tptacek

Why would you need another IP protocol besides UDP? Anything you can do directly under an IP header, you can do under a UDP header as well, and the UDP header itself is tiny.

Going back to David Reed, this is specifically why UDP exists: as the extension interface to build more non-TCP transport protocols.

Oct 9, 2025 at 2:16pmWeb
Show threadmtoner23Oct 9, 2025
Because it's an extra header. Making data transfer that much less efficient and working to make sure that clients can decide it properly
Show threadthadtOct 9, 2025
Yeah? It's an eight byte header. The OS needs something to tag IP packets to get them delivered to the correct application. So you're thinking maybe a four byte header for 50% savings here?
Show threadlxgrOct 9, 2025

Good point on there needing to be some application-level addressing anyway.

On top of that, I believe the UDP checksum can be omitted as well at least on some OSes (and is arguably not necessary for fully encrypted/authenticated payloads) – leaving really just the two bytes for the "length field".

Show threadtptacekOct 9, 2025
You can't omit the UDP checksum in IPv6.
Show threadsupertropeOct 9, 2025

IPSec originally ran on raw IP. These days it has to be tunneled in UDP due to TCP or UDP only ossification.

PMTUD breaks when ICMP is blocked.

The same argument can be made that everything but HTTP being blocked is not a problem because everything can be transported on top of HTTP.

Show threadtptacekOct 9, 2025
The same argument is made about HTTP. But at least in the HTTP case, you can point to protocol behavior the middle-layer protocol is enforcing on you. You can't do that with UDP; UDP is just IP, with some ports, and a checksum.