ROS2 topic bandwidth seem doubled on netstat apps

asked 2022-10-28 02:50:42 -0500

chivas1000
1 ●1 ●4 ●5

updated 2022-10-28 02:59:04 -0500

Hi I'm using ROS2 foxy on a client and a server, the client transmits raw image data to server via ethernet the data transmits successfully but as I uses ros2 topic bw /camera/infra1/image_rect_raw to see the bandwidth overhead and uses bmon to see the overall network traffic. It has difference that the traffic at bmon are approximately doubled than ros2 bw.

And this is just a testing so I only open the camera nodes at client side and uses ros2 topic bw at server side

ubuntu@ubuntu-Default-string:~$ ros2 topic bw /camera/realsense_splitter_node/output/infra_1

Subscribed to [/camera/realsense_splitter_node/output/infra_1]

12.33 MB/s from 30 messages Message size mean: 0.41 MB min: 0.41 MB max: 0.41 MB

12.27 MB/s from 60 messages Message size mean: 0.41 MB min: 0.41 MB max: 0.41 MB

12.25 MB/s from 90 messages Message size mean: 0.41 MB min: 0.41 MB max: 0.41 MB

12.25 MB/s from 100 messages Message size mean: 0.41 MB min: 0.41 MB max: 0.41 MB

12.26 MB/s from 100 messages Message size mean: 0.41 MB min: 0.41 MB max: 0.41 MB

12.27 MB/s from 100 messages Message size mean: 0.41 MB min: 0.41 MB max: 0.41 MB

12.28 MB/s from 100 messages Message size mean: 0.41 MB min: 0.41 MB max: 0.41 MB

for the bmon since I cannot upload screenshots, the outputs are bmon: RX bps eno1 23.91MiB

so when I turn off the ros2 bw, the ros2 bw and bmon traffic are all dropped, bmon traffic are about 2KBps

is there anything wrong or am I missing something in ROS2? Any assistance would be appreciated, thanks.

answered 2022-10-29 14:33:26 -0500

Mike Scheutzow
4918 ●2 ●430 ●45

This is expected behavior. ros2 topic bw subscribes to the topic, so all the data is sent to two destinations.Therefore the bandwidth may double on a particular interface while bandwidth measurement is running.

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Thanks for the reply

But still I am not quite understand why all the data is sent to two destinations since I thought there would be only one subscriber at server if I only use ros2 topic bw and no other subscriber, could you explain more details about what is these two destinations?

and for the actuall traffic, is that the data only transmit one time on the network(I mean between the client and server)

Thank you for your help!

chivas1000 ( 2022-10-29 23:20:50 -0500 )edit

If you are sure that ros2 topic bw is the only subscriber, then something else is using that extra bandwidth. Which DDS Quality of Service (QoS) is the topic using?

http://design.ros2.org/articles/qos.html

Mike Scheutzow ( 2022-11-01 08:46:25 -0500 )edit

Have you figured out the cause of this apparent bandwidth doubling?

Mike Scheutzow ( 2022-11-20 09:25:13 -0500 )edit

@Mike Scheutzow, Hi and thanks for the concern, I switched to node discovery server which runs like ROS1 https://fast-dds.docs.eprosima.com/en... and the problem disappears, but I hasn't further explore the original problems, thank you

chivas1000 ( 2022-11-20 23:50:16 -0500 )edit

I don't have any idea about the discovery server.

I see the exact same double bandwidth consumption issue in ROS1 noetic too.

I tried switching the client and server, but the result is the same, every time sender and receiver consumes double bandwidth than 'rostopic bw -w 30 \topic_image\compressed'. Bandwidth is monitored with 'system monitor' app.

Is there anyone observing the same issue? Any solution?

Master:
export ROS_IP=10.72.111.48
export ROS_MASTER_URI=http://10.72.111.48:11311

Slave
export ROS_IP=10.72.111.58
export ROS_MASTER_URI=http://10.72.111.48:11311