396 lines
10 KiB
Plaintext
396 lines
10 KiB
Plaintext
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Network Working Group P. Hoffman
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Request for Comments: 3491 IMC & VPNC
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Category: Standards Track M. Blanchet
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Viagenie
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March 2003
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Nameprep: A Stringprep Profile for
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Internationalized Domain Names (IDN)
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Status of this Memo
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This document specifies an Internet standards track protocol for the
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Internet community, and requests discussion and suggestions for
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improvements. Please refer to the current edition of the "Internet
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Official Protocol Standards" (STD 1) for the standardization state
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and status of this protocol. Distribution of this memo is unlimited.
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Copyright Notice
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Copyright (C) The Internet Society (2003). All Rights Reserved.
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Abstract
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This document describes how to prepare internationalized domain name
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(IDN) labels in order to increase the likelihood that name input and
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name comparison work in ways that make sense for typical users
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throughout the world. This profile of the stringprep protocol is
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used as part of a suite of on-the-wire protocols for
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internationalizing the Domain Name System (DNS).
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1. Introduction
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This document specifies processing rules that will allow users to
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enter internationalized domain names (IDNs) into applications and
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have the highest chance of getting the content of the strings
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correct. It is a profile of stringprep [STRINGPREP]. These
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processing rules are only intended for internationalized domain
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names, not for arbitrary text.
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This profile defines the following, as required by [STRINGPREP].
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- The intended applicability of the profile: internationalized
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domain names processed by IDNA.
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- The character repertoire that is the input and output to
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stringprep: Unicode 3.2, specified in section 2.
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Hoffman & Blanchet Standards Track [Page 1]
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RFC 3491 IDN Nameprep March 2003
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- The mappings used: specified in section 3.
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- The Unicode normalization used: specified in section 4.
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- The characters that are prohibited as output: specified in section
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5.
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- Bidirectional character handling: specified in section 6.
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1.1 Interaction of protocol parts
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Nameprep is used by the IDNA [IDNA] protocol for preparing domain
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names; it is not designed for any other purpose. It is explicitly
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not designed for processing arbitrary free text and SHOULD NOT be
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used for that purpose. Nameprep is a profile of Stringprep
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[STRINGPREP]. Implementations of Nameprep MUST fully implement
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Stringprep.
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Nameprep is used to process domain name labels, not domain names.
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IDNA calls nameprep for each label in a domain name, not for the
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whole domain name.
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1.2 Terminology
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The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
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in this document are to be interpreted as described in BCP 14, RFC
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2119 [RFC2119].
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2. Character Repertoire
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This profile uses Unicode 3.2, as defined in [STRINGPREP] Appendix A.
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3. Mapping
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This profile specifies mapping using the following tables from
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[STRINGPREP]:
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Table B.1
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Table B.2
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4. Normalization
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This profile specifies using Unicode normalization form KC, as
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described in [STRINGPREP].
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Hoffman & Blanchet Standards Track [Page 2]
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RFC 3491 IDN Nameprep March 2003
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5. Prohibited Output
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This profile specifies prohibiting using the following tables from
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[STRINGPREP]:
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Table C.1.2
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Table C.2.2
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Table C.3
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Table C.4
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Table C.5
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Table C.6
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Table C.7
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Table C.8
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Table C.9
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IMPORTANT NOTE: This profile MUST be used with the IDNA protocol.
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The IDNA protocol has additional prohibitions that are checked
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outside of this profile.
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6. Bidirectional characters
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This profile specifies checking bidirectional strings as described in
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[STRINGPREP] section 6.
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7. Unassigned Code Points in Internationalized Domain Names
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If the processing in [IDNA] specifies that a list of unassigned code
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points be used, the system uses table A.1 from [STRINGPREP] as its
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list of unassigned code points.
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8. References
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8.1 Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
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Requirement Levels", BCP 14, RFC 2119, March 1997.
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[STRINGPREP] Hoffman, P. and M. Blanchet, "Preparation of
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Internationalized Strings ("stringprep")", RFC 3454,
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December 2002.
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[IDNA] Faltstrom, P., Hoffman, P. and A. Costello,
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"Internationalizing Domain Names in Applications
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(IDNA)", RFC 3490, March 2003.
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Hoffman & Blanchet Standards Track [Page 3]
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RFC 3491 IDN Nameprep March 2003
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8.2 Informative references
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[STD13] Mockapetris, P., "Domain names - concepts and
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facilities", STD 13, RFC 1034, and "Domain names -
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implementation and specification", STD 13, RFC 1035,
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November 1987.
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9. Security Considerations
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The Unicode and ISO/IEC 10646 repertoires have many characters that
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look similar. In many cases, users of security protocols might do
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visual matching, such as when comparing the names of trusted third
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parties. Because it is impossible to map similar-looking characters
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without a great deal of context such as knowing the fonts used,
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stringprep does nothing to map similar-looking characters together
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nor to prohibit some characters because they look like others.
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Security on the Internet partly relies on the DNS. Thus, any change
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to the characteristics of the DNS can change the security of much of
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the Internet.
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Domain names are used by users to connect to Internet servers. The
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security of the Internet would be compromised if a user entering a
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single internationalized name could be connected to different servers
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based on different interpretations of the internationalized domain
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name.
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Current applications might assume that the characters allowed in
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domain names will always be the same as they are in [STD13]. This
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document vastly increases the number of characters available in
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domain names. Every program that uses "special" characters in
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conjunction with domain names may be vulnerable to attack based on
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the new characters allowed by this specification.
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Hoffman & Blanchet Standards Track [Page 4]
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RFC 3491 IDN Nameprep March 2003
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10. IANA Considerations
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This is a profile of stringprep. It has been registered by the IANA
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in the stringprep profile registry
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(www.iana.org/assignments/stringprep-profiles).
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Name of this profile:
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Nameprep
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RFC in which the profile is defined:
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This document.
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Indicator whether or not this is the newest version of the
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profile:
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This is the first version of Nameprep.
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11. Acknowledgements
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Many people from the IETF IDN Working Group and the Unicode Technical
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Committee contributed ideas that went into this document.
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The IDN Nameprep design team made many useful changes to the
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document. That team and its advisors include:
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Asmus Freytag
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Cathy Wissink
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Francois Yergeau
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James Seng
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Marc Blanchet
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Mark Davis
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Martin Duerst
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Patrik Faltstrom
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Paul Hoffman
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Additional significant improvements were proposed by:
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Jonathan Rosenne
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Kent Karlsson
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Scott Hollenbeck
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Dave Crocker
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Erik Nordmark
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Matitiahu Allouche
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Hoffman & Blanchet Standards Track [Page 5]
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RFC 3491 IDN Nameprep March 2003
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12. Authors' Addresses
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Paul Hoffman
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Internet Mail Consortium and VPN Consortium
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127 Segre Place
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Santa Cruz, CA 95060 USA
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EMail: paul.hoffman@imc.org and paul.hoffman@vpnc.org
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Marc Blanchet
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Viagenie inc.
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2875 boul. Laurier, bur. 300
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Ste-Foy, Quebec, Canada, G1V 2M2
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EMail: Marc.Blanchet@viagenie.qc.ca
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Hoffman & Blanchet Standards Track [Page 6]
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RFC 3491 IDN Nameprep March 2003
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13. Full Copyright Statement
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Copyright (C) The Internet Society (2003). All Rights Reserved.
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This document and translations of it may be copied and furnished to
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others, and derivative works that comment on or otherwise explain it
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or assist in its implementation may be prepared, copied, published
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and distributed, in whole or in part, without restriction of any
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kind, provided that the above copyright notice and this paragraph are
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included on all such copies and derivative works. However, this
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document itself may not be modified in any way, such as by removing
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the copyright notice or references to the Internet Society or other
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Internet organizations, except as needed for the purpose of
|
|||
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developing Internet standards in which case the procedures for
|
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copyrights defined in the Internet Standards process must be
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followed, or as required to translate it into languages other than
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English.
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The limited permissions granted above are perpetual and will not be
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revoked by the Internet Society or its successors or assigns.
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This document and the information contained herein is provided on an
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"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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|||
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BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
|
|||
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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|||
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MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Acknowledgement
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|||
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Funding for the RFC Editor function is currently provided by the
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Internet Society.
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Hoffman & Blanchet Standards Track [Page 7]
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