Cat8 ethernet cables at cheap cheap prices? Yeah I have my doubts… but they kinda look cool so I bought some: https://www.aliexpress.com/item/1005001571443619.html

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    • 5m CAT8 with braided nylon sheath – $25.45 AUD
    • 1m CAT8 with braided nylon sheath – $6.28 AUD
    • 0.25m CAT7 flat cable with rubber shell – $2.75 AUD

    If you’re familiar with network cabling you’ll know that Cat7 and Cat8 specs are nothing to sneeze at. At the very least you’re going to need some shielding, on the twisted pairs, or around the whole bundle, or over both. Incidentally, Cat7 exists in this weird twilight zone where it’s kind of pointless because if you want 10gig you just use Cat6A, and if you need anything faster you’ve got Cat8 for up to 40gig. Cat7 was designed with new TERA or GG45 connectors in mind, but they never really took off because RJ45 is king.

    That’s before we even get into the logic of trying to sell higher grade cables to average home users – no one (really) has connectivity needs exceeding gigabit, and even if you do, Cat6A is entirely sufficient.

    But look at that, you can have FOURTY GIGABITS to your laptop and wifi! And that’s terrible.

    Anyway let’s look at the cables.

    Appearance and expectations

    Let’s be clear about expectations here. As an unqualified statement I suspect it’s possible to make and sell decent quality cables at this price point, whereby “decent” means that they meet the relevant TIA or ISO specs. However, I don’t think we’ll get that in practice.

    I should also note that I have no way to properly test these cables beyond “it brings up the link and passes data”. I can’t even test them at the rated speeds because I don’t have any NICs faster than 1Gbps. The most damning thing I’ll be able to find is that the cable causes low-level errors that the NIC can report to the OS.

    • The cable should light up on the link
    • Data transfers at gigabit speeds
    • No link-level errors reported beyond normal amounts
    • Cable should at least pretend to meet the physical construction requirements of the spec
    • Cable should be what’s what’s marked on the bag

    I think the last couple of points are the most interesting here. Let’s face it, the cable has to be amazingly crappy to fail at passing gigabit traffic over a couple metres distance.

    The bags say “S/FTP”, which means foil shielding on each of the four twisted pairs, and a braided metal screen wrapping around the bundle of pairs. It should look like this when you pull it apart. Something tells me we’re not going to see that on the flat cable, but we might be very pleasantly surprised. It looks plausible enough on the alleged Cat8 cable.

    The cables feel nice enough, they’ve got anti-snag clips, the connectors have a metal shell which might couple the outer screen to the jack at each end, and they’re aesthetically pleasing. Okay so far, let’s cut ‘er open!

    Flat Cat7 cable

    You’re never gonna believe this, but there’s no outer screen on the flat cable. It’s just four foiled pairs moulded into the PVC sheath, making this a U/FTP cable. Yeah no this is exactly what I expected, but at least the pairs are foiled.

    In a really weird way this technically fits with Category 8.1 cable: “minimum cable design U/FTP or F/UTP, fully backward compatible and interoperable with Class EA (Category 6A) using 8P8C connectors”, assuming that the copper and connectors are up to spec with regards to attenuation at the higher (up to 2000MHz) signalling frequencies. Let’s keep digging.

    Conductor with insulation stripped off in the middle, and a suspected drain wire on the right

    Interestingly there appears to be a drain wire inside each foiled pair, which is more than I expected (or it’s just for tensile strength). Each wire in the twisted pair appears to be stranded copper, and it’s accompanied by even finer fibre strands of some description, not sure what that’s about.

    The brass-coloured shell wraps around the clear plastic and slips in underneath the latch, where the folded wires are
    It took a lot of yanking to get this far into the plug!

    The plug actually seems to be very well built. The metal shell around the plug is crimped on nicely and folds under the clear plastic, apparently to make contact with the drain/shield wires from each twisted pair. The black plastic of the plug body is moulded in very well and took a lot of force to tear it away from the clear shell. I think I’m happy with the way the conductors are terminated in the plug, the gold RJ45 contacts seem to be biting the stranded conductors securely.

    I forgot to test this cable before tearing it apart, which is a shame.

    Cat8 cable with braided sheath

    Let’s get on with the next one. Expectations are a bit higher here because the cable is physically chunkier (about 6.5mm outer diameter), noticeably stiffer, and should be higher spec.

    We’re off to a good start, the anti-snag clip is a bit longer so it won’t slip out from the protection, and the cable is thick and stiff.

    Cutting it open, it’s evident that all the expected physical features are present, and they look well executed. There’s also an extra copper wire running alongside the bundle of twisted pairs, not sure what its purpose is, but it can’t be a rip wire because it’s not up against the PVC jacket.

    The conductors in each pair look the same as in the flat cable, a 7-stranded copper wire for each conductor in the pair. This time there’s no plasticky looking extra fibres found when I strip the insulation from each conductor, I don’t think I was causing it last time with my crappy insulation stripping skills.

    Everything stripped off, a layer at a time

    The PVC sheath feels nice and tough, and everything inside feels like it’s in order. I’m satisfied with the construction so now we’re onto the last question – does it work?

    Does it work?

    Honestly, yeah it works fine. The only interesting statistic I’ve seen in ethtool -S eno1 | grep err is rx_csum_offload_errors, and it’s all of… 12, twelve bad packet checksums, and those were probably already there.

    They look snazzy and so far work well so I’m happy.