27.4 Summary

27.4 Summary

FTP is the Internet standard for file transfer. Unlike most other TCP applications, it uses two TCP connections between the client and server ” a control connection that is left up for the duration of the client “server session, and a data connection that is created and deleted as necessary.

The connection management used by FTP for the data connection has let us examine in more detail the connection management requirements of TCP. We saw the interaction of TCP's 2MSL wait state on clients that don't issue PORT commands.

FTP uses NVT ASCII from Telnet for all commands and replies across the control connection. The default data transfer mode is often NVT ASCII also. We saw that newer Unix clients automatically send a command to see if the server is an 8-bit byte Unix host, and if so, use binary mode for all file transfers, which is more efficient.

We also showed an example of anonymous FTP, a popular form of software distribution on the Internet.



TCP.IP Illustrated, Volume 1. The Protocols
TCP/IP Illustrated, Vol. 1: The Protocols (Addison-Wesley Professional Computing Series)
ISBN: 0201633469
EAN: 2147483647
Year: 1993
Pages: 378

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