Network Working Group J. Klensin
Internet-Draft
Updates: 959 (if approved) A. Hoenes
Intended status: Standards Track TR-Sys
Expires: June 6, 2010 December 3, 2009
FTP Command and Extension Registry
draft-klensin-ftp-registry-03
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
mechanism for specifying and negotiating FTP extensions. The number
of extensions, both supported by the mechanism and some that are not,
continues to increase. An IANA registry of FTP Command and Feature
names is established to reduce the likelihood of conflict of names
and the consequent ambiguity. This specification establishes that
registry.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on June 6, 2010.
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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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 . . . . . . . . . . . . . . . . . . . . 6
2.5. Obsolete Commands . . . . . . . . . . . . . . . . . . . . 6
3. Initial Contents of Registry . . . . . . . . . . . . . . . . . 7
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 11
A.1. Changes in Version -01 . . . . . . . . . . . . . . . . . . 12
A.2. Changes in Version -02 . . . . . . . . . . . . . . . . . . 12
A.3. Changes in Version -03 . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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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, by means of
"FEAT Strings" identifying extensions supported by the FTP server,
and sent in response to a "FEAT" command. The number of extensions
continues to grow, not all of them supported by FEAT. An IANA
registry is established to reduce the likelihood of conflict of names
and the consequent ambiguity and to encourage the sharing of
information. 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 Commands and
Extensions".
2.2. Registry Format
IANA is requested to establish a registry for FTP commands and
extensions. Registration requests and registry 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 of this column (including the "+" suffix if
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present).
Extension name - The name of the extension.
FTP extensions predating RFC 2389 [RFC2389], and some extensions
published after it, did not specify a keyword to identify the
extension in a FEAT response. Some later specifications
established FEAT strings with the respective command names as
their keywords. In order to provide for keywords for future
specifications in such cases, this document establishes
'placeholder' keywords to reserve reasonable feature names for
future standardization. Similarly, placeholder keywords are used
for the basic FTP commands specified in RFC 959 [RFC0959] and
those of its predecessors that are still in use. These
placeholder keywords are placed in the registry for convenience;
it is not intended that they be returned in FEAT responses.
To compensate 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 (henceforth called "pseudo FEAT
codes") are listed in lowercase. Future specifications are
allowed to "upgrade" a placeholder to a true keyword unless it is
specifically declared 'immutable' below, 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 [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 mandatory elements other than
the "FEAT Code" itself.
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.
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Command Type - The type (or 'kind') of the command.
Section 4.1 of RFC 959 [RFC0959] 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.
RFC 959 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. Similarly, obsoleted or historic entries are left
in the registry to avoid conflicts with deployed implementations,
and these entries are marked with 'h' (for "historic").
Beyond the initial registrations, Standards Action [RFC5226] is
needed to register new "mandatory" entries or to move such entries
to "historic".
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 at least 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. RFCs published in any
stream [RFC4844] are assumed to have been adequately reviewed.
For other documents, registration requires that the expert
determine that the document was effectively and critically
reviewed by parties other that the author(s) and their
associates.
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.
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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
The following commands are part of the base FTP specification
[RFC0959] and are listed in the registry with the immutable pseudo
FEAT code "base".
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] clarified and updated the status and
implementation requirements of these standard FTP commands, and it
contains important complementary information for the following
commands:
LIST, NLST, PASV, REST, SITE, STOU
2.5. Obsolete Commands
The following commands were specified as experimental in an extension
to an early version of the FTP specification[RFC0775] but later
deprecated by RFC 1123 [RFC1123], because Standard FTP [RFC0959]
specifies their standard successors. They are listed in the registry
with the immutable pseudo FEAT code "hist".
XCUP, XCWD, XMKD, XPWD, XRMD
Implementation note: Deployed FTP clients still make use of the
deprecated commands and most FTP servers support them as aliases
for the standard commands.
The following commands were specified as part of the "FOOBAR" IPng
effort in RFC 1545 [RFC1545] and, later, RFC 1639 [RFC1639] and are
now obsolete. They are listed in the registry with the immutable
pseudo FEAT code "hist".
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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 to the time of this writing are to be included
into the registry upon creation.
The following pseudo FEAT codes have been assigned, according to
Section 2:
base - FTP standard commands [RFC0959]
hist - Historic experimental commands [RFC0775], [RFC1639]
secu - FTP Security Extensions [RFC2228]
feat - FTP Feature Negotiation [RFC2389]
nat6 - FTP Extensions for NAT/IPv6 [RFC2428]
+-------+-----------+------------------+------+------+--------------+
| cmd | FEAT Code | description | type | conf | RFC#s/ |
| | | | | | References |
| | | | | | and Notes |
+-------+-----------+------------------+------+------+--------------+
| ABOR | base | Abort | s | m | 959 |
| ACCT | base | Account | a | m | 959 |
| ADAT | secu | Authentication/ | a | o | 2228, 2773, |
| | | Security Data | | | 4217 |
| ALLO | base | Allocate | s | m | 959 |
| APPE | base | Append (with | s | m | 959 |
| | | create) | | | |
| AUTH | secu | Authentication/ | a | o | 2228 |
| | | Security | | | |
| | | Mechanism | | | |
| AUTH+ | AUTH | Authentication/ | a | o | 2773, 4217 |
| | | Security | | | #2 |
| | | Mechanism | | | |
| CCC | secu | Clear Command | a | o | 2228 |
| | | Channel | | | |
| CDUP | base | Change to Parent | a | o | 959 |
| | | Directory | | | |
| CONF | secu | Confidentiality | a | o | 2228 |
| | | Protected | | | |
| | | Command | | | |
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| CWD | base | Change Working | a | m | 959 |
| | | Directory | | | |
| DELE | base | Delete File | s | m | 959 |
| ENC | secu | Privacy | a | o | 2228, 2773, |
| | | Protected | | | 4217 |
| | | Command | | | |
| EPRT | nat6 | Extended Port | p | o | 2428 |
| EPSV | nat6 | Extended Passive | p | o | 2428 |
| | | Mode | | | |
| FEAT | feat | Feature | a | m #1 | 2389 |
| | | Negotiation | | | |
| HELP | base | Help | s | m | 959 |
| LANG | UTF8 | Language (for | p | o | 2640 |
| | | Server Messages) | | | |
| LIST | base | List | s | m | 959, 1123 |
| LPRT | hist | Data Port | p | h | 1545, 1639 |
| | | {FOOBAR} | | | |
| LPSV | hist | Passive Mode | p | h | 1545, 1639 |
| | | {FOOBAR} | | | |
| MDTM | MDTM | File | s | o | 3659 |
| | | Modification | | | |
| | | Time | | | |
| MIC | secu | Integrity | a | o | 2228, 2773, |
| | | Protected | | | 4217 |
| | | Command | | | |
| MKD | base | Make Directory | s | o | 959 |
| MLSD | MLST | List Directory | s | o | 3659 |
| | | (for machine) | | | |
| MLST | MLST | List Single | s | o | 3659 |
| | | Object | | | |
| MODE | base | Transfer Mode | p | m | 959 |
| NLST | base | Name List | s | m | 959, 1123 |
| NOOP | base | No-Op | s | m | 959 |
| OPTS | feat | Options | p | m #1 | 2389 |
| PASS | base | Password | a | m | 959 |
| PASV | base | Passive Mode | p | m | 959, 1123 |
| PBSZ | secu | Protection | p | o | 2228 |
| | | Buffer Size | | | |
| PBSZ+ | PBSZ | Protection | p | o | 4217 |
| | | Buffer Size | | | |
| PORT | base | Data Port | p | m | 959 |
| PROT | secu | Data Channel | p | o | 2228 |
| | | Prot. Level | | | |
| PROT+ | PROT | Data Channel | p | o | 4217 |
| | | Prot. Level | | | |
| PWD | base | Print Directory | s | o | 959 |
| QUIT | base | Logout | a | m | 959 |
| REIN | base | Reinitialize | a | m | 959 |
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| REST | base | Restart | s/p | m | 959, 1123 |
| REST+ | REST | Restart (for | s/p | m | 3659 #3 |
| | | STREAM mode) | | | |
| RETR | base | Retrieve | s | m | 959 |
| RMD | base | Remove Directory | s | o | 959 |
| RNFR | base | Rename From | s/p | m | 959 |
| RNTO | base | Rename From | s | m | 959 |
| SITE | base | Site Parameters | s | m | 959, 1123 |
| SIZE | SIZE | File Size | s | o | 3659 |
| SMNT | base | Structure Mount | a | o | 959 |
| STAT | base | Status | s | m | 959 |
| STOR | base | Store | s | m | 959 |
| STOU | base | Store Unique | a | o | 959, 1123 |
| STRU | base | File Structure | p | m | 959 |
| SYST | base | System | s | o | 959 |
| TYPE | base | Representation | p | m | 959 #4 |
| | | Type | | | |
| USER | base | User Name | a | m | 959 |
| XCUP | hist | {precursor for | s | h | 775, 1123 |
| | | CDUP} | | | |
| XCWD | hist | {precursor for | s | h | 775, 1123 |
| | | CWD} | | | |
| XMKD | hist | {precursor for | s | h | 775, 1123 |
| | | MKD} | | | |
| XPWD | hist | {precursor for | s | h | 775, 1123 |
| | | PWD} | | | |
| XRMD | hist | {precursor for | s | h | 775, 1123 |
| | | RMD} | | | |
| -N/A- | TVFS | Trivial Virtual | p | o | 3659 |
| | | File Store | | | |
+-------+-----------+------------------+------+------+--------------+
Table 1
Notes:
#1 While an IETF Standards Action would be required to make the FEAT
mechanism [RFC2389] mandatory, implementation of that extension
mechanism is clearly required in conjunction with any extension or
feature that depends on it.
#2 FEAT String for RFC 4217: AUTH TLS
FEAT String for RFC 2773: AUTH KEA-SKIPJACK
#3 FEAT String: REST STREAM
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#4 FEAT String: TYPE {semicolon-separated list of supported types}
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.
Anthony Bryan spotted a few typographical errors.
Scott Bradner suggested a clarification to the "expert review" text
that has been incorporated.
The authors appreciate the comments and support for this work
received from FTP implementers and many IETF participants. Comments
from the IESG helped to shape this document and registry to improve
its utility.
5. IANA Considerations
IANA is requested to establish the registry described in Section 2
using the initial content specified in Section 3 and including the
body of 2.4 and 2.5 as explanatory text in the preface of the
registry.
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 a slightly relaxed version of
"Specification Required" [RFC5226] with Expert Review. See
Section 2.3 for specifics and exceptions.
6. Security Considerations
The creation of this registry provides improved documentation and
protection against interoperability problems. It introduces no new
security issues.
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7. References
7.1. Normative References
[RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol",
STD 9, RFC 959, October 1985.
[RFC2389] Hethmon, P. and R. Elz, "Feature negotiation mechanism for
the File Transfer Protocol", RFC 2389, August 1998.
[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.
[RFC2228] Horowitz, M., "FTP Security Extensions", RFC 2228,
October 1997.
[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.
[RFC4844] Daigle, L. and Internet Architecture Board, "The RFC
Series and RFC Editor", RFC 4844, July 2007.
Appendix A. Change Log
[[ RFC Editor: Please remove this Appendix before publication. ]]
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A.1. Changes in Version -01
Updated document to reflect new date and IPR statement.
A.2. Changes in Version -02
o Several small changes in response to initial AD review.
o Changed registry model from "extension" to "command" +
"extension".
o Corrections from Alfred Hoenes, followed by adding his initial
registry list and adding him as co-author.
o Added description of the derivation of Table 1 to Section 3.
o Swapped columns 2 and 3 in Table 1.
o Consolidated "cmd" column content format to tag command amendments
and FTP features without a particular command, and renamed space
eating column 5 to "conf".
o Added missing footnotes to Table 1.
o Aligned Section 2 with Table 1, adding much information on column
format; removed orphan; specified collation of entries by "cmd".
o 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.
o Split list in Section 2.4 into Mandatory and Optional, added
pointer to RFC 1123.
o Mention std. replacements per RFC 959 in Section 2.5.
o Numerous editorial fixes.
A.3. Changes in Version -03
Version -03 was produced in response to IETF Last Call and subsequent
IESG comments:
o Removed References section entry for RFC 2119 -- not used.
o Added all "base" (RFC 959/ 1123) commands and obsolete commands
(RFCs 0775, 1545/1639) to registry after discussion during Last
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Call and with IESG. Tentatively recast title and several bits of
the document to refer to "FTP Commands and Extensions", not just
extensions and made related text changes.
o Clarified instructions to IANA including the "peer reviewed
publication" requirement in Section 2.3.
o Adjusted references so that those which support commands in the
registry are all informative.
o Removed language more appropriate to a proposal than to a finished
spec (e.g., a few uses of "it appears useful").
o Clarified the IANA Considerations text about "specification
required" to make it consistent with Section 2.3. Specifically,
specifications of a quality needed to permit interoperable
implementations are not required although they are certainly
desirable.
o After an extended discussion about the possible role of this
document in making some extensions mandatory to implement,
returned it to its status as a registry specification only. The
former text that made the RFC 2389 and 2428 extensions mandatory
has been removed. RFC 2389 (the FEAT mechanism itself) is now
identified as mandatory for the extensions that depend on it (with
a new Note); RFC 2389 (the nat6 extensions) are now simply
optional as far as FTP is concerned as they should probably remain
unless the IETF concludes that nat6 is either required or very
broadly deployed.
o More editorial fixes.
Authors' Addresses
John C Klensin
1770 Massachusetts Ave, Ste 322
Cambridge, MA 02140
USA
Phone: +1 617 245 1457
Email: john+ietf@jck.com
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Alfred Hoenes
TR-Sys
Gerlinger Str. 12
Ditzingen D-71254
Germany
Email: ah@TR-Sys.de
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