Network Working Group J. Klensin
Internet-Draft
Updates: 959 (if approved) A. Hoenes
Intended status: Standards Track TR-Sys
Expires: April 19, 2010 October 16, 2009
FTP Extension Registry
draft-klensin-ftp-registry-02.txt
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Abstract
Every version of the FTP specification has added a few new commands,
with the early ones summarized in RFC 959. RFC 2389 established a
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mechanism for specifying and negotiating FTP extensions. As the
number of those extensions increases, it appears useful to establish
an IANA registry of FTP Command and Feature names to reduce the
likelihood of conflict of names and the consequent ambiguity. This
specification establishes that registry.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Discussion List . . . . . . . . . . . . . . . . . . . . . 3
2. Registry Definition . . . . . . . . . . . . . . . . . . . . . 3
2.1. Registry Name . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Registry Format . . . . . . . . . . . . . . . . . . . . . 3
2.3. Criteria for Registration . . . . . . . . . . . . . . . . 5
2.4. Base FTP Commands Not Listed in Registry . . . . . . . . . 5
2.5. Obsolete Commands not Listed . . . . . . . . . . . . . . . 6
3. Initial Contents of Registry . . . . . . . . . . . . . . . . . 6
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 10
A.1. Changes in Version-01 . . . . . . . . . . . . . . . . . . 10
A.2. Changes in Version-02 . . . . . . . . . . . . . . . . . . 10
A.3. Changes in Version-03 . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
Every version of the FTP specification has added a few new commands,
with the early ones summarized in RFC 959 [RFC0959]. RFC 2389
[RFC2389] established a mechanism for specifying and negotiating
extensions to the FTP protocol specified in RFC 959 [RFC0959], by
means of "FEAT Strings" identifying extensions supported by the FTP
server, and sent in response to a "FEAT" command. As the number of
those extensions increases, it appears useful to establish an IANA
registry to reduce the likelihood of conflict of names and the
consequent ambiguity. This specification establishes that registry.
1.1. Discussion List
[[ RFC Editor: please remove this section before publication. ]]
Until and unless a WG is created, this proposal will be discussed on
the list apps-discuss@ietf.org
2. Registry Definition
2.1. Registry Name
The recommended name of this registry is "FTP Extensions".
2.2. Registry Format
IANA is requested to establish a registry for FTP commands and
extensions whose entries should include the following:
Command Name - The FTP command, either new or modified, used in the
extension or with which the extension is used. Following the
long-standing practice to capitalize command names in
specification documents for FTP, the command names are entered in
all uppercase. For extensions amending the operation of a
command, a plus sign ("+") is appended to the command name.
However, an extension might not be bound to one command (or a
small number of commands), but affect the overall command
parameter handling and/or transaction processing; in this case,
the string "-N/A-" is entered.
It is intended to have the registry entries ordered by ascending
ASCII collation order.
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Extension name - The name of the extension. FTP extensions
predating [RFC2389], and some extensions published after it as
well, did not specify a keyword to identify the extension in a
FEAT response. Some other specifications later have established
FEAT strings with the respective command names as their keywords.
In order to reserve keywords for future specifications in such
cases, this document establishes 'placeholder' keywords to reserve
reasonable feature names for future standardization. To
accommodate for this idiosyncrasy, the column in the registry is
entitled "FEAT Code", and to clearly distinguish between the two
cases, defined FEAT keywords codes are listed in all uppercase,
whereas 'placeholder' keywords are listed in lowercase. Future
specifications are allowed to "upgrade" a placeholder to a true
keyword, but otherwise IANA maintains uniqueness of feature names
(FEAT codes) based on case-insensitive comparison.
Description - A brief description of the extension and, where
appropriate, the command.
FEAT String - (optional in registration requests to the IANA) The
string expected to be included in the response to the FEAT command
(see RFC 2389 [RFC2389]) if the extension is supported.
In many cases, the FEAT string required to identify an extension
only consists of the "FEAT Code", making this item redundant.
Therefore, this item should only be specified if it is intended to
register a FEAT string that contains more mandatory elements than
the mere "FEAT Code".
Due to space restrictions, and to allow registrants to provide
additional information as well, IANA should present these
registration items (if given) in numbered footnotes to the table,
not in an additional table column.
Command Type - The type (or 'kind') of the command. Section 4.1 of
RFC 959 [RFC0959] has introduced a subdivision of FTP commands
into three types: Access control, transfer Parameter {setting},
and Service {execution}. For clarity and as a service to the user
of the registry, this subdivision is extended to all registered
FTP commands, using the characteristic initial of the type, 'a',
'p', or 's', respectively, filed in the registry column entitled
"type"; combinations are allowed, e.g. 'p/s'
Conformance Requirements - The support expectation for the command.
[RFC0959] specifies mandatory-to-implement commands and optional
commands. This classification is carried over to all registered
commands, using a column entitled "conf" carrying a single
character -- either 'm' or 'o', for "mandatory" and "optional",
respectively. Beyond the initial registrations, Standards Action
[RFC5226] is needed to register new "mandatory" entries.
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Reference - A reference to an RFC or other definition of the
extension and/or to implementations supporting it (see the next
section).
2.3. Criteria for Registration
This registry is primarily intended to avoid conflicting uses of the
same extension names and command keywords for different purposes, not
to demonstrate that an extension is somehow "approved". The "expert
review" method will be used, but the designated expert is expected to
check only that one of the two criteria that follow are met.
1. The extension is described in an RFC or other generally-available
publication for which the fact of publication indicates some
level of peer review of document quality.
2. The extension is actually implemented in FTP client and server
systems that are generally available (not necessarily either free
or unencumbered, but available) and those systems are identified
as part of the documentation requirement above.
For an extension or command to be marked "mandatory" ('m' in the
"conf" column), an IETF Standards Track Specification is required.
An IESG Standards Action is allowed to direct IANA to change the
Conformance Requirements listed for any entry.
2.4. Base FTP Commands Not Listed in Registry
The following commands are part of the base FTP specification
[RFC0959] and hence are not listed in the registry.
Mandatory commands:
ABOR, ACCT, ALLO, APPE, CWD, DELE, HELP, LIST, MODE, NLST, NOOP,
PASS, PASV, PORT, QUIT, REIN, REST, RETR, RNFR, RNTO, SITE, STAT,
STOR, STRU, TYPE, USER
Optional commands:
CDUP, MKD, PWD, RMD, SMNT, STOU, SYST
Note: STD 3 [RFC1123] contains important complementary information
for the following commands:
LIST, NLST, PASV, REST, SITE, STOU
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2.5. Obsolete Commands not Listed
The following commands were specified as experimental in [RFC0775]
but later deprecated by [RFC1123] and are hence not listed, because
[RFC0959] specifies their standard successors.
XCUP, XCWD, XMKD, XPWD, XRMD
The following commands were specified as part of the "FOOBAR" IPng
effort in [RFC1545][RFC1639] and are now obsolete.
LPRT, LPSV
3. Initial Contents of Registry
As a service to users of the registry and the authors of existing
specifications, all FTP commands and features published in RFCs after
STD 3 [RFC1123] and up at the time of this writing are included into
the registry upon creation.
The following pseudo FEAT codes have been assigned, according to
Section 2:
secu - FTP Security Extensions [RFC2228]
feat - FTP Feature Negotiation [RFC2389]
nat6 - FTP Ext'ns for NAT/IPv6 [RFC2428]
Using conservative judgment of implementation requirements as
contemporarily seen, the extensions specified in [RFC2389] and
[RFC2428] have been marke "mandatory" below: without RFC 2389
[RFC2389], feature negotiation is impossible, and RFC 2428 [RFC2428]
specifies commands that are essential for FTP operation in many parts
the of the current Internet, in the presence of middleboxes and
firewalls, and for FTP transport over IPv6.
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+-------+--------+-----------------+------+------+------------------+
| cmd | FEAT | description | type | conf | RFC#s/References |
| | Code | | | | and Notes |
+-------+--------+-----------------+------+------+------------------+
| ADAT | secu | Authent./ | a | o | 2228,2773,4217 |
| | | Security Data | | | |
| AUTH+ | secu | Authent./ | a | o | 2228 |
| | | Security | | | |
| | | Mechanism | | | |
| AUTH+ | AUTH | Authent./ | a | o | 2773,4217 #1 |
| | | Security | | | |
| | | Mechanism | | | |
| CCC | secu | Clear Command | a | o | 2228 |
| | | Channel | | | |
| CONF | secu | Confident. | a | o | 2228 |
| | | Protected | | | |
| | | Command | | | |
| ENC | secu | Privacy | a | o | 2228,2773,4217 |
| | | Protected | | | |
| | | Command | | | |
| EPRT | nat6 | Extended Port | p | m | 2428 |
| EPSV | nat6 | Extended | p | m | 2428 |
| | | Passive Mode | | | |
| FEAT | feat | Feature | a | m | 2389 |
| | | Negotiation | | | |
| LANG | UTF8 | (Server | p | o | 2640 |
| | | Messages) | | | |
| | | Language | | | |
| MDTM | MDTM | File | s | o | 3659 |
| | | Modification | | | |
| | | Time | | | |
| MIC | secu | Integrity | a | o | 2228,2773,4217 |
| | | Protected | | | |
| | | Command | | | |
| MLSD | MLST | List Directory | s | o | 3659 |
| | | (for machine) | | | |
| MLST | MLST | List Single | s | o | 3659 |
| | | Object | | | |
| OPTS | feat | Options | p | m | 2389 |
| PBSZ | secu | Protection | p | o | 2228 |
| | | Buffer Size | | | |
| PBSZ+ | PBSZ | Protection | p | o | 4217 |
| | | Buffer Size | | | |
| PROT | secu | Data Channel | p | o | 2228 |
| | | Prot. Level | | | |
| PROT+ | PROT | Data Channel | p | o | 4217 |
| | | Prot. Level | | | |
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| REST | REST | Restart (for | s/p | m | 3659 #2 |
| | | STREAM mode) | | | |
| SIZE | SIZE | File Size | s | o | 3659 |
| -N/A- | TVFS | Trivial Virtual | p | o | 3659 |
| | | File Store | | | |
+-------+--------+-----------------+------+------+------------------+
Table 1
Footnotes:
#1 FEAT String for [RFC4217]: AUTH TLS
FEAT String for [RFC2773]: AUTH KEA-SKIPJACK
#2 FEAT String: REST STREAM
4. Acknowledgments
Any work to update or extend FTP depends on the base specification in
RFC 959. The contributions of its editors, Jon Postel and Joyce
Reynolds, are gratefully acknowledged. The option negotiation
mechanism specified in RFC 2389 and the accumulation of features that
has followed it made this registry relevant; the authors of those
documents are acknowledged as well.
Barry Leiba and Alexey Melnikov made several suggestions about
earlier drafts of this document, most of which have been
incorporated.
5. IANA Considerations
IANA is requested to establish the registry described in Section 2.
New entries should be added to this registry when extensions to FTP
are approved or defined in published RFCs or when extensions that are
already in use and well-documented are identified. In other words,
the requirement for registration is "Specifications Required"
[RFC5226] with Expert Review. See Section 2.3 for specifics and one
exception.
6. Security Considerations
The creation of this registry provides improved documentation and
protection against interoperability problems. It introduces no new
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security issues.
7. References
7.1. Normative References
[RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol",
STD 9, RFC 959, October 1985.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2228] Horowitz, M., "FTP Security Extensions", RFC 2228,
October 1997.
[RFC2389] Hethmon, P. and R. Elz, "Feature negotiation mechanism for
the File Transfer Protocol", RFC 2389, August 1998.
[RFC2428] Allman, M., Ostermann, S., and C. Metz, "FTP Extensions
for IPv6 and NATs", RFC 2428, September 1998.
[RFC2773] Housley, R. and P. Yee, "Encryption using KEA and
SKIPJACK", RFC 2773, February 2000.
[RFC4217] Ford-Hutchinson, P., "Securing FTP with TLS", RFC 4217,
October 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
7.2. Informative References
[RFC0775] Mankins, D., Franklin, D., and A. Owen, "Directory
oriented FTP commands", RFC 775, December 1980.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989.
[RFC1545] Piscitello, D., "FTP Operation Over Big Address Records
(FOOBAR)", RFC 1545, November 1993.
[RFC1639] Piscitello, D., "FTP Operation Over Big Address Records
(FOOBAR)", RFC 1639, June 1994.
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Appendix A. Change Log
A.1. Changes in Version-01
Updated document to reflect new date and IPR statement.
A.2. Changes in Version-02
Several small changes in response to initial AD review.
Changed registry model from "extension" to "command" + "extension".
While ???
Corrections from Alfred Hoenes, followed by adding his initial
registry list and adding him as co-author.
A.3. Changes in Version-03
Added description of the derivation of Table 1 to Section 3.
Swapped columns 2 and 3 in Table 1.
Consolidated "cmd" column content format to tag command amendments
and FTP features without a particular command, and renamed space
eating column 5 to "conf".
Added missing footnotes to Table 1.
Aligned Section 2 with Table 1, adding much information on column
format; removed orphan; specified collation of entries by "cmd".
Introduced Standards Track requirement for commands in the registry
to be designated as mandatory in Section 2.3 and Section 2; specified
particular IESG change control for the "conf" column in the registry.
Split list in Section 2.4 into Mandatory and Optional, added pointer
to RFC 1123.
Mention std. replacements per RFC 959 in Section 2.5.
Numerous editorial fixes.
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Authors' Addresses
John C Klensin
1770 Massachusetts Ave, Ste 322
Cambridge, MA 02140
USA
Phone: +1 617 245 1457
Email: john+ietf@jck.com
Alfred Hoenes
TR-Sys
Gerlinger Str. 12
Ditzingen D-71254
Germany
Email: ah@TR-Sys.de
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