Comcast XFINITY → Re: [Speed] new "Performance Promo" is mostly unusable

UPDATE: two technicians (field tech and upstream network tech) spent almost four hours working on my situation.

Interim conclusion: there is a single wonky channel which they tested and could not even login to, in order to do testing. Something is wrong upstream.

STATUS: neither my ARRIS 822G nor their ARRIS 722 nor their XFINITY super-duper modems (all DOCSIS 3.0 spec) behave any differently. In other words, it is not my (owned) modem. It is how the DOCSIS 3.0 modems are connecting in my specific location. It may be the one wonky channel since the 3.0 modems bond multiple channels - but that is to be determined.

RIGHT NOW: I am using a loaned (hence leased $$$ ) 2.0 Motorola modem. It is running at advertised speeds (~20/7) and not augured in. Direct replacement and reprovisioning of ANY of the 3.0 modems results in the late afternoon cratering. We proved this.

Remaining to see: what the techs find out and get repaired, and then reprovision my 3.0 modem.

This much is certainty, here at my location....

The 3.0 modems (any of them) when not connecting to the wonky channel (or whatever proves to be the root cause) manage 15-25 down, and 30-40 up. With ease.

The 2.0 modem connects at 15-25 down, and 6-8 up. With ease.

More to follow.

So...not congestion eh?

Glad they're on the trail...sounds like if they've isolated a specific channel, it should be much easier for them to diagnose and fix!

Until the channel gets sorted, even they would not rule it out.

This channel issue does not explain the clockwork-like time of day slowness....

I really don't see how it's congestion given you're getting 20 Mbps easily on a single channel that has a maximum of 39 Mbps (after overhead). More likely the hosed channel is causing the modem to shuffle things dynamically and it's wreaking havoc. Did you ask if others had reported problems in your vicinity?

Yeah, I did. No one has said anything. It may be simply that they lack any perspective or are not here at worst times, etc. My neighbors are 386/4MB RAM, ex-modem users....there is no place like numb.

As you said, it is some scenario, perhaps unanticipated with the way the spec is implemented, that results in this (apparently poor handling of a failed channel). But I am GUESSING.

I think that is logical. The good news: both tech folks saw it and saw the results and showed me the wonky channel. Something will change - or it won't . But at least I an exonerated from having fabricated a story and, more importantly, IT IS NOT MY PURCHASED MODEM. ha ha ha

I don't think that anyone here even suggested that you had fabricated a story, only that your automatic assumption of congestion was not likely on a DOCSIS 3 16mbps downstream connection with 6 downstream bonded channels.

Indeed, I meant no disrespect. Congestion just didn't add up! In any event, sounds like the OP is on their way to a solution, hopefully.

If this is the case it seems pretty sad. I have seen a few other forum users with an issue on one or two channels, which causes the whole connection to go to crap. It sure would be nice if the modems could handle something like that a bit more gracefully.

It would be interesting to get a look at the signals when your speeds are slow and see if you can see anything odd with one of the channels.

Wow! Learn something new every day... I've heard of them losing a channel and dropping off but it's odd that it's at certain times of the day and not all the time. Maybe they are rotating channels at certain times of the day to adjust for usage? That would be about the only explanation for your timed issue... Hopefully, they will get everything back in order for you...

UPDATE: Friday morning.

SUMMARY: After installing their DOCSIS 2.0 modem (a Motorola of some flavor) ran for 30 hours without issue (averaging 15/8 speeds), and thus avoided the afternoon cratering. We did install one of their DOCSIS 3 units, and it behaved exactly like my owned one. So we installed the 2.0 to see what happens over time.

The second level tech (one step above the installer, but not into the core routers/gateways I presume) arrived this morning and he described having changed out three things upstream.

Changed: removed a 10db shunt on my physical drop as he found it was causing all sorts of "reflections" and replaced it with a three way split, with two of the drops capped off which he says imparts a smoother attenuation - (just repeating what he said folks, he appears to be pretty experienced)

The 10db was installed because my Upstream Receive Power was measuring over 12db, and apparently that is bad but no one has described how that manifests itself and it surely doesn't explain time of day cratering. The number is now almost 0, and this morning's tech says it is as close to ideal as he can make it.

Changed: two unnamed connection points/taps up the pipe. He mentioned the new ones were 1Ghz versus the 750Mb ones in place - one of you might be able to translate this? He said he was able to see the "modem signatures" of my neighborhood and we were all showing the same irregular hills and valleys. He said after he made these changes he measured and got a lot more level and less hill and valley (tech talk ha ha)

bobjohnson - he said these can degrade when it gets hot, is this what you alluded to in a previous reply?

Previously, jacked into the green box he was unable to login to one of the channels as I previously reported. Now he can login and said everything is pretty much on spec.

SO.....I cut over to my ARRIS 822G, the DOCSIS 3 modem. It's nearly 11:00 AM here now, so in the next 3-5 hours we will either continue to run at splendid speeds or augur in again. If we augur, I will revert to the DOCSIS 2.0 and report to the local Field Supervisor of having done so.The field tech said the trucks will roll until they figure this out. Nice people.

Speeds, for clarity - on my drop this morning...these speeds are NO DIFFERENT than I was seeing before parts were swapped, including the 10db attenuator. Just for clarity, nothing has changed unless it holds these speeds ALL day.

DOCSIS 2 modem - ~ 15/ ~8
DOCSIS 3 modem - ~ 21/ ~ 35

Kinda liking what apparently is the channel bonding taking place.

I'll post back after we see how it flies over the course of what historically we call the Bad Hours.

patrick

So in short... You got the lineman for the job... Cool. I can mostly summarize in layman's terms. The shunt (attenuator) was there because there was a hot (or bad) 760mhz tap somewhere upstream and your signal was too high. The original installer put a band-aid on the issue which doesn't work with D3 as well as it does with the older Docsis specs, if at all. Your channels rotate frequencies depending on the demands of that particular system and one or more of your area's downstream channels are outside of that 760mhz range therefore throwing your whole system off balance and probably was not bonding because of the bad channel...

Come on man, it was congestion!

In speaking with the tech, he said until around 2 months ago, it WAS congestion as they added two channels at that point. Now it is not, and he pretty much assured me of that.

If you are "inside" you can research this. Santa Cruz,CA was only upgraded a couple of months ago. Prior to that is was apparently fugly.

I only found this out today. I've overjoyed that we do not have congestion.

But in the absence of facts, versus conjecture, how would YOU depict time of day cratering? Just asking.

I was making fun of your original stance that it couldn't be anything BUT congestion. I guess I should have put the sarcasm tag on my post.

It's all good. No harm, no offense.

But I have been frustrated by lack of facts. I'm hoping a root cause is within reach.

That would be nice

One simple explanation is that time of day can also mean temperature changes. Those temperature changes cause expansion and contraction which can cause connection problems (especially with loose or corroded connections). Temperature changes also mean resistance changes in the coax and in other components in the connection, and that can also have an effect.

You have to remember that the actual signals are analog, not digital (that is why you have to use a modem*), and anything in the path that causes the analog signal strength or quality to vary, can produce unpleasant results on the digital and IP side of things.

* »en.wikipedia.org/wiki/Modem

quote:

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A modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from light emitting diodes to radio.

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Also, there may be something (some kind of machinery / equipment) that may be kicking on at around the same time in the neighborhood (close proximity to cable lines / hardware) that may be injecting noise in to the system..

That's what DOCSIS 3.0 is supposed to do. Provide faster speeds and add more bandwidth for everyone.I understand the system but have no association with Comcast.Actually, technically speaking it is or was congestion causing your slowdowns. The problem isn't a congested node though. Even though they added channels your modem and the areas modems weren't able to use all of them so the root cause of the problem was actually in your neighborhood's lines but once everyone started using them there weren't enough usable channels to provide everyone with enough bandwidth to stay at speed, as the tech said he could see the ups and downs on the whole node. Since they are able to utilize all the available channels you shouldn't have the issue anymore.

edit: I can't spell.
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where do you get the 760 number from? amps are 750 or 860. taps are 1000mhz.

The anon is correct btw. It would be the amp that I was talking about. A 750 amp but I can't see very well on my tablet so sometimes I just guess