Information technology - International Standardized Profile RA - Relaying the Connectionless-mode Network Service - Part 20: Security employing the Network Layer Security Protocol - Connection-mode with SDT-PDU based protection over X.25 packet switched data networks using virtual calls, for RA1111/RA1121 profiles (ISO/IEC DISP 10613-20:1996) prEN ISP 10613-20
