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INTERNET-DRAFT                                            M. Yevstifeyev
Intended Status: Standards Track                            May 20, 2011
Updates: 959, 1738 (if approved)
Expires: November 21, 2011

                          The 'ftp' URI Scheme
                  draft-yevstifeyev-ftp-uri-scheme-00

Abstract

   This document specifies the 'ftp' Uniform Resource Identifier (URI)
   scheme, that is used to refer to resources accessible via File
   Transfer Protocol (FTP).  It updates RFC 959 and RFC 1738.


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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   Internet-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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Copyright and License Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   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



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   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 Simplified BSD License.


Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  URI Scheme Specification . . . . . . . . . . . . . . . . . . .  3
     2.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . .  3
     2.2. URI Scheme Semantics  . . . . . . . . . . . . . . . . . . .  3
       2.2.1. The <user-pass> Part  . . . . . . . . . . . . . . . . .  4
       2.2.2. The <host-port> Part  . . . . . . . . . . . . . . . . .  5
       2.2.3. The <ftp-path> Part . . . . . . . . . . . . . . . . . .  5
         2.2.3.1. A Note on <typecode-part> Part  . . . . . . . . . .  5
     2.3. Encoding Considerations . . . . . . . . . . . . . . . . . .  5
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
   5.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     5.1.  Normative References . . . . . . . . . . . . . . . . . . .  7
     5.2.  Informative References . . . . . . . . . . . . . . . . . .  7
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9


1  Introduction

   File Transfer Protocol (FTP) is a standard network protocol used to
   copy a file from one host to another over a TCP-based network.  It
   has had a very long history; the protocol is rooted in the early
   1970s, the times of ARPANET, with the first specification being RFC
   114 [RFC0114]; however, the most current FTP specification is RFC 959
   [RFC0959].  (Also visit Section 4 pf RFC 1123 [RFC1123] for
   "narrative" description of FTP.)

   Historically, there has been a Uniform Resource Identifier (URI)
   scheme for referencing resources accessible via FTP - 'ftp' URI
   scheme.  The first mention of it appears in RFC 1630 [RFC1630] - pre-
   Standard Track RFC on URIs.  Later, RFC 1738 [RFC1738], Section 3.2
   specified this scheme on IETF Standards Track.  Subsequently, RFC
   1738 was formally obsoleted by RFC 4248 [RFC4248] and RFC 4266
   [RFC4266]; in fact RFC 2396 [RFC2396] and its successor - RFC 3986
   [RFC3986] - replaced and deprecated it (formally they both updated
   RFC 1738).  Currently, almost all of URI schemes specified in RFC
   1738 have been given a separate specification; one of the rare
   exceptions is the 'ftp' URI scheme.  This document removes this
   uncertainty; it gives the 'ftp' URI scheme an official, Standard



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   Track documentation. It updates RFC 959 [RFC0959] and RFC 1738
   [RFC1738].

   Please note that the 'ftp' and 'file' URI schemes are not the same,
   even though they both might refer to the resource on the local host.

   Generic URI syntax is described in RFC 3986 [RFC3986]; registration
   procedures for new URI schemes - in RFC 4395 [RFC4395].

1.1  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


2.  URI Scheme Specification

2.1. URI Scheme Syntax

   The 'ftp' URI takes the form of <ftp-uri> rule below, specified using
   Augmented Backus-Naur Form (ABNF) [RFC5234]:

   ftp-uri       = "ftp:" ftp-hier-part
   ftp-hier-part = "//" [user-pass "@"] host-port [ftp-path]
   user-pass     = user [":" pass]
   user          = *usp-char
   pass          = *usp-char
   usp-char      = *(unreserved / pct-encoded / sub-delims)
   host-port     = host [":" port]
   ftp-path      = path-abempty [typecode-part]
   typecode-part = ";typecode=" typecode
   typecode      = "a" / "i" / "d"

   where the <host>, <port>, <unreserved>, <pct-encoded>, <sub-delims>
   and <path-abempty> rules are defined in RFC 3986 [RFC3986], Appendix
   A.  The semantics of each part are defined below, in Section 2.2.

2.2. URI Scheme Semantics

   The 'ftp' URI specifies either a FTP server for establishing a
   connection (when <ftp-path> is omitted) or a resource on such FTP
   server (when <ftp-path> is present).

   The application resolving the 'ftp' URI SHALL follow the following
   algorithm:

   o Request the password, if not supplied in the URI (per Section



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   2.1.1);

   o Establish the Transmission Control Protocol (TCP) [RFC0793]
   connection to the resource identified by the <host> on the port
   identified by the <port> (or 21, if not supplied there);

   o Authenticate itself to the server, using either the credentials of
   the URI, those requested from the user or anonymous FTP [RFC1635];

   o Perform a series of commands according to <ftp-path> part (see
   Section 2.2.3).

   'ftp' URIs may also be used for other operations; for instance, it is
   possible to update or remove a file on a remote file server.  The
   mechanism for doing so is not specified in this document.

     Note:  The 'ftp' URI scheme supports FTP over TCP only; such
     derivations as FTP over User Datagram Protocol (UDP) [RFC0768] are
     not supported by it.

   More detailed description of each URI's parts' semantics is below.

2.2.1. The <user-pass> Part

   The <user> part of the 'ftp' URI specifies the user name that will be
   used for FTP authentication; <pass> part - the password.  The user
   name and password SHALL be transmitted using the "USER" and "PASS"
   FTP commands, respectively, defined in RFC 959 [RFC0959].  The user
   name and password are delimited by the colon (":") character (ASCII
   [ASCII] character 0x3A).

   The <user-pass> part is OPTIONAL in 'ftp' URIs.  Thus, if the whole
   <user-pass> part is omitted, the following "anonymous FTP" convention
   [RFC1635] SHALL be used:

   (1) the user name "anonymous"; and

   (2) the password that is an e-mail address [RFC5322] of the client is
       supplied.

   The <pass> part in the <user-path> is OPTIONAL as well.  Therefore,
   if there is a user name but no password supplied in the 'ftp' URI, it
   SHALL be requested from the user.

   The <user> and <pass> parts of the URI is composed of the characters
   of <usp-char> ABNF production; any other characters SHALL be percent-
   encoded if occur in these parts.  The <usp-chair> rule includes
   characters allowed in RFC 3986 <userinfo> production, excluding the



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   colon (":") character, whose use is explicitly specified above.

   RFC 3986 deprecated the use of "user:pass" pair in the <userinfo>
   part of URIs.  However, for some historical reasons, the benefits of
   the use of such construction for denoting the user information are
   valuable enough to overlook this issue.

2.2.2. The <host-port> Part

   The <host-port> part specifies the FTP server the resource identified
   by a particular 'ftp' URI is located on.

   If the ":<port>" is omitted, the port SHALL default to 21, as
   registered in [IANA-PORTREG].

2.2.3. The <ftp-path> Part

   The <ftp-path> part, which is OPTIONAL, has the following non-
   normative syntax:

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

   where ";type=<typecode>" is OPTIONAL as well.  This part SHALL be
   interpreted as follows (in this algorithm productions from the
   aforementioned non-normative syntax are enclosed in angle brackets):

    (1) each of <cwd> parts are consistently supplied as arguments to
        the CWD (change working directory) FTP command after
        establishing the FTP connection to the server identified by the
        <host-port> part of the URI;

   (2a) if the <typecode> is equal to "d", the NLST (name list) FTP
        command (see Section 4.1.3 of RFC 959 [RFC0959]) with <name> as
        the argument is sent out;

   (2b) otherwise, the TYPE FTP command (see Section 3.1.1 of RFC 959
        [RFC0959]) with the <typecode> as an argument is performed; and

    (3) access the file identified by the <name> in an appropriate way.

2.2.3.1. A Note on <typecode-part> Part

   The <typecode-part> part has rarely been seen in the wide
   development.  It is not often used in 'ftp' URIs and is included in
   this specification for historical reasons.  Thus, if the <typecode-
   part> is omitted, the client program interpreting the URI SHOULD
   guess the appropriate mode to use.




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2.3. Encoding Considerations

   The 'ftp' URIs may contain characters form the Universal Character
   Set (UCS) [UCS], encoded using UTF-8 character encoding [RFC3629], as
   suggested by RFC 3986 [RFC3986].  Those octets that do not correspond
   to the characters in the unreserved set of RFC 3986 SHALL be percent-
   encoded.  In fact, there are no other encoding considerations for
   'ftp' URIs not discussed in Section 2 of RFC 3986.

   Please visit RFC 3536 [RFC3536] for definitions of the terms related
   to encoding and internalization.


3.  Security Considerations

   Generic security considerations for URIs are discussed in Section 7
   of RFC 3986 [RFC3986].

   Security considerations for FTP are addressed in RFC 2577 [RFC2577].
   RFC 2228 [RFC2228] and RFC 4217 [RFC4217] provided a bunch of ways
   for securing FTP.


4.  IANA Considerations

   IANA is asked to update the registration of the 'ftp' URI scheme
   using the following template, per RFC 4395 [RFC4395]:

   o URI scheme name: ftp

   o Status: Permanent

   o URI scheme syntax: see Section 2.1 of RFC xxxx

   o URI scheme semantics: see Section 2.2 of RFC xxxx

   o URI scheme encoding considerations: see Section 2.3 of RFC xxxx

   o Protocols that use the scheme: File Transfer Protocol (FTP)
     [RFC0959]

   o Security considerations: see Section 3 of RFC xxxx

   o Contact: IESG <iesg@ietf.org>

   o Author/Change controller: IETF <ietf@ietf.org>

   o References: see Section 5 of RFC xxxx



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   [RFC Editor: Please replace xxxx with assigned RFC number]


5.  References

5.1.  Normative References

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, September 1981.

   [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.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC5234]  Crocker, D., Ed., and P. Overell, "Augmented BNF for
              Syntax Specifications: ABNF", STD 68, RFC 5234, January
              2008.

5.2.  Informative References

   [ASCII]    American National Standards Institute (ANSI), "Coded
              Character Set -- 7-bit American Standard Code for
              Information Interchange", ANSI X3.4, 1986.

   [IANA-PORTREG]
              Internet Assigned Numbers Authority (IANA), "Port
              Numbers". <http://www.iana.org/assignments/port-numbers>

   [RFC0114]  Bhushan, A., "File Transfer Protocol", RFC 114, April
              1971.

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              August 1980.

   [RFC1123]  Braden, R., Ed., "Requirements for Internet Hosts -
              Application and Support", STD 3, RFC 1123, October 1989.

   [RFC1630]  Berners-Lee, T., "Universal Resource Identifiers in WWW: A
              Unifying Syntax for the Expression of Names and Addresses



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              of Objects on the Network as used in the World-Wide Web",
              RFC 1630, June 1994.

   [RFC1635]  Deutsch, P., Emtage, A., and A. Marine, "How to Use
              Anonymous FTP", FYI 24, RFC 1635, May 1994.

   [RFC1738]  Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
              Resource Locators (URL)", RFC 1738, December 1994.
              Obsoleted by RFC4248, RFC4266.

   [RFC2228]  Horowitz, M. and S. Lunt, "FTP Security Extensions",
              RFC 2228, October 1997.

   [RFC2396]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax", RFC 2396,
              August 1998. Obsoleted by RFC3986.

   [RFC2577]  Allman, M. and S. Ostermann, "FTP Security
              Considerations", RFC 2577, May 1999.

   [RFC3536]  Hoffman, P., "Terminology Used in Internationalization in
              the IETF", RFC 3536, May 2003.

   [RFC4217]  Ford-Hutchinson, P., "Securing FTP with TLS", RFC 4217,
              October 2005.

   [RFC4248]  Hoffman, P., "The telnet URI Scheme", RFC 4248, October
              2005.

   [RFC4266]  Hoffman, P., "The gopher URI Scheme", RFC 4266, November
              2005.

   [RFC4395]  Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
              Registration Procedures for New URI Schemes", BCP 35,
              RFC 4395, February 2006.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              October 2008.

   [UCS]      International Organization for Standardization (ISO),
              "Information Technology - Universal Multiple-Octet Coded
              Character Set (UCS)", ISO/IEC Standard 10646, December
              2003.


Appendix A.  Acknowledgments

   The authors of RFC 1738 were Tim Berners-Lee, Larry Masinter and Mark



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   McCahill, who worked on the initial 'ftp' URI scheme definition.
   Another attempts to specify this URI scheme were undertaken by Paul
   Hoffman, {who else?}.

   Considerable input to this document was provided by {TBD}.


Authors' Addresses

   Mykyta Yevstifeyev
   8 Kuzovkov St., flat 25
   Kotovsk
   Ukraine

   EMail: evnikita2@gmail.com




































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