KS X ISO/IEC 21889:2003 Information technology-Telecommunications and information exchange between systems-Private Integrated Services Network-Inter-exchange signalling protocol-Call Identification and Call Linkage Additional Network Feature
2003KS X ISO/IEC 21889:2003 Information technology-Telecommunications and information exchange between systems-Private Integrated Services Network-Inter-exchange signalling protocol-Call Identification and Call Linkage Additional Network Feature