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CMoore2004
Premium
join:2003-02-06
Jonesville, MI

[Connectivity] What's the max speed per upstream channel?


speedofme
Click for full size
Signal levels

testmy.net graph
I'm on the "Blast Plus" package and when they called and offered it to me they said it was 50mbps. They never mentioned upstream but I assumed it'd be the 50/10 I had seen posted online so much. Usually my speed tests show around 36/6. Could it be that the 2 upstream channels aren't enough to support the 10mbps? I only show two upstream channels. The first is channel 1 @ 2.560Msym/sec with [3] QPSK and [2] 16QAM modulation. The second is channel 2 @ 5.120Mysm/sec with [3]QPSK and [3] 64QAM modulation. Signal levels are OK all the way around. I'm just wondering if the upstream is a limit of the local CMTS or if I should be complaining that I'm not getting the speeds I'm supposed to.

I also have the issue of sustained downloads kind of stuttering. It'll download for a few seconds at reasonable speed, then cut out for a few seconds, then go back to full speed. You can see it in the graph of the last attached image. That test finished at a whopping 24Mbps.

Edit: I'm sure it'll come up, so the modem is a SB6121.


Speed_Tiers

@comcast.net
The signal levels you post are more than adequate for getting 50/10. Unfortunately, Comcast's use of marketing names for their speed tiers instead of actual numeric values (and including the unreliable temporary PowerBoost as part of the formula even when they quote numbers) makes knowing what you are paying for (deliberately) difficult. The fact that each franchise can modify the nationally advertised tiers makes it even more difficult.

I suggest that you connect a PC directly to your modem (if you currently use a router), reboot the modem and PC, and then run ShaperProbe instead of using on-line speed tests. That should tell us what speed you are actually capable of running. The reason for eliminating any router from the equation is because many routers (especially older routers) can not handle 50/10 or faster speed tiers.


bradyr
Columbia College IT
Premium
join:2008-10-27
Sonora, CA
reply to CMoore2004
regardless of whether or not this info helps resolve your issue, to answer your original question about max speed per upstream channel, here's the specs (source: »en.wikipedia.org/wiki/DOCSIS)

typical upstream 64QAM channel, max throughput: 30.72Mbps (27Mbps max usable)

typical upstream 16QAM channel, max throughput: 10.24Mbps (9Mbps max usable)

typical Downstream 256QAM channel, max throughput: 42.88Mbps (38Mbps max usable)

hope that info helps, if not, then it's good for educational value.

CMoore2004
Premium
join:2003-02-06
Jonesville, MI
Thanks for the info. Perhaps they don't do 50/10 here because they only have the two upstream channels. When I chatted with them to see what the speeds were supposed to be they said 50Mbps/5-10Mbps.


netcool
Premium,VIP
join:2008-11-05
Englewood, CO
kudos:109
said by CMoore2004:

Perhaps they don't do 50/10 here because they only have the two upstream channels. When I chatted with them to see what the speeds were supposed to be they said 50Mbps/5-10Mbps.

Jonesville is one of the few areas that has not had its Blast tier updated. It's currently provisioned for 25/4 sustained with powerboost up to 37.5/6.4. So the numbers you are seeing make sense with that in mind. Unfortunately these one offs tend to cause a lot of confusion.


bradyr
Columbia College IT
Premium
join:2008-10-27
Sonora, CA
reply to CMoore2004
two upstream channels, even one 64QAM and one 16QAM is plenty to cover 10Mbps upstream. it becomes more of an issue on the downstream side. 4 channels downstream is more than enough to cover 50Mbps.

however you can run into speed or congestion issues when you have a lot of subscribers on a particular node and on top of that a lot of nodes combined on a single downstream port at the CMTS.

comcast head-end techs just recently resolved a months long issue with my node where it was combined with 5 other nodes at the CMTS, causing that particular downstream port to be at 96+ percent capacity. Upstream was never an issue due to each node having its own dedicated upstream port at the CMTS.

CMoore2004
Premium
join:2003-02-06
Jonesville, MI
reply to CMoore2004
It wouldn't have been so confusing if they just posted the speeds somewhere. Especially when they call to offer 50 Mbps. But at least I know now. Thanks!


Caddyroger
Premium
join:2001-06-11
To the west
reply to CMoore2004
I have a Arris TM722g emta. I only have 4 down loads and 2 upstream channels I my speed tier is 50 down and 10 up but I always around 60 down and a little over 11 up, @ channels can support 10 up.
--
Caddy


Cjaiceman
Premium,MVM
join:2004-10-12
Parker, CO
kudos:2
reply to CMoore2004

105/20 + 50/10
 
Click for full size
levels
I would seriously challenge them on that... 2 upstream channels are way more than enough to do 10 mbps up. I'll prove it by combining my 105/20 and 50/10 together...

As you can see I have way more than enough bandwidth for 10mbps upload on 2 channels. You were fed a line of bull, there is some other reason for them not offering it to you. Might be to many people on that node?
--
TorDek: "DSLR... Here, were not just experts... were also vindictive bastards..."

CMoore2004
Premium
join:2003-02-06
Jonesville, MI
They didn't claim they couldn't offer 10Mbps up with the two channels. I was thinking that maybe they assigned a slower uplink because the two channels wouldn't be enough for multiple users to use their higher upload speeds at the same time. I also didn't think the node would be that congested during the summer months as I live in a college town and the students just came back a few weeks ago.
Anyways, I don't download large amounts like I used to so it's not really a big deal. When you come from Frontier's DSL, you learn to appreciate real broadband. Web browsing at home feels the same as at work with a 200/200 connection.