[HN Gopher] USB-C Hubs and Ethernet (2020)
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USB-C Hubs and Ethernet (2020)
Author : defaulty
Score : 29 points
Date : 2021-09-10 19:57 UTC (3 hours ago)
(HTM) web link (lucumr.pocoo.org)
(TXT) w3m dump (lucumr.pocoo.org)
| Isthatablackgsd wrote:
| I have USB 3.0 and 3.1 hubs; I am not surprised about this
| article. USB 3.0/3.1 hubs are fickle as heck! And I noticed that
| they seem to emit some kind of EMF around the port which means
| they are unshielded. It rendered some USB dongle non-functional
| until I unplug the hub.
|
| Now I have Anker 3.1 Mini-Dock (without the ethernet), it works
| well but it has issues with HDMI. For whatever the reason, the
| system think that the HDMI is plugged in the hub whereas it is
| not. So, It cause a strange issue with multimonitor since the
| system believes that there is a second monitor plugged to it. But
| yet it couldn't show the second monitor in the display setting
| but it insists that it is plugged.
| asdff wrote:
| I don't know if it was just my hub or the crappy router that
| Spectrum gives me, but whenever I used the ethernet on my hub
| with my laptop, it killed the ethernet connection to the
| desktop.
| the_mitsuhiko wrote:
| Author here: so since I wrote this blog post I get an email once
| every few weeks about this. Apparently that blog post ranks quite
| well now for the keywords that frustrated users are typing into
| Google.
|
| I have now heard that this problem happens with a lot of devices
| and the most common element in most of them is that people also
| have netgear switches on their network but not exclusively.
|
| The most reliable workaround is to ensure that the USB-C adapter
| with an ethernet card in it is powered off when the laptop goes
| to sleep. Many do that if they are not also used for USB-C PD or
| whatever it's called.
| cbhl wrote:
| I've had good luck with a Thunderbolt 4 Hub from Anker as of
| late. The hub has a power button of its own, and when the hub is
| turned off it turns off the attached USB-C-to-Ethernet adapter.
| recursivedoubts wrote:
| over under on when USB-C will finally "just work"?
|
| five years ago I would have said five years
|
| now I'd say 10
| wyager wrote:
| 2 months before USB-D hits consumer devices.
| oneplane wrote:
| This has very little to do with USB-C. The same problem can be
| observed using a classic USB-A to ethernet adapter when
| connected to a class USB-A hub that has its own power supply.
|
| The problem is the 'feature' of some USB Ethernet controllers
| where they keep the ethernet link active when the host
| disconnects. As described in the article, it's the PAUSE frame
| that some switches forward to all devices on the network
| causing them to... pause sending data. The link stays up but
| nothing happens. Perhaps the idea was that you get a fast
| connection resume, but it's not like ethernet handshaking takes
| a lot of time so they might as well simply disconnect the
| ethernet link when the USB ethernet controller notices the host
| computer has disconnected.
| sannee wrote:
| > Perhaps the idea was that you get a fast connection resume
|
| This seems unlikely for the reasons you listed. Since USB is
| a polled bus and has shared bandwidth, implementing the flow
| control is likely very beneficial in case the bus can't
| temporarily handle the full Ethernet speed.
|
| So, a USB-to-Ethernet gizmo just monitors its internal
| Ethernet-to-USB queue and if it starts to overflow, it
| attempts to flow control the switch. But, if no USB host is
| connected, no USB data requests ever arrive, the queue
| overflows and never gets cleared...
|
| There may also be some WoL/USB remote wakeup stuff at play,
| which may be why these ICs do not drop the link on USB host
| disconnect by default. In fact, I wonder if messing with
| those settings on the host side could remediate the issue...
| markstos wrote:
| tl;dr: cheap hubs with ethernet failed, dedicated Apple ethernet
| adapter worked. Author still isn't sure exactly why.
| procarch2019 wrote:
| TBF, hubs in general seem to fail regardless of brand. See my
| other comment about Dell hubs vs docking stations. A model of
| 'hubs are cheap because they fail frequently' is a poor one.
| Hubs should be cheap because they can't deliver power and
| device connections or they have limited port types.
| jscheel wrote:
| I have been consistently blown away at just how bad usb hubs
| really are. The market is absolutely saturated with garbage,
| but it seems like even the high quality ones aren't really
| _that_ good.
| hectormalot wrote:
| I just went through exactly this. I'd unplug my laptop, walk
| downstairs and suddenly the WiFi would stop working.
|
| To troubleshoot, I'd plug into the hub to have Ethernet
| connectivity, and the network would seem to work fine. Took me
| weeks of guessing before considering that a powered-but-
| disconnected USB hub could be the culprit.
|
| Odd that this is an issue across so many vendors. Perhaps they
| share a chip, but still, it reads as a mistake on the Hub as well
| as the Switch side of things.
| [deleted]
| procarch2019 wrote:
| USB-C hubs that I've used have been garbage. They've all crapped
| out after less than a year or so of use. The Dell USB-C docking
| stations I've had have been flawless. Not sure what the diff is
| as my Dell puck USB-C hub sucked (went through 2 of them in a
| year), but the docking stations are solid.
|
| The one difference I see is that the docking stations are meant
| to be independently powered and I think it has its own fan. I'm
| sure the internals are different too, but I don't know how.
| Curious if anyone knows more about the difference between the
| hardware/firmware on the hubs vs the stations.
| cptskippy wrote:
| I have used two Lenovo Thunderbolt docks, a Cable Matters, and
| a Dell; they all had some odd behavior but the Dell was by far
| the best.
|
| I think the use of Display Port a plays a big factor. The
| Cables Matters and Dell docks only had dual HDMI and had far
| fewer issues.
| readams wrote:
| Note that this doesn't seem to actually be related to USB-C, but
| rather to a quirk of how the docking station the author was using
| behaved when not connected to a computer. This could just as
| easily happen with any dock. But maybe USB-C and Apple's dongle
| life has made such docks more common.
| soneil wrote:
| I'm not sure how this relates to Apple. I have a Thinkpad, and
| still vastly prefer the one-cable-solves-all for
| monitor/power/peripherals.
| oneplane wrote:
| This has happened with other ethernet controllers too. It's about
| the fact that they can send pause frames when the host
| disconnects while the power is still on.
|
| You can also do this with USB-A, get an USB-A controller that
| sends pause frames, plug it into a powered USB hub and connect to
| your computer. Unplug, watch the ethernet link still being online
| and suddenly the network dies. Mostly happens with Realtek USB
| Ethernet controllers.
|
| This is a firmware feature so technically you can turn it off.
|
| If you want to try it with PCI or PCIe: get a powered backplane
| or bifurcation board or thunderbolt-to-pci bridge. Connect/use as
| normal then disconnect the host while leaving power on. Same
| problem happens with controllers that send pause frames.
| Quollified wrote:
| I use a USB-C/Thunderbolt dock from CalDigit that seemingly has
| the same problem. Luckily they released a firmware update that
| supposedly fixes it several months back.
|
| I'm guessing a lot of the manufacturers just ended up using the
| same chip for their docks/hubs, and some manufacturers just don't
| care if there was a firmware update from the chip vendor.
| xg15 wrote:
| > _nodes sending PAUSE message to the special multicast address
| 01:80:C2:00:00:01 are instructing the switch to not send them any
| more frames. My switch seems to honor this, but also forwards the
| frames to the other nodes on the network, in effect telling THEM
| to pause in sending frames, which would explain the observed
| behavior._
|
| The what now? I've never heard of "PAUSE" frames before, but
| those sound like a feature just waiting to be exploited.
|
| Do we know how common the behaviour to forward the frames is?
| This sounds like it could bring down any vulnerable public
| network of their choice by just logging on and sending that
| special packet...
| citrin_ru wrote:
| You cannot exploit this in a network which uses non-broken
| switches - pause frames must not be forwarded to other ports
| [1].
|
| But vendors who make home switches often ignore standards.
|
| 1.
| https://en.wikipedia.org/wiki/Ethernet_flow_control#Pause_fr...
| jzwinck wrote:
| Why do these hubs (or the chips they're made with) want to send
| PAUSE frames in the first place? What's the potential advantage
| vs just behaving as a switch with no other devices connected?
| citrin_ru wrote:
| A year ago spend relatively long time troubleshooting my home
| network problem and the root cause was the same: 1. USB-C hub
| with an Ethernet port send pause frames when it is powered but a
| laptop is disconnected 2. TP-Link Wi-Fi router broadcasts pause
| frames to all ports which causes all connected devices to stop
| sending traffic.
|
| TP-Link (or more specifically Atheros AR8327 used inside it) here
| is likely breaks a IEEE standard (may be even the most basic one
| - 801.2d), but when no-one send pause frames this goes unnoticed.
|
| As workaround now don't connect power to the hub and instead
| connect charger to a laptop directly (if a hub is powered you can
| connect only one cable to s laptop to get both - power and
| external USB+Ethernet).
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