FDX/Unified DOCSIS

fmd · 2025-02-13T20:05:09+00:00

While we wait for the announcement that N+X deployment has officially begun... Unified is the new version of FDX that has downstream going all the way to 1.8 GHz (currently limited by old taps). The return still stops at 684 MHz. Comcast has presented this spectrum layout to begin with: This is sufficient to offer symmetrical 2 Gbps. When more of the legacy channels go away, higher speeds can be offered. 3.1 modems that get FDX-L (limited) firmware can use the FDX channels.

Aceq2jot

hex0101 Thank you 🙂 Somehow I think that will happen after the tech visit I have next week.

meerkathalon

Aceq2jot I’m jealous all of your upstream channels are locking! Did you switch plans as well?

I wonder what is wrong with mine.

Aceq2jot

meerkathalon I did not change plans I was at 2 Gig down and 300 up. I got a speed upgrade to 2Gig X 2Gig. As for the monthly bill I have 3 lines on Xfinity Mobile so I get a $55 monthly discount. Which worked for me in two ways as i kept the Verizon network and saved $100 a month on my cell bill and $55 on my internet.

fmd

meerkathalon A Comcast guy on reddit calls it bad node/amp installation. You are not alone in having this issue.

It shows that the isolation of the legacy upstream works as intended. If noise takes the FDX upstream down, the modem stays online.

meerkathalon

fmd Do you think incorrect boot profile is a possibility or doubtful?

Regarding noise, isn’t that something these sophisticated amps and automated plant monitoring would alert on? Everyone in support claims the signal is healthy. The second tech visit is on the 16th.

fmd

meerkathalon An incorrect config file would’t try to bond the channels, so it’s doubtful to be the cause.

Comcast has talked about different amp generations. Newer generations will automate more of the setup procss, which should take some of the human errors out of the equation.

As to why the support keep saying that…

meerkathalon

fmd It’s too bad these XB modems lack useful logs. The channels showing up does not necessarily mean the modem attempted to bond, right? I thought that just meant that the CMTS advertises them, and the modem can see them.

fmd

meerkathalon The modem doesn’t touch the channels unless the CMTS assigns them.

FDX uses an extended bonding process. The initial bonding, which occur during registration, only bonds the regular channels. The FDX channels are added to the modem after. FDX uses a sounding process, which much occur before the channels can be used (this is not related to your issue).

We know your modem is assigned a symmetrical gigabit profile due to your speed test.

Edit. Comcast writes about a few “early lessons” is this expo paper from last year:

Not Your Grandfather’s Amplifier!
https://nctatechnicalpapers.com/?p=40308

This year’s expo is three weeks away. We may get new stories.

videomatic3

just took a look at one of comcast’s old articles.
“Comcast has targeted symmetrical speeds of 3 Gbps by 2025 and 5 Gbps by 2026 on its DOCSIS 4.0 network.”
woops. looks like that was a bit aggressive.

Moffetts

They probably could, at least in N+0 areas.

Chris313AllNight

videomatic3

Aggressive indeed. Meanwhile in areas like mine which is still sub-split and takes at least 5 years or more for upgrades: Still waiting.

Anyone who gets to enjoy the upgrades years before I get them, enjoy them.

Here, I think the last upgrades and the XB8 were October of 22

fmd

Moffetts Comcast has said that N+0 will be the first to get symmetrical 3 Gbps. It requires four FDX OFDMA, so spectrum for one more channel must be freed up first.

Before the end of 2026 is another date that has been given. We’ll see.

videomatic3

fmd
we have 4, perhaps you meant 5?

fmd

videomatic3 If you are counting the OFDMA below 85 MHz, it’s five.

Zenit_IIfx

Comcast has finished their Mid-Split upgrade in my subdivision in Purcellville. It is underwhelming and the prices are a poor response to Verizon’s FiOS.

It’s like they didn’t even try. Sad! This would have been good a few years BEFORE Verizon rolled out FiOS at the end of 2025.

Verizon’s pricing:

And all tiers are symmetric, and have $0 gateway rental.

It’s like Verizon is clubbing a baby seal.

Moffetts

Short of them deploying FDX rather than midsplit, I’m not sure what you expected. That pricing is consistent across their entire midsplit footprint, and the average person looks at that and sees that Comcast is cheaper for at least 2 of the speed options, including the ever popular 1gb tier.

bigcoda

Zenit_IIfx Comcast has finished their Mid-Split upgrade in my subdivision in Purcellville. It is underwhelming and the prices are a poor response to Verizon’s FiOS.

And to top it off, that Comcast pricing only applies to new customers. Existing customers that can’t get that new customer promotion. Will generally have to pay closer to the regular rack rate, that is crossed out in the fine print, above the promotion price.

smilingbob

It’s awesome to have a pair of wired broad band ISPs to play them off each other though. That’s what I plan to do, we should have +1 soon with Ezee Fiber so that will be 3. Promo ends and they get greedy, off to the next. Happy days!

Zenit_IIfx

Moffetts With less upload, higher latency. None of those Comcast tiers are equivalent. Guess they win if you don’t want an ONT installed, which is oddly common when I talk w neighbors. They just don’t want to be bothered with a tech visit. Too much friction. Likewise if you rarely upload anything, the DOCSIS is fine. To me, the best value is the 300/300 tier from Verizon. I’d take that tier if I didn’t have two properties with a stretched LAN (i.e access NAS in house A from house B).

smilingbob

Zenit_IIfx With less upload, higher latency. None of those Comcast tiers are equivalent.

True enough, but we geeks here on ~~DSL Reports~~ Broadband Bulletin are maybe the 1%ers of the tech world. I have friends who work in IT who are so f’ing stupid it would amaze you when it comes to this kind of stuff. I have one that makes big money as a software dev/programmer and I have to build and fix all his computers and Windows issues. He has Comcast 1.2Gbps tier but not a single PC in his house has faster than Gigabit Ethernet and most of his devices are WiFi5 adapters. I’m not making this shit up. Most people just want “WiFi that works good.”

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