Why does wifi 6 (802.11ax) provide faster data transfer than lan cable on my MacBook Pro?

All I can say is that the third party USB-C to Gigabit Ethernet Adapters don't always work for every situation. I've tried multiple brands of Ethernet adapters and sometimes things just don't work correctly with them, but I have never investigated to learn the specific details. Since Apple does not provide their own official Ethernet adapter I have resorted to using an Apple USB-C to Thunderbolt 2 Adapter paired with a Apple Thunderbolt 2 to Gigabit Ethernet Adapter which seems to overcome the limitations/issues with the third party Ethernet adapters (silly, but it no longer surprises me that Apple does not play well with third party items). If certain types of network usage fails with the third party adapters, then perhaps their speeds are also impacted.

Edit: I'm not a networking specialist, but perhaps the WiFi 6 transmissions are naturally leaner or better compressed than a wired connection? Does WiFi 6 send data to more than one antenna at a time?

what are the numbers you get?

There are some subtle changes to speed up Ethernet, make sure you have a full duplex connection and enabling Jumbo frames, which provides better throughput. You can set frame sizes as high as about 8,000 bytes, and most equipment can handle it. Some equipment starts to choke just shy of 8100 bytes. (8192 less frame overhead).

DexterII wrote:

Doesn't enabling jumbo frame mess up other devices on the LAN that don't support jumbo frame?

Typically, jumbo frames would be configured per device that support it. Those that can't will not be affected. For example, if you configure a NAS for jumbo frames, devices that also support jumbo frames, accessing the NAS, will connect with those frames enabled. Those that don't will only be able to connect at the frame rate they can support. Of course, your overall network throughput performance would benefit if all devices can be configured with the same frame rates.

Another way to look at this would be let's say you configured your Mac and your router for Jumbo Frames. When you open a web page on a browser with that Mac, the traffic to the router will most likely proceed with those frames, but once it leaves the router and heads out to the Internet, those frames will change based on each router hop they take to get to their destination and back.

Most likely they are not configured for jumbo frames because traditionally most network devices don't support it. At least that is my experience. Also, jumbo frames are not the panacea for all networking bandwidth woes. Instead they are just one "tool" to use.

FWIW, I have a number of RPis (3B+ & 4B+) on my network, mainly used for DNS proxying. I do have one, running OMV, to perform as a backup file server for a soon to be retired Time Capsule. For media serving (& Time Machine backups) I have a dedicated Synology NAS. That NAS, btw, is configured for both aggregated Ethernet & jumbo frames ... as it comes equipped with dual Ethernet ports.

Anyways, back to your issue, without doing a complete set of bandwidth tests for each of your network links, as well as, data captures, it would be somewhat difficult to pinpoint where the culprit(s) is(are) ... and, as you can imagine, there are numerous diagnostics tools available to do both.

So basically having it enabled on the router doesn't hurt anything connected to the router that doesn't support it (going beyond the default 1500 MTU). Can't figure out why routers don't have this turned on by default then.

I do have a NAS on my LAN with an external HDD connected to a Raspberry Pi media server. It does take quite a few minutes to transfer a multi GB file from my computer to the drive. Perhaps I will play around with this jumbo frame feature to help reduce transfer times.

Still can't figure out why my speed is suffering on the new laptop compared to my old one when they both have a 1500 MTU. Seems like the issue the OP and I are experiencing isn't necessarily related to the packet sizes.

You will have to do the ping tests to see what the natural maximum frame size is on your NAS (before rejecting as too big, requiring re-transmit at smaller packet size).

I tired some of my devices, and found that cabling through the Switch section of an old Router was slowing things down because it could not support large frame sizes. Some other devices could not support larger than 8163. Some re-cabling was required to speed things up a bit.

What happens with Ethernet at those speeds is that you run out of frame numbers with default 1500 frame size. Jumbo MTU (frame size) gets more data through before you have to sit and wait for Ack from the other end. It is not intuitive, but you may find it speeds things up a bit.

HWTech wrote:

...but perhaps the WiFi 6 transmissions are naturally leaner or better compressed than a wired connection? Does WiFi 6 send data to more than one antenna at a time?

FWIW. Wi-Fi 6, aka, 802.11ax introduced OFDMA which provides (amongst a few other improvements) both uplink & downlink directions for both MIMO & MU-MIMO configurations. The previous Wi-Fi 5 (aka, 802.11ac only provided this in the download direction.

OFDMA = Orthogonal Frequency Division Multiple Access works by subdividing channels into subcarriers and allowing for transmission to multiple endpoints (devices) at the same time. A Wi-Fi 6 router can send different signals in the same transmission window. This results in a single transmission from the router being able to communicate with multiple devices, instead of each device having to wait its turn as the router serves up the data across the network.

Wi-Fi 6 also includes Overlapping Basic Service Sets (OBSS). Older wireless devices, that try to connect to a network, used a "listen before talking" process. That meant, any noise in the network was "heard" as the network being busy and to hold off transmitting. OBSS overcomes this obstacle by "color" prioritizes network traffic. If it sees a different color than it is using, it ignores it and transmits.

Finally, Wi-Fi 6 improves on the beamforming technology introduced with Wi-Fi 5

Of course, all of this is only useful, if both the wireless router/access point and the wireless clients can support Wi-Fi 6.

<< Does WiFi 6 send data to more than one antenna at a time? >>

Most Wi-Fi transmission, even older stuff, takes advantage of multiple antennas, provided there is not too much interference. The data are encoded as the differences between the signals sent on the different antennas, all talking at once. Newer Routers feature antennas spaced farther apart, for better differentiation. The latest ones I bought resemble King Crabs, and are nearly a foot across.

--------

NOW read Tesserax answer, which provides much more in-depth detail about how Wi-Fi 6 moves well beyond multiple antennas to gain even more speed. Other terms used to describe these features are 'beam-forming' and 'spatial streams'.

To add a bit to Grant Bennet-Alder's reply, the proper MTU value to use on an Ethernet segment will depend on what is supported by that segment. By that I mean, if you use an analogy of water pipes, if Ethernet traffic must travel across multiple pipes between hosts, the smallest diameter pipe will be the capping level for MTU. Of course, if it is a straight shot between two Jumbo frame-capable devices, then going "full speed ahead" using an MTU of 9000 should be the most beneficial.

One method to determine the maximum MTU to use, can be down with a technique known as a Ping Sweep.

To perform this, you would enter the following command in the Terminal on your Mac:

• ping -D -s 8184 <LAN IP address of your router>

If you see either "Message too long" or "packet needs to be fragmented," try reducing 8184 by 10, and then, try again. Keep doing so, until the error message no longer appears. Then add back by 1 until that error returns. That would be the maximum MTU for that connection.

Note: Macs do support packets up to 9000 bytes, but will require increasing the datagram size to do so.

• To determine the current datagram size: sysctl net.inet.net.raw.maxdgram
• To increase it: sudo sysctl -w net.inet.raw.maxdgram=16384
• To return it to the previous setting: sudo sysctl net.inet.raw.maxdgram=8192

Doesn't enabling jumbo frame mess up other devices on the LAN that don't support jumbo frame?

I'm having a similar issue as the OP. Using a Belkin USB-C to ethernet adapter on my MBP and only getting 830Mbps. Meanwhile I'm getting 940Mbps with an older MBP in the house also on the LAN (not wireless) using Apples Thunderbolt to gigabit ethernet adapter.

I tried using a Thunderbolt 3 -> Thunderbolt 2 -> Gigabit adapter but had the same results. (about 100 mbps slower) So it's telling me it's the laptop not the adapter.

My wifi 6 connection to the MBP comes close if not exceeds the LAN speeds. (700-860Mbps)

Also having LAG speed issues -> https://discussions.apple.com/thread/253037055 but this might be unrelated.

The buffer was set to 8192. I did increase it to 16384 but made no difference on MTU setting.

On a hunch it was hardware related I did some research earlier and apparently Apple’s recommended Belkin USB-C to Ethernet adapter does not support jumbo frames. Hence the 1500 MTU max settings.

But might be a restriction of the MacBook vs. iMac and Mac mini. Or a limitation of the USB-C. I don’t know and I’m getting mixed answers to this. But it does sound like the Thunderbolt 2 to Ethernet supported jumbo frames.

Seems Apple has really dropped the ball on not creating a Thunderbolt 3 to Ethernet adapter and relying on third party vendors to take it from here.

I’ll continue to play with things.

But would really like to hit at least 940 Mbps single link and 1.2 Gbps with link aggregation.

I have a third brand adapter to try tonight and a dual Ethernet adapter coming tomorrow. I’ll try LAGG with the single adapter with 2 Ethernet ports rather than two separate adapters. See if maybe that improves anything. But I have a hunch I’m wasting my time.

Just an update to this:

I connected the Thunderbolt 3 -> Thunderbolt 2 adapter -> Thunderbolt 2 to gigabit Ethernet. To my surprise more options were available including flow control and energy saving Ethernet as well as the option to change the MTU for jumbo frames.

Just for kicks before I changed the MTU I ran a speed test and was hitting about 920-930Mbps.

I unplugged all that and plugged the Belkin in again and once again about 750-830Mbps. Swapped it once more and it was back to 920-930Mbps.

So I’ve concluded the Thunderbolt is definitely faster than the USB-C also it supports jumbo frames while the USB-C doesn’t.

It does seem silly to have an adapter plugged into another adapter. But until Apple makes a Thunderbolt 3 to -> Gigabit Ethernet (Or even possible 2.5G) this will have to work.

I have yet to try LAGG with this setup. I need to purchase more adapters first.