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284 lines
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284 lines
9.9 KiB
Plaintext
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Network Working Group K. Zeilenga
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Request for Comments: 4526 OpenLDAP Foundation
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Category: Standards Track June 2006
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Lightweight Directory Access Protocol (LDAP)
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Absolute True and False Filters
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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 (2006).
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Abstract
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This document extends the Lightweight Directory Access Protocol
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(LDAP) to support absolute True and False filters based upon similar
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capabilities found in X.500 directory systems. The document also
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extends the String Representation of LDAP Search Filters to support
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these filters.
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Table of Contents
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1. Background ......................................................1
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2. Absolute True and False Filters .................................2
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3. Security Considerations .........................................2
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4. IANA Considerations .............................................3
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5. References ......................................................3
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5.1. Normative References .......................................3
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5.2. Informative References .....................................3
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1. Background
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The X.500 Directory Access Protocol (DAP) [X.511] supports absolute
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True and False assertions. An 'and' filter with zero elements always
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evaluates to True. An 'or' filter with zero elements always
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evaluates to False. These filters are commonly used when requesting
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DSA-specific Entries (DSEs) that do not necessarily have
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'objectClass' attributes; that is, where "(objectClass=*)" may
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evaluate to False.
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Zeilenga Standards Track [Page 1]
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RFC 4526 LDAP Absolute True and False Filters June 2006
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Although LDAPv2 [RFC1777][RFC3494] placed no restriction on the
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number of elements in 'and' and 'or' filter sets, the LDAPv2 string
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representation [RFC1960][RFC3494] could not represent empty 'and' and
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'or' filter sets. Due to this, absolute True or False filters were
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(unfortunately) eliminated from LDAPv3 [RFC4510].
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This documents extends LDAPv3 to support absolute True and False
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assertions by allowing empty 'and' and 'or' in Search filters
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[RFC4511] and extends the filter string representation [RFC4515] to
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allow empty filter lists.
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It is noted that certain search operations, such as those used to
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retrieve subschema information [RFC4512], require use of particular
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filters. This document does not change these requirements.
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This feature is intended to allow a more direct mapping between DAP
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and LDAP (as needed to implement DAP-to-LDAP gateways).
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In this document, the key words "MUST", "MUST NOT", "REQUIRED",
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"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
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and "OPTIONAL" are to be interpreted as described in BCP 14
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[RFC2119].
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2. Absolute True and False Filters
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Implementations of this extension SHALL allow 'and' and 'or' choices
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with zero filter elements.
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An 'and' filter consisting of an empty set of filters SHALL evaluate
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to True. This filter is represented by the string "(&)".
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An 'or' filter consisting of an empty set of filters SHALL evaluate
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to False. This filter is represented by the string "(|)".
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Servers supporting this feature SHOULD publish the Object Identifier
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1.3.6.1.4.1.4203.1.5.3 as a value of the 'supportedFeatures'
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[RFC4512] attribute in the root DSE.
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Clients supporting this feature SHOULD NOT use the feature unless
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they know that the server supports it.
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3. Security Considerations
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The (re)introduction of absolute True and False filters is not
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believed to raise any new security considerations.
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Implementors of this (or any) LDAPv3 extension should be familiar
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with general LDAPv3 security considerations [RFC4510].
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Zeilenga Standards Track [Page 2]
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RFC 4526 LDAP Absolute True and False Filters June 2006
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4. IANA Considerations
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Registration of this feature has been completed by the IANA
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[RFC4520].
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Subject: Request for LDAP Protocol Mechanism Registration Object
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Identifier: 1.3.6.1.4.1.4203.1.5.3 Description: True/False filters
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Person & email address to contact for further information:
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Kurt Zeilenga <kurt@openldap.org> Usage: Feature Specification:
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RFC 4526 Author/Change Controller: IESG Comments: none
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This OID was assigned [ASSIGN] by OpenLDAP Foundation, under its
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IANA-assigned private enterprise allocation [PRIVATE], for use in
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this specification.
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5. References
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5.1. 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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[RFC4510] Zeilenga, K., Ed, "Lightweight Directory Access
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Protocol (LDAP): Technical Specification Road Map", RFC
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4510, June 2006.
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[RFC4511] Sermersheim, J., Ed., "Lightweight Directory Access
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Protocol (LDAP): The Protocol", RFC 4511, June 2006.
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[RFC4512] Zeilenga, K., "Lightweight Directory Access Protocol
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(LDAP): Directory Information Models", RFC 4512, June
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2006.
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[RFC4515] Smith, M., Ed. and T. Howes, "Lightweight Directory
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Access Protocol (LDAP): String Representation of Search
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Filters", RFC 4515, June 2006.
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5.2. Informative References
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[RFC1777] Yeong, W., Howes, T., and S. Kille, "Lightweight
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Directory Access Protocol", RFC 1777, March 1995.
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[RFC1960] Howes, T., "A String Representation of LDAP Search
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Filters", RFC 1960, June 1996.
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[RFC3494] Zeilenga, K., "Lightweight Directory Access Protocol
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version 2 (LDAPv2) to Historic Status", RFC 3494, March
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2003.
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Zeilenga Standards Track [Page 3]
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RFC 4526 LDAP Absolute True and False Filters June 2006
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[RFC4520] Zeilenga, K., "Internet Assigned Numbers Authority
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(IANA) Considerations for the Lightweight Directory
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Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006.
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[X.500] International Telecommunication Union -
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Telecommunication Standardization Sector, "The
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Directory -- Overview of concepts, models and
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services," X.500(1993) (also ISO/IEC 9594-1:1994).
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[X.501] International Telecommunication Union -
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Telecommunication Standardization Sector, "The
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Directory -- Models," X.501(1993) (also ISO/IEC 9594-
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2:1994).
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[X.511] International Telecommunication Union -
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Telecommunication Standardization Sector, "The
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Directory: Abstract Service Definition", X.511(1993)
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(also ISO/IEC 9594-3:1993).
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[ASSIGN] OpenLDAP Foundation, "OpenLDAP OID Delegations",
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http://www.openldap.org/foundation/oid-delegate.txt.
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[PRIVATE] IANA, "Private Enterprise Numbers",
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http://www.iana.org/assignments/enterprise-numbers.
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Author's Address
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Kurt D. Zeilenga
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OpenLDAP Foundation
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EMail: Kurt@OpenLDAP.org
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Zeilenga Standards Track [Page 4]
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RFC 4526 LDAP Absolute True and False Filters June 2006
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Full Copyright Statement
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Copyright (C) The Internet Society (2006).
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This document is subject to the rights, licenses and restrictions
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contained in BCP 78, and except as set forth therein, the authors
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retain all their rights.
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This document and the information contained herein are provided on an
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"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
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ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
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WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Intellectual Property
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The IETF takes no position regarding the validity or scope of any
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Intellectual Property Rights or other rights that might be claimed to
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pertain to the implementation or use of the technology described in
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this document or the extent to which any license under such rights
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might or might not be available; nor does it represent that it has
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made any independent effort to identify any such rights. Information
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on the procedures with respect to rights in RFC documents can be
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found in BCP 78 and BCP 79.
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Copies of IPR disclosures made to the IETF Secretariat and any
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assurances of licenses to be made available, or the result of an
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attempt made to obtain a general license or permission for the use of
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such proprietary rights by implementers or users of this
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specification can be obtained from the IETF on-line IPR repository at
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http://www.ietf.org/ipr.
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The IETF invites any interested party to bring to its attention any
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copyrights, patents or patent applications, or other proprietary
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rights that may cover technology that may be required to implement
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this standard. Please address the information to the IETF at
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ietf-ipr@ietf.org.
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Acknowledgement
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Funding for the RFC Editor function is provided by the IETF
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Administrative Support Activity (IASA).
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Zeilenga Standards Track [Page 5]
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