Published in September 1981 by Jon Postel, RFC 790 ("Assigned Numbers") served as the central registry for network parameters, defining early Class A, B, and C address structures and port assignments. This document standardized communication for the growing network, defining now-familiar ports like SMTP (25) and Telnet (23) while superseding previous RFCs. View the full report via the IETF Datatracker . RFC 790 - Assigned numbers - IETF Datatracker