did not paste the Error Codewords; they are zero (0) on all 32 channels, in every instance (signal is perfect via adjacent ONU)
  • The DS power level may appear high; however, this is a “feature” of the ONU which regulates the RF output to +19 dBmV (according to Arris)
  • You can see this is a 32x3 D3.0 Bonded modulation, yet we were promised true FTTH Gigabit
  • This is a new, fresh build by Comcast (8yr contract), finished only 2.5 months ago
  • We received an HPON running RF only (no PON passthrough) on the legacy/traditional ~500/40 Mhz bands
  • We did not receive a true FTTH/PON, not even DOCSIS 3.1 (OFDM 2x2)

 

I’m not making these points to complain.

 

Rather, I believe the difference between what was promised -- versus what we received -- may be playing a role in the mysterious issue affecting everyone. That, and the lack of information/schooling by anyone involved in supporting this network.

 

For example, it appears to be clear that Comcast intended to install a true PON, or at least 3.1, and something happened along the way.

 

None the less, we’ve had dozens of techs, the supervisors, and the head of the departments. Not one of them has determined the cause of our issues, or any working fix.

 

The primary issues again:

(1) More than half of our homeowners XB6 modems are re-syncing to the headend multiple times per day, causing 8+ minute outages in each instance.

(2) Speeds are exceptionally slow. Both privately to Comcast’s local Ookla server 9ms away, and worse, the On-net speeds (Comcast claims utilization is at 25%)

(3) Real-world browsing is ever slower than speed-tests/downloads. Slower than previously “Blast” packages with Comcast. Almost appears to be an issue with the XB6 Puma-7 SoC. For example, I’ve max’ed the upload speed and been unable to download until the upload completes.

 

Is there anyone within Comcast who is more familiar with this topology, who can get involved? While I will give you all the time in the world with my setup and aiding your testing -- please know this is affecting most of our 1,100 homes for the next 8 years and is causing many people a great deal of problems (particularly home-workers).

 

Thank you in advance for any insight!

 

 

Expert

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

Only one thing pops out at me right now. The downstream power levels are WAY too high. Have you tried putting more attenutation on the line, like -10dB. Those power levels need to be readjusted by Comcast.
Frequent Visitor

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

@ 

Thank you for the reply.  I absolutely agree about the downstream signal level.

 

I don't know whether you noticed, but towards the end of the post I mentioned the Arris ONU / CPE that converts fiber to RF, intentionally regulates the output to +19 dBmV and this cannot be regulated by Comcast because the ONU is fixed and will adjust to this output no matter the RF signal over fiber.  My guess is that it's intended to be used with the SV8G 8-port splitters (10.8 to 12 dB loss across each output) installed on the other homes that have TV's.  In my case, I don't have TV's, but I have tested the SV8G and it does bring me down to about 7.99 dBmV on average.  The SNR stays the same, the performance stays the same, etc.  It's surprising to me that everything runs the same between ~19 and ~8 dBmV, but that is the case currently.

 

If you're interested, you can see the Arris CP8051U ONU (Fiber-to-RF) here:

http://www.arris.com/globalassets/resources/data-sheets/1510791-reva_cp80x3-5-6-8u-02-10_family-sdu-...

 

Most Importantly -- Is there anyone from Comcast that can involve someone with experience of this unique topology?  We don't have that person here locally in Palm Beach County that I know of.  If we do, we have not found him yet.

 

Thanks again!

Expert

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

I've asked a Comcast employee to help you. You should expect a reply in this thread. 

 


I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Expert

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

Comcast is delivering gig speeds over coax - if you are using an XB6, it's straight up RF with DOCSIS 3.1, not FTTH. I have no idea what Arris is talking about, those signal levels are way too high. What they conveyed to you makes no sense. Unless I'm not understanding something. ¯\_(ツ)_/¯

 

I'd get a tech out to swap that Arris for a Technicolor XB6 and address those signal levels. 


I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Diamond Problem Solver

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

FWIW, it's a unique HPON / RFoG system with an ONU terminal that has ALC guys..

 

You need on-site advanced Comcast tech employees ( Comm Tech 5 / engineers) to help you OP.

Frequent Visitor

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

@nerdburg - That you for your reply.  I suspect was my post ran a bit long and you may have missed some details.  This is not OFDM / DOCSIS 3.1.  Thiis is 32x bonded DOCSIS 3.0 (QAM256) channels down (3x up QAM64), using an HPON (Hybrid PON).  It may sound crazy, but the fiber is nothing more than a coax replacement -- between the Node and the SDU. 

 

To clarify, I've witnessed this topology first-hand, from the SDU to the EDFA (the EDFA in thsi case replaces a CMTS in a fiber-deep config).

 

 

@EG - Yes, You're 100% correct  -- We have a HPON / RFoG without any PON passthrough.  This is fiber passing RF-wave emulation to the SDU, not binary data.  The CPE is the Arris ONU with ALC  as you meneiond ( "ALC" is the Arris "automatic level control" that intentionally delivers +19dBmV).

 

As a reminder, this is affecting over 1,100+ homes, not limited to my service.  This is a new Comcast build under an 8-year "bulk deal" (HOA community). 

 

Most of the 1,100+ homes have similar issues.  This isn't a Comm Tech 5 application (IMHO) because it's not limited to a handful of installs with issues, it's the overall design/build (or possibly issues at the HPON or EDFA).

 

Comcast has provided us with two of their head "Technical Operations Managers" that do not have an in-depth knowledge of this specific technology, based on statements they made to me (in fact, they claimed it's impossible to provide gigabit over coax in a deep-fiber HFC, with a community of this size, at which point I realized I was dealing with the wrong people).  I've dealt with true technical engineers at MSO's and they are brilliant.  These are not engineers, but managers with a 10,000-foot understanding of the tech. 

 

II'm really hoping to get a true engineer/architect involved, in light of the size of the build.  Hoping I find someone familiar with this unnusual build.  Any ideas how I might find that person?

 

Thank you in advance!

Expert

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

@rkmfl

Sorry, I'm not so useful.   I'm an old school DOCSIS tech, so this stuff is new to me. I did talk to several CC employees about your issues, but the information about your system set-up is proprietary at the moment so they couldn't share much with me. I did escalate this for you, an employee from the Digital Care team will reply and get the right people out to address your issues. 


I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Frequent Visitor

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

@nerdburg,

Thank you for escalating.  Much appreciated.  I'm very eager to find an engineer with a hands-on knowledge of this build.  By the way, this is Arris' new turnkey setup that they seem to be pushing quite a bit. 

 

Part of me wonders if there are not many people within Comcast that know much about this.  I don't believe the reason is because it's proprietary (Arris publishes a great deal on this setup, promoting it so heavily). Instead, I wonder if the issue is that Comcast is simply following Arris' lead and Arris' marketing hyperbole, without having many people @Comcast who are up-to-speed on dialing-in the network issues, at this early stage.

Expert

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

I talked to 6 or 7 employees yesterday. They were all aware of Comcast's use of fiber in some capacity, but that was the limit of their knowledge on the matter. I did talk to a CC engineer who was knowledgeable about your specific set-up, but he was not authorized to share any info publicly. I couldn't even get a spec sheet out of him, lol. ¯\_(ツ)_/¯


I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Diamond Problem Solver

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync


@rkmfl wrote:

This isn't a Comm Tech 5 application (IMHO) because it's not limited to a handful of installs with issues, it's the overall design/build (or possibly issues at the HPON or EDFA). 

 


I am not certain about the exact level of training that a Comcast Comm Tech 5 receives, sorry. Best of luck with this !

Official Employee

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

Hello rkmfl. I can assist with troubleshooting your Gigabit speed issues. Please send me a private message and include your full name and account primary phone number so I can access your equipment.

New Poster

Re: 1,100 Homes, Gigabit + XB6, ALL Slow + Constant Reset/Sync

Did this issue get resolved?  What was the outcome?