China Mobile China Mobile The File transfer protocol, which is defined by the RFC 959, has a long history, but still being widely used. The original version of FTP specification defines IPv4 version of FTP. RFC 2428 defines IPv6 extensions of FTP, introducingEPRT and EPSV command. In the IPv6- IPv4 translation scenario, considerations should be applied to FTP client, server and translation box to ensure FTP protocol work properly. This document discusses the details for FTP to work in IPv4-IPv6 transitiion scenario. This document proposes to update IPv6 FTP client's specification to make it easier to work in 6to4 scenario.