Only one CAN frame in each UDP packet

[TorBerg]

Hi

I am setting up two PCAN-Ethernet Gateways for use over a custom ip radio link. To improve the efficiency of the link we would like to have multiple CAN frames in each UDP packet. I have set the config to do this, but looking on the actual trafick on the network I can see that the UDP packets are 78 bytes and only contain one CAN frame.

Is there some other setting I need to use?

Best regards
Tor Berg
Radionor Communications AS

[PEAK-Support]

Please take a look into the manual, page 31:

Frames per Packet: This value specifies how many CAN frames are
transmitted per IP packet. The higher the value, the greater the
delay in the transmission of CAN messages. However, the demand
on performance is lower in this case. This selection is only available
for Send routes when using the UDP protocol.

But for sending the max. CAN Frames in one package (15 CAN Msg is the max. we could add into one UDP Frame), you need also enough CAN Traffic. It looks like you have not enough CAN Msg., and the UDP Package will be send because time for sending is reached. But this is OK, if you will have CAN Bursts , you will see that more then one CAN Frame will be send with one UDS Frame.

[TorBerg]

Thank you for a quick reply.

I have tried sending with my PCAN-USB dongles at CAN-datarate 1Mbit/s and 1ms between each frame. Still only one CAN frame for each UDP packet.

Is there some timer I can adjust so that the frames are actually bundled. I would like to set this to about 20ms.

What kind of bursts would trigger the bundling?

Tor Berg

[PEAK-Support]

You could not change the UDP sending timeout. 20ms is in a CAN Network and also in an Ethernet Network a very long time! We have tested here and it works fine -wee see with Wireshark that the UDP stream include 4-8 CAN Frames per package. Try sending 6-8 CAN Frames with 8 Databyte with 1 ms on 1MBit - then you will generate Bursts (because timing of sender is jittering).

[TorBerg]

Hi

We are going to use your equipment with our ip radio system. When sending very small packets on the network the overhead in the radio system gets significant. Even if we couldn't have 20ms timeout before sendig a UDP fram, a 5 ms timeout would be much better.

I hope you can note it for future releases if there is no way to change this in the current release.

Tor Berg

[PEAK-Support]

This is part of the protokoll stack - i do not think that we could change anythink on this parameters.
When using TCP you could switch on the TCP Delay - this will add max. CAN Frames as possible in one TCP packet.
As i understood you use our cable module (PCAN-Ethernet Gateway) for CAN to Ethernet package creation. Give the TCP a try - i think it will be the best solution for your system.

[TorBerg]

Hi

TCP will absolutely not work. We have wireless link that will periodically encounter packet errors, and with every packet error the TCP window will be cut to half and the throughput will stop and we will get a timeout in the machine. We have tried this and are switching to your product to have access to UDP.

I do not think it will be very difficult for your devs to add a timeout to the UDP packet generator, but we can manage with the unit as it is today.

Best regards,

Tor Berg

[PEAK-Support]

As i wrote - the UDS package time out is not configurable. To change this, we need to complet retest all software units inside the socket driver. 5 or 20ms are so high values, that the complete system makes no sence anymore. We transfer CAN Data - up to 8000 MSG per second, per channel. What you are looking for is a package bundler - a small device that wait until x CAN Frames arrived, send then as bulk. Maybe you could use a smal LINUX board to do it this way. It is a complete different approach as we have implemented in the Ethernet/CAN Driver. Our goal is to transfer the CAN Data as near as possible in the original timing. For thet we have a "sw bridge" from CAN/ETH and back that works in Kernel mode - not user mode.

[thomas_r3]

Hi,

we're running into the same issue.
Can you tell is the timeout value? Then we can try to configure the CAN side accordingly.

Thanks
Thomas

[PEAK-Support]

What exact are you looking for ? It is not clear from your request...

Can you tell is the timeout value?