Experimental Physics and Industrial Control System
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Hello, Mark, I thought also about the MTU right away, just like Michael. With 10Gbit/s Ethernet this is 9000 bytes
as default and not 1500 bytes as with the 1Gbit/s Ethernet. We had similar problems with a small Omron PLC. It only supported 10Mbit/s and it could handle UDP even only with a MTU of 768 bytes. Omron's internal buffer was simply designed too small. Here we had to connect a router to make it work.
Heinz
P.S.
I found this in 82599-datasheet-v3-4.pdf:
On 23. Dec 2019, at 23:46, Mark Rivers via Tech-talk <[email protected]> wrote:
Folks, I am having a strange problem which I am wondering if someone might shed some light on. 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. 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. 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. 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. Any ideas what can cause these symptoms? Thanks, Mark
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ANJ, 24 Dec 2019 |
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