Network Working Group J. Klensin Internet-Draft November 30, 2010 Updates: 959 (if approved) Intended status: Standards Track Expires: June 3, 2011 FTP Extension for Internationalized Text draft-ietf-ftpext2-typeu-00.txt Abstract The original FTP protocol supported TYPE values for ASCII and EBCDIC text, plus binary ("IMAGE") transmission. As the Internet becomes more international, there is a growing requirement to be able to transmit textual data, encoded in Unicode, in a way that is independent of the coding and line representation forms of particular operating systems. This memo specifies a new FTP TYPE value for Unicode data. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on June 3, 2011. Copyright Notice Copyright (c) 2010 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 Klensin Expires June 3, 2011 [Page 1] Internet-Draft FTP Unicode TYPE November 2010 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Context and Overview . . . . . . . . . . . . . . . . . . . 3 1.2. Summary of History of Internationalization of FTP . . . . . 3 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 1.4. Discussion List . . . . . . . . . . . . . . . . . . . . . . 3 2. Specification . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Existing TYPEs . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Unicode TYPE . . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Data Structure . . . . . . . . . . . . . . . . . . . . . . 5 2.4. Feature Negotiation . . . . . . . . . . . . . . . . . . . . 5 3. Net-Unicode Format for FTP . . . . . . . . . . . . . . . . . . 5 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. New Version and File Name: draft-ietf-ftpext2-unicode-00 . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Klensin Expires June 3, 2011 [Page 2] Internet-Draft FTP Unicode TYPE November 2010 1. Introduction 1.1. Context and Overview The original FTP protocol [RFC0959] supported TYPE values for ASCII and EBCDIC text, plus binary ("IMAGE") transmission. The Host Requirements specification [RFC1123] made other changes to FTP, but did not alter the TYPE environment. As the Internet becomes more international, there is a growing requirement to be able to transmit textual data, encoded in Unicode [Unicode52], in a way that is independent of the coding and line representation forms of particular operating systems. This memo specifies a new FTP TYPE value for Unicode data. 1.2. Summary of History of Internationalization of FTP RFC 2640 [RFC2640] is described as providing internationalization of FTP, but only addresses the use of FTP in internationalized (non- ASCII or extended ASCII [ASCII]) file systems. Its facilities were slightly enhanced in a more general extensions specification [RFC3659], which builds on a more general FTP extension mechanism [RFC2389]. The specification in this document addresses the transfer of non-ASCII text files only, building on the TYPE command of the original FTP specification [RFC0959]. 1.3. 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 [RFC2119]. This document assumes that the reader is familiar with the terminology of RFC 959. Those terms, especially reply, server-FTP process, user-FTP process, server-PI, user-PI, logical byte size, and user, if used here, are used in the same way. It also uses the ABNF of [RFC2389] and [RFC5234] in preference to the BNF of RFC 959. For the convenience of contemporary readers, the terms "client" and "server" are used interchangeably with the historic terms "user-FTP process" and "server-FTP process". The document also assumes the termology and changes in the updates to FTP specified in RFC 1123 and RFC 2389. 1.4. Discussion List [[anchor5: RFC Editor: please remove this section before publication.]] Klensin Expires June 3, 2011 [Page 3] Internet-Draft FTP Unicode TYPE November 2010 This proposal is being discussed in the IETF FTPEXT2 Working Group. Its mailing list is at ftpext@ietf.org. 2. Specification 2.1. Existing TYPEs The FTP TYPE command, described in [RFC0959] accepts four possible first argument values, as described below. Note that these descriptions are provided for the reader's convenience; the definitions in RFC 959 remain normative. A The data are expected to be in, and are transformed by the server if needed to, an ASCII [ASCII] data stream conforming to the "NVT" specification (See RFC 959 [RFC0959] and Appendix B of RFC 5198 [RFC5198] for more information). E The data are expected to be in, and are transformed by the server if needed to, an EBCDIC data stream as specified in RFC 959. I The data are transferred in "image" form, i.e., exactly as they appear in the server. Because it is the only TYPE form in which true binary data can be transferred, TYPE I is often referred to as "binary" or "binary transfer". L The data are transmitted in logical bytes of a size specified in an additional argument. See RFC 959. Any of these four argument variations to TYPE except "TYPE A" (with non-print format) MAY be rejected by the server-FTP process with a 504 response code if it does not support that type and the necessary conversions. 2.2. Unicode TYPE The client-PI MAY transmit TYPE U to the server-PI as an alternative to other TYPE commands and arguments. If it does, the server MAY return reply-code 504, indicating that the TYPE U feature is not supported (unchanged from RFC 959) or MUST respond to any data retrieval request (e.g., GET) by sending the data in a stream conformant to the Net-Unicode format specified in Section 3. Similarly, if the client-PI sends TYPE U and the server accepts it, the client MUST send any data streams in that format while the option is in effect. No second parameter is used or permitted for TYPE U. Klensin Expires June 3, 2011 [Page 4] Internet-Draft FTP Unicode TYPE November 2010 2.3. Data Structure The default and only permitted data structure for TYPE U is "file structure". Use of the STRU command SHOULD be avoided. If is used, its argument MUST be "F". 2.4. Feature Negotiation RFC 2389 [RFC2389] specifies a feature negotiation mechanism for new extensions to FTP. Since the TYPE command is a required part of the base FTP specification, the client-PI is not required to issue the FEAT command prior to issuing TYPE U. However, it MAY do so and Server-FTP implementations that include TYPE U SHOULD support FEAT as described below. If the FEAT command is transmitted from the client-PI to the server-PI, and this extension and FEAT are supported, the response MUST include a TYPE line that lists all TYPE values supported by the server (including the required ones). For example, if an FTP-server supports all of TYPEs A, E, I, and U, the FEAT response line would contain each of the possible arguments separated by semicolons, e.g., TYPE A;E;I;U This specification does not change either RFC 959 or RFC 2389. In particular, no FEAT response line is required for TYPE unless this, or some other, extension to TYPE is supported by the FTP-server. 3. Net-Unicode Format for FTP This section specifies a profile of Net-Unicode [RFC5198] for use with FTP TYPE U. Unicode characters must be transmitted in UTF-8 as specified for Net- Unicode. Because FTP is used in data transmission, the characters and sequences that are discouraged in Section 2 of RFC 5198 are permitted to be transported by FTP. However, line-ending sequences MUST conform to the CRLF convention specified there. Consistent with Paragraph 4 of that Section, strings SHOULD be normalized before transmission if at all possible. The implicit logical byte size for this transmission type is eight bits. 4. Acknowledgments This document draws heavily on RFC 959; appreciation is expressed to Klensin Expires June 3, 2011 [Page 5] Internet-Draft FTP Unicode TYPE November 2010 its authors and to the authors of RFC 2398. The work of Mark P. Peterson and Douglas J. Papenthien on other FTP extensions finally motivated production of this document in 2008 after a long delay; that contribution is appreciated as well. 5. IANA Considerations When this specification is approved, an entry for "TYPE U" that refers to it should be incorporated into the FTP Extensions Registry established by RFC 5797 [RFC5797]. 6. Security Considerations This specification makes no substantive change to the FTP command stream but only alters the presentation of data in the data stream. Consequently, it should have no negative security implications that are not already present in the earlier FTP specifications described in Section 1 and in the Net-Unicode specification [RFC5198]. By specifying an exact canonical form for the identification and transfer of Unicode strings, it may eliminate some problems that might be encountered when such strings are transmitted without identification or without restrictions. 7. Change Log RFC Editor: Please remove this section 7.1. New Version and File Name: draft-ietf-ftpext2-unicode-00 This version of the document is a slight update to draft-klensin-ftp-typeu-00, posted in July 2008). It includes some updated references to work completed in the interim, information about the FTPEXT2 WG, a new Security Considerations section (omitted from the prior draft), and a few other minor corrections. 8. References 8.1. Normative References [ASCII] American National Standards Institute (formerly United States of America Standards Institute), "USA Code for Information Interchange", ANSI X3.4-1968, 1968. ANSI X3.4-1968 has been replaced by newer versions with Klensin Expires June 3, 2011 [Page 6] Internet-Draft FTP Unicode TYPE November 2010 slight modifications, but the 1968 version remains definitive for the Internet. [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. [RFC2389] Hethmon, P. and R. Elz, "Feature negotiation mechanism for the File Transfer Protocol", RFC 2389, August 1998. [RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network Interchange", RFC 5198, March 2008. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [Unicode52] The Unicode Consortium. The Unicode Standard, Version 5.2.0, defined by:, "The Unicode Standard, Version 5.2.0", (Mountain View, CA: The Unicode Consortium, 2009. ISBN 978-1-936213-00-9)., . 8.2. Informative References [RFC1123] Braden, R., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, October 1989. [RFC2640] Curtin, B., "Internationalization of the File Transfer Protocol", RFC 2640, July 1999. [RFC3659] Hethmon, P., "Extensions to FTP", RFC 3659, March 2007. [RFC5797] Klensin, J. and A. Hoenes, "FTP Command and Extension Registry", RFC 5797, March 2010. Klensin Expires June 3, 2011 [Page 7] Internet-Draft FTP Unicode TYPE November 2010 Author's Address John C Klensin 1770 Massachusetts Ave, Ste 322 Cambridge, MA 02140 USA Phone: +1 617 245 1457 Email: john+ietf@jck.com Klensin Expires June 3, 2011 [Page 8]