of most general interest would probably be the ones about basic internet protocols and packets: - https://datatracker.ietf.org/doc/html/rfc791 Internet Protocol (IPv4) - https://datatracker.ietf.org/doc/html/rfc8200 Internet Protocol, version 6 (IPv6) - https://datatracker.ietf.org/doc/html/rfc4253 SSH protocol - https://datatracker.ietf.org/doc/html/rfc2616 HTTP/1.1 - https://datatracker.ietf.org/doc/html/rfc9113 HTTP/2 - https://datatracker.ietf.org/doc/html/rfc8446 TLS 1.3
another interesting read is the wireguard paper (although not a RFC) https://www.wireguard.com/papers/wireguard.pdf it's not that long but describes the entire protocol, it's quite clever how they achieve security with such low overhead and coordination