4 ms·

The root cause of the problem is that copper coaxial cable tv based (DOCSIS3.0, DOCSIS3.1, etc) last mile internet infrastructure is a shared/contended access m

The root cause of the problem is that copper coaxial cable tv based (DOCSIS3.0, DOCSIS3.1, etc) last mile internet infrastructure is a shared/contended access medium for many modems connected to it. It's built on a limited number of RF channels in a certain segment that have many modems all going to a single "port" on a DOCSIS CMTS (cablemodem termination system). There is a great deal of absurdity in their claims to be selling a gigabit service product using coax-based technology, when the oversubscription ratio is INSANE. If you had more than a few customers on a segment trying to actually make use of gigabit speeds at one time (just 2 or 3 people downloading a torrent of a popular linux ISO at 980 Mbps will eat a huge amount of the total aggregate capacity of that coax segment). Cox and Comcast and RCN and similar operators are squeezing every last dollar possible for the ROI out of legacy copper coaxial last mile stuff. Only in places where the local phone company or another operator is building proper FTTH (GPON/XGSPON) are they starting to overbuild their own network with their own FTTH. Comcast is doing it in the Seattle area, for instance, in areas where the local telco (Ziply or Centurylink) offers a symmetric 1 Gbps product based on single strand FTTH/GPON. Your average coaxial cable tv last mile operator like Cox is a telecom industry dinosaur. The article here was published in early 2020 during peak covid19 lockdown but the general technology problem of copper/coaxial last mile stuff from 25+ years ago is exactly the same today.

wmf 2y ago
Cable is definitely shared but CMTSes added bandwidth management features years ago. Cox could just slow down the "hogs" but they're too lazy/incompetent or they're using really old equipment.
zamadatix 2y ago
The FTTH offerings from Ziply, Cox, Comcast, Google, ATT, Centurylink etc are all the same "shared media with high oversubscription" design too. Among them the typical ratio is ~32 PON users for the given "base rate" PON standard, similar to a typical ~20-50 for coax at a given DOCSIS standard. Both have better/worse examples (particularly early gigabit PON deployments were 64) but FTTH has rarely been about getting dedicated bandwidth up to the neighborhood box... honestly most of the time the lion's share of the benefits are "it's a sign your area just got upgraded cabling and equipment for the first time in many many years" than anything to do with the physicalities of the wire. For GPON that's 2.5 Gbps for downstream and 1.25 Gbps for upstream. So with a 32 split it's the same story of 2-3 people downloading a popular Linux ISO at 980 Mbps still eat up the entire fiber line for all 32 people. The difference on the fiber, outside the better upload symmetry we already see, is it will be able to scale a lot more in the future. Some places already have 10G PON (which, unlike GPON, is usually actually said speed) such as where ATT offers 2G and 5G symmetric service. The next step will be 25G PON (again, about the actual nominal speed).
- wincy 2y ago
  An actual Google PM called me up the other day trying to upsell me to $200 a month 20 gigabit. Said they’d give me a router but I’m free to hook whatever I want to the fiber, saturate it as much as I want, no worries. They must have a lot of extra bandwidth if this is a service they’re offering in my neighborhood.
  - zamadatix 2y ago
    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 2y ago
      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.
condiment 2y ago
This reads as though the cable companies aren’t aware of the limitations of their tech and that couldn’t be farther from the truth. The last mile isn’t the same as today. Docsis technology continues to improve, more RF channels are being allocated to high speed internet, and cable companies are wholesale replacing their CMTS infrastructure with higher frequency (read: more channels) equipment. The truth is that only some cable companies make these investments - you can look up “fiber node size” for respective performance across different companies. A fiber node being the place where optical is terminated and switched to coax. These have been getting smaller everywhere, but it only makes sense to invest there when the upstream infrastructure can support it. So from a consumer perspective, your “Linux isos” will be slow to download in any case until the upstream network is upgraded and your node is split to offer higher performance.
- walrus01 2y ago
  > This reads as though the cable companies aren’t aware of the limitations of their tech and that couldn’t be farther from the truth. I know, and you know, that the people doing the more serious engineering for DOCSIS based cable last mile segments are well aware of the limitations of the tech. What I was saying is that they are milking every last dollar of ROI out of the existing physical plant because overbuilding your entire network with XGSPON (it would be dumb to do 2.5G PON in 2024/2025) is a very capital intensive endeavour. The shareholder value and profits of the company are increased in the short term by continuing to do copper as long as possible, even at the cost of thousands of unhappy customers dragging your company's name into the mud. It's the fundamental business model problem, and executives at big dinosaur coax operator telecoms that have made the decision to do it this way as long as possible, until the coax/oversubcription situation becomes completely untenable in an area, or until a real XGSPON operator (maybe Lumen, or Ziply, or similar) which overlaps with your historical cable tv network rolls out a better product and you have no choice but to spend the money to keep up with the local competition. You and I also know that no matter how much they mess about with DOCSIS3.1 and channel sizes and different RF configurations, the aggregate capacity of a few strands of fiber (using even the lowest cost and most rudimentary WDM) is much greater than RF over coax. Squeezing 2048/4096QAM RF stuff into coax is polishing the brass doorknobs on the titanic. It's not a viable long term solution!

wmf 2y ago

Cable is definitely shared but CMTSes added bandwidth management features years ago. Cox could just slow down the "hogs" but they're too lazy/incompetent or they're using really old equipment.

zamadatix 2y ago

The FTTH offerings from Ziply, Cox, Comcast, Google, ATT, Centurylink etc are all the same "shared media with high oversubscription" design too. Among them the typical ratio is ~32 PON users for the given "base rate" PON standard, similar to a typical ~20-50 for coax at a given DOCSIS standard. Both have better/worse examples (particularly early gigabit PON deployments were 64) but FTTH has rarely been about getting dedicated bandwidth up to the neighborhood box... honestly most of the time the lion's share of the benefits are "it's a sign your area just got upgraded cabling and equipment for the first time in many many years" than anything to do with the physicalities of the wire. For GPON that's 2.5 Gbps for downstream and 1.25 Gbps for upstream. So with a 32 split it's the same story of 2-3 people downloading a popular Linux ISO at 980 Mbps still eat up the entire fiber line for all 32 people. The difference on the fiber, outside the better upload symmetry we already see, is it will be able to scale a lot more in the future. Some places already have 10G PON (which, unlike GPON, is usually actually said speed) such as where ATT offers 2G and 5G symmetric service. The next step will be 25G PON (again, about the actual nominal speed).

wincy 2y ago
An actual Google PM called me up the other day trying to upsell me to $200 a month 20 gigabit. Said they’d give me a router but I’m free to hook whatever I want to the fiber, saturate it as much as I want, no worries. They must have a lot of extra bandwidth if this is a service they’re offering in my neighborhood.
- zamadatix 2y ago
  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 2y ago
    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.

condiment 2y ago

This reads as though the cable companies aren’t aware of the limitations of their tech and that couldn’t be farther from the truth. The last mile isn’t the same as today. Docsis technology continues to improve, more RF channels are being allocated to high speed internet, and cable companies are wholesale replacing their CMTS infrastructure with higher frequency (read: more channels) equipment. The truth is that only some cable companies make these investments - you can look up “fiber node size” for respective performance across different companies. A fiber node being the place where optical is terminated and switched to coax. These have been getting smaller everywhere, but it only makes sense to invest there when the upstream infrastructure can support it. So from a consumer perspective, your “Linux isos” will be slow to download in any case until the upstream network is upgraded and your node is split to offer higher performance.

walrus01 2y ago
> This reads as though the cable companies aren’t aware of the limitations of their tech and that couldn’t be farther from the truth. I know, and you know, that the people doing the more serious engineering for DOCSIS based cable last mile segments are well aware of the limitations of the tech. What I was saying is that they are milking every last dollar of ROI out of the existing physical plant because overbuilding your entire network with XGSPON (it would be dumb to do 2.5G PON in 2024/2025) is a very capital intensive endeavour. The shareholder value and profits of the company are increased in the short term by continuing to do copper as long as possible, even at the cost of thousands of unhappy customers dragging your company's name into the mud. It's the fundamental business model problem, and executives at big dinosaur coax operator telecoms that have made the decision to do it this way as long as possible, until the coax/oversubcription situation becomes completely untenable in an area, or until a real XGSPON operator (maybe Lumen, or Ziply, or similar) which overlaps with your historical cable tv network rolls out a better product and you have no choice but to spend the money to keep up with the local competition. You and I also know that no matter how much they mess about with DOCSIS3.1 and channel sizes and different RF configurations, the aggregate capacity of a few strands of fiber (using even the lowest cost and most rudimentary WDM) is much greater than RF over coax. Squeezing 2048/4096QAM RF stuff into coax is polishing the brass doorknobs on the titanic. It's not a viable long term solution!