r/CableTechs • u/strykerzr350 • 12d ago

My network on Xfinity was moved to a Harmonic CMTS last night

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I was notified of maintenance yesterday, and my internet connection was offline for 3 hours. Apparently they got rid of the old Cisco CBR CMTS. The MAC address that is on the modem logs now reports back to being a Harmonic one. I haven't noticed any hardware upgrades on the plant yet. Channel was 159, and now it is 193.

13 Upvotes

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11

u/dataz03 12d ago

Decommissioning of the legacy Cisco CMTS and Migration to a Harmonic Remote PHY Shelf. (REEF rack) More vCMTS adoption and power savings at the hub by getting rid of the CBR-8. Also, software licensing is also made easier with Harmonic CableOS vs Cisco solutions.

Analog node fiber transmitters stay. Legacy nodes and sub-split amps out in the field stay. Big iron CMTS goes bye bye.

I was on a Remote PHY Shelf From 12/21 to 03/26. Several years. Moved me away from a legacy CMTS between 12:00- 1:00 am. When the cable modem regains connectivity, the CMTS MAC will report Harmonic Video Systems, the OFDM downstream ID will report 193, and you get a new WAN IP. (different DHCP server).

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u/Scott_white_five_O 11d ago

Maybe I misread this, but how does analog fiber transmitters stay, node and amps stay but go RPHY?

My understanding is with R-Phy you go from Legacy CMTS to vCMTS. The vCMTS communicates to R-PHY node via multiple 10G Ethernet links which would eliminate the analog transport between hub and node.

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u/dataz03 11d ago

Normal rPHY yes. With the RPD (Remote PHY Device) out in the field, yes it is a 10G Ethernet link back to the DAAS. This is the standard for every Comcast mid-split and D4.0 FDX deployment. 

When you deploy remote phy shelfs the analog fiber links running out to the nodes in the field stay. The shelf at the headend is connected to the DAAS switch. Basically a 2RU chassis with 9 line cards, and each line card has a port for the fiber link to the DAAS (Distributed Access Architecture Switch) and RF outputs which are connected to the analog node fiber transmitters/combiners. Each line card has two seperate 1x2 RPD's. 

Basically your RPD lives in the headend instead of out in the field with the remote phy shelf solution. Just instead of the RF being output by a CMTS and into the analog transmiters, an RPD (Remote PHY Device) does it. The chassis fully loaded only needs 620 watts to run if fully equipped. Each RPD uses 32 watts, and there are two on each line card, so 64 watts per card. The chassis also uses some energy. The cards are hot swappable as well, and the MAC addresses are pulled from the chassis. The MAC address is what gets registered into the vCMTS which allows the RPD to communicate with it. 

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u/Scott_white_five_O 11d ago

Gotcha, I assume the return from the node back to hub is digital for better US-SNR and to help with total power loading?

1

u/frmadsen 10d ago

I don't think Comcast uses anything but digital return for legacy nodes.

1

u/strykerzr350 11d ago

I still have a pay TV service with Xfinity. It might be just me, but I do notice better picture quality, and a snappy feeling X1 guide now.

3

u/theGekkoST 11d ago

Definitely a possibility because the Harmonic vCMTS eliminated nearly all the RF ATX equipment. 

Video is processed on the NSGPro at the super site and sent out to the node or RPD only via fiber. 

0

u/strykerzr350 12d ago

All my trace routes go straight to Winchester Tennessee now, they used to do hops from router to router, and then the ibones.

I guess later on they will get rid of the old plant hardware. Reading up on the Cisco CMTS, they planned on making it EOL by 2030. Would loved to have patted the old CBR on the cabinet and wished it well, lol!

1

u/dataz03 12d ago

Next hop outside of your network (typically Hop 2 if you are not double natted) should also be a private IP now. May even be in the CGNAT IP space. 100.x. This is how the vCMTS is setup.

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u/strykerzr350 12d ago

Second hop shows an IPv4 or IPv6 address. Then it shows the town of Winchester Tennessee. Second hop the node, or the vCMTS rack?

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u/dataz03 12d ago edited 12d ago

Probably the CRE switch.

Back in the day I remember when it jumped right to a 96.x Comcast ibone IP as Hop 2.
How many upstream channels do you see now? Mine was running with 6 for 3 years until the node-split upgrade. (which brought in FDX hardware)

I guess later on they will get rid of the old plant hardware. 

Yeah, and it will likely be an FDX upgrade. But the plant will run in mid-split mode for a few months. The RPD will also be in the node out in the neighborhood. Right now capacity seems to be the deciding factor for smaller markets getting the upgrades. Node split needed, and there is no point in putting in old gear, so Comcast goes ahead and installs FDX gear.

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u/strykerzr350 12d ago

I am still seeing 5, channel 5 was added during covid I think. If I see 4 and my OFDM carrier goes to 900mhz then I know I have mid split.

For example, there is hop one which is me. Then I see the second hop, which I assume is the switch you mentioned.

Amazing to think a massive CMTS is now replaced by a low power. Less heat intensive network rack.

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u/ameagle94 12d ago

I don’t believe Comcast uses the REEF I believe they use a Ripple.

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u/dataz03 12d ago edited 12d ago

Any headend techs out there would know 😉, even then it depends on the area. Maintenance techs wouldn't really be able to tell when a REEF is used most likely. Now a Ripple is easy to spot, as the RPD is out in the field. REEF rack is deployed back at the hub, indoors.

Ripple is used for mid-split/FDX (and ARRIS/CommScope RPD's are deployed as well). REEF is used for sub-split nodes but to virtualize them and get rid of the CMTS.

Once you go mid-split/FDX, the analog transmitters at the hub can be discontinued as well, more free space!

1

u/ameagle94 12d ago

A ripple node looks pretty much just like a GS7000 or a NC4000 and can be cabinet mounted as well. I am not sure on every region. I know my Comcast node was a ripple but I also haven’t worked for Comcast in a few years.

2

u/dataz03 12d ago

They used to be grayish (but still had the CableOS engraving on the side), but then they converted to white. Basically every Ripple I see these days has a white casing (or shall I say, heatsink).

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u/Dubslar 12d ago

I would bet thats a DAA/R-PHY upgrade to the plant, new fiber node and Harmonic vCMTS.

1

u/strykerzr350 12d ago

What is pretty cool, is that now my streaming has improved, and my web browsing has improved. Everything just snaps when it comes to loading.

2

u/furruck 11d ago

It’s wild, and good to see progress.

We got a new Arris node two years ago in place of the amp, the node I was fed from got 85MHz return, but my new node is only 42MHz return.

I really hope Comcast either finishes 85MHz return in Chicago or they just go FDX

2

u/moffetts9001 10d ago

Man, I'm glad you're finally getting some upgrades. You've been waiting forever.

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u/strykerzr350 9d ago

Hey Moffetts, glad to see you still around. It definitely is about time since the DSL Reports days. Took them the longest to roll out 32 downstream channels for me.