Experimental Physics and Industrial Control System
Do these devices use Jumbo frames other features which are not not standard Ethernet?
I've personally never encountered a problem with ethernet speed/encoding negotiation.
However, what you describe (no reply) for some messages sounds like problems I've
have with jumbo frames. The short replies get through, but the long replies are ignored.
On 12/23/19 2:46 PM, Mark Rivers via Tech-talk wrote:
> Folks,
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> I am having a strange problem which I am wondering if someone might shed some light on.
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> I have some old Ethernet data acquisition devices, the Canberra AIM MCAs. These are not TCP/IP, but rather use the IEEE 802.2 Extended SNAP protocol. I have been talking to these devices for many years from vxWorks, Windows (using WinPCAP) and Linux (using libnet and libpcap). I recently found that I was not able to talk to them from a number of my Linux systems. It partly works: I can build a list of the devices on the network, I can take “ownership” of the device, and I can read what auxiliary Instrument Control Bus devices are connected to it (ADCs, amplifiers, HVPS, etc.). However, some messages I send to the device never get answered. When I look with Wireshark and compare the packet sent with a Windows machine and the non-functioning Linux machine the packets look the same. But the Windows machine gets a reply and Linux does not.
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> On further investigation I found that the problem only occurs when using 10 Gbit Ethernet adapters. When using a 1 Gbit adapter it works fine. I was able to see this in a single machine that has both 10 Gbit and 1 Gbit adapters. If I use the 1 Gbit adapter it works fine, if I use the 10 Gbit adapter it fails (but kind of works as described above). On 3 separate systems 1 Gbit works, and 3 other systems 10 Gbit fails.
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> This does not make sense to me. The Canberra device itself is 10 Mbit Ethernet. It is plugged into a 1 Gbit switch. The packets are all “slowed-down” in the switch to 10 Mbit, so I don’t understand why it matters if the network card is 1 Gbit or 10 Gbit.
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> I also used ethtool to lower the speed/duplex of the 10000T interface to 1000/Full and then to 100/Full and that did not help. I could still see the module, but much functionality does not work. So a 1 Gbit adapter works, but a 10 Gbit adapter slowed down to 1 Gbit or even 100 Mbit does not work.
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> Any ideas what can cause these symptoms?
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> Thanks,
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> Mark
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