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New DOCSIS 3.1 modem slower?

Regular Contributor

New DOCSIS 3.1 modem slower?

Hi all, I am wondering if anyone has seen this or understands what is happening. About 6 weeks ago, as it was time, I purchased a new modem and activated it. The modem is an ARRIS SB8200 DOCSIS 3.1 modem, my prior modem was an older DOCSIS 3.0 modem. I live in the Baltimore area. My tier is extreme 150, 150/20, on comcast's speed tests I get about 178/24. Signals are all good, I recently had my lines checked by Comcast and I actually removed an old switch to a TV cable that's no longer used, so it is a straight shot of cable to my modem.

 

After activation of the SB8200, everything was fine - 178/24 down/up, approximately. But then last week, we had a power outage from a rain storm, and power was out for 2 hours. When power came back on, the first thing I noticed was that the lights had changed - formerly on the 8200 all lights were green, specifically d/l and u/l lights were green, which means DOCSIS 3.0. Now, d/l light is blue - meaning DOCSIS 3.1! I wondered, is DOCSIS 3.1 in the area now and my d/l speed has increased?

 

With excitement I ran the speed test in off hours, and to my surprise d/l speed was around 145 - it had gone down! U/l speed is still the same, 24. Over the last week I have continued to test it, always the same - 142-148. There are zero errors, and the signals look good to me (see picture below).

 

So it seems the use of DOCSIS 3.1 is slowing down the downloads - and a significant amount, about 20% - why would that be? A local comcast guy said "We are getting our plant ready to launch docsis 3.1 across our footprint. It is not fully launched in all areas. This just may be temporary until we are fully launched." 

 

What do you think, have others experienced this?

Screen Shot 2017-08-10 at 9.14.53 AM.png

 

Thanks!

Expert

Re: New DOCSIS 3.1 modem slower?

I’m gonna was put my money on the bug Comcast is aware of with their own equipment. I’m not sure what kind of CMTS you have but if you could find the CMTS MAC address and out it into a MAC lookup that would show everything. I think you might have the Arris E6000 at your headend facility. There is a known glitch known by D3.1 modem manufacturers and Comcast and Arris where it affects all D3.1 modems. The glitch results in download speeds about 10-20% slower compared to just DOCSIS 3.0. Comcast still hasn’t touched the system to fix it. Arris has a fix but Comcast hasn’t deployed the fix to their own. It should only be temporary but I’m not sure how long temporary will be for them. Even in areas that already have it deployed with the E6000 it hasn’t been fixed yet anywhere. The Cisco CMTS only comes out a few megabits slower so it isn’t really noticeable.
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Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Ah thanks for the reply! So it sounds like I may want to put my old modem back on, as it had no problems and got close to 180 Mbps speeds? I can keep the 8200 until such time as 3.1 is fully operational in this area? What do you thnk?

Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Oh and 1 other question - if it makes sense to put my old DOCSIS 3.0 modem back on, I can re-activate a modem that was previously activated, and in the same manner as activating a brand new modem, is that correct?

Expert

Re: New DOCSIS 3.1 modem slower?

I personally think you should keep the SB8200 on personally. You’re still pulling pretty near 150 which is good. It’s ultimately up to you though. However your downstreams to me are a bit high but still in spec so I don’t think that’s the problem but since you do say that you noticed it after it looks like D3.1 came on that’s the most logical conclusion I can come up with. Have you checked for your CMTS-MAC? It should be in any logs and if you can’t find it take your CM-MAC of your 8200 and go to dslreports.com and send a DM to netcool
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Expert

Re: New DOCSIS 3.1 modem slower?

Yes you can activate the old one if you want. Just so that nothing happens just make sure the one you aren’t using gets taken off the account so no glitches happen in the system and think you are using the other. For example if you go back to the old D3 just unplug the 8200 and plug the old one back in and get it activated along with the 8200 being removed from the account so that it’ll only show one modem so no confusion should come out of that and vice versa when doing it the other way around with reactivating the 8200 if need be. As I said, it’s up to you. Your speed is still pretty good still however.
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Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Thanks jwever. FYI I am on an Arris CMTS. It's MAC address: CMTS-MAC=00:01:5c:6f:ee:68.

I based that on finding this:

If the MAC address starts with 00:01:5c then you're on an Arris. If it's 00:17:10 then it's a Casa. If it's 00:12:43 then it's a Cisco.

 

By reading around I am on what appears to be the lastest firmware, and I did find this thread where other people have exactly the same problem I do. Apparently a user/comcast employee maybe, netcool, who might be here, might be able to shed more light on the subject. I didn't really see any resolution of the problem although it does appear that another problem of lack of provisioning/getting IP address did appear to be solved.

 

 

Expert

Re: New DOCSIS 3.1 modem slower?

Sorry that the CMTS is plaguing you with your slower speed though D3.1. I believe this does require a line card update if I’m not mistaken to be done to the CMTS. I’m personally not sure when that timeline might be for them doing the fixes if they might be shortly after enabling D3.1 or the plan might be waiting until D3.1 rollout is complete. That’s the only thing even manufactures aren’t sure of yet and pretty much anyone isn’t sure of yet, the time aspect of when. Even by reading the link provided looks like with a Cisco one. You could try DM to netcool since netcool is a senior engineer with Comcast, according to the thread there, and see what netcool can do to try to get you back up to your normal numbers.
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Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Thank you, if I hear anything back from netcool I will post it here!

Authorized Vendor

Re: New DOCSIS 3.1 modem slower?

First your getting your advertised speeds lets be clear about that..  Yes there is a known issue with OFDM that was corrected via CMTS code it is being tested for deployment

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Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Expert

Re: New DOCSIS 3.1 modem slower?

The OP has actually stated slightly below advertised speeds with the 8200, 145 down, but don’t get me wrong but in a 150 plan 145 is close enough.
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Regular Contributor

Re: New DOCSIS 3.1 modem slower?

I understand that, but clearly something significant changed in a 20% drop in download speed. This is not about contractual compliance it's about understanding what changed and if it can be fixed. 

Expert

Re: New DOCSIS 3.1 modem slower?

Hopefully testing will finish sometime soon and get a rapid deployment.
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Authorized Vendor

Re: New DOCSIS 3.1 modem slower?

ok got it..  you can not disable the OFDM channel on a D3.1 device once Comcast enables it on the CMTS..  I will check and see if I can disable the OFDM channel on the cable modem for you..  give me a day or two to find out..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Thanks you Arris, will this have an implication down the line, like the modem won't work with DOCSIS 3.1 once it is rolled out? If it will be hard to get onto to 3.1 I would prefer not to do anything hard....if it's simple sure. I could still just go back to my prior modem too until I read that docsis 3.1 is out in my area, as I do intend to upgrade my speed once it is out. Thank you for your help in figuring out best way to go, I am just trying to learn what might be the best course (including do nothing as weaver suggested lol).

Authorized Vendor

Re: New DOCSIS 3.1 modem slower?

But D3.1 is rolled out in your area..  That is what your Channel 25 is, it is the OFDM channel

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Expert

Re: New DOCSIS 3.1 modem slower?

I did say you could go back to your older modem if you would like to. It’s your preference so it’s up to you.
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Regular Contributor

Re: New DOCSIS 3.1 modem slower?

I gthoguht it was in the process of being rolled out, but no plans are available yet? I was told by one of the comcast field guys it's in process?

Authorized Vendor

Re: New DOCSIS 3.1 modem slower?

Well for you the process is done Smiley Happy..  That would be the Channel 25, Comcast only does 24 QAM channels and 1 OFDM channel right now..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Wow! So I can call and find out what plans are available at my address?

 

Regular Contributor

Re: New DOCSIS 3.1 modem slower?

If I upgrade my account to a higher tier will it also be 20% slower for now? If so maybe I should wait until this tier is getting what it was before?

Expert

Re: New DOCSIS 3.1 modem slower?

That would possibly be so unless upgrading to the gigabit plan because you would be capped by Gigabit Ethernet anyhow ao you wouldn’t notice it and you get about 980ish max down was what I saw through people reporting their gigabit speed tests and about 41 up.
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Authorized Vendor

Re: New DOCSIS 3.1 modem slower?


dawalt wrote:

Wow! So I can call and find out what plans are available at my address?

 


Didnt say that Smiley Happy..  takes a little bit for the billing systems and CSR agents to know when things are available..  Just becuase it is enabled on the CMTS doesnt mean you can upgrade your service..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Diamond Problem Solver

Re: New DOCSIS 3.1 modem slower?


dawalt wrote:

I understand that, but clearly something significant changed in a 20% drop in download speed. This is not about contractual compliance it's about understanding what changed and if it can be fixed. 


Hello once again dawalt. FWIW, I don't believe that Comcast does their typical 20% speed overprovisioning through the DOCSIS 3.1 OFDM channel.

 

That may explain it. Just sayin'. YMMV.

Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Well this has been an interesting afternoon! I just got off chat with Xfinity, for only $5 more per month I got Gigabit Internet being installed next Thursday (installation fee too I know). I figure even if it's lower due to this problem for awhile that's probably more visible, plus it will stioll be a ton faster for only $5 a month. Thank you weaver and arris for your help, I'll post back how it all goes!!! Keep your fingers crossed!

Expert

Re: New DOCSIS 3.1 modem slower?

I’ve have seen a thread https://www.dslreports.com/forum/r31459294-Speed-Provisioning-question?search=Cm1000%20 where some customers have been reporting that they still have the 20% overprovisiong with OFDM active on their modem. Some depending on time of day and plans like Blast 75.
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Diamond Problem Solver

Re: New DOCSIS 3.1 modem slower?

A variable *could* be whether or not one's OFDM carrier is the primary or the secondary, or the 3.0 carriers are the primary or the secondary. I prefer not to speculate. Perhaps an official employee can answer authoritatively ?

Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Thanks for the replies, I am learning about this - can't wait for next week to see what happens!

Authorized Vendor

Re: New DOCSIS 3.1 modem slower?


jweaver0312 wrote:
I’ve have seen a thread https://www.dslreports.com/forum/r31459294-Speed-Provisioning-question?search=Cm1000%20 where some customers have been reporting that they still have the 20% overprovisiong with OFDM active on their modem.

So for as far as I remember the CMTS class of service has always had a little overprovisioning in them..  I cant say the amount becuase I dont know but there has always been a little..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Diamond Problem Solver

Re: New DOCSIS 3.1 modem slower?

20% has always been typical. Not sure if it matters if it's the OFDM or the legacy DOCSIS 3 carriers. AFAIK, the COS is controlled by the bootfile in the modem no matter the transport.

Expert

Re: New DOCSIS 3.1 modem slower?

I sent a DM to netcool and I got the response I was hoping for. “Yes, the over provisioning will stay the same.” The question I asked is whether the 20% over provisioning still exists with DOCSIS 3.1 regardless of the OFDM carrier is primary or not.
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Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Jweaver was does that mean I should expect to see with the gigabit service? Thanks for inquiring on this!
Expert

Re: New DOCSIS 3.1 modem slower?

The max I believe people have seen is around 980ish around that for download and about 41 for upload. Some reporting around 860 as well. You are capped by Gigabit Ethernet so you likely won’t see a Gigabit per second so even with the CMTS bug you won’t notice the CMTS bug this time around when having the Gigabit tier of service because of the Gigabit Ethernet cap. Like this, with 20% over provisioning you would see about 1.2Gbps download but as I said since the Gigabit Ethernet cap comes into play you’re not going to notice the bug take effect.
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Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Thanks for the explanation!
Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Ah I have another question! I received my email confirmation of the service change and upcoming installation appointment. If I go to my account page now, it says there is an upcoming appointment with its details, but if I go to look at my existing service it already says "Gigabit Internet". On a lark I tried power cycling my modem, but the speed is the same. Since the modem shows DOCSIS 3.1 DL, is there a way to actually get the higher speeds now before the service person comes? I would still keep the appointment as there may be something that needs replacing at the box etc., it would be good to have Comcast check everything since the speed requirements will be much higher. I was thinking even if there's a little hardware tuning to be done at the box and I only get 800 Mbps that's way better thn what I have now. Any chance I can make it flip to new service that's reported, or are they holding a new provisioning of the modem until a service person gives the go ahead?

 

Thanks!

Expert

Re: New DOCSIS 3.1 modem slower?

You could try calling Comcast and asking the CSR to reprovision the 8200 for Gigabit even though they have been iffy for some people to use their own device as you will also find on these forums but a good amount of people have reported success of their own equipment getting provisioned for a Gigabit. They might also hold it for the tech to do it just to make sure everything is ok. You might be able to get it to work.

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Authorized Vendor

Re: New DOCSIS 3.1 modem slower?


dawalt wrote:

Ah I have another question! I received my email confirmation of the service change and upcoming installation appointment. If I go to my account page now, it says there is an upcoming appointment with its details, but if I go to look at my existing service it already says "Gigabit Internet". On a lark I tried power cycling my modem, but the speed is the same. Since the modem shows DOCSIS 3.1 DL, is there a way to actually get the higher speeds now before the service person comes?

 

Thanks!


reboot your modem if your billing is already set there is a chance you will get the new bootfile.. 

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Regular Contributor

Re: New DOCSIS 3.1 modem slower?

Thanks guys. Arris I did do a power cycle but I'll sent the restartr command via the mobile app and see if that makes a change!

Regular Contributor

Re: New DOCSIS 3.1 modem slower?


jweaver0312 wrote:

You could try calling Comcast and asking the CSR to reprovision the 8200 for Gigabit even though they have been iffy for some people to use their own device as you will also find on these forums but a good amount of people have reported success of their own equipment getting provisioned for a Gigabit. They might also hold it for the tech to do it just to make sure everything is ok. You might be able to get it to work.


Ah, I spoke to tech support, they won't re-provision. They said the tech had to come and do the upgrade first. MOdem good, but they must check the wiring.

 

I guess I'll juyst have to be patient. I was liking the idea of doing it early, then when the tech came if I had any questions or there were issues they could fix it. Oh well!

Expert

Re: New DOCSIS 3.1 modem slower?

Hope all goes well with that visit. Keep us updated on any results or outcomes.
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Regular Contributor

Re: New DOCSIS 3.1 modem slower?

I sure will jweaver0312!

Regular Contributor

Gigabit Ethernet installed today - D/L speed not so hot

Hi all, well today was the day they came and turned on Gigabit ethernet, an upgrade from Extreme 150.

 

In reality they did just need to provision the modem, I have my own Arris SB8200. The tech insisted I had to use their modem, I insisted not, and then he tried it and it worked. I was glad I had seen others using that modem with success on this forum. thanks! (Of course when I ordered the aservice the online system said that was acceptable too).

 

My upload speed seems the same as what others have found, around 41 Mbps. But my download speeds are 550-600, you can see the attachment. The tech checked all the signals at the box etc. and said everything was good. I had another guy from Comcast come out in mid-June that I know who really knows his stuff, and he checked things at that time, and after tweaking things said all was good. Yet, I am disappointed with 550-600 - I expected at least 800 from reading the forums, maybe even getting lucky and hitting 900. I am nowhere close to that, even though it is an upgrade. The cable goes straight to my cable modem once inside the house, no splitters or anything else.

 

Is there anything I should do? I wonder about:

1) Different modem?

2) One of the Comcast gurus on here checking my signls etc. (no errors showing, attached are my signals)

3) Make a service call? I wondered if this tech guy knew as much as he should about the service since it is new and he was wrong about the modem.

4) Just live with it (it is much better after all) and it will get better over time?

 

I am in the Baltimore area, and Gigabit was just announced June 21st or so in their official presser. So maybe it needs to get settled in/equipment tuned etc.?

 

Let me know if you think I should do anything or just accept it as it is, thanks!

Screen Shot 2017-08-17 at 6.20.43 PM.pngSpeedsScreen Shot 2017-08-17 at 6.18.49 PM.pngSignals

Expert

Re: Gigabit Ethernet installed today - D/L speed not so hot

Would you happen to know if you’re computer Ethernet card is currently using half-duplex or full duplex 1Gbps? You should be able to see it in your network adapter settings.
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Regular Contributor

Re: Gigabit Ethernet installed today - D/L speed not so hot

Let me check and report back - I did fail to mention the speeds are direct connect laptop to cable modem (although WiFi speeds are very close to the same), and I am using an upgraded 2017 Macbook Pro so a late model computer.

Authorized Vendor

Re: Gigabit Ethernet installed today - D/L speed not so hot

I get 950 on my SB8200 but I never tried it with my MAC direct will try that on Friday..

-------------------------------------
Network Engineer, IP Engineer, Docsis..; the views expressed on this post are mine and do not necessarily reflect the views of my employer..

Gamer.. Living the dream one catastrophe at a time Smiley Happy ..
Regular Contributor

Re: Gigabit Ethernet installed today - D/L speed not so hot

Thanks for the replies guys! This time I plugged Ethernet into my router, and things looked about the same. My Mac reports the connection is 1000baseT, full duplex, MTU 1500 (standard).  The results were about the same, Xfinity's speed test reporting about 550 Mbps.  Which raises a couple of questions in trying to figure this out:

 

1. In another thread you may remember I originally got the SB8200 while on Extreme 150/DOCSIS 3, and the speeds dropped - likely from a known problem with the Arris headend that Comcast may be rolling fixes out for. Does this same speed drop affect DOCSIS 3.1 performance? 

2. I notice something pretty regularly in running the speed test, that I used to see years ago - even when running it today in the early hours, and with nothing going on inside the house, the speed meter quickly and steadily rises to about 700+, then falls right down to 300 or so , then reporting a final result in the 500s. The upload speed meter goes right up to 41 or so, and stays very close to that number the whole way - very stable. Why such variation in the download speed measurement during the test? I used to see this years ago when people first started measuring their speeds, it was very unstable. Is this indication of a network problem at the headend or higher? 

3. Should I try another modem, especially if there is a headend issue per #1?

Thanks!

Regular Contributor

Re: Gigabit Ethernet installed today - D/L speed not so hot

I forgot to mention ArrisTuska re: your comment, the only reason I direct connected my laptop to the cable modem was to eliminate any contributing issues that the router might be introducing. I figure if it ran at a high performance that way, the loss of speed was due to my router/cable/something on my side of the cable modem; if the speeds were still low, it was an issue from cable modem and outside. Hence my questions above, wondering about the modem, headend, etc..

 

Thanks!

Expert

Re: Gigabit Ethernet installed today - D/L speed not so hot

Since you said you’re using the 2017 MacBook Pro, what kind of adapter are you using that’s connected to it.
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Regular Contributor

Re: Gigabit Ethernet installed today - D/L speed not so hot

I am not completely sure, it's hard to find info. I use an official "Gigabit Ethernet adapter" that the cable plugs into, and then the other end plugs into a Thunderbolt 3 (40 gps)/USB 3.1 (10gbps) port, which is plenty fast enough.
Expert

Re: Gigabit Ethernet installed today - D/L speed not so hot

There might be a chance that even though Gigabit is available in your area, their might still be some node work that might or might not need to be done. In some cases they might have to do some other upgrades and in other cases not.
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