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.

fmd

cypherstream I wanna resume each time I take a car ride

Oh, while driving. 🙂 It is easier to understand when you can follow the slides though. :-)

cypherstream

fmd I finally was able to complete it, and yes watching it, at least from 43 minutes onward when the interesting FDX bits were being talked about.

The site has a tone of great videos. I’m also checking out last years 2024 video Getting the download on fdx

videomatic3

my internet went offline for several hours last night, just checked it now and its only bonding 2 ofdma channels.
upload only working at 700mbit to 1gbps (boohoo)
rebooting the modem it showed 4 ofdma channels, but speed tests were still coming up short, and shortly after it dropped 2 extra ofdma channels. interestingly enough one of the ofdma channels that disappeared was showing around 26 dbmv power level. something goofy happened.

fmd

videomatic3 You haven’t noticed additional OFDM channels during this loss of service?

Has the transmit power increased (the channels that are working)?

videomatic3

fmd nope nothing has really changed, just losing the 2 ofdma channels.
would really much just prefer fiber where it either works or doesnt work. none of this half ass shit.
so in theory right now i can just max out the upload and fuck everyone else on the node.

kmax

videomatic3 so in theory right now i can just max out the upload and fuck everyone else on the node.

Sometimes to make a difference or inspire a change, do the needful.

fmd

videomatic3 Okay. The relationship between the missing channels is that they belong to sub-band 1. It may be a coincidence, it may not be. :-)

videomatic3

kmax I’ve done it for many years, not sure if I’m a contribution to how I ended up with n+0, but I do know my node has been congested for since I’ve lived in my house, 10+ years. Even after getting the new node it was still congested, it wasn’t till I noticed a drop in upstream dbmv by 3.5 that it got cleared up majorly, I think they split up the upstream within the node itself.

cypherstream

fmd Do you think they are playing with the interference groups?

fmd

cypherstream I don’t think that is likely to be the reason. If something goes wrong in that context, it only hurts the OFDM channels (those in the FDX sub-bands, if there are any).

videomatic3

cypherstream
Hopefully playing with full duplex channel, would be neat.

hex0101

RPD may need to be rebooted.

cypherstream

videomatic3 I think it’s just issues with docsis. Signal issues, firmware and software issues… it’s just really a lot of moving pieces and heavy engineering to get working. Me for example lost internet on Thursday ALL day just about 10 AM until my daughter got home and I walked her through rebooting the modem while I was at work. The modem reboot worked, got me back online (10am-3:40pm dead window there). No idea why the modem didn’t recover on its own. And now since then my 100mbps upload is all over the place. Here’s speedtests from the past 14 days where they run hourly. Towards the end the upload is now in the 40’s. I just did a speedtest and only got 48.4mbps upload when I usually can cap out around 103mbps. All the channels are there, 4 SC-QAM and 1 OFDMA….

I just think PON would have been a much better solution, less engineering tricks and hacks- which I can appreciate… but the more complicated you make it, the harder it is to get all the pieces of software and firmware to keep it stable.

Hope the bugs are ironed out! You have a state of the art “bleeding edge” device.. XB10, and I’m running the tried and true SB8200 still. Either way if this was PON (which I should have this time next year) I bet my 14 day speedtest will look pretty consistent on both upload and download, instead of all of these random spikes.

badtlc4

Just saw my first FDX amp on an overhead line here in Olathe, KS.

plat2on1

Looks like they installed a BLE120-085 here when they did the upgrade in june, guessing we won’t be seeing FDX for a very long time around here.

badtlc4

plat2on1 you never know. Mid-split amps here arent more than about 2 years old and already getting replaced with FDX amps.

hex0101

CommScope FDX Amplifier

crucialcolin

badtlc4 facts they seem be slowly replacing mid-split amps with FDX in Roseville, CA. They only installed mid-split in most city neighborhoods a little over a year ago.

Right now it’s anyone’s guess as when they will finish/enable FDX speed tiers but my guess is soon because plenty of the neighborhoods already have fiber competition here.

The bigger issue may be nodes located in neighborhoods with a higher percentage of legacy cable subs (such as senior citizens) as I’ve heard older X1 STBs aren’t compatible with either DOCSIS 4.0 or FDX. I believe the wireless Xi6 is the only current box that is and that’s a lot of customers boxes to swap out(Roseville has several retirement communities).

cypherstream

There’s been some complaining on FDX complexity and reliability with AGC. Also questioning setup procedures, led status , green, blue, solid, blinking, etc.

Some techs like it while others are experiencing a ton of problems in temperature swings keeping the network online. If you have FDX, please comment on reliability as the temperatures change this winter.

Chris313AllNight

cypherstream

Your comment here has come to play. In a certain area of town according to the outage map, there’s a recent upgrade in play that has had issues damn near daily. Network damage, impaired, etc. I’m thinking temps have something to do with it. High 30s at the lowest so far. I’d hate to live in that section. They’ve probably hit their quote of credits for all this too.

cypherstream

I noticed two FDX amplifiers in Douglassville, PA, Amity Township. Comcast came into this area with mid split Node+2 in 2023. They were a new competitor alongside Windstream Kinetic Fiber to the home and Service Electric Cablevision mid split docsis 3.1.

This was really neat to see because they literally just installed these amps (and the entire system not even 2 years ago. Back in the day you would have to let the equipment depreciate off accounting’s books before you can replace it so quickly.

BUT Service Electric Cablevision is installing FTTH and in this particular area the system is live with speeds up to 8gbps. So I guess Comcast has to compete and switch those amp lids before they are paid off.

This amp was recently changed because in this Google Streetview its the MB120 as of September 2025
https://www.google.com/maps/@40.2562422,-75.7273204,3a,15.5y,178.31h,107.83t/data=!3m8!1e1!3m6!1smMXKLGXh9OwyMRUpecQ0Yg!2e0!5s20250901T000000!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D-17.83449061825857%26panoid%3DmMXKLGXh9OwyMRUpecQ0Yg%26yaw%3D178.3070252990216!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI1MTIwMi4wIKXMDSoASAFQAw%3D%3D

The previous streetview was taken in May 2023 and Comcast did not exist there yet.

In that picture its Comcast on top, followed by SECV Fiber, then SECV HFC below that, then Windstream is the telco.

I checked a nearby address and FDX speeds are not listed yet in the planbuilder.

Anyway I wanted to share a datapoint of a NEW system maybe a year old already getting switched out to FDX. I’d ask myself why didn’t they put FDX in in the firstplace, but I guess the amps weren’t ready in quantities required at that time. My second question was, when building a brand new system in late 2023 throughout 2024, why not go EPON like they did in Morgantown, PA?

Anyway this is part of the PA Freedom region and they actually have very good routing and ping times. 11ms ping to 1.1.1.1 on DOCSIS, 4ms ping to 1.1.1.1 on Metro Ethernet. Thats typically 10 to 15ms better than the market to the left, Keystone region (for both docsis and metro e).

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