Quelle: http://www.faqs.org/rfcs/rfc959.html File Transfer Protocol 2.3. THE FTP MODEL With the above definitions in mind, the following model (shown in Figure 1) may be diagrammed for an FTP service. ------------- |/---------\| || User || -------- ||Interface|<--->| User | |\----^----/| -------- ---------- | | | |/------\| FTP Commands |/----V----\| ||Server|<---------------->| User || || PI || FTP Replies || PI || |\--^---/| |\----^----/| | | | | | | -------- |/--V---\| Data |/----V----\| -------- | File |<--->|Server|<---------------->| User |<--->| File | |System| || DTP || Connection || DTP || |System| -------- |\------/| |\---------/| -------- ---------- ------------- Server-FTP USER-FTP NOTES: 1. The data connection may be used in either direction. 2. The data connection need not exist all of the time.