The important RFCs and Internet Drafts relating to FTP are: rfc959 The core standard. rfc1123 Various clarifications and requirements. rfc2389 Feature negotiation. rfc2428 FTP extensions for IPv6 and NATs. rfc2577 FTP security considerations. rfc2640 Internationalization of the protocol. draft-ietf-ftpext-mlst-11.txt Proposed extensions. Other references of interest: http://cr.yp.to/ftp/security.html