I'm using the sonnet at work. Work paid for it. Yes it's more expensive. I have gotten over 25 gbps bidirectional, but not by much. Maybe 27. A big downside is that it only supports 15W upstream power which I didn't think to check, so since that laptop only has 2 usb-c ports for power input, it's a bit limiting.

The upside, though, was that I plugged it in, got my throughput, and never had to worry ever again. Remember that engineering time is mucho $$. So troubleshooting overheating, divising a solution, manufacturing it, etc, that all eats into the savings.

The $400 dock would be cool though. It seems smaller than the sonnet and fixes my charging problem. Weirdly I didn't think I'd care about not including transceivers but they did actually come in handy, so that is a downside. Might try to get one of these if I need another one in the future.

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.

One of the YouTube comments pointed out the issue is most likely the lack of support for SMB Direct (RDMA) in macOS. Would be nice to repeat the test on a Windows/Linux laptop.

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.

> I can edit 4K video straight off my NAS over the network,

Nothing against Jeff Geerling and I love his YouTube channel and I'm glad he's one of us HNer but this crop of circular "I make YouTube vids about big tx speeds and big NAS because I make vids hence I need big tx speeds and big NAS so I can speak about big tx speeds and big NAS because I make YouTube vids about big tx speeds and big NAS" videos is a bit tiring IMO.

I'm not into cryptocurrencies but, I don't know, host a full Ethereum node, host a Plex/Jellyfin server serving thousands of movies, host LLMs, etc.

I mean: talk about something else than editing vids because you make vids about vids.

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?

What are typical use cases for needing 25Gbps?

Author talks about 4k video, but AI tells me that for "4K production mastering (ProRes 422 HQ, 4:2:2, 10-bit)" the rate is under 2Gbps.

I'm not saying it's not needed, - just curious.

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.

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.

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.

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).

is 10W a lot of power? I absolutely don't believe the cpu is using less than that while pushing 25Gb out

you can look up the rated power use of a connectx4 card, they do a lot of offloaded computation, too

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.

Something like 5 percent of AI datacenter usage is just optics.

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?

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.

NAS stuff can benefit greatly and straightforwardly.

A typical NVMe SSD can easily do sequential reads at 7GB/s, which outpaces a 25Gbps connection by more than 2x. NAS is more typically backed by SATA HDDs, but there's some relatively easy way to put an NVMe disk in front of them as a cache.

Do you ever _need_ it? Perhaps not, but there's plenty of common activities just stemming from NAS usage which see a linear speedup, and would continue to get faster up to 100Gbps even.

Running local LLMs split across machines. Pretty sure the author has some other posts about doing that.

Edit: https://www.jeffgeerling.com/blog/2025/15-tb-vram-on-mac-stu...

> Author talks about 4k video, but AI tells me that for "4K production mastering (ProRes 422 HQ, 4:2:2, 10-bit)" the rate is under 2Gbps.

That'd be the rate for 1 stream at 1x playback. Multiple streams because of overlays/crossfades/etc... along with playback at >1x (such as during rendering in particular) will change that significantly.

We refurbish laptops and hence distribute .iso / ipsw images to various refurbishing stations. (or also, think of PXE/network boot situations). More images x more laptops refurbished at once = more bandwidth.

Obviously it's possible to move this to a NAS, not use a mac, etc. etc. - but just wanted to chime in with my little use case of moving multi-gig-files around. :-)

I was just looking for a thunderbolt-sfp solution. Super timely!

What if it’s uncompressed footage at 60fps? And dealing with many shots. And on top of that maybe working with multiple projects in parallel.

If you're editing video you're not just streaming in real time one copy. You have many streams that you're going to want to work around quickly.

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=39003469

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.

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.

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/...

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.

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.

[1]: https://en.wikipedia.org/wiki/RNDIS