Network Working Group                                         P. Hoffman
Internet-Draft                                            VPN Consortium
Expires: April 20, 2005                                 October 20, 2004


                           
The ftp URI Scheme
                      
draft-hoffman-ftp-uri-02.txt

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on April 20, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   This document specifies the ftp Uniform Resource Identifier (URI)
   scheme that was originally specified in RFC 1738.  The purpose of
   this document is to allow RFC 1738 to be moved to historic while
   keeping the information about the scheme on standards track.

.  Introduction

   URIs are were previously defined in RFC 2396 [RFC2396], which was



Hoffman                  Expires April 20, 2005                 [Page 1]

Internet-Draft             The ftp URI Scheme               October 2004


   updated by draft-fielding-uri-rfc2396bis [2396bis].  Those documents
   also specify how to define schemes for URIs.

   The first definition for many URI schemes appeared in RFC 1738
   [RFC1738].  Because that document has been moved to Historic status,
   this document copies the ftp URI scheme from it to allow that
   material to remain on standards track.

.  Scheme Definition

   The FTP URL scheme is used to designate files and directories on
   Internet hosts accessible using the FTP protocol described in STD 9
   [FTP], RFC 959.

   A FTP URL follows the standard syntax described in
   draft-fielding-uri-rfc2396bis [2396bis].  If :<port> is omitted, the
   port defaults to 21.

2.1  FTP Name and Password

   A user name and password may be supplied; they are used in the ftp
   "USER" and "PASS" commands after first making the connection to the
   FTP server.  If no user name or password is supplied and one is
   requested by the FTP server, the conventions for "anonymous" FTP are
   to be used, as follows:

   o  The user name "anonymous" is supplied.

   o  The password is supplied as the Internet e-mail address of the end
      user accessing the resource.

   If the URL supplies a user name but no password, and the remote
   server requests a password, the program interpreting the FTP URL
   should request one from the user.

2.2  FTP url-path

   The url-path of a FTP URL has the following syntax:

   <cwd1>/<cwd2>/.../<cwdN>/<name>;type=<typecode>

   <cwd1> through <cwdN> and <name> are (possibly encoded) strings and
   <typecode> is one of the characters "a", "i", or "d".  The <cwdx> and
   <name> parts may be empty.  The part ";type=<typecode>" may be
   omitted.  In fact, the whole url-path may be omitted, including the
   "/" delimiting it from the prefix containing user, password, host,
   and port.




Hoffman                  Expires April 20, 2005                 [Page 2]

Internet-Draft             The ftp URI Scheme               October 2004


   The url-path is interpreted as a series of FTP commands as follows:

   o  Each of the <cwd> elements is to be supplied, sequentially, as the
      argument to a CWD (change working directory) command.

   o  If the typecode is "d", perform a NLST (name list) command with
      <name> as the argument, and interpret the results as a file
      directory listing.

   o  Otherwise, perform a TYPE command with <typecode> as the argument,
      and then access the file whose name is <name> (for example, using
      the RETR command.)

   Within a name or CWD component, the characters "/" and ";" are
   reserved and must be encoded.  The components are decoded prior to
   their use in the FTP protocol.  In particular, if the appropriate FTP
   sequence to access a particular file requires supplying a string
   containing a "/" as an argument to a CWD or RETR command, it is
   necessary to encode each "/".

   Historical note: Most FTP client implementations precede the <cwd1>
   with a "/" before sending the CWD command.  This is arguably in
   conflict with RFC 1738, although the practice is quite widespread.
   Thus, a client that is presented with the URL
   <URL:ftp://myname@example.com/abc/def> might send the two commands
   "CWD /abc" and "RETR def" or it might send the two commands "CWD abc"
   and "RETR def".  Server implementers should be aware of these two
   different interpretations of the same URL.

   FTP URLs may also be used for other operations; for example, it is
   possible to update a file on a remote file server, or infer
   information about it from the directory listings.  The mechanism for
   doing so is not spelled out here.

2.3  FTP Typecode is Optional

   The entire ;type=<typecode> part of a FTP URL is optional and is
   rarely used.  Historically, the typecode option was rarely
   implemented and in practice, dereferencing is done by guessing.  If
   the typecode is omitted, the client program interpreting the URL must
   guess the appropriate mode to use.  In general, the data content type
   of a file can only be guessed from the name, such as from the suffix
   of the name; the appropriate type code to be used for transfer of the
   file can then be deduced from the data content of the file.

2.4  Hierarchy

   For some file systems, the "/" used to denote the hierarchical



Hoffman                  Expires April 20, 2005                 [Page 3]

Internet-Draft             The ftp URI Scheme               October 2004


   structure of the URL corresponds to the delimiter used to construct a
   file name hierarchy, and thus, the filename will look similar to the
   URL path.  This does NOT mean that the URL is a filename in the Unix
   or similar filesystems.

2.5  Optimization

   Clients accessing resources via FTP may employ additional heuristics
   to optimize the interaction.  For some FTP servers, for example, it
   may be reasonable to keep the control connection open while accessing
   multiple URLs from the same server.  However, there is no common
   hierarchical model to the FTP protocol, so if a directory change
   command has been given, it is impossible in general to deduce what
   sequence should be given to navigate to another directory for a
   second retrieval, if the paths are different.  The only reliable
   algorithm is to disconnect and reestablish the control connection.

.  Security Considerations

   There are many security considerations for URI schemes discussed in
   draft-fielding-uri-rfc2396bis [2396bis].

  Informative References

   [RFC1738]  Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
              Resource Locators (URL)", RFC 1738, December 1994.

   [RFC2396]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax", RFC 2396,
              August 1998.

   [2396bis]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax", work in
              progress, draft-fielding-uri-rfc2396bis-nn.txt.

   [FTP]      Postel, J. and J. Reynolds, "File Transfer Protocol", STD
              9, RFC 959, October 1985.


Author's Address

   Paul Hoffman
   VPN Consortium
   127 Segre Place
   Santa Cruz, CA  95060
   US

   EMail: paul.hoffman@vpnc.org



Hoffman                  Expires April 20, 2005                 [Page 4]

Internet-Draft             The ftp URI Scheme               October 2004


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Disclaimer of Validity

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Copyright Statement

   Copyright (C) The Internet Society (2004).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.




Hoffman                  Expires April 20, 2005                 [Page 5]