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Internet Draft                                                Mark Bakke
<draft-ietf-ips-iscsi-string-prep-02.txt>                          Cisco
Standards Track
Expires December 2002

June 2002

                     String Profile for iSCSI Names

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.


   The 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.

   This document describes how to prepare internationlized iSCSI names
   to increase the likelihood that name input and comparison work in
   ways that make sense for typical users throughout the world.

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   This draft 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

   Thanks also to Bob Snively for suggesting the use of the nameprep
   process for iSCSI name normalization.

   Most of this draft was copied from the stringprep profile for
   nameprep [NAMEPREP], written by Paul Hoffman and Marc Blanchet.

1.  Introduction

   The iSCSI protocol [ISCSI] 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

   An iSCSI name is a string of UTF-8 [RFC2044] 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
   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

   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

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   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
   should 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 inport or other information that contains international

   In particular, it defines the following, as required by [STRINGPREP]:

   - The intended applicability of the profile: internationalized iSCSI

   - The character repertoire that is the input and output to
     stringprep: Unicode 3.1, specified in section 2.

   - The mappings used: specified in section 3.

   - The Unicode normalization used: specified in section 4.

   - The characters that are prohibited as output: specified in section

   This profile MUST be used with the iSCSI protocol.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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 [Unicode3.1] 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.

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3.  Character Repertoire

   This profile uses Unicode 3.1, as defined in [STRINGPREP] Appendix

4.  Mapping

   This profile specifies mapping using the following tables from
   [STRINGPREP].  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 [STRINGPREP].

6.  Prohibited Output

   This profile specifies prohibiting using the following tables from
   [stringprep].  Characters appearing within these tables MUST NOT be
   used within an iSCSI name.

      Table C.1
      Table C.2
      Table C.3
      Table C.4
      Table C.5
      Table C.6
      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.

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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 [NDT] are also used in protocol elements such as URIs [URI].
   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.  Unassigned Code Points in Internationalized Domain Names

   If the processing in [iSCSI] specifies that a list of unassigned code
   points be used, the system uses table A.1 from [STRINGPREP] as its
   list of unassigned code points.

8.  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.

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9.  IANA Considerations

   This is a profile of stringprep. When it becomes an RFC, it should be
   registered in the stringprep profile registry.

10.  Summary

   This document describes a stringprep profile to be used with programs
   generating names for iSCSI initiators and targets.

11.  Normative References

            Paul Hoffman and Marc Blanchet, "Preparation of
            Internationalized Strings ("stringprep")", draft-hoffman-
            stringprep-03, May 2002.

[ISCSI]     J. Satran, et. al.  "iSCSI", draft-ietf-ips-iscsi-12.txt,
            June 2002.

12.  Informative References

[NDT]       K. Voruganti, et. al.  "iSCSI Naming and Discovery
            Requirements", draft-ietf-ips-iscsi-name-disc-05, May 2002.

[NAMEPREP]  Paul Hoffman and Marc Blanchet.  Nameprep: A Stringprep
            Profile for Internationalized Domain Names.  draft-ietf-idn-
            nameprep-10, May 2002.

[RFC2119]   Scott Bradner, "Key words for use in RFCs to Indicate
            Requirement Levels", March 1997, RFC 2119.

[SAM2]      ANSI T10.  "SCSI Architectural Model 2", March 2000.

[RFC2044]   F. Yergeau, "UTF-8, a transformation format of Unicode and
            ISO 10646", October 1996, RFC 2044.

            The Unicode Standard, Version 3.1.0: The Unicode Consortium.
            The Unicode Standard, Version 3.0. Reading, MA, Addison-
            Wesley Developers Press, 2000. ISBN 0-201-61633-5, as
            amended by: Unicode Standard Annex #27: Unicode 3.1

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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.

[URI]       For example: Roy Fielding et al., "Uniform Resource
            Identifiers: Generic Syntax", August 1998, RFC 2396; Robert
            Hinden et. al, "IPv6 Literal Addresses in URL's", December
            1999, RFC 2732. Note that there are many other RFCs that
            define additional URI schemes.

Author Contact Information

       Mark Bakke
       Cisco Systems, Inc.
       6450 Wedgwood Road
       Maple Grove, MN
       USA 55311

       Voice:  +1 763-398-1000
       E-Mail: mbakke@cisco.com

13.  Full Copyright Statement

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
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   or assist in its implementation may be prepared, copied, published
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   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an

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

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