04-17-2012 07:32 PM
04-17-2012 08:10 PM
Experiencing the same issue on "Blast" right now and anxious to hear more about how upstream power impacts my Internet speed as well... please elaborate Jim721?
04-17-2012 08:25 PM
Your Upstream power levels can have a big effect on your over all connection if they go out of spec. 50 dbmv is right at the high point, low to mid 40's is what you want to see.
04-17-2012 08:44 PM
04-17-2012 09:35 PM - edited 05-15-2012 06:22 PM
Sounds like noise, Comcast will not throttle your data . and since you live in an apartment who knows what kind of cable is being ran through it to your rental
what speed tier are you paying for
you could have RG59 line running to the modem also it could be a sucked out connector or possibly be water in the line. untll they eliminate all these variables you will never get the problem fixed. depending where you are at the apartment I would have them run a line from the modem to the tap on the side of the building to eliminate the wiring.
04-17-2012 10:57 PM
Your speeds are fine according to ShaperProbe. At the time you ran the test your sustained speeds were about 15/2 and 23/7 with Powerboost. You might want utilize a download manager to open multiple connections to a server, this will allow you to take advantage of your bandwidth.
Blast speeds vary by area, you'll probably want to call in and be sure your modem is correctly provisioned.
You might want to run a tracert and grab another set of levels when you feel you speed is at its worse for comparison.
04-17-2012 11:06 PM
Thanks for all the responses guys!
Jim721 - thanks for the input, tech is coming out tomorrow.
shuck1 - thanks for your input as well.. .Comcast doesn't throttle/shape? I've heard so many people talk about it. I was also under the impression it's being throttled due to the shaperprobe results... I am very new to all this stuff though so I am learning from all your input
I pay for the 30 mb down BLAST service. I had the Preformance before (20mb tier) at my old apartment, with the older SB6120 modem and it was triple the speed, but I believe my line was fed directly from the outside as you reccommend shuck1.
I'll see what happens tomorrow and then report back!
04-17-2012 11:12 PM - edited 04-17-2012 11:15 PM
i-am-nerdburg - Those speeds are acceptable for the 30mb blast service? I am using a dedicated newsgroup server to test my connection speed with up to 50 connections at once, so the download manager isn't the issue. It still doesn't explain why I was getting up to 5mb down at my old place with Comcast, an older modem, and the lower tier, but get 1.7 megs MAX now, in a new place at the higher tier.
That just makes absolutely no sense.
It's either throttling/shaping or the line issues as people have said. I don't use the speedtests, as they are worthless, I'm using something I used in the exact same manner at my old apartment.. .trying to eliminate all variables.
Also, I've called multiple times and they have re-provisioned my modem and made sure the MAC was tied to my account etc etc
04-17-2012 11:38 PM
First, you have to understand how Comcast advertises their speed tiers. Blast is 16/2 or 20/4 or 25/4 depending on your local system. These are sustained speeds not including PowerBoost. All of them are advertised as "speeds up to 30 Mbps" which is what you'll see briefly due to PowerBoost. So if you are in an area where Blast is 16/2, your speeds are about right.
ShaperProbe shows your sustained speed and your speed with PowerBoost. In this case, shaping is a good thing --you get a short burst of speed to address the bursty nature of the internet.
Your modem may not be configured correctly, which is why I suggested you ask Comcast to check the provisioning.
Comcast does not throttle speeds except under specific conditions as part as their congestion management scheme. If you are a heavy user on a busy node, your speeds could be reduced temporarily. What you are describing does not sound like congestiona management tho.
04-17-2012 11:43 PM
nerdburg - ok cool.. taking this info in.. What should I tell them specifically? I have told them countless time to check my provisioning etc on the modem, but their customer service is completely out of it.
I even start to lose connection quality while streaming a hockey game last night on a great server.. it really sucks.
04-17-2012 11:53 PM
Shuck1 might be on to something. Your return power level is high and your SNR is just OK. Plus apartment buildings are notorious for noise issues. There is a fair chance that you have some intermittent noise issues. You might want to call Comcast and ask for your upstream SNR (uSNR).
04-18-2012 12:22 AM
yes what is BPI+?
Sorry for the technical jargon.
"Baseline Privacy Plus (BPI+) provides cable modem users with data privacy across the cable network.
It does this by encrypting traffic flows between CM and CMTS.
In addition, BPI+ provides cable operators with strong protection from theft of service.
The protected DOCSIS MAC data communications services fall into three categories:
• best-effort, high-speed, IP data services
• QoS (e.g., constant bit rate) data services
• IP multicast group services
Under BPI+, the CMTS protects against unauthorized access to these data transport services by enforcing encryption of the associated traffic flows across the cable network.
BPI+ employs an authenticated client/server key management protocol in which the CMTS (the server), controls distribution of keying material to client CMs (Cable Modems).
The original BPI specification had “weak” service protection because the underlying key management
protocol did not authenticate CMs. BPI+ strengthens this service protection by adding digital certificate
based CM authentication to its key management protocol.
04-18-2012 02:25 PM - edited 04-18-2012 02:31 PM
Tech came out and said there were huge amounts of BER (?) errors, fluctuations, as well as failure rates within the line and even from the main line in the cable room. He is referring it over to Comcast maintenance to fix the problem.. I asked him if there is any way I could follow up on the request or be notified on progress/fix, but he said once it was out of his hands he doesn't know.... How will I be able to know when/if the problem will be handled?
Could I also seek some kind of credit due to my service tier not being what I pay for due to line errors with a mystery date of when it will be fixed?
04-18-2012 02:47 PM - edited 04-18-2012 02:47 PM
B.E.R. = Bit Error Rate. The SNR (Signal to Noise Ratio) as read by a modem's measuring mechanism is actually an abstraction of the BER. If the bit errors are high the SNR is low and vice versa. Noise ingress is the typical cause of a high BER.
04-18-2012 03:25 PM
Just a little more definitions
BER is an acronym bit error ratio, sometimes referred to as bit error rate. The ratio of bit errors is the number of errors received compared to the total number of bits received in a specified time period.
CNR is an acronym for carrier to noise ratio. On a cable plant, CNR is measured in dBmV. The measurement is the distance between a modulated RF carrier and the inherent noise floor. As of June 30th 1995, CATV plants with a subscriber base larger than 1000 must meet a minimum CNR of 43 dBmV.
MER is an acronym for modulation error ratio. MER is the digital equivalent to Signal-to-Noise which is the baseband measurement equivalent to Carrier-to-noise. MER measures the ratio of error power to average power on an ideal QAM signal. MER measures the difference in quality between the transmitted modulation of a digital signal the received modulation. This measurement can be made with a digital signal analyzer and can be graphically represented if the analyzer supports constellation display.
04-18-2012 04:50 PM
lol, ok thanks guys... So anyone know of a way to follow up w/ the maintenance to make sure it is in fact fixed? He said the BER was huge even in the cable room.
So I guess it wasn't throttling, hardware/line error
04-18-2012 04:55 PM
I would try to call comcast and see if a ticket was made usually at least with me Maint was usually out the same day. just stay on top of it Or it may still be an issue
04-18-2012 07:11 PM - edited 04-18-2012 07:23 PM
will do.. keeping everyone posted.
Definetely need the main line fixed, i'm experiencing major upsets during peak hours. The Tech said with this type and amount of BER errors, multiple users would just exacerbate the issue
04-19-2012 01:51 AM
04-19-2012 07:24 AM
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12-27-2012 08:35 AM
I am very sorry you feel your connection is being throttled but you, as most users, are still very uneducated as your initial post concerning speeds of 4-5 MB / Sec puts to evidence... It wasn't long ago Comcast didn't have a pay-per-tier (or as I call it pay-to-play) system, and not long before that I used to get speeds of 300 MB per second, you did read that correct... One gig used to take 2-3 seconds on a good day.
Unfortunately, it is users like us who have prompted these measures, when you speak of raiding arrays and dedicated servers and downloading large files and backing up hard drives via the Internet you are also what many consider to be, abusing the system, and it is because of people like you (and I) that they are doing this except...
Their little tier plan does give away a slight indication that another factor (such as GREED) could be at play.
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