Chapter 27

p. 419

FTP is one of the oldest applications for the Internet. It has gained a new lease of life via URLs of the form ftp://$\ldots$, where the browser creates an automatic anonymous FTP, and retrieves the file requested. Various extension to FTP are described in RFC 2428. FTP is almost unchanged in the transition to IPv6: Barry Margolin <barmar@genuity.net> writes:

The general operation of the FTP protocol is unchanged. The only additions are the new commands that are used when creating the data channel, since the commands in the v4 protocol contain v4 addresses, and they now need to be able to contain either v4 or v6 addresses. The EPRT and EPSV commands use the familiar dotted-quad format for v4 addresses and colon format for v6 addresses. There's an example right there in the RFC:

The following are sample EPRT commands:

EPRT |1|132.235.1.2|6275|

EPRT |2|1080::8:800:200C:417A|5282|

Note that ``colon format'' is also often used for MAC (Ethernet) addresses.

p. 422

Option (c) at the top of the page, ``Page structure'', is essentially obsolete, as TOPS-20, the only operating system really to support it, has, despite its elegance, bitten the dust.

p. 422

The second option (c), ``compressed mode'' is essentially obsolete, as software such as gzip do a far better compression of text files. There is also now an RFC (3173) describing IP-level compression.

p. 423

Not only does SMTP use the same conventions for error codes, so does HTTP. Thus the dreaded ``401'' is to be interpreted in the light of this convention.

p. 423

Note that, since the PORT command contains IP addresses and port numbers, it must be interpreted by Network Address Translators (see Appendix B).

p. 437

The Unix command compress, resulting in files ending in .Z, has largely been replaced by gzip, resulting in files ending in .gz, as specified in RFC 1952.