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.

hex0101

cypherstream Motorola. Looks the same as a General Instruments or ARRIS Starline though. Also probably means that my serving HFC plant was bulit/re-bulit in the year 2000 or later when Motorola took over General Instruments. (January 5th, 2000)

The inside of the mini-bridger also said Motorola at the top right on the board.

Two-way HFC plant upgrade/buildout, and Digital Cable. Was likely when this particular minibridger was cut in.

Post 2026 HFC plant upgrades, just the tap is present. New node location due to node split project.

bigcoda

crucialcolin Same (Roseville, California)

Same for me in Stockton CA.

crucialcolin

bigcoda Same for me in Stockton CA.

Hrm I’m not getting my hopes up. It’s probably just some backend software or billing related systems update lol

hex0101

Same

Also had one on 10/12/2026 at 2:00 am, no loss of Internet connectivity though. Was also over in 30 mins.

Both 10/12/2026 and 10/16/2026 maintenance is for FDX nodes only. Sub-Split nodes in my town all had their maintenance on 10/14/2026 at 2:30 am. Makes me thing that some FDX nodes are getting RF Spectrum changes. (dual downstream 3.1 OFDM mid-split config, a Pre-FDX config, FDX config, or RPD/FDX Amplifier Firmware Updates).

Also, all of last week, Comcast performed maintenance every night that affected TV service only. This was also confirmed via the Xfinity app. During the maintenance, Internet service showed no issues detected, but TV service showed that their was an outage in the area.

TV maintenance applied to all nodes served off of the headend. Sub-Split, Mid-Split, or FDX, did not matter.
Channels Impaired was in the afternoon on 10/8/2026. Thankfully in the real world, I didn’t really notice any interruptions but I also didn’t have the TV on at the time that the impairment started. Also didn’t notice any interruptions to TV service overnight, but I did not watch it the entire time to see.

Saw on Reddit that Comcast uses these for TV distribution. Video feeds are sent over Fiber to the headend. Satellite Dishes Not Needed like the Old Days (Satellite Dishes were removed in 2008 at all of the hub sites in the area)
NSG Pro High-Density Chassis

bigcoda

crucialcolin Hrm I’m not getting my hopes up. It’s probably just some backend software or billing related systems update lol

What’s interesting, is the area about 4 blocks from my street that had the nodes & amps replaced. About 1 month before my neighborhood got the node & amp upgrades, has no maintenance scheduled? That area seems to be on a different maintenance schedule or something? I’ve seen it reversed were that area has scheduled maintenance, and my neighborhood doesn’t.

crucialcolin

bigcoda What’s interesting, is the area about 4 blocks from my street that had the nodes & amps replaced. About 1 month before my neighborhood got the node & amp upgrades, has no maintenance scheduled? That area seems to be on a different maintenance schedule or something? I’ve seen it reversed were that area has scheduled maintenance, and my neighborhood doesn’t.

I’ve noticed that too with Roseville. There are like three different areas all on different schedules. An outage in typically does not effect other areas either. Areas must be on separate cable plants or even headends.

hex0101

bigcoda You could be on a different vCMTS.

My system is pretty small. Few hundred nodes tops. With modern rPHY and vCMTS technology, the amount of rack space required to house all of the hub equipment is probably not much. Remote PHY Shelfs were deployed years ago. More space and power saving measures without having to upgrade equipment out in the field.

A Comcast tech could tell your node’s ID is and what vCMTS you are on hehe. It shows in the Tech360 app.

crucialcolin

hex0101 Also had one on 10/12/2026 at 2:00 am, no loss of Internet connectivity though

It’s weird they can make changes to RF spectrum or channel frequencies without causing an outage or an immediate forced gateway reboot these days.

hex0101

crucialcolin No, it causes an interruption, I was just saying that if another node that is on my vCMTS is getting an RF Spectrum change but mine is not, then my modem won’t lose sync. However, the maintenance outage still would show on the map/in-app. If something goes wrong and Comcast has to reboot/troubleshot the vCMTS, that could end up taking me offline. So in their eyes, just schedule the maintenance for all of these nodes to cover all of the bases. Most people are sleeping anyway. important since customers can request credits, and downtime caused by network maintenance is not eligible for a credit.

crucialcolin

hex0101 You could be on a different vCMTS.

My system is pretty small. Few hundred nodes tops. With modern rPHY and vCMTS technology, the amount of rack space required to house all of the hub equipment is probably not much. Remote PHY Shelfs were deployed years ago. More space and power saving measures without having to upgrade equipment out in the field.

In theory they could also be splitting a system up into geographic areas too. Maybe that’s why my city has 3 separate areas. Central/South Roseville, East, then Northwest Roseville 🤔

I believe the city size is about 44 square miles / 167K population. All serviced by Comcast.

crucialcolin

hex0101 , it causes an interruption, I was just saying that if another node that is on my vCMTS is getting an RF Spectrum change but mine is not, then my modem won’t lose sync. However, the maintenance outage still would show on the map/in-app. Also if something goes wrong and Comcast has to reboot/troubleshot the vCMTS, that could end up taking me offline. So in their eyes, just schedule the maintenance for all of these nodes to cover all of the bases. Most people are sleeping anyway

Makes since. I have noticed the majority of my maintenance over the last year don’t cause outages though. I tend to either be awake during those hours or my Smartthings hub notifies me of any minor outage.

hex0101

crucialcolin There is no doubt a bunch of different reasons for maintenance behind the scenes, which can all have different impacts, but to keep things simple the customers just see a maintenance notice. Comcast tracks them all though and assigns ticket numbers.

crucialcolin

So that was a quick scheduled maintenance 2:04 am and it’s over with already. 4 minutes afterwards and No service outage either.

Doubt much changed towards eventually enabling FDX as expected.

Edit nevermind 2:16 am my gateway just reset…

Additional edit a second OFDM (193 at 722mhz) has just been added

@hex0101 called it! some FDX nodes are getting RF Spectrum changes (for me it was an dual downstream 3.1 OFDM mid-split config). Assuming next comes a Pre-FDX config.

soxrok2212

hex0101
Here’s my XB10s and an open XB8 for fun

Dumaine

Scheduled Maintenance here started approx 12:15am EST and lasted almost 2 hours. Internet was out during that time. Funny thing is this is the first text I received notifying of maintenance yet no time was stated, just Oct 16 work should occur overnight etc etc. Wonder why it started so early this time?

hex0101

crucialcolin They could also probably update the vCMTS without causing an outage too. By running a primary and standby vCMTS. Cisco had a patent on it from 2015-2016.

Virtual cable modem termination system redundancy in a cable modem network environment

Therefore, you wouldn’t notice any interruptions in service during an on-going maintenance window.

Comcast, being as big as they are, likely has in-house software engineers for this stuff, that work alongside with Harmonic to resolve any tough issues or bugs. A smaller ISP may reach out to Harmonic and need a greater level of support. Harmonic’s vCMTS runs in K8’s.

luism1023

This is the equipment that serves my address here in Chicago

hex0101

luism1023 FDX amplifier.

luism1023

hex0101 do you know if Xfinity is turning on FDX amplifiers too or specifically turning on nodes or better yet is there a difference between the two?

hex0101

luism1023 Started enablements for N+X architecture in Late July Early August 2026. So yes. How long ago were you upgraded?

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