draft-ietf-dane-srv-07.txt   draft-ietf-dane-srv-08.txt 
DNS-Based Authentication of Named Entities (DANE) T. Finch DNS-Based Authentication of Named Entities (DANE) T. Finch
Internet-Draft University of Cambridge Internet-Draft University of Cambridge
Intended status: Standards Track M. Miller Intended status: Standards Track M. Miller
Expires: January 24, 2015 Cisco Systems, Inc. Expires: April 24, 2015 Cisco Systems, Inc.
P. Saint-Andre P. Saint-Andre
&yet &yet
July 23, 2014 October 21, 2014
Using DNS-Based Authentication of Named Entities (DANE) TLSA Records Using DNS-Based Authentication of Named Entities (DANE) TLSA Records
with SRV Records with SRV Records
draft-ietf-dane-srv-07 draft-ietf-dane-srv-08
Abstract Abstract
The DANE specification (RFC 6698) describes how to use TLSA resource The DANE specification (RFC 6698) describes how to use TLSA resource
records in the DNS to associate a server's host name with its TLS records in the DNS to associate a server's host name with its TLS
certificate, where the association is secured with DNSSEC. However, certificate, where the association is secured with DNSSEC. However,
application protocols that use SRV records (RFC 2782) to indirectly application protocols that use SRV records (RFC 2782) to indirectly
name the target server host names for a service domain cannot apply name the target server host names for a service domain cannot apply
the rules from RFC 6698. Therefore this document provides guidelines the rules from RFC 6698. Therefore this document provides guidelines
that enable such protocols to locate and use TLSA records. that enable such protocols to locate and use TLSA records.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 24, 2015. This Internet-Draft will expire on April 24, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. DNS Checks . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. DNS Checks . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. SRV Query . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. SRV Query . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Address Queries . . . . . . . . . . . . . . . . . . . . . 4 3.2. Address Queries . . . . . . . . . . . . . . . . . . . . . 4
3.3. TLSA Queries . . . . . . . . . . . . . . . . . . . . . . 5 3.3. TLSA Queries . . . . . . . . . . . . . . . . . . . . . . 4
3.4. Impact on TLS Usage . . . . . . . . . . . . . . . . . . . 5 3.4. Impact on TLS Usage . . . . . . . . . . . . . . . . . . . 5
4. TLS Checks . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. TLS Checks . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. SRV Records Only . . . . . . . . . . . . . . . . . . . . 5 4.1. SRV Records Only . . . . . . . . . . . . . . . . . . . . 5
4.2. TLSA Records . . . . . . . . . . . . . . . . . . . . . . 6 4.2. TLSA Records . . . . . . . . . . . . . . . . . . . . . . 6
5. Guidance for Application Protocols . . . . . . . . . . . . . 7 5. Guidance for Protocol Authors . . . . . . . . . . . . . . . . 6
6. Guidance for Server Operators . . . . . . . . . . . . . . . . 7 6. Guidance for Server Operators . . . . . . . . . . . . . . . . 7
7. Internationalization Considerations . . . . . . . . . . . . . 8 7. Guidance for Application Developers . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. Internationalization Considerations . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9.1. Mixed Security Status . . . . . . . . . . . . . . . . . . 8 10. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9.2. A Service Domain Trusts its Servers . . . . . . . . . . . 8 10.1. Mixed Security Status . . . . . . . . . . . . . . . . . 8
9.3. Certificate Subject Name Matching . . . . . . . . . . . . 9 10.2. A Service Domain Trusts its Servers . . . . . . . . . . 8
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 10.3. Certificate Subject Name Matching . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . 9 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . 10 12.1. Normative References . . . . . . . . . . . . . . . . . . 9
12.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 11 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 11
A.1. IMAP . . . . . . . . . . . . . . . . . . . . . . . . . . 11 A.1. IMAP . . . . . . . . . . . . . . . . . . . . . . . . . . 11
A.2. XMPP . . . . . . . . . . . . . . . . . . . . . . . . . . 11 A.2. XMPP . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Appendix B. Rationale . . . . . . . . . . . . . . . . . . . . . 12 Appendix B. Rationale . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
The base DANE specification [RFC6698] describes how to use TLSA The base DANE specification [RFC6698] describes how to use TLSA
resource records in the DNS to associate a server's host name with resource records in the DNS to associate a server's host name with
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this memo are to be interpreted as described in "OPTIONAL" in this memo are to be interpreted as described in
[RFC2119]. [RFC2119].
This draft uses the definitions for "secure", "insecure", "bogus", This draft uses the definitions for "secure", "insecure", "bogus",
and "indeterminate" from [RFC4035]. This draft uses the acronyms and "indeterminate" from [RFC4035]. This draft uses the acronyms
from [RFC7218] for the values of TLSA fields where appropriate. from [RFC7218] for the values of TLSA fields where appropriate.
3. DNS Checks 3. DNS Checks
To expedite connection to the intended service, where possible the
queries described in the following sections SHOULD be performed in
parallel (this is similar to the "happy eyeballs" approach for IPv4
and IPv6 connections described in [RFC6555]).
3.1. SRV Query 3.1. SRV Query
When the client makes an SRV query, a successful result will When the client makes an SRV query, a successful result will
typically be a list of one or more SRV records (or possibly a chain typically be a list of one or more SRV records (or possibly a chain
of CNAME / DNAME aliases leading to such a list). of CNAME / DNAME aliases leading to such a list). Implementers need
to be aware that unsuccessful results can occur because of various
DNS-related errors; a helpful summary can be found in section 2.1 of
[I-D.ietf-dane-smtp-with-dane].
For this specification to apply, the entire DNS RRset that is For this specification to apply, the entire DNS RRset that is
returned MUST be "secure" according to DNSSSEC validation ([RFC4033] returned MUST be "secure" according to DNSSSEC validation ([RFC4033]
section 5). In the case of aliases, the whole chain of CNAME and section 5). In the case of aliases, the whole chain of CNAME and
DNAME RRsets MUST be secure as well. This corresponds to the AD bit DNAME RRsets MUST be secure as well. This corresponds to the AD bit
being set in the response(s); see [RFC4035] section 3.2.3. being set in the response(s); see [RFC4035] section 3.2.3.
If the the entire RRset is "insecure" or "indeterminate", this If the the entire RRset is "insecure", this protocol has not been
protocol has not been correctly deployed. The client SHOULD fall correctly deployed. The client SHOULD fall back to its non-DNSSEC,
back to its non-DNSSEC, non-DANE behavior (this corresponds to the AD non-DANE behavior (this corresponds to the AD bit being unset). If
bit being unset). If the entire RRset is "bogus", the client MUST the entire RRset is "bogus", the client MUST abort the attempt.
abort the attempt.
In the successful case, the client now has an authentic list of In the successful case, the client now has an authentic list of
target server host names with weight and priority values. It target server host names with weight and priority values. It
performs server ordering and selection using the weight and priority performs server ordering and selection using the weight and priority
values without regard to the presence or absence of DNSSEC or TLSA values without regard to the presence or absence of DNSSEC or TLSA
records. It also takes note of the DNSSEC validation status of the records. It also takes note of the DNSSEC validation status of the
SRV response for use when checking certificate names (see Section 4). SRV response for use when checking certificate names (see Section 4).
The client can now proceed to making address queries on the target The client can now proceed to making address queries on the target
server host names as described in the next section. server host names as described in the next section.
3.2. Address Queries 3.2. Address Queries
For each SRV target server host name, the client makes A / AAAA For each SRV target server host name, the client makes A and AAAA
queries, performs DNSSEC validation on the address (A, AAAA) queries, performs DNSSEC validation on the address (A or AAAA)
response, and continues as follows based on the results: response, and continues as follows based on the results:
o If the response is "secure" and usable, the client MUST perform a o If the response is "secure" and usable, the client MUST perform a
TLSA query for that target server host name as described in the TLSA query for that target server host name as described in the
next section. next section.
o If the response is "insecure", the client MUST NOT perform a TLSA o If the response is "insecure", the client MUST NOT perform a TLSA
query for that target server host name; the TLSA query will most query for that target server host name; the TLSA query will most
likely fail. likely fail.
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[RFC6698]. [RFC6698].
If the TLS server's certificate -- or the public key of the server's If the TLS server's certificate -- or the public key of the server's
certificate -- matches a usable TLSA record with Certificate Usage certificate -- matches a usable TLSA record with Certificate Usage
"DANE-EE", the client MUST consider the server to be authenticated. "DANE-EE", the client MUST consider the server to be authenticated.
Because the information in such a TLSA record supersedes the non-key Because the information in such a TLSA record supersedes the non-key
information in the certificate, all other [RFC5280] and [RFC6125] information in the certificate, all other [RFC5280] and [RFC6125]
authentication checks (e.g., reference identifier, key usage, authentication checks (e.g., reference identifier, key usage,
expiration, issuance) MUST be ignored or omitted. expiration, issuance) MUST be ignored or omitted.
5. Guidance for Application Protocols 5. Guidance for Protocol Authors
This document describes how to use DANE with application protocols in This document describes how to use DANE with application protocols in
which target servers are discovered via SRV records. Although this which target servers are discovered via SRV records. Although this
document attempts to provide generic guidance applying to all such document attempts to provide generic guidance applying to all such
protocols, additional documents for particular application protocols protocols, additional documents for particular application protocols
could cover related topics, such as: could cover related topics, such as:
o Fallback logic in the event that a client is unable to connect o Fallback logic in the event that a client is unable to connect
securely to a target server by following the procedures defined in securely to a target server by following the procedures defined in
this document. this document.
o How clients ought to behave if they do not support SRV lookups, or o How clients ought to behave if they do not support SRV lookups, or
if clients that support SRV lookups encounter service domains that if clients that support SRV lookups encounter service domains that
do not offer SRV records. do not offer SRV records.
o Whether the application protocol has a functional equivalent for o Whether the application protocol has a functional equivalent for
TLS SNI that is preferred within that protocol. TLS SNI that is preferred within that protocol.
o Use of SRV records with additional discovery technologies, such as
the use of both SRV records and NAPTR records [RFC3403] for
transport selection in the Session Initiation Protocol (SIP).
For example, [I-D.ietf-xmpp-dna] covers such topics for the For example, [I-D.ietf-xmpp-dna] covers such topics for the
Extensible Messaging and Presence Protocol (XMPP). Extensible Messaging and Presence Protocol (XMPP).
6. Guidance for Server Operators 6. Guidance for Server Operators
To conform to this specification, the published SRV records and To conform to this specification, the published SRV records and
subsequent address (A, AAAA) records MUST be secured with DNSSEC. subsequent address (A and AAAA) records MUST be secured with DNSSEC.
There SHOULD also be at least one TLSA record published that There SHOULD also be at least one TLSA record published that
authenticates the server's certificate. authenticates the server's certificate.
When using TLSA records with Certificate Usage "DANE-EE", it is not When using TLSA records with Certificate Usage "DANE-EE", it is not
necessary for the deployed certificate to contain an identifier for necessary for the deployed certificate to contain an identifier for
either the source domain or target server host name. However, either the source domain or target server host name. However,
servers that rely solely on validation using Certificate Usage "DANE- operators need to be aware that servers relying solely on validation
EE" TLSA records might prevent clients that do not support this using Certificate Usage "DANE-EE" TLSA records might prevent clients
specification from successfully connecting with TLS. that do not support this specification from successfully connecting
with TLS.
For TLSA records with Certificate Usage types other than "DANE-EE", For TLSA records with Certificate Usage types other than "DANE-EE",
the certificate(s) MUST contain an identifier that matches: the certificate(s) MUST contain an identifier that matches:
o the service domain name (the "source domain" in [RFC6125] terms, o the service domain name (the "source domain" in [RFC6125] terms,
which is the SRV query domain); and/or which is the SRV query domain); and/or
o the target server host name (the "derived domain" in [RFC6125] o the target server host name (the "derived domain" in [RFC6125]
terms, which is the SRV target). terms, which is the SRV target).
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"multi-tenanted environments") can implement the Transport Layer "multi-tenanted environments") can implement the Transport Layer
Security Server Name Indication (TLS SNI) [RFC6066] or its functional Security Server Name Indication (TLS SNI) [RFC6066] or its functional
equivalent to determine which certificate to offer. Clients that do equivalent to determine which certificate to offer. Clients that do
not support this specification will indicate a preference for the not support this specification will indicate a preference for the
service domain name, while clients that support this specification service domain name, while clients that support this specification
will indicate the target server host name. However, the server will indicate the target server host name. However, the server
determines what certificate to present in the TLS handshake; e.g., determines what certificate to present in the TLS handshake; e.g.,
the presented certificate might only authenticate the target server the presented certificate might only authenticate the target server
host name. host name.
7. Internationalization Considerations 7. Guidance for Application Developers
Developers of application clients that depend on DANE-SRV often would
like to prepare as quickly as possible for making a connection to the
intended service, thus reducing the wait time for end users. To make
this optimization possible, a DNS library might perform the SRV
queries, address queries, and TLSA queries in parallel (because a
TLSA record can be ignored if it turns out that the address record on
which it depends is not secure, performing the TLSA queries in
parallel with the SRV queries and address queries is not harmful from
a security perspective and can yield some operational benefits).
8. Internationalization Considerations
If any of the DNS queries are for an internationalized domain name, If any of the DNS queries are for an internationalized domain name,
then they need to use the A-label form [RFC5890]. then they need to use the A-label form [RFC5890].
8. IANA Considerations 9. IANA Considerations
No IANA action is required. No IANA action is required.
9. Security Considerations 10. Security Considerations
9.1. Mixed Security Status 10.1. Mixed Security Status
We do not specify that clients checking all of a service domain's We do not specify that clients checking all of a service domain's
target server host names are consistent in whether they have or do target server host names are consistent in whether they have or do
not have TLSA records. This is so that partial or incremental not have TLSA records. This is so that partial or incremental
deployment does not break the service. Different levels of deployment does not break the service. Different levels of
deployment are likely if a service domain has a third-party fallback deployment are likely if a service domain has a third-party fallback
server, for example. server, for example.
The SRV sorting rules are unchanged; in particular they have not been The SRV sorting rules are unchanged; in particular they have not been
altered in order to prioritize secure servers over insecure servers. altered in order to prioritize secure servers over insecure servers.
If a site wants to be secure it needs to deploy this protocol If a site wants to be secure it needs to deploy this protocol
completely; a partial deployment is not secure and we make no special completely; a partial deployment is not secure and we make no special
effort to support it. effort to support it.
9.2. A Service Domain Trusts its Servers 10.2. A Service Domain Trusts its Servers
By signing their zone with DNSSEC, service domain operators By signing their zone with DNSSEC, service domain operators
implicitly instruct their clients to check their server TLSA records. implicitly instruct their clients to check their server TLSA records.
This implies another point in the trust relationship between service This implies another point in the trust relationship between service
domain holders and their server operators. Most of the setup domain holders and their server operators. Most of the setup
requirements for this protocol fall on the server operator: requirements for this protocol fall on the server operator:
installing a TLS certificate with the correct name (where necessary), installing a TLS certificate with the correct name (where necessary),
and publishing a TLSA record for that certificate. If these are not and publishing a TLSA record for that certificate. If these are not
correct then connections from TLSA-aware clients might fail. correct then connections from TLSA-aware clients might fail.
9.3. Certificate Subject Name Matching 10.3. Certificate Subject Name Matching
Section 4 of the TLSA specification [RFC6698] leaves the details of Section 4 of the TLSA specification [RFC6698] leaves the details of
checking names in certificates to higher level application protocols, checking names in certificates to higher level application protocols,
though it suggests the use of [RFC6125]. though it suggests the use of [RFC6125].
Name checks are not necessary if the matching TLSA record is of Name checks are not necessary if the matching TLSA record is of
Certificate Usage "DANE-EE". Because such a record identifies the Certificate Usage "DANE-EE". Because such a record identifies the
specific certificate (or public key of the certificate), additional specific certificate (or public key of the certificate), additional
checks are superfluous and potentially conflicting. checks are superfluous and potentially conflicting.
Otherwise, while DNSSEC provides a secure binding between the server Otherwise, while DNSSEC provides a secure binding between the server
name and the TLSA record, and the TLSA record provides a binding to a name and the TLSA record, and the TLSA record provides a binding to a
certificate, this latter step can be indirect via a chain of certificate, this latter step can be indirect via a chain of
certificates. For example, a Certificate Usage "PKIX-TA" TLSA record certificates. For example, a Certificate Usage "PKIX-TA" TLSA record
only authenticates the CA that issued the certificate, and third only authenticates the CA that issued the certificate, and third
parties can obtain certificates from the same CA. Therefore, clients parties can obtain certificates from the same CA. Therefore, clients
need to check whether the server's certificate matches one of the need to check whether the server's certificate matches one of the
expected reference identifiers to ensure that the certificate was expected reference identifiers to ensure that the certificate was
issued by the CA to the server the client expects. issued by the CA to the server the client expects.
10. Acknowledgements 11. Acknowledgements
Thanks to Mark Andrews for arguing that authenticating the target Thanks to Mark Andrews for arguing that authenticating the target
server host name is the right thing, and that we ought to rely on server host name is the right thing, and that we ought to rely on
DNSSEC to secure the SRV lookup. Thanks to James Cloos, Viktor DNSSEC to secure the SRV lookup. Thanks to James Cloos, Viktor
Dukhovni, Ned Freed, Olafur Gudmundsson, Paul Hoffman, Phil Pennock, Dukhovni, Ned Freed, Olafur Gudmundsson, Paul Hoffman, Phil Pennock,
Hector Santos, Jonas Schneider, and Alessandro Vesely for helpful Hector Santos, Jonas Schneider, and Alessandro Vesely for helpful
suggestions. suggestions.
11. References 12. References
11.1. Normative References 12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782, specifying the location of services (DNS SRV)", RFC 2782,
February 2000. February 2000.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC Rose, "DNS Security Introduction and Requirements", RFC
skipping to change at page 10, line 40 skipping to change at page 10, line 40
Submission/Access Services", RFC 6186, March 2011. Submission/Access Services", RFC 6186, March 2011.
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication [RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS) of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, August 2012. Protocol: TLSA", RFC 6698, August 2012.
[RFC7218] Gudmundsson, O., "Adding Acronyms to Simplify [RFC7218] Gudmundsson, O., "Adding Acronyms to Simplify
Conversations about DNS-Based Authentication of Named Conversations about DNS-Based Authentication of Named
Entities (DANE)", RFC 7218, April 2014. Entities (DANE)", RFC 7218, April 2014.
11.2. Informative References 12.2. Informative References
[I-D.ietf-dane-smtp-with-dane] [I-D.ietf-dane-smtp-with-dane]
Dukhovni, V. and W. Hardaker, "SMTP security via Dukhovni, V. and W. Hardaker, "SMTP security via
opportunistic DANE TLS", draft-ietf-dane-smtp-with-dane-05 opportunistic DANE TLS", draft-ietf-dane-smtp-with-dane-05
(work in progress), February 2014. (work in progress), February 2014.
[I-D.ietf-xmpp-dna] [I-D.ietf-xmpp-dna]
Saint-Andre, P. and M. Miller, "Domain Name Associations Saint-Andre, P. and M. Miller, "Domain Name Associations
(DNA) in the Extensible Messaging and Presence Protocol (DNA) in the Extensible Messaging and Presence Protocol
(XMPP)", draft-ietf-xmpp-dna-05 (work in progress), (XMPP)", draft-ietf-xmpp-dna-05 (work in progress),
February 2014. February 2014.
[RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with [RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
Dual-Stack Hosts", RFC 6555, April 2012. Part Three: The Domain Name System (DNS) Database", RFC
3403, October 2002.
Appendix A. Examples Appendix A. Examples
In the following, most of the DNS resource data is elided for In the following, most of the DNS resource data is elided for
simplicity. simplicity.
A.1. IMAP A.1. IMAP
; mail domain ; mail domain
_imap._tcp.example.com. SRV 10 0 9143 imap.example.net. _imap._tcp.example.com. SRV 10 0 9143 imap.example.net.
skipping to change at page 13, line 40 skipping to change at page 13, line 40
Matthew Miller Matthew Miller
Cisco Systems, Inc. Cisco Systems, Inc.
1899 Wynkoop Street, Suite 600 1899 Wynkoop Street, Suite 600
Denver, CO 80202 Denver, CO 80202
USA USA
Email: mamille2@cisco.com Email: mamille2@cisco.com
Peter Saint-Andre Peter Saint-Andre
&yet &yet
P.O. Box 787
Parker, CO 80134
USA
Email: peter@andyet.com Email: peter@andyet.com
URI: https://andyet.com/
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