[zamadatix]

That'd be the testing of the 25G-PON. They say you can do that because they known oversubscription ratios of 32:1 really aren't such a horrible concept. Think about it - they told you and a couple dozen others to blast it with 20G up and 20G down as much as you want... and how often do you actually use anywhere near that much? When you do, how long are you actually using the full pipe? For 99.999% of home users high last mile oversubscription makes perfect sense and allows the network to be built out SIGNIFICANTLY cheaper.

High last mile oversubscription is a net good for home consumers, it almost always works out in everyone's favor. The exception is that 1 guy in 10000 that will actually somehow use 20 gbps a day all day every day in some neighborhood and create some drama in the news because ISPs can't be bothered to try to explain why oversubscription is good to everyone who already doubts them.

[walrus01]

In the active ethernet FTTH and GPON/XGSPON last mile world, to put it in the most casual language possible, you can put a metric fuckton of 1 Gbps symmetric residential last mile users on a single 10 Gbps full duplex uplink before anyone starts to notice that they aren't seeing 1 Gbps speed tests.

Or before you can no longer claim that you are delivering 1 Gbps.

Your average residential user does not move that much traffic at all, if you have a traffic chart that's something like 60s SNMP interface bit counter poller interval for their CPE, fed into a time series db, and draw grafana charts for that customer over a 1 day or 1 week or 1 month period of time.

Even when a customer does something like buy several new 140GB xbox games in one day, the actual amount of time that they're really utilizing that link near full capacity in the same 24 hour period is very minimal.

The only caveat is that you need to be able to watch out for the 1 or 2% of outlier/heavy use customers who will really use their link for huge amounts of data. In many neighborhoods there won't be any of those.

[zamadatix]

You can put the same number of 1 GBPs users on a 10G-PON link as a 10G DOCSIS3.1 link. The determination is total bandwidth, which is why the over subscription profile of each is identical despite being physically different. You are correct that the over subscription ratio itself is almost never a problem. The common cause of it still being able to become a problem being whenever bandwidth increases ISPs start offering higher speeds. E.g. with 10G transports carriers start offering >gbps plans so the story repeats where some isolated case of 2 or 3 users on the same segment thrash it.

I'm not saying this as anti-PON, just that the existing coax improvements are sometimes very sensible and extremely comparable in the current generation. I've architected and deployed several small city G-PON and 10G-PON networks with Nokia gear and it's fantastic for net new and probably the only real option to continue growing 5-10 years from now. That said, if you've already got decent coax for the last mile DOCSIS 3.1 can be extremely comparable and behave near identically at the moment.

[walrus01]

It's true that the capacity is nearly the same at the moment with docsis3.1, but consider that a docsis3.1 system that is using pretty much EVERY viable RF channel can just barely have the same capacity as a 10G XGSPON system that is using maybe 1-2% of the THz channels available in normal singlemode fiber.

If you look at a typical residential 16:1 or 32:1 split XGSPON system on an optical spectrum analyzer that's capable of all DWDM ranges, it looks gapingly empty. There's just a few channels used for the downstream and upstream with the timeslicing for the various CPEs' usage. And vast ranges of totally empty optical space.

What I find interesting is that your average residential user does NOT really use much more traffic in (in average Mbps per CPE or GB per month) if you give them a 2.5Gbps or 5 Gbps or 10 Gbps connection. I have plenty of 2.5Gbps and 5 Gbps and 10 Gbps customers. Maybe 1-2% of them are really heavy users. The rest of them use exactly the same amount of traffic as the 1 Gbps users, because the vast majority of non-technical residential end users these days have only wifi client devices. Finding someone who has a desktop PC with a 1000BaseT or 2.5GBaseT LAN port to do a proper speed test is maybe 1 in 50 customers.

Even if you've got people with 3x3 802.11ax stuff running in 80 MHz channels they're just barely going to approach 900 Mbp speed tests downstream one way.

If we had offered 10G FTTH to the home in 2002 the sort of power user who would buy that might actually try to run a small server farm out of their spare bedroom. But now it's 2024 and people who are serious about hosting their own stuff are doing it with their own VM/VPS/cloud based stuff, or by colocating a few servers, etc. They know that a residential last mile gigabit+ connection is not the best place for it. There's outliers and exceptions of course, but they're getting even rarer every year as a percentage of the total customers (eg: someone who wants to run a torrent seedbox from their house or something).

[zamadatix]

Agreed. I think the most underrated feature of PON is the ability to run future generations simultaneously on the same line, without any impact at all to the existing install. The bandwidth on SM fiber is so enormous it will pretty much always (for my lifetime at least) leave other wavelengths open. This allows for deploying 25G-PON on the same fiber as existing 10G-PON with no negative impact to the existing customers. That's huuuuge in terms of long term operations budget and upgrade logistics.