Keywords: iSCSI, Internet Small Computer Systems Interface, transport, unique, global
Network Working Group M. Bakke
Request for Comments: 3722 Cisco
Category: Standards Track April 2004
String Profile for Internet Small Computer
Systems Interface (iSCSI) Names
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document describes how to prepare internationalized iSCSI names
to increase the likelihood that name input and comparison work in
ways that make sense for typical users throughout the world.
The Internet Small Computer Systems Interface (iSCSI) protocol
provides a way for hosts to access SCSI devices over an IP network.
The iSCSI end-points, called initiators and targets, each have a
globally-unique name that must be transcribable, as well as easily
compared.
1. Introduction
The iSCSI protocol [RFC3720] provides a way for hosts to access SCSI
[SAM2] devices over an IP network. The iSCSI end-points, called
initiators and targets, each have a globally-unique name, defined in
[RFC3721].
An iSCSI name is a string of UTF-8 [RFC3629] characters that includes
a type designator, a naming authority based on domain names, and a
unique part within the naming authority. The unique part may be
generated based on anything the naming authority deems useful, and
may include user input.
These names may need to be transcribed (sent between two
administrators via email, voice, paper, etc), so a case-insensitive
comparison would be desirable. However, these names must often be
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compared by initiator and target implementations, most of which are
done in simple, embedded software. This makes case-sensitive
comparison highly desirable for these implementors.
However, a completely case-sensitive implementation would result in
identifiers such as "example-name" and "Example-Name" being
different, which could lead to confusion as these names are
transcribed.
The goal, then, is to generate iSCSI names that can be transcribed
and entered by users, and also compared byte-for-byte, with minimal
confusion. To attain these goals, iSCSI names are generalized using
a normalized character set (converted to lower case or equivalent),
with no white space allowed, and very limited punctuation.
For those using only ASCII characters (U+0000 to U+007F), the
following characters are allowed:
- ASCII dash character ('-' = U+002d)
- ASCII dot character ('.' = U+002e)
- ASCII colon character (':' = U+003a)
- ASCII lower-case characters ('a'..'z' = U+0061..U+007a)
- ASCII digit characters ('0'..'9' = U+0030..U+0039)
In addition, any upper-case characters input via a user interface
MUST be mapped to their lower-case equivalents.
This document specifies the valid character set for iSCSI names,
along with the rules for normalizing and generating iSCSI names based
on user input or other information that contains international
characters.
In particular, it defines the following, as required by [RFC3454]:
- The intended applicability of the profile: internationalized iSCSI
names.
- The character repertoire that is the input and output to
stringprep: Unicode 3.2, specified in section 3.
- The mappings used: specified in section 4.
- The Unicode normalization used: specified in section 5.
- The characters that are prohibited as output: specified in section
6.
This profile MUST be used with the iSCSI protocol.
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2. 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].
Examples in this document use the notation for code points and names
from the Unicode Standard [Unicode3.2] and ISO/IEC 10646 [ISO10646].
For example, the letter "a" may be represented as either "U+0061" or
"LATIN SMALL LETTER A". In the lists of prohibited characters, the
"U+" is left off to make the lists easier to read. The comments for
character ranges are shown in square brackets (such as "[SYMBOLS]")
and do not come from the standards.
3. Character Repertoire
This profile uses Unicode 3.2, as defined in [RFC3454] Appendix A.
4. Mapping
This profile specifies mapping using the following tables from
[RFC3454]. The following mapping tables MUST be used when generating
iSCSI names from Unicode characters.
Table B.1
Table B.2
5. Normalization
Unicode normalization form KC MUST be used with this profile, as
described in [RFC3454].
6. Prohibited Output
This profile specifies prohibiting using the following tables from
[RFC3454]. Characters appearing within these tables MUST NOT be used
within an iSCSI name.
Table C.1.1
Table C.1.2
Table C.2.1
Table C.2.2
Table C.3
Table C.4
Table C.5
Table C.6
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Table C.7
Table C.8
Table C.9
Important note: this profile MUST be used with the iSCSI protocol.
The iSCSI protocol has additional naming rules that are checked
outside of this profile.
In addition, this profile adds the following prohibitions. The full
set of prohibited characters are those from the tables above plus
those listed individually below.
6.1. Inappropriate Characters from Common Input Mechanisms
u+3002 is used as if it were u+002e in many domain name input
mechanisms used by applications, particularly in Asia. The character
u+3002 MUST NOT be used in an iSCSI name.
3002; ideographic full stop
6.2. Currently-prohibited ASCII characters
Some of the ASCII characters that are currently prohibited in iSCSI
names by [RFC3721] are also used in protocol elements such as URIs.
Some examples are described in [RFC2396] and [RFC2732]. Note that
there are many other RFCs that define additional URI schemes.
The other characters in the range U+0000 to U+007F that are not
currently allowed are prohibited in iSCSI names to reserve them for
future use in protocol elements. Note that the dash (U+002D), dot
(U+002E), and colon (U+003A) are not prohibited.
The following characters MUST NOT be used in iSCSI names:
0000-002C; [ASCII CONTROL CHARACTERS and SPACE through ,]
002F; [ASCII /]
003B-0040; [ASCII ; through @]
005B-0060; [ASCII [ through `]
007B-007F; [ASCII { through DEL]
7. Bidirectional Characters
This profile specifies checking bidirectional strings as described in
[RFC3454] section 6.
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8. Unassigned Code Points in Internationalized Domain Names
If the processing in [RFC3720] specifies that a list of unassigned
code points be used, the system uses table A.1 from [RFC3454] as its
list of unassigned code points.
9. Security Considerations
ISO/IEC 10646 has many characters that look similar. In many cases,
users of security protocols might do visual matching, such as when
comparing the names of trusted third parties. This profile does
nothing to map similar-looking characters together.
iSCSI names may be used by an initiator to verify that a target it
has discovered is the correct one, and by a target to verify that an
initiator is to be allowed access. If these names are interpreted
and compared differently by different iSCSI implementations, an
initiator could gain access to the wrong target, or could be denied
access to a legitimate target.
10. IANA Considerations
This is a profile of stringprep. It has been registered in the IANA
"Stringprep Profiles" registry. This process is described in the
IANA Considerations section of [RFC3454].
11. Summary
This document describes a stringprep profile to be used with programs
generating names for iSCSI initiators and targets.
12. Acknowledgements
This document was produced as a result of discussions on iSCSI name
formats with Joe Czap, Jim Hafner, Howard Hall, Jack Harwood, John
Hufferd, Marjorie Krueger, Lawrence Lamers, Todd Sperry, Joshua
Tseng, and Kaladhar Voruganti, as well as discussions on the
normalization of names into identifiers with Paul Hoffman and Marc
Blanchet.
Thanks also to Bob Snively for suggesting the use of the nameprep
process for iSCSI name normalization.
Most of this document was copied from the stringprep profile for
Internationalized Domain Names [RFC3491], written by Paul Hoffman and
Marc Blanchet.
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13. References
13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
[RFC3720] Satran, J., Meth, K., Sapuntzakis, C. Chadalapaka, M.
and E. Zeidner, "Internet Small Computer Systems
Interface (iSCSI)", RFC 3720, April 2004.
13.2. Informative References
[RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers", RFC 2396, August 1998.
[RFC2732] Hinden, R., Carpenter, B. and L. Masinter, "Format for
Literal IPv6 Addresses in URL's", RFC 2732, December
1999.
[RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
Profile for Internationalized Domain Names", RFC 3491,
March 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC3721] Bakke, M., Hafner, J., Hufferd, J., Voruganti, K. and M.
Krueger, "Internet Small Computer Systems Interface
(iSCSI) Naming and Discovery", RFC 3721, April 2004.
[SAM2] ANSI T10. "SCSI Architectural Model 2", March 2000.
[Unicode3.2] The Unicode Standard, Version 3.2.0: The Unicode
Consortium. The Unicode Standard, Version 3.2.0 is
defined by The Unicode Standard, Version 3.0 (Reading,
MA, Addison-Wesley, 2000. ISBN 0-201-61633-5), as
amended by the Unicode Standard Annex #27: Unicode 3.1
(http://www.unicode.org/unicode/reports/tr27/) and by
the Unicode Standard Annex #28: Unicode 3.2
(http://www.unicode.org/unicode/reports/tr28/).
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[ISO10646] ISO/IEC 10646-1:2000. International Standard --
Information technology -- Universal Multiple-Octet Coded
Character Set (UCS) -- Part 1: Architecture and Basic
Multilingual Plane.
14. Author's Address
Mark Bakke
Cisco Systems, Inc.
6450 Wedgwood Road
Maple Grove, MN
USA 55311
Voice: +1 763-398-1000
EMail: mbakke@cisco.com
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15. Full 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.
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.
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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