Ask : The data sent rate is greater than the bandwidth

[yuzu-ogura]

The amount of data sent per second is very large, approximately 500 MB/s, but the bandwidth is only 100 MB/s. What are some good solutions for this scenario when using FastDDS?
Thanks all~

[JesusPoderoso]

Hi @yuzu-ogura, thanks for using Fast DDS.
There are several options to improve the rates, which are explained in the large data use case section of the Fast DDS documentation.
Let us know if even though applying those configurations your rates are not being improved.

[yuzu-ogura]

Thank you for your response. I have tried using the LARGE_DATA built-in transport and increasing the socket buffer size. When using a reliable transmission strategy, I encountered the issue of the TCP window being filled, causing sending to block. I haven't tried adjusting the heartbeat period yet. I am considering whether it would be necessary to compress the data before sending.

[JesusPoderoso]

Sorry @yuzu-ogura, I misunderstood your question. My previous answer applies if you want to transmit large date (let's say 500MB) with low bandwidth. In your case, the 500 MB/s rate gives you no more options than data compression.
There are two alternatives, with different advantages based on the kind of data transmitted:

• Application level compression: this would be useful in few large data scenario.
• Fast DDS custom chaining transport: this would be useful in multiple short data scenario.

If your scenario is related to image or video transmission, I would recommend following the application level compression approach.
Chaining transports is a feature that allows for injecting code in between the RTPS layer and the actual underlying transport (UDP/TCP/SHM) so it is possible to perform manipulations on the transport payload itself (in this case RTPS datagrams).

[yuzu-ogura]

Thanks, my scenario is related to image transmission. So, maybe I should compress following the application level, like zlib .