Rx

It reminded me a little bit of Rx, a fairly old RPC-transport used by AFS (and which also happens to have special kernel support as AF_RXRPC). From what I recall – if I recall correctly, that is –, Rx also does per-call congestion control instead of per-connection (it is connectionless), and it's what leads to its miserable performance over any sort of non-single-digit latency... But I guess it won't matter for a data center?

And while I too like some protocols having their own IP protocol numbers, it definitely seems like a very limiting choice here, when UDP would provide multiplexing and unprivileged userspace access alike without any kernel changes (it's literally what UDP was meant for).