What is the optimal size of a UDP packet for maximum throughput?

Question

I need to send packets from one host to another over a potentially lossy network. In order to minimize packet latency, I\'m not considering TCP/IP. But, I w

Answer 1

Another thing to consider is that some network devices don't handle fragmentation very well. We've seen many routers that drop fragmented UDP packets or packets that are too big. The suggestion by CesarB to use Path MTU is a good one.

Maximum throughput is not driven only by the packet size (though this contributes of course). Minimizing latency and maximizing throughput are often at odds with one other. In TCP you have the Nagle algorithm which is designed (in part) to increase overall throughput. However, some protocols (e.g., telnet) often disable Nagle (i.e., set the No Delay bit) in order to improve latency.

Do you have some real time constraints for the data? Streaming audio is different than pushing non-realtime data (e.g., logging information) as the former benefits more from low latency while the latter benefits from increased throughput and perhaps reliability. Are there reliability requirements? If you can't miss packets and have to have a protocol to request retransmission, this will reduce overall throughput.

There are a myriad of other factors that go into this and (as was suggested in another response) at some point you get a bad implementation of TCP. That being said, if you want to achieve low latency and can tolerate loss using UDP with an overall packet size set to the PATH MTU (be sure to set the payload size to account for headers) is likely the optimal solution (esp. if you can ensure that UDP can get from one end to the other.