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Versions: 00 01 02 03 04 RFC 5797

Network Working Group                                         J. Klensin
Internet-Draft
Updates: 959 (if approved)                                     A. Hoenes
Intended status: Standards Track                                  TR-Sys
Expires: June 20, 2010                                 December 17, 2009


                   FTP Command and Extension Registry
                     draft-klensin-ftp-registry-04

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
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   The list of current Internet-Drafts can be accessed at
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   This Internet-Draft will expire on June 20, 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the BSD License.


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  . . . . . . . . . . . . . . . . . . . . . . .  9
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 11
     A.1.  Changes in Version -01 . . . . . . . . . . . . . . . . . . 11
     A.2.  Changes in Version -02 . . . . . . . . . . . . . . . . . . 11
     A.3.  Changes in Version -03 . . . . . . . . . . . . . . . . . . 12
     A.4.  Changes in Version -04 . . . . . . . . . . . . . . . . . . 13
   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 documented in a permanent and readily available
       public specification (This is the same as the "Specification
       Required" registration policy defined in RFC 5226 [RFC5226].

   2.  The extension is actually implemented in FTP client and server
       systems that are generally available (not necessarily either free
       or unencumbered, but available).

   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.




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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".

      LPRT, LPSV








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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 | description       | type | conf | RFC#s/References |
   |       | Code |                   |      |      | and Notes        |
   +-------+------+-------------------+------+------+------------------+
   | ABOR  | base | Abort             | s    | m    | 959              |
   | ACCT  | base | Account           | a    | m    | 959              |
   | ADAT  | secu | Authentication/   | a    | o    | 2228, 2773, 4217 |
   |       |      | Security Data     |      |      |                  |
   | 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 #2    |
   |       |      | Security          |      |      |                  |
   |       |      | 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 |      |      |                  |
   | CWD   | base | Change Working    | a    | m    | 959              |
   |       |      | Directory         |      |      |                  |
   | DELE  | base | Delete File       | s    | m    | 959              |
   | ENC   | secu | Privacy Protected | a    | o    | 2228, 2773, 4217 |
   |       |      | Command           |      |      |                  |
   | EPRT  | nat6 | Extended Port     | p    | o    | 2428             |
   | EPSV  | nat6 | Extended Passive  | p    | o    | 2428             |
   |       |      | Mode              |      |      |                  |




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   | 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 Modification | s    | o    | 3659             |
   |       |      | Time              |      |      |                  |
   | MIC   | secu | Integrity         | a    | o    | 2228, 2773, 4217 |
   |       |      | Protected 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 Buffer | p    | o    | 2228             |
   |       |      | Size              |      |      |                  |
   | PBSZ+ | PBSZ | Protection Buffer | p    | o    | 4217             |
   |       |      | Size              |      |      |                  |
   | PORT  | base | Data Port         | p    | m    | 959              |
   | PROT  | secu | Data Channel      | p    | o    | 2228             |
   |       |      | Protection Level  |      |      |                  |
   | PROT+ | PROT | Data Channel      | p    | o    | 4217             |
   |       |      | Protection Level  |      |      |                  |
   | PWD   | base | Print Directory   | s    | o    | 959              |
   | QUIT  | base | Logout            | a    | m    | 959              |
   | REIN  | base | Reinitialize      | a    | m    | 959              |
   | 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              |



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   | 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

   #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



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   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.


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,



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              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. ]]

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".





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   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
      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.





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   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.

A.4.  Changes in Version -04

   Final editing patches -- probably will not be posted until after IESG
   signoff.

   o  Correction of small typos spotted after -03 was posted.

   o  Another attempt at reformatting the table for better readability.

   o  Cleanup of comments used in the XML to keep the editors
      synchronized.  These changes do not affect the text (or other)
      output forms of the document.

   o  Changed the registration criteria (See Section 2.3) at IESG
      request.














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Internet-Draft     FTP Command and Extension Registry      December 2009


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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