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IETF RFC 8553



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Internet Engineering Task Force (IETF)                        D. Crocker
Request for Comments: 8553                   Brandenburg InternetWorking
BCP: 222                                                      March 2019
Updates: 2782, 3263, 3529, 3620, 3832,
         3887, 3958, 4120, 4227, 4386,
         4387, 4976, 5026, 5328, 5389,
         5415, 5518, 5555, 5617, 5679,
         5766, 5780, 5804, 5864, 5928,
         6120, 6186, 6376, 6733, 6763,
         7208, 7489, 8145
Category: Best Current Practice 
ISSN: 2070-1721


                         DNS AttrLeaf Changes:
         Fixing Specifications That Use Underscored Node Names

 Abstract

   Using an underscore for a prefix creates a space for constrained
   interoperation of resource records.  Original uses of an underscore
   character as a domain node name prefix were specified without the
   benefit of an IANA registry.  This produced an entirely uncoordinated
   set of name-creation activities, all drawing from the same namespace.
   A registry for these names has now been defined by RFC 8552.
   However, the existing specifications that use underscored naming need
   to be modified in order to be in line with the new registry.  This
   document specifies those changes.  The changes preserve existing
   software and operational practice, while adapting the specifications
   for those practices to the newer underscore registry model.

 Status of This Memo

   This memo documents an Internet Best Current Practice.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   BCPs is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/RFC 8553.







Crocker                   Best Current Practice              PAGE 1 top


RFC 8553 DNS AttrLeaf Fix March 2019 Copyright Notice Copyright (c) 2019 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 Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Underscored RRset Use in Specifications . . . . . . . . . . . 3 2.1. TXT RRset . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. SRV RRset . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. URI RRset . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Underscored Template Specifications . . . . . . . . . . . . . 7 3.1. SRV Specification Changes . . . . . . . . . . . . . . . . 7 3.2. URI Specification Changes . . . . . . . . . . . . . . . . 8 3.3. DNSSEC Signaling Specification Changes . . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.1. Normative References . . . . . . . . . . . . . . . . . . 11 6.2. Informative References . . . . . . . . . . . . . . . . . 12 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 15 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15 1. Introduction Original uses of an underscore character as a domain node name [RFC 1035] prefix, which creates a space for constrained interpretation of resource records, were specified without the benefit of an IANA registry [IANA-reg]. This produced an entirely uncoordinated set of name-creation activities, all drawing from the same namespace. A registry has now been defined (see Section 4 of [RFC 8552]); the RFC that defined it discusses the background for the use of underscored domain names [RFC 8552]. Crocker Best Current Practice PAGE 2 top

RFC 8553 DNS AttrLeaf Fix March 2019 The basic model for underscored name registration, as specified in [RFC 8552], is to have each registry entry be unique in terms of the combination of a resource record type and a "global" (highest-level) underscored node name; that is, the node name beginning with an underscore that is the closest to the DNS root. The specifications describing the existing uses of underscored naming do not reflect the existence of this integrated registry. For the new reader or the new editor of one of those documents, there is currently nothing signaling that the underscored name(s) defined in the document are now processed through an IANA registry. This document remedies that, by marking such a published document with an update that indicates the nature of the change. Further, the documents that define the SRV [RFC 2782] and URI [RFC 7553] DNS resource records provide a meta-template for underscored name assignments, partially based on separate registries [RFC 6335]. For the portion that selects the global (highest-level) underscored node name, this perpetuates uncoordinated assignment activities by separate technical specifications, out of the same namespace. This document remedies that by providing detail for revisions to the SRV and URI specifications to bring their use in line with the single, integrated "Underscored and Globally Scoped DNS Node Names" registry. The result of these changes preserves existing software and operations practices while adapting the technical specifications to the newer underscore registry model. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC 2119] [RFC 8174] when, and only when, they appear in all capitals, as shown here. 2. Underscored RRset Use in Specifications The use of underscored node names is specific to each RR TYPE that is being scoped. Each name defines a place but does not define the rules for what appears underneath that place, either as additional underscored naming or as a leaf node with resource records. Details for those rules are provided by specifications for individual RR TYPEs. The sections below describe the way that existing underscored names are used with the RR TYPEs that they name. Crocker Best Current Practice PAGE 3 top

RFC 8553 DNS AttrLeaf Fix March 2019 2.1. TXT RRset NOTE - Documents falling into this category include: [RFC 5518], [RFC 5617], [RFC 6120], [RFC 6376], [RFC 6763], [RFC 7208], and [RFC 7489]. This section provides a generic approach for changes to existing specifications that define straightforward use of underscored node names when scoping the use of a TXT RRset. The approach provides the information needed for adapting such specifications to the use of the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552]. Hence, the approach is meant both as an update to these existing specifications and as guidance for changes when those documents are revised. For any document that specifies the use of a TXT RRset under one or more underscored names, the global node name is expected to be registered in the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552]. An effort has been made to locate existing documents that do this, to register the global underscored node names, and to list them in the initial set of names added to the registry. If a public specification defines use of a TXT RRset and calls for the use of an underscored node name, here is a template of suggested text for registering the global underscored node name -- the one closest to the root -- that can be used through the IANA Considerations section of the specification: "Per [RFC 8552], please add the following entry to the "Underscored and Globally Scoped DNS Node Names" registry:" +--------+----------------+-----------------------------------------+ | RR | _NODE NAME | Reference | | Type | | | +--------+----------------+-----------------------------------------+ | TXT | _{DNS node | {citation for the document making the | | | name} | addition} | +--------+----------------+-----------------------------------------+ Table 1: Entry for the "Underscored and Globally Scoped DNS Node Names" Registry for TXT RR Use Crocker Best Current Practice PAGE 4 top

RFC 8553 DNS AttrLeaf Fix March 2019 2.2. SRV RRset NOTE - Documents falling into this category include: [RFC 3263], [RFC 3529], [RFC 3620], [RFC 3832], [RFC 3887], [RFC 3958], [RFC 4120], [RFC 4227], [RFC 4386], [RFC 4387], [RFC 4976], [RFC 5026], [RFC 5328], [RFC 5389], [RFC 5415], [RFC 5555], [RFC 5679], [RFC 5766], [RFC 5780], [RFC 5804], [RFC 5864], [RFC 5928], and [RFC 6186]. Specification of the SRV resource record [RFC 2782] provides a template for use of underscored node names. The global node name is characterized as referencing the 'protocol' that is associated with SRV RRset usage. This section provides a generic approach for changes to existing specifications that define the use of an SRV RRset. The approach provides the information needed for adapting such specifications to the use of the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552]. Hence, the approach is meant both as an update to these existing specifications and as guidance for changes when those documents are revised. For any document that specifies the use of an SRV RRset, the global ('protocol') underscored node name is expected to be registered in the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552]. An effort has been made to locate existing documents that do this, to register the global underscored node names, and to list them in the initial set of names added to the registry. If a public specification defines use of an SRV RRset and calls for the use of an underscored node name, here is a template of suggested text for registering the global underscored node name -- the one closest to the root -- that can be used through the IANA Considerations section of the specification: Crocker Best Current Practice PAGE 5 top

RFC 8553 DNS AttrLeaf Fix March 2019 "Per [RFC 8552], please add the following entry to the "Underscored and Globally Scoped DNS Node Names" registry: +--------+----------------------+-----------------------------------+ | RR | _NODE NAME | Reference | | Type | | | +--------+----------------------+-----------------------------------+ | SRV | _{DNS 'protocol' | {citation for the document making | | | node name} | the addition} | +--------+----------------------+-----------------------------------+ Table 2: Entry for the "Underscored and Globally Scoped DNS Node Names" Registry for SRV RR Use 2.3. URI RRset Specification of the URI resource record [RFC 7553] provides a template for use of underscored node names. The global node name is characterized as naming the 'protocol' that is associated with URI RR usage or by reversing an Enumservice sequence [RFC 6117]. This section provides a generic approach for changes to existing specifications that define use of a URI RRset. The approach provides the information needed for adapting such specifications to the use of the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552]. Hence, the approach is meant both as an update to these existing specifications and as guidance for changes when those documents are revised. For any document that specifies the use of a URI RRset, the global ('protocol' or highest-level Enumservice) underscored node name is expected to be registered in the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552]. An effort has been made to locate existing documents that do this, to register the global underscored node names, and to list them in the initial set of names added to the registry. If a public specification defines use of a URI RRset and calls for the use of an underscored node name, here is a template of suggested text for registering the global underscored node name -- the one closest to the root -- that can be used through the IANA Considerations section of the specification: Crocker Best Current Practice PAGE 6 top

RFC 8553 DNS AttrLeaf Fix March 2019 "Per [RFC 8552], please add the following entry to the "Underscored and Globally Scoped DNS Node Names" registry: +-------+----------------------------+------------------------------+ | RR | _NODE NAME | Reference | | Type | | | +-------+----------------------------+------------------------------+ | URI | _{DNS 'protocol' or | {citation for the document | | | Enumservice node name} | making the addition} | +-------+----------------------------+------------------------------+ Table 3: Entry for the "Underscored and Globally Scoped DNS Node Names" Registry for URI RR Use 3. Underscored Template Specifications 3.1. SRV Specification Changes The specification for a domain name, under which an SRV resource record [RFC 2782] appears, provides a template for use of underscored node names. The global underscored node name is characterized as indicating the 'protocol' that is associated with SRV RR usage. The text of [RFC 2782] is changed as described below. In addition, note that a normative reference to RFC 8552 is added to the References section of RFC 2782. OLD: The format of the SRV RR Here is the format of the SRV RR, whose DNS type code is 33: _Service._Proto.Name TTL Class SRV Priority Weight Port Target ... Proto The symbolic name of the desired protocol, with an underscore (_) prepended to prevent collisions with DNS labels that occur in nature. _TCP and _UDP are at present the most useful values for this field, though any name defined by Assigned Numbers or locally may be used (as for Service). The Proto is case insensitive. Crocker Best Current Practice PAGE 7 top

RFC 8553 DNS AttrLeaf Fix March 2019 NEW: The format of the SRV RR Here is the format of the SRV RR, whose DNS type code is 33: "_Service._Proto.Name TTL Class SRV Priority Weight Port Target" _..._ Proto The symbolic name of the desired protocol with an underscore (e.g., "_name") prepended to prevent collisions with DNS labels that occur in nature. _TCP and _UDP are at present the most useful values for this field. The Proto is case insensitive. The SRV RRset 'protocol' (global) underscored node name SHOULD be registered in the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552]. 3.2. URI Specification Changes Specification for the domain name (under which a URI resource record [RFC 7553] occurs) is similar to that for the SRV resource record [RFC 2782], although the text refers only to 'service' name, rather than distinguishing 'service' from 'protocol'. Further, the URI RR specification permits alternative underscored naming schemes: One matches what is used for SRV, with the global underscored node name called 'protocol'. The other is based on a reversing of an Enumservice [RFC 6117] sequence. Text of [RFC 7553] is changed as described below. In addition, a normative reference to RFC 8552 is added to the References section of RFC 7553. Crocker Best Current Practice PAGE 8 top

RFC 8553 DNS AttrLeaf Fix March 2019 OLD: 4.1. Owner Name, Class, and Type The URI owner name is subject to special conventions. Just like the SRV RR [RFC 2782], the URI RR has service information encoded in its owner name. In order to encode the service for a specific owner name, one uses service parameters. Valid service parameters are those registered by IANA in the "Service Name and Transport Protocol Port Number Registry" [RFC 6335] or as "Enumservice --- Registrations [RFC 6117]. The Enumservice Registration parameters are reversed (i.e., subtype(s) before type), prepended with an underscore (_), and prepended to the owner name in separate labels. The underscore is prepended to the service parameters to avoid collisions with DNS labels that occur in nature, and the order is reversed to make it possible to do delegations, if needed, to different zones (and therefore providers of DNS). For example, suppose we are looking for the URI for a service with ENUM Service Parameter "A:B:C" for host example.com. Then we would query for (QNAME,QTYPE)=("_C._B._A.example.com","URI"). As another example, suppose we are looking for the URI for a service with Service Name "A" and Transport Protocol "B" for host example.com. Then we would query for (QNAME,QTYPE)=("_A._B.example.com","URI"). NEW: 4.1. Owner Name, Class, and Type The URI owner name is subject to special conventions. As for the SRV RRset [RFC 2782], the URI RRset global (highest- level) underscored node name SHOULD be registered in the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552]. Just like the SRV RRset, the URI RRset has service information encoded in its owner name. In order to encode the service for a specific owner name, one uses service parameters. Valid service parameters are: + Those registered by IANA in the "Service Name and Transport Protocol Port Number Registry" [RFC 6335]. The underscore is prepended to the service parameters to avoid collisions with Crocker Best Current Practice PAGE 9 top

RFC 8553 DNS AttrLeaf Fix March 2019 DNS labels that occur in nature, and the order is reversed to make it possible to do delegations, if needed, to different zones (and therefore providers of DNS). + Those listed in "Enumservice Registrations" [RFC 6117]. The Enumservice Registration parameters are reversed (i.e., subtype(s) before type), prepended with an underscore (e.g., "_name"), and prepended to the owner name in separate labels. The highest-level (global) underscored Enumservice name becomes the global name per RFC 8552 to register. For example, suppose we are looking for the URI for a service with ENUM Service Parameter "A:B:C" for host example.com. Then we would query for (QNAME,QTYPE)=("_C._B._A.example.com","URI"). As another example, suppose we are looking for the URI for a service with Service Name "A" and Transport Protocol "B" for host example.com. Then we would query for (QNAME,QTYPE)=("_A._B.example.com","URI"). 3.3. DNSSEC Signaling Specification Changes "Signaling Trust Anchor Knowledge in DNS Security Extensions (DNSSEC)" [RFC 8145] defines a use of DNS node names that effectively consumes all names beginning with the string "_ta-" when using the NULL RR in the query. Text of Section 5.1, "Query Format", of RFC 8145 is changed as described below. In addition, a normative reference to RFC 8552 is added to the References section of RFC 8145. OLD: For example, a validating DNS resolver ... QNAME=_ta-4444. NEW: For example, a validating DNS resolver ... "QNAME=_ta-4444". Under the NULL RR, an entry is registered in the IANA "Underscored and Globally Scoped DNS Node Names" registry [RFC 8552] for all node names beginning with "_ta-". Crocker Best Current Practice PAGE 10 top

RFC 8553 DNS AttrLeaf Fix March 2019 4. IANA Considerations Although this document makes reference to IANA registries, it introduces no new IANA registries or procedures. 5. Security Considerations This memo raises no security issues. 6. References 6.1. Normative References [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC 2119, March 1997, <https://www.rfc-editor.org/info/RFC 2119>. [RFC 6117] Hoeneisen, B., Mayrhofer, A., and J. Livingood, "IANA Registration of Enumservices: Guide, Template, and IANA Considerations", RFC 6117, DOI 10.17487/RFC 6117, March 2011, <https://www.rfc-editor.org/info/RFC 6117>. [RFC 6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. Cheshire, "Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry", BCP 165, RFC 6335, DOI 10.17487/RFC 6335, August 2011, <https://www.rfc-editor.org/info/RFC 6335>. [RFC 7553] Faltstrom, P. and O. Kolkman, "The Uniform Resource Identifier (URI) DNS Resource Record", RFC 7553, DOI 10.17487/RFC 7553, June 2015, <https://www.rfc-editor.org/info/RFC 7553>. [RFC 8145] Wessels, D., Kumari, W., and P. Hoffman, "Signaling Trust Anchor Knowledge in DNS Security Extensions (DNSSEC)", RFC 8145, DOI 10.17487/RFC 8145, April 2017, <https://www.rfc-editor.org/info/RFC 8145>. [RFC 8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC 8174, May 2017, <https://www.rfc-editor.org/info/RFC 8174>. [RFC 8552] Crocker, D., "Scoped Interpretation of DNS Resource Records through "Underscored" Naming of Attribute Leaves", RFC 8552, DOI 10.17487/RFC 8552, March 2019, <https://www.rfc-editor.org/info/RFC 8552>. Crocker Best Current Practice PAGE 11 top

RFC 8553 DNS AttrLeaf Fix March 2019 6.2. Informative References [IANA-reg] IANA, "Protocol Registries", <https://www.iana.org/protocols>. [RFC 1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC 1035, November 1987, <https://www.rfc-editor.org/info/RFC 1035>. [RFC 2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, DOI 10.17487/RFC 2782, February 2000, <https://www.rfc-editor.org/info/RFC 2782>. [RFC 3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol (SIP): Locating SIP Servers", RFC 3263, DOI 10.17487/RFC 3263, June 2002, <https://www.rfc-editor.org/info/RFC 3263>. [RFC 3529] Harold, W., "Using Extensible Markup Language-Remote Procedure Calling (XML-RPC) in Blocks Extensible Exchange Protocol (BEEP)", RFC 3529, DOI 10.17487/RFC 3529, April 2003, <https://www.rfc-editor.org/info/RFC 3529>. [RFC 3620] New, D., "The TUNNEL Profile", RFC 3620, DOI 10.17487/RFC 3620, October 2003, <https://www.rfc-editor.org/info/RFC 3620>. [RFC 3832] Zhao, W., Schulzrinne, H., Guttman, E., Bisdikian, C., and W. Jerome, "Remote Service Discovery in the Service Location Protocol (SLP) via DNS SRV", RFC 3832, DOI 10.17487/RFC 3832, July 2004, <https://www.rfc-editor.org/info/RFC 3832>. [RFC 3887] Hansen, T., "Message Tracking Query Protocol", RFC 3887, DOI 10.17487/RFC 3887, September 2004, <https://www.rfc-editor.org/info/RFC 3887>. [RFC 3958] Daigle, L. and A. Newton, "Domain-Based Application Service Location Using SRV RRs and the Dynamic Delegation Discovery Service (DDDS)", RFC 3958, DOI 10.17487/RFC 3958, January 2005, <https://www.rfc-editor.org/info/RFC 3958>. [RFC 4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The Kerberos Network Authentication Service (V5)", RFC 4120, DOI 10.17487/RFC 4120, July 2005, <https://www.rfc-editor.org/info/RFC 4120>. Crocker Best Current Practice PAGE 12 top

RFC 8553 DNS AttrLeaf Fix March 2019 [RFC 4227] O'Tuathail, E. and M. Rose, "Using the Simple Object Access Protocol (SOAP) in Blocks Extensible Exchange Protocol (BEEP)", RFC 4227, DOI 10.17487/RFC 4227, January 2006, <https://www.rfc-editor.org/info/RFC 4227>. [RFC 4386] Boeyen, S. and P. Hallam-Baker, "Internet X.509 Public Key Infrastructure Repository Locator Service", RFC 4386, DOI 10.17487/RFC 4386, February 2006, <https://www.rfc-editor.org/info/RFC 4386>. [RFC 4387] Gutmann, P., Ed., "Internet X.509 Public Key Infrastructure Operational Protocols: Certificate Store Access via HTTP", RFC 4387, DOI 10.17487/RFC 4387, February 2006, <https://www.rfc-editor.org/info/RFC 4387>. [RFC 4976] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions for the Message Sessions Relay Protocol (MSRP)", RFC 4976, DOI 10.17487/RFC 4976, September 2007, <https://www.rfc-editor.org/info/RFC 4976>. [RFC 5026] Giaretta, G., Ed., Kempf, J., and V. Devarapalli, Ed., "Mobile IPv6 Bootstrapping in Split Scenario", RFC 5026, DOI 10.17487/RFC 5026, October 2007, <https://www.rfc-editor.org/info/RFC 5026>. [RFC 5328] Adolf, A. and P. MacAvock, "A Uniform Resource Name (URN) Namespace for the Digital Video Broadcasting Project (DVB)", RFC 5328, DOI 10.17487/RFC 5328, September 2008, <https://www.rfc-editor.org/info/RFC 5328>. [RFC 5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, "Session Traversal Utilities for NAT (STUN)", RFC 5389, DOI 10.17487/RFC 5389, October 2008, <https://www.rfc-editor.org/info/RFC 5389>. [RFC 5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, Ed., "Control And Provisioning of Wireless Access Points (CAPWAP) Protocol Specification", RFC 5415, DOI 10.17487/RFC 5415, March 2009, <https://www.rfc-editor.org/info/RFC 5415>. [RFC 5518] Hoffman, P., Levine, J., and A. Hathcock, "Vouch By Reference", RFC 5518, DOI 10.17487/RFC 5518, April 2009, <https://www.rfc-editor.org/info/RFC 5518>. [RFC 5555] Soliman, H., Ed., "Mobile IPv6 Support for Dual Stack Hosts and Routers", RFC 5555, DOI 10.17487/RFC 5555, June 2009, <https://www.rfc-editor.org/info/RFC 5555>. Crocker Best Current Practice PAGE 13 top

RFC 8553 DNS AttrLeaf Fix March 2019 [RFC 5617] Allman, E., Fenton, J., Delany, M., and J. Levine, "DomainKeys Identified Mail (DKIM) Author Domain Signing Practices (ADSP)", RFC 5617, DOI 10.17487/RFC 5617, August 2009, <https://www.rfc-editor.org/info/RFC 5617>. [RFC 5679] Bajko, G., "Locating IEEE 802.21 Mobility Services Using DNS", RFC 5679, DOI 10.17487/RFC 5679, December 2009, <https://www.rfc-editor.org/info/RFC 5679>. [RFC 5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)", RFC 5766, DOI 10.17487/RFC 5766, April 2010, <https://www.rfc-editor.org/info/RFC 5766>. [RFC 5780] MacDonald, D. and B. Lowekamp, "NAT Behavior Discovery Using Session Traversal Utilities for NAT (STUN)", RFC 5780, DOI 10.17487/RFC 5780, May 2010, <https://www.rfc-editor.org/info/RFC 5780>. [RFC 5804] Melnikov, A., Ed. and T. Martin, "A Protocol for Remotely Managing Sieve Scripts", RFC 5804, DOI 10.17487/RFC 5804, July 2010, <https://www.rfc-editor.org/info/RFC 5804>. [RFC 5864] Allbery, R., "DNS SRV Resource Records for AFS", RFC 5864, DOI 10.17487/RFC 5864, April 2010, <https://www.rfc-editor.org/info/RFC 5864>. [RFC 5928] Petit-Huguenin, M., "Traversal Using Relays around NAT (TURN) Resolution Mechanism", RFC 5928, DOI 10.17487/RFC 5928, August 2010, <https://www.rfc-editor.org/info/RFC 5928>. [RFC 6120] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC 6120, March 2011, <https://www.rfc-editor.org/info/RFC 6120>. [RFC 6186] Daboo, C., "Use of SRV Records for Locating Email Submission/Access Services", RFC 6186, DOI 10.17487/RFC 6186, March 2011, <https://www.rfc-editor.org/info/RFC 6186>. [RFC 6376] Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed., "DomainKeys Identified Mail (DKIM) Signatures", STD 76, RFC 6376, DOI 10.17487/RFC 6376, September 2011, <https://www.rfc-editor.org/info/RFC 6376>. Crocker Best Current Practice PAGE 14 top

RFC 8553 DNS AttrLeaf Fix March 2019 [RFC 6763] Cheshire, S. and M. Krochmal, "DNS-Based Service Discovery", RFC 6763, DOI 10.17487/RFC 6763, February 2013, <https://www.rfc-editor.org/info/RFC 6763>. [RFC 7208] Kitterman, S., "Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1", RFC 7208, DOI 10.17487/RFC 7208, April 2014, <https://www.rfc-editor.org/info/RFC 7208>. [RFC 7489] Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based Message Authentication, Reporting, and Conformance (DMARC)", RFC 7489, DOI 10.17487/RFC 7489, March 2015, <https://www.rfc-editor.org/info/RFC 7489>. Acknowledgements Thanks go to Bill Fenner, Dick Franks, Tony Hansen, Peter Koch, Olaf Kolkman, and Andrew Sullivan for diligent review of the (much) earlier draft versions. For the later enhancements, thanks to Tim Wicinski, John Levine, Bob Harold, Joel Jaeggli, Ondrej Sury, and Paul Wouters. Special thanks to Ray Bellis for his persistent encouragement to continue this effort, as well as the suggestion for an essential simplification to the registration model. Author's Address Dave Crocker Brandenburg InternetWorking 675 Spruce Dr. Sunnyvale, CA 94086 United States of America Phone: +1.408.246.8253 Email: dcrocker@bbiw.net URI: http://bbiw.net/ Crocker Best Current Practice PAGE 15 top

RFC TOTAL SIZE: 33458 bytes PUBLICATION DATE: Thursday, March 21st, 2019 LEGAL RIGHTS: The IETF Trust (see BCP 78)


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© RFC 8553: The IETF Trust, Thursday, March 21st, 2019
© the RFC Archive, 2024, RFC-Archive.org
Maintainer: J. Tunnissen

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