Internet DRAFT - draft-crocker-dns-attrleaf
draft-crocker-dns-attrleaf
Network Working Group D. Crocker
Internet-Draft Brandenburg InternetWorking
Updates: lots of rfc, to be listed (if November 14, 2015
approved)
Intended status: Best Current Practice
Expires: May 17, 2016
DNS Scoped Data Through '_Underscore' Attribute Leaves
draft-crocker-dns-attrleaf-07
Abstract
Historically, any DNS RR may occur for any domain name. Recent
additions have defined DNS leaf nodes that contain a reserved node
name, beginning with an underscore. The underscore construct is used
to define a semantic scope for DNS records that are associated with
the parent domain. This specification explores the nature of this
DNS usage and defines the "underscore names" registry with IANA.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 17, 2016.
Copyright Notice
Copyright (c) 2015 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
(http://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
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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. Scaling Benefits and TXT and SRV Resource Records . . . . . . 3
3. Underscore DNS Registry Function . . . . . . . . . . . . . . 4
4. DNS Underscore Registry Definition . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Related and Updated Registries . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. References -- Informative . . . . . . . . . . . . . . . . 9
8.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The core DNS technical specifications assign no semantics to domain
names or their parts, and no constraints upon which resource records
(RRs) are permitted to be associated with particular names. Over
time, some leaf node names, such as "www" and "ftp" have come to
imply support for particular services, but this is a matter of
operational convention, rather than defined protocol semantics .
This freedom in the basic technology has permitted a wide range of
administrative and semantic policies to be used -- in parallel. Data
semantics have been limited to the specification of particular
resource records, on the expectation that new ones would be added as
needed.
As an alternative to defining new RRs, some DNS service enhancements
have specified a restricted scope for the occurrence of particular
resource records. That scope is a leaf node, within which the uses
of specific resource records can be formally defined and constrained.
The leaf has a distinguished naming convention: It uses a reserved
DNS node name that begins with an underscore ("_"). Because a "host"
domain name is not allowed to use the underscore character, this
distinguishes the name from all legal host names.[RFC1035]
Effectively, this convention creates a space for attributes that are
associated with the parent domain, one level up.
An established example is the SRV record [RFC2782] which generalizes
concepts long-used for email routing by the MX record
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[RFC0974][RFC2821]. The use of special DNS names has significant
benefits and detriments. Some of these are explored in [RFC5507].
[Comment]: The terms "resolution context" and "scoping rules" have
been suggested, in place of "semantic scope". In order to avoid
concern for matters of semantics, this specification uses the term
"scoping rules", to create a focus on the mechanics being defined,
rather than nuances of interpretation for the mechanism.
The scoping feature is particularly useful when generalized resource
records are used -- notably TXT and SRV. It provides efficient
separation of one use of them from another. Absent this separation,
an undifferentiated mass of these RRs is returned to the DNS client,
which then must parse through the internals of the records in the
hope of finding ones that are relevant; in some cases the results are
ambiguous, because the records do not adequately self-identify. With
underscore-based scoping, only the relevant RRs are returned.
This specification discusses the underscore "attribute" enhancement,
provides an explicit definition of it, and establishes an IANA
registry for the reserved names that begin with underscore. It
updates the many existing specifications that have defined underscore
names, in order to aggregate the references to a single IANA table.
Discussion Venue: Discussion about this draft is directed to the
apps-discuss@ietf.org [1] mailing list.
2. Scaling Benefits and TXT and SRV Resource Records
Some resource records are generic and support a variety of uses.
Each additional use defines its own rules and, possibly, its own
internal syntax and node-naming conventions to distinguish among
particular types. The TXT and SRV records are the notable examples.
Used freely, some of these approaches scale poorly, particularly when
the same RR can be present in the same leaf node, but with different
uses. An increasingly-popular approach, with excellent scaling
properties, uses an underscore-based name, at a defined place in the
DNS tree, so as to constrain to particular uses for particular RRs
farther down the branch using that name. This means that a direct
lookup produces only the desired records, at no greater cost than a
typical DNS lookup.
In the case of TXT records, different uses have developed largely
without coordination. One side-effect is that there is no
consistently distinguishable internal syntax for the record; even the
inefficiencies of internal inspection might not provide a reliable
means of distinguishing among the different uses. Underscore-based
names therefore define an administrative way of separating TXT
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records that might have different uses, but otherwise would have no
syntactic markers for distinguishing among them.
In the case of the SRV RR distinguishing among different types of use
was part of the design. [RFC2782] The SRV specification serves as a
template, defining an RR that might only be used for specific
applications when there is an additional specification. The template
definition includes reference to tables of names from which
underscore-names should be drawn. The set of <service> names is
defined in terms of other IANA tables, namely any table with symbolic
names. The other SRV naming field is <proto>, although its pool of
names is not explicitly defined.
3. Underscore DNS Registry Function
This specification creates a registry for DNS nodes names that begin
with an underscore and are used to define scope of use for specific
resource records (RR). A given name defines a specific, constrained
context for the use of such records. Within this scope, use of other
resource records that are not specified is permitted. The purpose of
the Underscore registry is to avoid collisions resulting from the use
of the same underscore-based name, for different applications.
Structurally, the registry is defined as a single, flat table of
names that begin with underscore. In some cases, such as for SRV, an
underscore name might be multi-part, as a sequence of underscore
names. Semantically, this is a hierarchical model and it is
theoretically reasonable to allow re-use of an underscore name in
different underscore contexts. That is, a subordinate name is
meaningful only within the scope of the first (parent) underscore
name. As such, they can be ignored by this global Underscore
registry. That is, the registry is for the definition of highest-
level underscore node name used.
+----------------------------+
| NAME |
+----------------------------+
| _service1 |
| _service2._protoB |
| _service3._protoB |
| _service3._protoC |
| _service4._protoD._useX |
| _protoE._region._authority |
+----------------------------+
Example of Underscore Names
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Only the left-most names are registered in the IANA table.
Definition and registration of the subordinate names is the
responsibility of the specification that creates the highest-level
(left-most) registry entry.
4. DNS Underscore Registry Definition
A registry entry contains:
Name: Specifies a textual name for a scoped portion of the DNS.
The name will usually be taken from the specification cited in
the "Purpose" column and is intended for use in discussions
about the entry.
DNS Label: Specifies a single underscore name that defines a
name reservation; this name is the "global" entry name for the
scoped resource records that are associated with that name.
Constraints: Specifies any restrictions on use of the name.
RR(s): Lists the RRs that are defined for use within this
scope.
References Lists specifications that define the records and their
use under this Name.
Purpose: Specifies the particular purpose/use for specific
RR(s), defined for use within the scope of the registered
underscore name.
5. IANA Considerations
Per [RFC2434], IANA is requested to establish a DNS Underscore Name
Registry, for DNS node names that begin with the underscore character
(_) and have been specified in any published RFC, or are documented
by a specification published by another standards organization. The
contents of each entry are defined in Section 4.
Initial entriess in the registry are:
{ Enhancement of this table to include all underscore name
reservations in effect at the time this document is published is
left as an exercise to the readers... /d }
+------------+--------------+-------+-----------+-------------------+
| NAME | LABEL | RR | REFERENCE | PURPOSE |
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+------------+--------------+-------+-----------+-------------------+
| SRV | _srv | SRV | [RFC2782] | SRV template |
| LDAP | _ldap | SRV | [RFC2782] | LDAP server |
| SIP | _sip | NAPTR | [RFC3263] | Locating SIP |
| | | | [RFC6011] | Servers and UA |
| | | | | configuration |
| SPF | _spf | TXT | [RFC4408] | Authorized IP |
| | | | | addresses for |
| | | | | sending mail |
| DKIM | _domainkey | TXT | [RFC4871] | Public key for |
| | | | | verifying DKIM |
| | | | | signature. |
| ADSP | _adsp. | TXT | [RFC5617] | Published DKIM |
| | | | | usage practices |
| PKI LDAP | _PKIXREP | SRV | [RFC4386] | PKI Repository |
| VBR | _vouch | TXT | [RFC5518] | Vouch-by- |
| | | | | refererence |
| | | | | domain assertion |
| DDDS | --???!-- | SRV | [RFC3404] | Mapping DDDS |
| | | | | query to DNS |
| | | | | records |
| SOAP BEEP | _soap-beep | SRV | [RFC4227] | SOAP over BEEP |
| | | | | lookup, when no |
| | | | | port specified |
| XMLRPC | _xmlrpc-beep | SRV | [RFC3529] | Resolve url for |
| BEEP | | | | XML-RPC using |
| | | | | BEEP |
| Diameter | _diameter | SRV | [RFC3588] | Diameter |
| | | | | rendezvous |
| Tunnel | _tunnel | SRV | [RFC3620] | Finding the |
| | | | | appropriate |
| | | | | address for |
| | | | | tunneling into a |
| | | | | particular domain |
| SLP | _slpda | SRV | [RFC3832] | Discovering |
| | | | | desired services |
| | | | | in given DNS |
| | | | | domains |
| IM | _im | SRV | [RFC3861] | Instant Messaging |
| | | | | address |
| | | | | resolution |
| Pres | _pres | SRV | [RFC3861] | Presence address |
| | | | | resolution |
| Msg Track | _mtqp | SRV | [RFC3887] | Assist in |
| | | | | determining the |
| | | | | path that a |
| | | | | particular |
| | | | | message has taken |
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| | | | | through a |
| | | | | messaging system |
| XMPP | _xmpp-client | SRV | [RFC6120] | XMPP client |
| Client | | | | lookup of server |
| XMPP | _xmpp-server | SRV | [RFC6120] | XMPP server- |
| Server | | | | server lookup |
| DDDS SRV | _??? | SRV | [RFC3958] | Map domain name, |
| | | (and | | application |
| | | NAPTR | | service name, and |
| | | ?) | | application |
| | | | | protocol |
| | | | | dynamically to |
| | | | | target server and |
| | | | | port |
| Kerberos | _kerberos | SRV | [RFC4120] | purpose |
| PKI | _pkixrep | SRV | [RFC4386] | Enables |
| | | | | certificate-using |
| | | | | systems to locate |
| | | | | PKI repositories |
| Certificat | _certificate | SRV | [RFC4387] | Obtain |
| es | s | | | certificates and |
| | | | | certificate |
| | | | | revocation lists |
| | | | | (CRLs) from PKI |
| | | | | repositories |
| PGP Key | pgpkeys | SRV | [RFC4387] | Obtain |
| Store | | | | certificates and |
| | | | | certificate |
| | | | | revocation lists |
| | | | | (CRLs) from PKI |
| | | | | repositories |
| MSRP Relay | _msrp | SRV | [RFC4976] | purpose |
| Locator | | | | |
| Mobile | _mip6 | SRV | [RFC5026] | Bootstrap Mobile |
| IPv6 | | | [RFC5555] | IPv6 Home Agent |
| Bootstrap | | | | information from |
| | | | | non-topological |
| | | | | information |
| Digital | _dvbservdsc | SRV | [RFC5328] | Discover non- |
| Video Broa | | | | default DVB entry |
| dcasting | | | | points addresses |
| CAPWAP AC | _capwap- | rrs | [RFC5415] | Discover the |
| | control | | | CAPWAP AC |
| | | | | address(es) |
| IM | _im | SRV | [RFC5509] | For resolving |
| | | | | Instant Messaging |
| | | | | and Presence |
| | | | | services with SIP |
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| Presence | _pres | SRV | [RFC5509] | For resolving |
| | | | | Instant Messaging |
| | | | | and Presence |
| | | | | services with SIP |
| IEEE | _mihis | NAPTR | [RFC5679] | Discovering |
| 802.21 | | , SRV | | servers that |
| Mobility | | | | provide IEEE |
| | | | | 802.21-defined |
| | | | | Mobility Services |
| STUN Clien | _stun | SRV | [RFC5389] | Find a STUN |
| t/Server | | | | server |
| TURN | _turn | SRV | [RFC5766] | Control the |
| | | | [RFC5928] | operation of a |
| | | | | relay to bypass |
| | | | | NAT |
| STUN NAT | _stun- | SRV | [RFC5780] | Discover the |
| Behavior | behavior | | | presence and |
| Discovery | | | | current behavior |
| | | | | of NATs and |
| | | | | firewalls between |
| | | | | the STUN client |
| | | | | and the STUN |
| | | | | server |
| Sieve | _sieve | SRV | [RFC5804] | Manage Sieve |
| Management | | | | scripts on a |
| | | | | remote server |
| AFS VLDB | _afs3-vlserv | SRV | [RFC5864] | Locate services |
| | er | | | for the AFS |
| | | | | distributed file |
| | | | | system |
| AFS PTS | _afs3-prserv | SRV | [RFC5864] | Locate services |
| | er | | | for the AFS |
| | | | | distributed file |
| | | | | system |
| Mail MSA | _submission | SRV | [RFC6186] | Locate email |
| Submission | | | | services |
| IMAP | _imap | SRV | [RFC6186] | Locate email |
| | | | | services |
| POP | _pop3 | SRV | [RFC6186] | Locate email |
| | | | | services |
| POP TLS | _pop3s | SRV | [RFC6186] | Locate email |
| | | | | services |
+------------+--------------+-------+-----------+-------------------+
Table 1: DNS Underscore SCOPE Name Registry (with initial values)
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6. Related and Updated Registries
This section needs to contained details specification of the
updates to existing underscore "registries", in order to have
those specifcations point to this new registry.
Numerous specifications have defined their own, independent
registries for use of underscore names. It is likely that adoption
of the proposed, integrated registry should render these piecemeal
registries obsolete
Registries that are candidates for replacement include:
Instant Messaging SRV Protocol Label Registry
Public Key Infrastructure using X.509 (PKIX) Parameters
Presence SRV Protocol Label Registry
7. Security Considerations
This memo raises no security issues.
8. References
8.1. Normative References
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 2434, October
1998.
8.2. References -- Informative
[RFC0974] Partridge, C., "Mail routing and the domain system",
RFC 974, January 1986.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001.
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[RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation
Protocol (SIP): Locating SIP Servers", RFC 3263, June
2002.
[RFC3404] MMealling, M., "Dynamic Delegation Discovery System (DDDS)
Part Four: The Uniform Resource Identifiers (URI)
Resolution Application", RFC 3404, October 2002.
[RFC3529] Harold, W., "Using Extensible Markup Language-Remote
Procedure Calling (XML-RPC) in Blocks Extensible Exchange
Protocol (BEEP)", RFC 3529, April 2003.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", September 2003.
[RFC3620] New, D., "The TUNNEL Profile", RFC 3620, October 2003.
[RFC3832] Columbia University, Columbia University, Sun
Microsystems, IBM, and IBM, "Remote Service Discovery in
the Service Location Protocol (SLP) via DNS SRV", July
2004.
[RFC3861] Peterson, J., "Address Resolution for Instant Messaging
and Presence", RFC 3861, August 2004.
[RFC3887] "Message Tracking Query Protocol", September 2007.
[RFC3958] Daigle, L. and A. Newton, "Domain-Based Application
Service Location Using SRV RRs and the Dynamic Delegation
Discovery Service (DDDS)", RFC 3958, January 2005.
[RFC4120] USC-ISI, MIT, MIT, and MIT, "The Kerberos Network
Authentication Service (V5)", RFC 4120, July 2005.
[RFC4227] O'Tuathail, E. and M. Rose, "Using the Simple Object
Access Protocol (SOAP) in Blocks Extensible Exchange
Protocol (BEEP)", RFC 4227, January 2006.
[RFC4386] Boeyen, S. and P. Hallam-Baker, "Internet X.509 Public Key
Infrastructure: Repository Locator Service", February
2006.
[RFC4387] Gutmann, P., Ed., "Internet X.509 Public Key
Infrastructure Operational Protocols: Certificate Store
Access via HTTP", RFC 4387, February 2006.
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[RFC4408] Wong, M. and W. Schlitt, "Sender Policy Framework (SPF)
for Authorizing Use of Domains in E-Mail, Version 1",
RFC 4408, April 2006.
[RFC4871] Allman, E., Callas, J., Delany, M., Libbey, M., Fenton,
J., and M. Thomas, "DomainKeys Identified Mail (DKIM)
Signatures", RFC 4871, May 2007.
[RFC4976] Jennings, C., Mahy, R., and Roach, "Relay Extensions for
the Message Session Relay Protocol (MSRP)", RFC 4976,
September 2007.
[RFC5026] Giaretta, G., Ed., Kempf, J., and V. Devarapalli, Ed.,
"Mobile IPv6 Bootstrapping in Split Scenario", RFC 5026,
October 2007.
[RFC5328] Adolf, A. and P. MacAvock, "A Uniform Resource Name (URN)
Namespace for the Digital Video Broadcasting Project
(DVB)", RFC 5328, September 2008.
[RFC5389] Rosenberg, , Mahy, , Matthews, , and Wing, "Session
Traversal Utilities for NAT (STUN)", RFC 5389, October
2008.
[RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control And Provisioning of Wireless Access Points
(CAPWAP) Protocol Specification", RFC 5415, March 2009.
[RFC5507] Faltstrom, P., Ed. and R. Austein, Ed., , RFC 5507, April
2009.
[RFC5509] Loreto, S., "Internet Assigned Numbers Authority (IANA)
Registration of Instant Messaging and Presence DNS SRV RRs
for the Session Initiation Protocol (SIP)", RFC 5509,
April 2009.
[RFC5518] Hoffman, P., Levine, J., and A. Hathcock, "Vouch By
Reference", RFC5 5518, April 2009.
[RFC5555] Soliman, H., Ed., "Mobile IPv6 Support for Dual Stack
Hosts and Routers", RFC 5555, June 2009.
[RFC5617] Sendmail, Inc., Cisco Systems, Inc., Yahoo! Inc., and
Taughannock Networks, "DomainKeys Identified Mail (DKIM)
Author Domain Signing Practices (ADSP)", August 2009.
[RFC5679] Bajko, G., "Locating IEEE 802.21 Mobility Services Using
DNS", RFC 5679, December 2009.
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[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766, April 2010.
[RFC5780] MacDonald, D. and B. Lowekamp, "NAT Behavior Discovery
Using Session Traversal Utilities for NAT (STUN)",
RFC 5780, May 2010.
[RFC5804] Melnikov, A., Ed. and T. Martin, "A Protocol for Remotely
Managing Sieve Scripts", RFC 5804, July 2010.
[RFC5864] Allbery, R., "NS SRV Resource Records for AFS", RFC 5864,
April 2010.
[RFC5928] Petit-Huguenin, M., "Traversal Using Relays around NAT
(TURN) Resolution Mechanism", RFC 5928, August 2010.
[RFC6011] Lawrence, S., Ed. and J. Elwell, "Session Initiation
Protocol (SIP) User Agent Configuration", RFC 6011,
October 2010.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
[RFC6186] Daboo, C., "Use of SRV Records for Locating Email
Submission/Access Services", RFC 6186, March 2011.
8.3. URIs
[1] mailto:we-need-a-list
Appendix A. Acknowledgements
Thanks go to Bill Fenner, Tony Hansen, Peter Koch, Olaf Kolkman, and
Andrew Sullivan for diligent review of the earlier drafts. Special
thanks to Ray Bellis for nearly 10 years of persistent encouragement
to pursue this document.
Author's Address
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Dave Crocker
Brandenburg InternetWorking
675 Spruce Dr.
Sunnyvale, CA 94086
USA
Phone: +1.408.246.8253
Email: dcrocker@bbiw.net
URI: http://bbiw.net/
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