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- Hacker News
- I wonder if similar results would come from just adding a second 10 Gb NIC. If his workload runs SMB multichannel at sufficient queue depth, the load should spread across the multiple paths. If the queue depth is always 1, SMB multichannel is not helping on the 25 Gb NIC either.by mgerdts
- For us <25Gbps plebes out there: For god's sake do not buy a USB-C RealTek RTL8156-equipped multi-gig ethernet dongle to use with your Mac. I went through 3, and they're all trash:
Plugable 2.5G USB-C to ethernet adapter (bought November 2025), SABRENT USB C to 2.5Gbps ethernet adapter (bought October 2024), UGREEN USB C 2.5G ethernet adapter (also October 2024). In my experience they immediately fall on their face in a speedtest and drop to a couple hundred Mbps, experience packet loss, etc. This is testing across a few modern Apple Silicon Macs.
I now have a WavLink WL-NWU341G 5Gbps dongle with the RTL-8157 that seems to work well, but I've only run a couple of tests-- I am away from my home setup and don't have wired ethernet run to all the rooms where I'm living.
If you do some Googling, there's some good information out there about it, but when I bought the bad ones, I couldn't find any information corroborating my experience.
by rconti - I use several of those UGREENs and they work perfectly fine out of the box and for sustained load as well.by egorfine
- > do not buy a USB-C RealTek RTL8156-equipped multi-gig ethernet dongle to use with your Mac.
Buying a Mac with built in 10gbe is so nice compared to dongle hell.
But it’s not 25gbe
by lostlogin - Seconded - those RealTek dongles are no good.
For my Macs, the IOCrest USB4 adapters with the AQC113 chipset have been rock-solid and can saturate my 10Gbe network. They do run hot but no stability issues. That's what I use and recommend.
The newer RTL8159 based dongles are smaller, cheaper, cooler, and can do 10 Gbe on paper. But they top out at 7 Gbps on Macs, which don't implement the USBx2 spec.
- YMMV - I have three RTL8156 2.5G dongles - one in my Synology NAS, and two in different spots where I usually sit down in a chair and plug in my M1 Pro or iPhone to charge (on USB-C charger hubs) and have never had any issues where they drop out from throughput - at once point I had it running full bore overnight. They're from Cable Matters (2025) and Planex (2024). The only issues I have is sometimes they just don't show up when I connect and I have to disconnect and reconnect. That could also just be an issue with USB-C hubs.by kalleboo
- I've had a lot of luck with the Plugable 2.5G USB-C adapters, although on some ports they're incredibly unreliable -- I'm guessing maybe something about the power supply?
On a CalDigit TS3 dock, I've had one working off the rear Thunderbolt socket for over a year, but it fails in minutes if plugged into the USB-C one. I've never had issues with a CalDigit Elements (TB4) hub. I've had success plugging them directly into various Chromebooks. On one Windows laptop, they seemed to work on one USB-C port but not the other.
So... reliable once working, but getting there can be a pain.
by myelin - I have the SABRENT USB-C to 2.5Gbps adapter as well (also bought late 2024) and can echo this sentiment. I had it connected to a M3 Pro MacBook Pro and could never get anywhere close to 2.5Gbps from it. I never found other complaints at the time either and was starting to blame poor wiring in my walls until I replaced it with Ubiquiti's 5GbE adapter (which I believe uses a Marvell controller) and that has been rock solid for me.by a_carbon_rod
- Somewhat off-topic: has anyone implemented USB C based networking?
So for instance you have two or more machines that have USB 4 ports at 20 to 80 Gbps and you plug in the appropriate USB C cables to connect them.
What do you need to make the connections appear as a (point to point) part of a regular TCP/IP network? Seems much cheaper than Ethernet if you already have the ports.
by nutjob2 - Your so-called appropriate USB C cable is just two USB-C to Ethernet adapters plus an Ethernet cable. It’s very common on laptops without native Ethernet ports. But in my experience USB isn’t a very good protocol; it generally uses way more CPU than plain PCIe Ethernet. This is especially the case if the chipset is using ECM rather than NCM.by kccqzy
- You're limited in your network topology because there is no USB Switch. This HN post used two USB4 connections to create a 3-node cluster: https://news.ycombinator.com/item?id=39003469by undersuit
- USB-4 is basically Thunderbolt right? Thunderbolt networking is pretty automatic on Macs at least: https://support.apple.com/en-gb/guide/mac-help/mchld53dd2f5/...by robin_reala
- With USB 4, very strictly speaking: It's iffy. USB 4 doesn't require hosts to be able to switch roles and talk to other hosts. It can support this, but support is optional.
But for all certified Thunderbolt 4 and 5 ports, this kind of networking support is a requirement. (It is optional with Thunderbolt 3.)
The rest is up to the operating system.
by ssl-3 - Yes, there are a few standard(ish) mechanisms for doing this, like [RNDIS][1] and NCM. If you have two Thunderbolt-equipped Macs and connect their ports together, you can use Bonjour/zeroconf for network discovery between them.by warpflyght
- I used to have a thunderbolt ring network for a ceph backend on my k8s cluster. On Linux load the thunderbolt_net kernel module and they show up the same as any other Ethernet interfaces. Just directly connect them and configure the network settings on each end using your normal tools.
Latency was an order of magnitude higher than twisted pair but the throughput was greater than 10Gbps and I didn’t have to spend on 10GbE capable servers and network equipment. I vaguely remember that they had to be proper Thunderbolt not just USB-C but that could have changed it’s been quite a while.
by davkan - Yup, totally doable. Of course, it’s a point to point link so if you want to build a whole cluster that way then you’ll need a lot of usb-c ports or you’ll need to make more of a mesh topology.
I believe MacOS supports it via the usual network control panel. I’ve used it for transferring data from an older laptop to a newer one. The cable is more expensive than fiber, last time I checked.
- Jeff, I’m curious whether you really would have needed the $1,000 version of the Sonnet TB5 PCIe chassis. Would this $400 one have sufficed? https://www.bhphotovideo.com/c/product/1932655-REG/sonnet_ec...by dcrazy
- $400 is for the empty enclosure and $1,000 is for the enclosure with a NIC in it. Obviously it's still a ripoff because a 25G NIC does not cost $600.by wmf
- As mentioned in the blog post's footnote, the bottleneck may just be on the NAS side:
> this real-world speed limitation could also be related to my use of my lower-power Arm NAS (running on Ampere Altra, with 32 fairly-slow CPU cores). I was testing writing to an array of fast enterprise NVMe SSDs, so they shouldn't be the bottleneck here.
He was only getting 1 Gigabyte of throughput out of the built in 10 Gigabit Ethernet connection and moving to the 25 Gigabit connection only made a marginal impact on throughput, after all.
by GeekyBear - You're an order of magnitude off there. The 10 Gigabit connection was providing ~ 1 Gigabyte per second of throughput.by belthesar
- Dang, here I was feeling slick with 10Gb between my MBP and Mac mini and NAS. That’s the thing, it could always be bigger / faster / more. It’s enough for my workflow, but it’s fun to see people push further.by alsetmusic
- It’s crazy that the Ethernet chips consume more power (presumably - because of the heat) than the processor in the computer. How is driving 25Gb/s such a hot task compared to driving multiple 40Gb/s Thunderbolt ports?
- There are no shortcuts in networking. It's quite easy to spend a 2-3x+ premium on a switch or adapter capable of non blocking line rate on every port simultaneously only to then have it fall over to a fraction of that in the form of lots of tiny packets. This is why we have things like QoS, flow control, and ECMP
- > It’s crazy that the Ethernet chips consume more power (presumably - because of the heat)
The NIC in this setup was released 12 years ago. It's built on a very old process.
by Aurornis - Maybe the NIC does a lot? In past experience, a whole Xeon CPU couldn't keep up with a 10gig NIC if it was sending/receiving min-size UDP packets. Even with Intel DPDK iirc.by frollogaston
- A Mac Studio is over 100 W while a 25G NIC is under 25 W (that's the power limit for a normal PCIe slot).by wmf
- Ethernet is isolated through transformers on the physical layer and they're always sinking power. Thunderbolt is just pushing current directly through.
With ethernet it's for lots of reasons but a big one is not creating ground loops between distant equipment. If you didn't isolate the network cable would be sinking potentially amps of current between distant devices and that just isn't sustainable. You don't have this problem attaching USB between two devices.
- It's distance. 25GbaseT is good for 30m+. Thunderbolt is good for 1m without active cables. Making the much more rugged signal is a much more intense job.
And your computer already speaks the PCIe and thunderbolt. It has that probably on CPU. Here we have to receive USB, convert it to Ethernet. On much less up to date process nodes than your CPU.
Third, until very recently for even 10Gbit it meant using a usb4<->pcie bridge chip which itself was hot, to provide a generic pcie connection, which then talked to a conventional network chip, so it was a double hop: USB <-> pcie <-> nic. I don't know if 25Gbit to USB direct convert is available yet but we've seen a wave of vastly cheaper 10Gbit adapters come out that are single chip USB<->nic, probably not pcie at all, that are much much cooler. 25Gbit is probably still not here yet, maybe?
- They’re not that bad, but even a couple watts of power with no way to dissipate is going to get hot enough to burn you. Forced air cooling over a heatsink is really effective. 15W under load is much lower than a high end desktop CPU that can pull 150-200W.
See also NVMe drives? They draw enough idle power to drain a laptop battery overnight, and will easily hit 60+C in a bad enclosure. That’s only a 10Gbps module. The USB4 enclosures are all heatsink.
- As I understand it, it takes a bit of anger to get electromagnetism to wiggle that fast over copper. Imperfect transistors using their full operational envelope to control a sort of chaotic thing? Fields and stuff.by AnthonBerg