| [Connectivity] Slower Upload speeds with DOCSIS 3.0 SB6120 Modem I used to experience on average on any given point of the day/week around 20 down / 3.5-4.0 up consistently with my docsis 2.0 sb5120 modem. I am currently paying for the BLAST speed tier.
However yesterday I had decided to upgrade to a docsis 3.0 sb 6120 modem and called comcast to register/provision it and all.
My levels are all in the green, I've had numerous technicians come out and replace everything from the tap/drop to my junction box to the cables and splitters inside my home. All of my signal levels are quite optimal at this point from owning the sb5120 to recently yesterday purchasing the sb6120.
It's been about a day and a half and I have been noticing that my upload speeds have had quite a drop, I am now averaging around 1.5-2.5 now with my new docsis 3.0 sb6120. the down speeds are actually the same/higher with the downstream bonding...
I run speedtests from numerous sources from the comcast site to several others to get an idea/near accurate average of all the results
Has anyone else had problems like this?
I also got off the phone with comcast and they did not remove my old sb5120 modem from my account when I had asked to yesterday when registering my new sb6120, they also tell me that they cannot remove it for whatever unknown reason, they were also not able to verify the bootfile/speedtier as well. I am in contact with comcast steve right now awaiting a reply however I was just curious if anyone else had experienced this.
I am actually thinking about switching to the zoom 5341 docsis3.0 modem now.. I really would like this sb6120 to be optimized and to work... |
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| Re: [Connectivity] Slower Upload speeds with DOCSIS 3.0 SB6120 M I had this same problem. Ditch the SB6120, it doesn't work well with Comcast's network sometimes. I was experiencing the same symptoms as you. Signals and levels were fine, the download was awesome but the upload was lacking. I got a Arris modem from the service center in my area, and after provisioning my upload to the correct values, no other changes made. |
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| what do you mean by provisioning your upload to correct values?
i am leaning towards returning the sb6120 and maybe trying the zoom 5341
i much prefer to own than lease |
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| reply to daveofstreng
Comcast doesn't "provision uploads". You get your modem provisioned yes, but only one file is downloaded which determines your download AND upload speed.
I can tell you that I'm using the SB6120 on Blast and have no issues getting more than the speed I pay for on both up and down.
Reset All Defaults then Reset The Cable Modem and see if that helps.
Also, post your signal levels please. |
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| Sorry I meant provisioning my modem. |
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| reply to ExoticFish
I've done the reset all defaults then reset cable modem and no changes...
Here are my levels :
My usnr is stable as well from when I last called less than an hour ago |
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| reply to ExoticFish
attn:exotic fish
what kind of speeds do you get from speedtests? |
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andyrossPremium,MVM
join:2003-05-04
Schaumburg, IL | reply to daveofstreng
The slow upstream could be because you are on 32QAM upstream. That is a bit odd, as I've really only seen 16 or 64QAM. You are 5.12Msym/sec, which is the same as me, but that 32QAM means the upstream channel has less total bandwidth than 64QAM.
I'm on 64QAM in the same area, and am seeing about 21/3.3 on the standard Performance tier:
A Speakeasy test was about the same, although the upstream abruptly dropped to about 2.68M in the middle.
A Visualware test 21/4.
About the only other think I can think of is if you have rebooted your router since the modem change? I doubt if it makes a difference, but it can help to rule it out. Also, have you tested with the computer directly connected to the modem? |
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| said by andyross:The slow upstream could be because you are on 32QAM upstream. That is a bit odd, as I've really only seen 16 or 64QAM. You are 5.12Msym/sec, which is the same as me, but that 32QAM means the upstream channel has less total bandwidth than 64QAM. I was on 16QAM for years, until just recently when the upstream modulation was upgraded to 64QAM. My upstream bandwidth was between 7Mbps and 10Mbps with 16QAM, and hasn't changed either way with 64QAM. |
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| reply to daveofstreng
My upload is normally 3.75. Not sure why it's low today. I was told they're working on upgrading here so maybe that's why.
This is wireless too, not connected directly to the modem or via ethernet.
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»www.TheExoticFish.com |
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| reply to andyross
I have tried with a direct connection to the modem and it is the same.
Should I call and have them provision my modem again? |
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 hov
@comcast.net | Any luck figuring this out?
I think I have the exact same issue. I just *upgraded* to a SB 6120 modem and my uploads are like less than half of what they used to be. I have Blast service as well and my speed test numbers seem to match what you're getting. |
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mlody
join:2000-07-26
Des Plaines, IL | reply to andyross
said by andyross:The slow upstream could be because you are on 32QAM upstream. That is a bit odd, as I've really only seen 16 or 64QAM. You are 5.12Msym/sec, which is the same as me, but that 32QAM means the upstream channel has less total bandwidth than 64QAM.
I'm on 64QAM in the same area, and am seeing about 21/3.3 on the standard Performance tier:
[att=1]
A Speakeasy test was about the same, although the upstream abruptly dropped to about 2.68M in the middle.
A Visualware test 21/4.
About the only other think I can think of is if you have rebooted your router since the modem change? I doubt if it makes a difference, but it can help to rule it out. Also, have you tested with the computer directly connected to the modem?
I have ubee Docsis 3.0 modem and I am on 32QAM upstream, but my uploads are always hitting 4.25, so it is hard to say if the modulation has much impact. |
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 ScilicetMens et ManusPremium
join:2005-04-11
Aurora, CO
 ·Vonage
 ·Comcast
| reply to daveofstreng
Curious. I bought a 6120 2 months ago. With my situation I picked better than expected speeds. I have the Performance Tier at 12/2, but look what I get with the new modem:
It may not be the modem. Comcast may not be ready for you yet. They are in the process of upgrading. Perhaps you should check on the upgrade status and wait it out.
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Be kinder than necessary, for everyone you meet is fighting some kind of battle. Live simply, love generously, care deeply, speak kindly.... Life isn't about waiting for the storm to pass... It's about learning to dance in the rain.
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andyrossPremium,MVM
join:2003-05-04
Schaumburg, IL | reply to mlody
said by mlody:I have ubee Docsis 3.0 modem and I am on 32QAM upstream, but my uploads are always hitting 4.25, so it is hard to say if the modulation has much impact. What I was trying to say is that the TOTAL bandwidth is lower than 64QAM. It would take fewer users to saturate it with 32QAM, especially in prime time. |
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jg6789Premium
join:2011-03-31
Fort Lauderdale, FL | reply to daveofstreng
I am having the same exact problem. When I first upgraded from the 5120 to the 6120 in November 2010 my download speed shot up from 18 mb to 30 mb and my upload speed stayed the same, around 4 mb on blast!. Now for the past few months my upload speed has been around 2 mb and very very lossy. I could barely use skype. I had two techs out to look at it and the second one said it was a bad 6120. I had them provision my old 5120, (which I had stored in the closet) and bam my upload speed was back to normal and skype was working great. Too bad my download speed is back down to 18 mb again though... I'm not sure if I should get a different docsis 3 modem or get a new 6120... |
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| reply to daveofstreng
I know this is late but anytime on the 6120 your modulation is not correct or anything relevant to that just go to configuration when you go to the stats menu and hit reset to default then unplug it instead of the reboot option just power cycle it.That helps alot of the time and anybody posting that the 6120 does not work well with comcast networks I would never read another response they sent on any post.If it did not work they would not use it and mine is flawless but that's not the point the point is that if the modem did not work well or whatever the guy said that made no sense they would not use it because most service calls are considered overhead for comcast because as long as its comcast equipment their is no charge meaning they don't want to be sending trucks around to places where they have installed modems that do not "work well" with their networks. |
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jg6789Premium
join:2011-03-31
Fort Lauderdale, FL | reply to jg6789
So I bought a new 6120 at Best Buy today. Same exact problem as my other 6120, I guess there was nothing wrong with it. Looks like the 6120 is not working very well with Comcast for some reason. The 5120 is working great. Hopefully Comcast gets this fixed.. Maybe its a firmware issue or something. |
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andyrossPremium,MVM
join:2003-05-04
Schaumburg, IL | Out of curiosity, what type of upstream QAM was being used with each modem (you can always temporarily connect the other modem just to check the signals.) It could be the 6120 is using 64QAM, and the 5120 ended up on 16QAM, which is less sensitive to noise. |
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jg6789Premium
join:2011-03-31
Fort Lauderdale, FL | They were both on 64QAM upstream. I just returned the new SB6120 and picked up a Zoom 5341. I'll let you know what happens when I hook it up this evening. |
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