back to article CableLabs signs off MAC spec for DOCSIS full duplex

US standards outfit CableLabs has added another piece to the Full Duplex DOCSIS 3.1 jigsaw, with the release of the key MAC layer specification for the standard. DOCSIS 3.1 Full Duplex is designed to push symmetric 10 Gbps over the world's cable (or hybrid fibre-coax, HFC) networks. The spec expands the existing DOCSIS media …

  1. Voland's right hand Silver badge

    And here goes the last remaining holdout of true CSMA-CD.

  2. Blotto Bronze badge

    This’ll be great when it arrives in 2024.

    I wonder how far from the node a client on coax can be to still get 10gbs.

    I wonder what fttp/p will be offering at that time

    I wonder what Xg will be offering at that time

    I wonder what WiFi will be offering too.

    The funny thing is that most Home consumers will buy high bandwidth because it’s a big number and then put crummy WiFi gear on it. Crappy android tablets, phones and cheap laptops running Wifi G on 100mbs+ BB is sadly not uncommon. Their owners have no clue and their providers are happy to take their money for a service their customers are unable to fully consume. It makes OFCOM happy at least.

    1. DougS Silver badge

      What difference does it make what wifi router you put on it?

      No one is going to get the full 10 gigabit, that's the entire system bandwidth (nearly 1 GHz of spectrum required at QAM 4096) for everyone sharing your node.

      Even if you happened to have no one else you're sharing the node with active at 4am Christmas morning and got it all to yourself, what are you going to do with it that can make actual use of that much bandwidth? What site are you going to visit that can deliver it, and what is it going to send you that requires anything like that much? Is it really going to be a problem if your phone is "only" getting 800 Mbps?

      Dunno why people are so hung up on "oh my internet has $BIGNUM theoretical bandwidth I'll never actually get, I need a router with > $BIGNUM theoretical bandwidth so it doesn't slow me down!" That's just router makers marketers getting people to buy something that isn't of any use to them.

      At least that upcoming wifi standard (can't remember the name, 802.11 is alphabet soup) that lets it chop up the channels into smaller pieces so the entire channel isn't dedicated to a single client but can be use by a bunch at once will be useful in real world scenarios where you have a lot of active wifi users at once. That and WPA3 are the only things worth getting a new router for.

      1. Lee D Silver badge

        Re: What difference does it make what wifi router you put on it?

        More bandwidth = more simultaneous clients.

        There are probably at least 8-9 devices in the average family household connected to wifi. Phones for mum and dad, the kids tablet, dad's laptop, the Xbox, the Wii, the Chromecast, etc. etc. etc.

        800Mbps is thus only about 80Mbps per device. That's only 8Mbytes/sec (roughly) for downloading their new 50Gb update to their XBox game, for instance.

        Plus... if you buy kit that's capable of the higher speeds, you not only get lower bandwidth, but you're playing nicely with everything else that has those higher speeds (so instead of 10 devices all fighting and taking their percentage of overhead, they know to dial back and the one client needing more gets it). Latency is also a factor, plus that wireless is very noisy (so 1Gbps theoretical means you have more room for errors and retransmissions before you do start to affect the connection).

        Don't forget, a 4K stream, sucks up 25Mbps per second (according to Netflix). Say ten houses share 10Gbps. Now you have 1Gbps. That house has 8-10 devices. Each get 100Mbps on average. Add in noise, retransmission, upstream-and-downstream latency, broadcast traffic, interference from neighbouring networks, etc. You're now into less than they'd have got from a local Ethernet cable 20 years ago. Given that we're all using cloud for everything from home photos to school work to streaming movies, it quickly disappears. And the kids downloading the new maps for GTA V could easily knock the connection for six for an hour or more (I've yet to see ANYONE but myself run a router capable of proper QoS and fair airtime sharing, and it's trivially easy to knock someone off their games just by doing a large torrent or similar).

        And this is a protocol that you expect to be using 20+ years from now, too. Some hangers-on will still have whatever modems support this sitting in their living room long after everyone else has upgraded to terabit-internet, and they still need to do a half-decent job.

        Like the infamous (and apocryphal) quotes... 10Gbps should be enough for anybody. And there's only a need for a handful of computer in the entire world, right?

        To be honest, it all depends on your usage. I can run a school with 500 pupils off a 100Mbit leased line. But every member of staff probably has 75-100Mbps connections to their home, with an order of magnitude less devices dangling off it. And I guarantee you that their home connection is like treacle compared to the school one. I bet their iPhone gets a faster individual connection on 4G than on their Wifi too, once all's said and done.

        By the time this hardware is out, everyone will be on 5G and, embarrassingly, it'll outperform their home broadband. If they want to be able to keep up, the DOCSIS cable standards, or the latest DSL standard, have to be able to deliver 5G speeds times by the average number of devices in a household (to combat interference from the neighbour's devices too, even if they are idle), after all the losses, conversions, interference, channel-congestion, etc. Or else people will literally stop bothering buying home broadband.

        Case in point: I don't have a home broadband connection. I bought a Huawei 4G router, slapped a high-data-usage monthly recurring SIM into it, and I pay less than a BT line would cost, get all the data I need, at speeds twice those quoted for a BT line in my inside-the-M25 new house, with no commitment, no installation, and deals like "Netflix doesn't count towards your data allowance", etc. And I can pick it up and take it round a mate's house because it's about as big as the cheapest of smartphones and lasts 6 hours on battery.

        This DOCSIS standard, if anything, doesn't go far enough.

        1. rh587 Bronze badge

          Re: What difference does it make what wifi router you put on it?

          There are probably at least 8-9 devices in the average family household connected to wifi. Phones for mum and dad, the kids tablet, dad's laptop, the Xbox, the Wii, the Chromecast, etc. etc. etc.

          800Mbps is thus only about 80Mbps per device. That's only 8Mbytes/sec (roughly) for downloading their new 50Gb update to their XBox game, for instance.

          Of course anyone that cares about latency or large file transfers will have run a Cat6 to the back of the telly, disabled the device wifi and put the entire entertainment complex on a gigabit wired connection. No consoles, TV, or streaming boxen cluttering up the spectrum. Of course Chromecast has no ethernet port which is very tiresome and why I won't buy one (I can stream to the wired FireTV).

          If you've gone the extra mile and run cable to the office then desktops/printers can go wired too which really only leaves phones and tablets (and possible laptops) on wireless.

          We have an -ac access point, but it doesn't matter because the heavy-weight devices are plugged in. Why would you spend time and effort on proper QoS and time sharing when you can just give them a dedicated wired connection?

          Your contention that 5G will mean people stop buying home broadband is perhaps the downfall of your own argument. There is only a finite spectrum, and if demand for bandwidth does continue to grow as fast as you predict, it will eventually come to pass that cellular data starts bouncing off Shannon-Hartley (though we are a little way from that just yet) and it becomes necessary to look at wired connections again, each offering dedicated bandwidth that does not conflict or congest your neighbour's.

          Your 4G connection today would not outperform your home VDSL if every single house on your street was hammering the 4G for all their domestic usage - OS and Application updates, streaming, browsing, etc, etc. The only reason it is a viable option for you is that the vast majority of people are sending the bulk of their traffic down their phone or cable connections.

        2. mark l 2 Silver badge

          Re: What difference does it make what wifi router you put on it?

          "I can run a school with 500 pupils off a 100Mbit leased line. But every member of staff probably has 75-100Mbps connections to their home"

          I remember back about 15 years ago i was called out to a problem at a school site which had about 500 pupils and their internet was a 128 kilobit ISDN connection for the whole site, including the staff. To fix their issue I needed to download a service pack which came in at a few hundred megabyes in size. I worked out it was quicker to go home (a 40 minute round trip) and download it on my home cable internet connection put it on a USB drive and then go back than continue to wait for it to download on the schools internet connection.

        3. Carl Thomas

          Data doesn't bear this out

          Virgin Media's average customer uses less than 2Mb/s at peak times. This is an ISP where no-one is on less than 50Mb. Andrews and Arnold recently broke 1Mb/s per customer. They are the heaviest BT Wholesale customer. Sky, with their extensive reliance on broadband to deliver VoD, run at sub-2Mb/s per customer.

          There aren't a mass of people using tens of megabits per second. People aren't wringing their hands over their 76Mb or 100Mb connections because they run like treacle.

          Everyone isn't running all the devices in their home flat out all the time. I work from home, we barely watch any linear TV, there are 2 teens, both of whom stream and game and the 95th percentile on my service is about 4.5Mb.

          I don't see any issues with congestion on the WiFi. Our devices are spread across a dual-band 4x4 802.11ac radio running at well above the maximum speed of the broadband connection.

          If the scenario you describe were anything like accurate every ISP in the UK would have their network grind to a screeching halt all the time. As it is Virgin Media can share 1.2Gb/s between a few hundred customers without problems in most areas, Hyperoptic can sell 150Mb and 1Gb to hundreds of customers on a 2Gb LAG, and to a number of them on 1Gb without incident, and FTTC providers can aggregate hundreds of customers onto a single 1Gb GEA CableLink without problems.

          The CAGR is 40-60% at the moment. 10Gb being inadequate for a few dozen premises is a long, long way away yet.

          1. Anonymous Coward
            Anonymous Coward

            Re: Data doesn't bear this out

            It depends on how an ISP wants to carve up the capacity to generate extra revenue - providing a pipe that can provide service separation and QoS provides opportunities to sell additional services, like Wi-Fi offload for other providers, home security products, financial apps, etc over private networks opposed to the public Internet

            Although admittedly cable is a crappy product to do this on regardless to its bandwidth

        4. joed

          Re: What difference does it make what wifi router you put on it?

          I'm not sure about the need for more and more bandwidth, especially that progress is not reflected in falling prices of low tier data packages (at least not in the "free market" scheme of US). While 3.1 could deliver all Internet one wanted (but not necessarily needed), few would be willing to pay for the privilege. And the 4k streams are as needed as 3D - most consumers will never have viewing environment nor eyesight to see past 1080p (assuming monitor with decent contrast, color and refresh rate). 80Mbps stream per device - what cloud provider's koolaid is fed through this pipe. Should I even mention data caps?

          I've only recently been forced by Comcast to upgrade to docsis 3.0, to no benefit on my end (the seller of the refurb modem didn't mind my 50$ for sure). While I can understand the benefits to network provider monopolies, the technology is nearly meaningless outside rich gated communities with households willing to spend 200$+ a month for a service bundle.

          I'm just hoping that my 3.0 modem will last as long as 2.0 did (especially that my service speed does not meet FCC's revised definition of broadband and 3.1 won't help this).

      2. Christian Berger Silver badge

        Well...

        First of all a 10 Gigabit uplink is perfectly usable. Second, since DOCSIS networks are typically highly congested every little bit of extra capacity helps.

      3. Carl Thomas

        Re: What difference does it make what wifi router you put on it?

        'No one is going to get the full 10 gigabit, that's the entire system bandwidth (nearly 1 GHz of spectrum required at QAM 4096) for everyone sharing your node.'

        Full duplex DOCSIS requires different nodes and no amplifiers between node and end user so the restrictions of existing systems aren't really an issue.

        Most cable systems in North America have only 37 MHz of return path bandwidth and even in Europe most systems have 80 MHz. Obviously the full duplex signal can't ride on the same nodes and amplifiers.

        It'll require replacement of nodes with digital nodes and passive coax from there to homes, so any bridge or line extender amplifiers will need replacing with nodes too. The coax itself should be good for multiple GHz. To go above a GHz needs replacement of tap banks and splitters in cabinets along with splitters and isolators in homes. FDX DOCSIS is probably going to be a fibre to the tap solution with the main use for 'legacy' nodal cabinets being to act as power supplies for the digital nodes deeper into the network.

        1. DougS Silver badge

          Re: What difference does it make what wifi router you put on it?

          Full duplex DOCSIS uses the same band for upstream and downstream, thanks to some fancy echo cancellation type magic. That 5-42 MHz return path band may be left unused in a full duplex installation, but if it is used it is used for both upstream and downstream data.

          1. kallesen

            Re: What difference does it make what wifi router you put on it?

            FDX will not be operating in the legacy return path, so that will still be there. FDX begins at 108 MHz.

    2. Carl Thomas

      'I wonder how far from the node a client on coax can be to still get 10gbs.'

      This only works with node + 0, so no amplifiers or actives after the optical node. Range depends on thickness of coax and how many splits in the path.

  3. Pascal Monett Silver badge

    Another lease extension for the life of copper access

    I wonder what law there is on copper data bandwidth increase ? In any case, kudos to the boffins on this one, I imagine there will be rejoicing in many telecoms data centers.

    In response to the initial poster : currently people on cable in my area have, at best, 12Mbps for the household. Every phone in the house is capable of WiFi speeds exceeding that, which means that everyone in fighting for a piece of that bandwidth. Let us say that WiFi is capped at 30Mbps (don't know if that is case, just speculating). If you have 3 phones, that's a potential 90Mbps. And if you're streaming YouTube, you're likely to use a fair part of that. Add a torrent client on that and your Internet will be slow as molasses and everyone will be complaining.

    Get a 100Mbps connection and all of your phones have their 30Mbps available - no more fighting for bandwidth. That is why there is no problem having a connection that is greatly more capable than the things that are attached to it.

    Because let's be serious, even if overnight, by magic, all copper cables were replaced with fiber optics and everything was magically able to continue operating, ISPs will not be handing out gigabit connections to households. It'll be a looong time before Joe Schmoe can sign up for anything better than 100Mbps.

    1. Christian Berger Silver badge

      Re: Another lease extension for the life of copper access

      "I wonder what law there is on copper data bandwidth increase ?"

      Well there is the channel capacity

      https://en.wikipedia.org/wiki/Channel_capacity

      which gives you the maximum amount of data you can get through a channel, giving it's signal to noise ratio.

      If you have a bare cable, the SNR is limited by thermal noise in the receiver as well as the maximum allowable power before the cable leaks to much.

      If there is an amplifier in between, it's usually the limitation as it has a maximum input power as well as its own noise.

      So in reality your SNR is somewhere in between 20 and 50 dB, which is 1:100 to 1:100000 in linear units. That roughly translates to an overall channel capacity of 1-10 GBits/s, depending how rotten your network is.

      You can, BTW, estimate your SNR by looking at the picture of an analogue TV channel. If the image looks perfect, you have around 40-50 dB SNR, if you can see noise you are below that, and at 20dB you can still see the picture through the noise, but it's not preety.

    2. David Roberts Silver badge
      Windows

      Re: Another lease extension for the life of copper access

      Nice to know that I'm living in the distant futoure with my solid 160 Mb/sec VM cable service.

      I am eligible for 200 Mb/sec but that would involve having the crappy SH3 so I am sticking with my original Superhub in modem mode.

      Unless things have changed recently wireless is "round robin" so you don't have all the devices transferring data at the same time like you do with wired. So you would need high speed devices to get a slower speed average throughput on a shared router. No wireless device is likely to hit anywhere near the rated speed when contending for access to the router.

      Noted that even with 160 Mb/sec download speed iPlayer and Netflix have buffering issues at times so the whole network neds to be able to support these speeds.

      Helps to have a Gigabit switch under the stairs and all rooms wired, of course.

  4. LeahroyNake Bronze badge

    Virgin mafia

    Never worked out good for me but...If they served my area I know a guy that can sort me out:)

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Biting the hand that feeds IT © 1998–2019