KS X ISO/IEC 10614-4-2004(2009) 信息技术—国际标准化轮廓RC-X.25协议中继—第4部分:永久接入上虚拟呼叫的PSDN子网相关、媒体相关要求
Information technology-International Standardized Profile RC-X.25 protocol relaying-Part 4:PSDN subnetwork-dependent,media-dependent requirements for virtual calls over a permanent access