Experimental Physics and
Industrial Control System

"J. Lewis Muir via Tech-talk" <[email protected]> · Tue, 7 Jan 2020 11:14:21 -0600

On 01/06, Mark Rivers wrote:
> On 01/06, J. Lewis Muir wrote:
> > Could you show the output of "ethtool -S p5p1" just in case it shows
> > more detail about exactly what it means by RX "frame"?
> 
> Here is the current output of ifconfig and ethtool (abbreviated).  ifconfig "frame" is 235, which is the same as ethtool "rx_length_errors", so those are the same thing.  They are not CRC errors, which is what I think Michael was assuming.

Yes, I think that's a helpful clue.  The frame error indicates a
malformed packet, and if the packet is damaged, perhaps due to bad
network hardware or local collisions, the CRC checksum would be
incorrect.  But in this case, rx_crc_errors is 0 which means the CRC
checksum is correct and the problem is likely that the packet is an
invalid size, hence rx_length_errors being 235.

The packet might be too short (e.g., for Ethernet, too short would be
less than 64 bytes, but I'm not sure how SNAP might affect this), too
long (e.g., greater than the MTU of the network), or some other issue.
This could be the result of bad hardware or perhaps a network stack or
driver bug where the network stack or driver corrupts the packet or
rejects it as being malformed when it is not.

If there's a firewall running on the Linux machine, can you try
disabling it temporarily just to be sure that it's not causing a
problem?  (I know it works with the 1 GbE NIC, and I know the protocol
is SNAP which the firewall should not even touch assuming it's an IP
packet filter, but if there's a bug somewhere, then it seems worth at
least checking.)

Also, I'm not understanding how this works at all from your office.  You
said it's a Netgear X5712T, but according to the Product Data Sheet
listed at

  https://www.netgear.com/support/product/XS712T.aspx#docs

it doesn't support *any* IEEE 802.2 protocol.  It lists the following
IEEE network protocols as supported:

* IEEE 802.3 Ethernet
* IEEE 802.3u 100BASE-T (XS712T only)
* IEEE 802.3ab 1000BASE-T
* IEEE 802.1Q VLAN Tagging
* IEEE 802.3x Full-Duplex Flow Control
* IEEE 802.3z Gigabit Ethernet 1000BASE-SX/LX
* IEEE 802.3an 10GBASE-T 10 Gbit/s Ethernet Over Copper Twisted Pair Cable
* IEEE 802.3ae 10-Gigabit Ethernet Over Fiber (10GBASE-SR, 10GBASE-LR,
  10GBASE-ER, 10GBASE-LX4)
* IEEE 802.3ad Trunking (LACP)
* IEEE 802.1AB LLDP with ANSI/TIA-1057 (LLDP-MED)
* IEEE 802.1p Class of Service
* IEEE 802.1D Spanning Tree (STP)
* IEEE 802.1s Multiple Spanning Tree (MSTP)
* IEEE 802.1w Rapid Spanning Tree (RSTP)
* IEEE 802.1x RADIUS Network Access Control
* IEEE 802.3az Energy Efficient Ethernet (EEE) Compliant

How does this work at all?

I'm thinking the answer is that it's SNAP, and SNAP is using IEEE 802.3
(Ethernet)?  But I know next to nothing about SNAP.

> > Is the NIC driver the same for the 1 GbE and the 10 GbE NICs on Linux?
> 
> I'm not sure.  How can I tell that?

$ readlink -f /sys/class/net/eno1/device/driver
$ readlink -f /sys/class/net/p5p1/device/driver

or

$ ethtool -i eno1
$ ethtool -i p5p1

It would also be interesting to know the make and model of the 10 GbE
NIC:

$ lspci -v | grep -i ether

> > Do you have a Windows machine with a 10 GbE NIC that you could try?
> 
> Yes, I could try that, but I have not yet.

That might be interesting if there's a bug in the Linux network stack or
NIC driver.

Lewis

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System