INTERNET-DRAFT M. Yevstifeyev
Intended Status: Informational July 15, 2011
Updates: RFC-tbd
Expires: January 16, 2012
Internalization of 'ftp' URIs
draft-yevstifeyev-ftp-iri-00
Abstract
This document discusses internalization of 'ftp' Uniform Resource
Identifiers (URIs), which are used to reference resources accessible
via File Transfer Protocol (FTP). It updates RFC-tbd.
[NOTE TO RFC EDITOR: RFC-tbd refers to the [FTP-URI]. Please replace
"tbd" when [FTP-URI] becomes an RFC with its number.]
Status of this Memo
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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
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Internalized 'ftp' Resource Identifiers (RIs) . . . . . . . . . 3
2.1. 'ftp' IRIs . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. UCS Characters in 'ftp' URIs . . . . . . . . . . . . . . . 4
3. Handling Internalized 'ftp' RIs . . . . . . . . . . . . . . . . 4
3.1. Internalized <host> Part in 'ftp' URIs and <ihost> Part
in 'ftp' IRIs . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. The <user-pass> Part in 'ftp' URIs and IRIs . . . . . . . . 4
3.3. The <ftp-path> Part in 'ftp' URIs and <iftp-path> in
'ftp' IRIs . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Internalization of Actual Data Interchange . . . . . . . . . . 5
5. Mapping 'ftp' IRIs to 'ftp' URIs . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
RFC-tbd [FTP-URI] defined the Uniform Resource Identifier (URI)
scheme used to refer to the resources accessible via File Transfer
Protocol (FTP) [RFC0959]. RFC 3986 [RFC3986] allows a limited range
of characters to be present in URIs (particularly, only characters in
ASCII range [ASCII]). RFC 3987 [RFC3987] introduced a new protocol
element - Internationalized Resource Identifiers (IRIs) - which
supplements URIs by extending the allowed range of characters to all
Universal Character Set (UCS) characters. UCS is defined by
[ISO.10646] and [UNICODE] simultaneously, and includes the characters
which are able to represent almost any modern script and language.
See RFC 3536bis [RFC3536bis] for more information.
This document discusses the internalization of 'ftp' URIs and,
correspondingly, defines 'ftp' IRIs. It updates RFC-tbd [FTP-URI].
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
The reader is assumed to be familiar with the terminology of RFC 3987
[RFC3987], RFC 5890 [RFC5890], RFC 3536bis [RFC3536bis] and RFC-tbd
[FTP-URI].
In this document Resource Identifier (RI) refers to either URI or
IRI.
2. Internalized 'ftp' Resource Identifiers (RIs)
The internalized 'ftp' Resource Identifier is meant to be a 'ftp' IRI
and 'ftp' URI with UCS characters. The subsequent sections discusses
how to use UCS with 'ftp' RIs.
2.1. 'ftp' IRIs
As mentioned before, IRIs provide a way to include UCS characters in
the resource identifier preserving the functions of URI. Unlike
URIs, which also may contain UCS characters, which occur percent-
encoded, though (see Section 2.2), IRIs represent UCS characters
directly, by first encoding them using UTF-8 [RFC3629]. This makes
use of IRIs by humans much easier. This section defines the valid
syntax of 'ftp' IRIs.
The 'ftp' IRI takes the form of <ftp-iri> rule below, defined using
ABNF [RFC5234]:
ftp-iri = "ftp:" ftp-ihier-part
ftp-ihier-part = "//" [ user-pass "@" ] ihost-port [ iftp-path ]
user-pass = <as defined in RFC-tbd [FTP-URI]>
; not internalized - see below
ihost-port = ihost [ ":" port ]
iftp-path = [ icwd-part ] "/" ilast-segment [ typecode-part ]
icwd-part = *( "/" icwd )
icwd = isegment-nsc
last-segment = isegment-nsc
isegment-nsc = *ipchar-nsc
ipchar-nsc = iunreserved / pct-encoded / sub-delims-nsc / ":"
/ "@"
sub-delims-nsc = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" /
/ "," / "="
typecode-part = <as defined in RFC-tbd [FTP-URI]>
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where the rules <ihost> and <iunreserved> are defined in RFC 3987
[RFC3987], <pct-encoded> and <port> - in RFC 3986 [RFC3986], and
<user-pass> and <typecode-part> - in RFC-tbd [FTP-URI].
2.2. UCS Characters in 'ftp' URIs
Valid 'ftp' URIs MAY contain UCS characters in their <host> and <ftp-
path> parts, as mentioned in Section 3.3 of RFC-tbd and Section 2.5
of RFC 3986. In order to use such character in one of these parts,
it SHALL first be encoded with UTF-8 [RFC3629]. The resulting
sequence of octets SHALL be examined to conclude whether some octets
match corresponding ASCII characters. If one does, and such
character is allowed in a particular part of 'ftp' URI, it SHALL be
presented in the URI directly; otherwise, the octet SHALL be
represented percent-encoded.
3. Handling Internalized 'ftp' RIs
This section defines the rules which concern handling internalized
'ftp' RIs. The valid syntax for 'ftp' IRIs is defined above; how to
include UCS characters is also discussed above.
3.1. Internalized <host> Part in 'ftp' URIs and <ihost> Part in 'ftp'
IRIs
The <host> part in 'ftp' URIs and <ihost> part in 'ftp' IRIs may
contain internalized strings, with UCS characters being percent-
encoded and displayed directly, respectively.
As Domain Name System (DNS) does not allow the UTF-8 encoded data in
its interchange, limiting the allowed characters range to ASCII
[ASCII], the usual procedure of UTF-8 transformation is insufficient
here. Hence, in order to make up the valid domain name for lookup
and further processing the following step SHALL be applied:
(1) represent the domain name which contains UCS characters as an
octets stream in UTF-8 [RFC3629];
(2) apply the algorithm for IDN lookup defined in Section 5 of RFC
5891 [RFC5891].
The received A-label SHALL also be used with FTP HOST command [I-D
ietf-ftpext2-hosts], sent when establishing FTP connection per
Section 3.2.1 of RFC-tbd [FTP-URI].
3.2. The <user-pass> Part in 'ftp' URIs and IRIs
The <user-pass> part of 'ftp' IRIs is not internalized. FTP does not
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allow the UCS characters to be present in user names or passwords,
and does not allow to enable such feature. Correspondingly, when
processing 'ftp' RIs, either URIs or IRIs, the <user-pass> may
contain characters only allowed by RFC-tbd [FTP-URI].
3.3. The <ftp-path> Part in 'ftp' URIs and <iftp-path> in 'ftp' IRIs
The <ftp-path> and <iftp-path> parts allow to include UCS characters
in FTP pathnames present in URIs and IRIs, respectively.
In order to successfully process an internalized FTP pathname, a
client prior to its processing SHALL examine the server's response to
the FEAT command [RFC2389], issued upon authentication per Section
3.2.2 of RFC-tbd [FTP-URI]. If one of the lines of the response is
"UTF8", the server supports UTF-8 encoded pathnames [RFC2640].
Otherwise, if there is no such line, or the server does not support
the FEAT mechanism, the contrary SHALL be assumed.
Should it be determined that server supports UTF-8 encoded pathnames,
the internalized pathname parts SHALL be encoded with UTF-8 [RFC3629]
and then transmitted as an arguments to the corresponding FTP
commands as UTF-8 octets stream.
4. Internalization of Actual Data Interchange
'ftp' RIs may refer to the file which contains the internalized data.
When transmitting such file over data connection, it should be in
Net-Unicode format [RFC5198]. In order to indicate this, the
<typecode> equal to "u" [I-D ietf-ftpext2-typeu] SHALL be set in the
'ftp' RI.
5. Mapping 'ftp' IRIs to 'ftp' URIs
'ftp' IRIs are subject to the rules of Section 3.1 of RFC 3987 with
respect to their mapping to 'ftp' URIs.
6. Security Considerations
Security considerations for usage of IRIs are discussed in Section 8
of RFC 3987 [RFC3987]; for usage of Internalized Domain Names - in
RFC 5890 [RFC5890]. This document adds nothing to those security
considerations.
7. IANA Considerations
IANA is asked to list this document as an additional reference to
'ftp' URI scheme registration.
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8. References
8.1. Normative References
[ASCII] American National Standards Institute (ANSI), "Coded
Character Set -- 7-bit American Standard Code for
Information Interchange", ANSI X3.4-1986, December 1986.
[FTP-URI] Yevstifeyev, M., "The 'ftp' URI Scheme", Work in Progress
(draft-yevstifeyev-ftp-uri-scheme), July 2011.
[I-D ietf-ftpext2-typeu]
Klensin, J., "FTP TYPE Extension for Internationalized
Text", Work in Progress (draft-ietf-ftpext2-typeu), June
2011.
[ISO.10646]
International Organization for Standardization (ISO),
"Information technology -- Universal Coded Character Set
(UCS)", ISO/IEC 10646:2011, March 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2640] Curtin, B., "Internationalization of the File Transfer
Protocol", RFC 2640, July 1999.
[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.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234, January
2008.
[RFC5891] Klensin, J., "Internationalized Domain Names in
Applications (IDNA): Protocol", RFC 5891, August 2010.
[UNICODE] The Unicode Consortium, "The Unicode Standard, Version
6.0.0", (Mountain View, CA: The Unicode Consortium, 2011.
ISBN 978-1-936213-01-6), 2011,
<http://www.unicode.org/versions/Unicode6.0.0/>.
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8.2. Informative References
[I-D ietf-ftpext2-hosts]
Hethmon, P., and R. McMurray, "File Transfer Protocol HOST
Command for Virtual Hosts", Work in Progress (draft-ietf-
ftpext2-hosts), February 2011.
[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.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, March 2008.
[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010.
[RFC3536bis]
Hoffman, P., and J. Klensin, "Terminology Used in
Internationalization in the IETF", Work in Progress
(draft-ietf-appsawg-rfc3536bis), June 2011.
Appendix A. Acknowledgments
I'd like to thank <TBD> for their input to this document.
Authors' Addresses
Mykyta Yevstifeyev
8 Kuzovkov St., Apt 25
Kotovsk
Ukraine
EMail: evnikita2@gmail.com
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