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BiggA

join:2005-11-23
EARTH

[Connectivity] Super slow downloads, uploads fine

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I moved a couple of days ago, and brought my Comcast service along with me. Before I left the old place, it had somehow gone from 62mbps to .6mbps. When I got to the new place, it was doing the same thing. After talking with a completely clueless Comcast rep, we got it do a couple mbps, and then found out that we had yet another problem, our signal levels were low, between 0dB and -1dB, because of all the splits in the line, so we took a splitter out and voila! 63mbps and 0 to 2dB.

Fast forward a day and I move the modem and router downstairs, and plug them in there. The speeds sucked, but I figured we were on way too many splitters, so I figured we'd fix it after we went though the house and ID'ed the cable lines, and got the splits under control. In the mean time, the cable guy came out and put two more lines in for us, and replaced the ground block and connectors. Last night, my roommate and I tried for several hours to get the internet fully working again and couldn't. We went all the way to the point of hooking the modem up directly to the line coming into the house, which got us around 7dB, and we got one good Speedtest, a couple of decent ones in the 20's, and the rest were repeated 2-3mbps.

Does anything look wrong with these levels? I'm kind of baffled as to why the speeds are so bad. There isn't a clear pattern to it, it's kind of erratic, and it's hard to figure out whether it's an internal wiring issue or something in software on their end. The uploads are fine, 11mbps is right on the mark.


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5
Are you testing with a single machine bypassing a router?

Signal levels look ok - generally you don't want to see more than 1db difference between channels. What's in the modem logs?

Also 0 to -1 dbmv is by far not low signal. That may have pushed your upstream a little high, but still useable.

BiggA

join:2005-11-23
EARTH
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We have tested both ways, and get equally poor results.


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5
There are some T4 timeouts and other resets in there, which is never good given the small timeframe of that snapshot. You need to have a tech out with a meter to sweep for noise / bad fittings / etc.

BiggA

join:2005-11-23
EARTH
So there might be a noise issue, even though we have good levels? Wouldn't that be kind of obvious in the SNR? The guy who installed the two additional runs did check the levels, and was getting around 6-7dB over a bunch of different channels. Is there something else they need to check since we're still having issues?


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5
Intermittent noise will not always show on the SNR interpolation of a modem. It is almost showing, you have a 2 DB drop when you get around channel 100, that's not really normal given the small change in frequency.

Yes, the tech needs to check noise levels and not just signal levels.

BiggA

join:2005-11-23
EARTH
Ok, if we can't get it fixed through 1-800-Comcast, then we'll have to roll a truck. Once they do that do we get charged if it's something inside of the ground demarc, and not charged if it's something outside?


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:10
reply to BiggA
said by BiggA:

So there might be a noise issue, even though we have good levels? Wouldn't that be kind of obvious in the SNR? The guy who installed the two additional runs did check the levels, and was getting around 6-7dB over a bunch of different channels. Is there something else they need to check since we're still having issues?

FWIW, a modem can not read / display the uSNR (upstream Signal to Noise Ratio) value. There could be noise ingress in the upstream channel frequencies / return path only.


tshirt
Premium
join:2004-07-11
Snohomish, WA
kudos:5
Reviews:
·Comcast
reply to BiggA
said by BiggA:

Ok, if we can't get it fixed through 1-800-Comcast, then we'll have to roll a truck. Once they do that do we get charged if it's something inside of the ground demarc, and not charged if it's something outside?

You MIGHT get charged, IF it is your equipment(say an owned modem) causing the problem.
everything on the WAN said of the modem (including the cable in the house...UNLESS you messed with it )is their responsibility.
the tech can read the power and the SnR on the downstream, and the output from your modem/house, but calling in is the only way to find out what the CMTS is receiving back from you, to see if/where noise is being introduced.

ykram

join:2008-07-16
reply to BiggA
I'm in the same boat here.

Slow speeds (0.86 Mbps. Upload is fine though). Xfinity's speedtest site shows everything OK, Up/Down the way it should be but if I venture out of comcast's network e.g. speakeasy's speedtest, it's unbelievably slow.

BiggA

join:2005-11-23
EARTH
reply to BiggA
How would uSNR affect the downstream though?

I just tried the XFINITY Speed Test, and it showed almost triple what Speedtest.net showed, but going from 1.5mbps to ~4mbps isn't exactly solving the problem when it should be 50, and is normally 62-63...


tshirt
Premium
join:2004-07-11
Snohomish, WA
kudos:5
Reviews:
·Comcast
It's a 2 way conversation, ACKS must be sent so if the upstream has problems and must resend multiple times to get through, then the downstream is greatly diminished.
We have seen similar problems before, and it's frequently the downstream that shows up as slow on the speed test even when it's the upstream having problems.
Certainly worth checking


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:10
reply to BiggA
said by BiggA:

How would uSNR affect the downstream though?

Perhaps you could Google about how the TCP protocol functions.

BiggA

join:2005-11-23
EARTH
reply to tshirt
I get how bad upload would mess up the download, but how would 11mbps of upload mess up the download? We're literally getting more than triple the upload. It's a bit messed up.


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5
reply to tshirt
The cable in the house is not comcast's responsibility, although more times than not they treat it that way.


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5

1 recommendation

reply to BiggA
You have a signal problem, call in to get it fixed. That's the simplest answer.


Mr Peabody

join:2001-01-05
Ingleside, IL
reply to ykram
This is exactly what I'm seeing. 15mbps downloads if Speedtest.net uses Comcast's Chicago server, 1.0mbps if I pick any other. Upload stays at 5mbps regardless of server chosen.

Shouldn't this mean it's something external, somewhere farther up Comcast's network? I'm loathe to reboot my modem for no reason, as I don't want to spend an hour on tech support begging them to reopen port 25.

BiggA

join:2005-11-23
EARTH
reply to beachintech
They're coming out tomorrow to take a look at it. The guy offered to put me on the $4 monthly wiring protection thing, and he said I could cancel after two months. So even if it is our [landlord's] problem, we pay $8. If it's their problem, we still pay $8. Not a bad deal. They must assume most people forget or just leave it on.

I'm 95% sure it's a Comcast problem though, as the wire that we plugged the modem into is a straight ~6' run to the ground block/demarc. The weird part is that the previous tenants had an old D2 modem that was fine, and we've gotten a couple of good speedtests, but rather randomly/ sporadically.

The contractor guy who did the two runs was very professional and did a good job, with neat wire runs, so hopefully we get someone good again. Of course I'd prefer a real Comcast employee, although the last two times I've dealt with contractors they've been fine. I wish they were union, and only they could do the truck rolls, but oh well, in a perfect world...

ykram

join:2008-07-16
reply to Mr Peabody
My coworker reports the same issue. 90 kb/s everywhere. This sounds like a comcast issue more so than anything, imo.


Thundercamel

@fermassoc.com
I'm having the same problem in Lake Villa, IL, since 6/9/2013. Less than 1 Mbps down, normal 8 Mbps up. speedtest.comcast.net shows normal speeds only if you do the chicago test, and every other server is slow. It seems like a Comcast routing problem to me.

BiggA

join:2005-11-23
EARTH
reply to BiggA
So the guy game out, tested the levels, tested the wiring, and everything was fine. He said that the only thing it could be is the modem. He reiterated "it's all electronics" and added some interesting information about how Comcast is not going to upgrade more systems to 860mhz because it costs too much to do a total plant rebuild, and that our existing coax rolls off sharply after ~770, even if we had 860 electronics. He said that if he put a new modem in, and it fixed the problem, we would see a service charge, but if I went to the office and got it, it wouldn't cost anything beyond the rental charge. So I got their modem, and sure enough, it worked. I'm baffled as to why a Motorola SB6141 is having such horrendous issues, but yet maintaining great uploads. I'm going to have to play around with my modem more and get Comcast to play nice with it to get the rental modem off of there soon, but in the meantime, we have working internet.


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5
I suspect your problem will return. Most of the time just the act of touching the coax when changing the modem will discharge enough or kill whatever is causing noise at that moment to make the issue look to be gone. I hope it was just a faulty modem, but I have a hunch it's not.

For all the other people in this thread - your issue are not related to BiggA 's issue. You should call in as well to schedule a technician.

BiggA

join:2005-11-23
EARTH
I can't argue with the results. We had several days on several different jacks, including the line coming right in, and it was almost always a mess with my modem, and now with their off-brand piece of crap, it's consistently fast.

What I'm trying to figure out is how the modem checked out fine, worked fine with uploads, and was rock solid in maintaining the sub-par speeds. I can't believe that's hardware damage, as I would think it would be a lot worse, and it worked on this same system a week ago without issues. And it's not like I got something that is more resillent to some issue we have, since the other modem started acting up before I moved AND we now have some crappy 4-channel Ubee, when before we had a real Motorola with the full 8 channels. I'm baffled.

Yeah, likely other people have different issues. A modem going wonky like this is bizarre and probably rare.


beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5
I would be interested to see what is happening in a few weeks to a month from now.

BiggA

join:2005-11-23
EARTH
We'll see, but we already have a clear and repeatable pattern: My modem= 3mbps, their modem = 63mbps.

krafty1

join:2010-04-07
Hastings, MN
reply to Thundercamel
I AM ON TRIPLE PLAY PERFORMANCE TIER FOR $ 99 A MONTH AND THESE ARE MY RESULTS.
»stage.results.speedtest.comcast.···7702.png

BiggA

join:2005-11-23
EARTH
You're getting a lot more than you should. We're still at 60+mbps on Blast! with the rented modem.


IowaCowboy
Iowa native
Premium
join:2010-10-16
Springfield, MA
kudos:1
Reviews:
·Verizon Broadban..
·Comcast
reply to BiggA
From what I am reading it sounds like they are not pushing the correct config file. I would post in the direct forum.

I have a 6141 and it performs better than my 6120.

As for the landlord, they will probably say that the CATV wiring is your responsibility.
--
I've experienced ImOn (when they were McLeod USA), Mediacom, Comcast, and Time Warner and I currently have DirecTV. They are much better than broadcast TV.

I have not and will not cut the cord.

BiggA

join:2005-11-23
EARTH
The wiring is fine, as it works with the rental. Something's wrong with the modem or modem configuration. I have a bunch of other stuff that has to get done, but I'll get to that eventually...