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  • ARGVMI~1.PIFargv_minus_one@mastodon.sdf.org
    Jul 2, 2026, 5:20 AM

    @fivetonsflax

    Fiber seems to have finally solved that problem. Same bandwidth both ways.

    Until now, I figured the bandwidth asymmetry of DSL and cable was some kind of intentional “consume, don't produce” design decision, but…well, fiber ISPs would be throttling upstream if that were the case, so I guess bandwidth asymmetry was nothing more than a technical trade-off this whole time?

    Happy to see it, at any rate. Uploading a software build now takes seconds instead of minutes.

    @futurebird

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Replies

  • Cursed SiliconCursedSilicon@treehouse.systems
    Jul 2, 2026, 5:57 AM

    @argv_minus_one @fivetonsflax @futurebird *Puts hand up*

    Hi, I have worked in the ISP space before.

    Cable's asymmetry wasn't an intentional choice. But a design vestige of its history. Originally these systems were designed as a one-to-many (and one way) network. Radio waves were blasted down the wire and into the back of TV sets

    The lacking upload speed is because the networks were never *designed* with the idea of broadcasts coming back up the pipe. DOCSIS was grafted on to cable TV networks as an afterthought and required major cleanup of the design of the networks to accommodate them

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  • 🇺🇦 haxadecimal 🚫👑brouhaha@mastodon.social
    Jul 2, 2026, 7:18 AM

    @CursedSilicon @argv_minus_one @fivetonsflax @futurebird
    It was asymmetric because they want to partition the frequency spectrum used into separate upward and downward bands, to avoid the computationally heavy need for full echo cancellation, and they both expected and wanted end users to be mostly consumers of content, not producers.
    There was no _techincal_ reason it couldn't be reverse in the other direction, or fully symmetric (which existed: SDSL).
    1/

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  • D Ingramingram@mastodon.social
    Jul 2, 2026, 8:48 AM

    @brouhaha @CursedSilicon @argv_minus_one @fivetonsflax @futurebird Yep, symmetric DSL works fine if you need it. Some dedicated leased lines were SDSL and the some militaries use it to run megabit data over DON 10 field telephone wiring. Strange seeing binding posts and multiple 10G optical connections on the same router. I think power utilities are also using DSL to move data over pilot cables that previously carried tone signalling between substations

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  • the vessel of morgannaastraleureka@treehouse.systems
    Jul 2, 2026, 12:58 PM

    @CursedSilicon @argv_minus_one @fivetonsflax @futurebird yep, I came here to explain this but you already covered the bases. It's a similar story with ADSL/VDSL as well - symmetric DSL variants DO exist, but they have significantly reduced downstream bandwidth compared to their asymmetric cousins. Given the general traffic mix of a residential connection, the asymmetric profiles were generally a sensible tradeoff.

    Fun fact about DOCSIS: one of the side effects of grafting data service on top of cable TV networks is that all traffic is encapsulated in MPEG-2 transport stream frames - 188 byte (iirc?) chunks. Downstream traffic is also broadcast, so on early networks it was possible to see traffic destined for other customers. An encryption layer (BPI) was eventually added, giving each cable modem a separate encryption key

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  • RaffzahnRaffzahn@mastodon.bayern
    Jul 2, 2026, 8:06 AM

    @argv_minus_one @fivetonsflax @futurebird

    Of course it was - as it is for every medium. Thus total capacity (channels) have to be split for either direction depending on usage profile. This includes ofc fiber.

    Physics is the same with every medium, no matter if Air, Cable or Fiber (or Phone in ye olde days with 1200/75 :))

    The huge difference between cable and fiber is the amount of total bandwidth available - which for cable is way smaller, so it makes sense to give more of those channels to downstream, as one downloads way more than uploads.

    In fiber the bandwidth of a single channel (single colour of light) can already be way more than all channels (frequencies) that could fit in a cable. full bidirectional speed can be gained by using just two channels, one in each direction and both at the same bandwidth - at least for the few GBit we use nowadays at home.

    If we reach the need for TBit connections at home, the need to split bandwidth will hit us again ... except I would not think very soon :))

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  • David SmithCatfish_Man@mastodon.social
    Jul 2, 2026, 6:05 PM

    @Raffzahn @argv_minus_one @fivetonsflax @futurebird the nice(?) limiting factor on this sort of thing is that right around ~10Gbit we start slamming into the limits of what you can handle with ordinary programming techniques on home machines.

    Back in the day it was more “doesn’t matter what you do on the cpu, the network is slow”, but at 10Gb/s merely parsing json you downloaded with a very fast parser requires more than half of a core on a fast cpu.

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  • D Ingramingram@mastodon.social
    Jul 2, 2026, 8:43 AM

    @argv_minus_one @fivetonsflax @futurebird I think some of the assymetry of fibre is time slotting to share a wavelength through time slotting. Up and down use different colours, so if you give fractional UL you can save "colours", which can then be used for more DL.

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  • Uriel Fanelli (on Aktor)uriel@bbs.keinpfusch.net
    Jul 3, 2026, 8:15 AM

    @argv_minus_one @fivetonsflax @futurebird


    > Fiber seems to have finally solved that problem. Same bandwidth both ways.

    uhm.... nope.

    “Fiber optic” does not mean “symmetric bandwidth.” In fact, consumer fiber connections are almost never offered as symmetric.

    Most residential fiber plans still give you much higher download speed than upload speed, for example 1 Gbit/s down and 100 or 200 Mbit/s up. The word “fiber” only tells you about the access technology; it does not mean that the provider is giving you the same bandwidth in both directions.

    When a connection is actually symmetric, providers usually advertise that explicitly.

    --
    Uriel Fanelli
    Using Aktor: https://git.keinpfusch.net/loweel/Aktor-2
    XMPP: uriel@keinpfusch.net
    old blog: https://blog.keinpfusch.net
    new blog: https://keinpfusch.net

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