I went and skimmed the rfc you're citing and it's fro 1988, it's old enough to have samples in C code where the "register" keyword is still used (afaik nowadays most compilers will ignore it) along with assembly code for motorola 68020, Cray CPUs and the IBM-370.
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No. TCP, IP and UDP are all using Internet Checksum (RFC 1071). Ethernet uses CRC.
I went and skimmed the rfc you're citing and it's fro 1988, it's old enough to have samples in C code where the "register" keyword is still used (afaik nowadays most compilers will ignore it) along with assembly code for motorola 68020, Cray CPUs and the IBM-370.
EDIT: for reference: https://datatracker.ietf.org/doc/html/rfc1071.html
All of these are techniques for verifying a message. Galileo also uses a 24-bit CRC to verify its messages after performing forward error correction.