Hi Guys, I've been researching quantitatively various protocols QUIC, TCP, UDP, SCTP, etc. on modern hardware. And some TLS, DTLS and plain text variants of these protocols. I've avoided tuning kernel parameters so much and focused more on adjusting what I can in user space on an out of the box kernel, as if I was deploying on a machine where I did not have root access (lets say an Android phone, even though these results come from a laptop for simplicity). I did make a minor exception in that I had to turn on SCTP. I have a small client/server binary that implements bare bones versions of TCP, UDP and SCTP. The server allows you to specify which file clients will pull. And the client lets you specify which file to write the pulled data to (often I use /dev/null here). I run both on 127.0.0.1 . I would have thought (obviously I was wrong) that UDP would be faster, given no acks, retransmits, checksums, etc. as many laymen would tell you. But on this machine TCP is faster more often than not. This has been answered online with different answers of the reasoning (hardware offload, how packet fragmentation is handled, TCP tuned more for throughput, UDP tuned more for latency, etc.). I'm just curious if someone could let me know the most significant factor (or factors) here these days? Things like strace don't reveal much. Changing buffer size to the read/write/send/recv system calls alters things but TCP seems to still win regardless of buffer size. Another question, I detect the UDP client has finished by checking for a final (unsigned char) -1 byte, very error-prone of course. Is there a better way to detect when a simple UDP client should stop trying to pull/read/receive data, that you've seen or is commonplace? If my code is too simplistic and there's one or two setsockopt's etc. that might be interesting to add, my ears are open. Feel free to pull this repo and run this script and take a quick look at the few lines of code if needs be (currently pushing, at an airport might be slow, should be commit around time of this email): https://github.com/ericcurtin/DTLS-Examples The two files relevant: src/script.sh src/udp-tls.c To run my test case: cd src; ./script.sh I'd appreciate some thoughts from the gurus :) My hardware: ThinkPad-P1-Gen-3 CPU: i7-10850H RAM: 32GB Kernel version: $ cat /etc/*release | head -n2; uname -r Fedora release 34 (Thirty Four) NAME=Fedora 5.13.12-200.fc34.x86_64 Is mise le meas/Regards, Eric Curtin Check out this charity that's close to my heart: https://www.idonate.ie/fundraiser/11394438_peak-for-pat.html https://www.facebook.com/Peak-for-Pat-104470678280309 https://www.instagram.com/peakforpat/
