DNS Resolver Discovery Protocol (DRDP)
draft-mglt-add-rdp-01
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| Author | Daniel Migault | ||
| Last updated | 2020-03-24 | ||
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draft-mglt-add-rdp-01
add D. Migault
Internet-Draft Ericsson
Intended status: Informational March 24, 2020
Expires: September 25, 2020
DNS Resolver Discovery Protocol (DRDP)
draft-mglt-add-rdp-01
Abstract
This document describes the DNS Resolver Discovery Protocol (DRDP)
that enables a DNS client to discover various available local and
global resolving service. The discovery is primarily initiated by a
DNS client, but a resolver may also inform the DNS client other
resolving services are available and eventually preferred.
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 https://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 September 25, 2020.
Copyright Notice
Copyright (c) 2020 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.
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Table of Contents
1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. DRDP Requirements . . . . . . . . . . . . . . . . . . . . . . 3
5. DRDP outputs . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Resolving Service Identity . . . . . . . . . . . . . . . 4
5.2. DNS Transport related information . . . . . . . . . . . . 5
5.3. DNS Service related Information . . . . . . . . . . . . . 5
6. Architecture Overview . . . . . . . . . . . . . . . . . . . . 5
7. Domain Discovery with DRDP . . . . . . . . . . . . . . . . . 6
7.1. Global Domain . . . . . . . . . . . . . . . . . . . . . . 6
7.2. Local Domain . . . . . . . . . . . . . . . . . . . . . . 7
8. Resolving Service Discovery . . . . . . . . . . . . . . . . 8
8.1. Discovery of all service instances . . . . . . . . . . . 8
8.2. Discovery of specific service instances . . . . . . . . . 9
9. Resolver advertising other service sub type . . . . . . . . . 10
10. Migration to service sub types . . . . . . . . . . . . . . . 10
11. Security Considerations . . . . . . . . . . . . . . . . . . . 10
11.1. Use of protected channel is RECOMMENDED . . . . . . . . 11
11.2. DNSSEC is RECOMMENDED . . . . . . . . . . . . . . . . . 11
11.3. TLSA is RECOMMENDED . . . . . . . . . . . . . . . . . . 12
12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
15.1. Normative References . . . . . . . . . . . . . . . . . . 14
15.2. Informative References . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Requirements Notation
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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Introduction
A DNS client can proceed to DNS resolution using various resolving
services. These services can be local, global and can use a wide
range of DNS transport protocols such as, for example, standard DNS
[RFC1035], DNS over TLS[RFC7858] or DNS over HTTPS [RFC8484].
The purpose of the DNS Resolving service Protocol (DRDP) is to
discover these resolving services available to the DNS client so a
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selection process can be applied. The information returned by DRDP
typically includes information related to the identity of the
resolving service, the transport ( IP addresses, the transport
protocols, TLS parameters, HTTP version) as well as to
characteristics of the resolving service (filtering, associated
authoritative domains). The pieces of information can be extended to
meet future usage.
How the selection is performed is out of scope of this document.
3. Terminology
DNS client the client that sends DNS queries fro resolution. In
this document the DNS client designates also the end entity that
is collecting information about the available Resolving Services
and then proceed to the selection of a subset them. The selection
is processed according to the DNS client's policy.
Resolving Service designates a service that receives DNS queries
from a DNS client and resolves them. A Resolving Service is
implemented by one or multiple resolvers.
Resolver: A resolver designates the software or hardware handling the
DNS exchange. See [RFC7719] for more details.
DNS transport designates the necessary parameters a DNS client needs
to establish a session with a Resolving Service.
Resolving Domain a DNS domain that hosts one or multiple resolving
services.
4. DRDP Requirements
This section lists the DRDP requirements.
REQ 1: DRDP MAY be used by a DNS client (Do53, DoT, DoH, ...) to
discover resolving service or by a resolver to advertise other
resolving services are available.
REQ 2: DRDP MUST be able to list dynamically locally and globally
resolving services available to the DNS client.
The necessary inputs for the resolving service instances may be of
various form. Not all of them are expected to be in the scope of
DRDP and DRDP limits its scope to parameters that are inherent to the
resolving service. For example, an end user may simply willing to
know which DNS resolver provides the fastest resolution. Such inputs
are not inherent to a specific resolver and are out of scope of
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DRDP.Another example could be the activation of some services such as
parental protection.
REQ 3: DRDP MUST at least return DNS transport parameters associated
of the resolving services and MAY be extended with additional
parameters.
The selection of the resolving service MAY take various form between
fully automated to fully manual. This, in particularly includes
interaction with the end user on a subset of the selection parameters
as well as the ability for a resolving service operator to indicate a
preference toward a resolving service instance.
REQ 4: DRDP MUST return selection parameters in a standard format to
ease automation.
REQ 5: DRDP MUST return selection parameters that can be displayed to
an end user either as a simple notification of when user interaction
is involved in the selection process.
REQ 6: DRDP MUST enable a resolving service provider to indicate a
preference between multiple provided resolving services.
The resolving service selection MAY be performed over a subset of the
available resolvers as opposed as the full set of available
resolvers.
REQ 7: DRDP SHOULD be able to narrow down the discovery to a subset
of resolving services.
REQ 8: DRDP MUST provide authenticated information
REQ 9: DRDP deployment MUST NOT be disruptive for the legacy DNS
client or infrastructure and legacy client SHOULD be able to
incrementally include DRDP.
5. DRDP outputs
5.1. Resolving Service Identity
The identity of the resolving service is an important selection
parameter as it usually reflects the trust an end user puts into this
service. In addition, trust can hardly be inferred automatically and
is likely to require an interaction with the end user, unless
explicitly provided by the end user.
This document considers the resolver's FQDN resolver.example.com as
its identifier. example.com designates the resolver domain and
"resolver" represents hostname.
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a) The resolving domain is expected to be the part that will mostly
be used by the end user as a way to select trust as these are
expected to represent the brand or legal entity of the institution
the end user sends its data to. The resolving domain follows some
DNS encoding rules and as such may not be believed to be so user
friendly. Typically, it might be ericsson.com or ericsson which is
different from Ericsson (with appropriated police character and
color) which is probably what would be more meaningful for the end
user. On the other hand, the end user may also be familiar with that
format and the use or a standardize format helps automation in the
selection. As a result, this document will assume that the rdns
domain will reflect the legal entity administrating the resolver to
the user. Note that a user interface may also use the rdns domain to
derive more user friendly and additional specific information that
will be presented to the user. This could include for example
additional RDAP queries, favicons of web sites that are shown to the
end users. What is presented to the end user is out of scope of this
document, but the rdns domain can be used as the key.
b) The hostname part is only meaningful within the resolving domain.
While, it may carry some information that may be interpreted to the
end user, the constraint provided by the DNS format may be too
restricting. As a result, it is expected that a more user friendly
string might be associated with the hostname and that the hostname
remain reserved for networking administrators.
5.2. DNS Transport related information
Parameters associated to the DNS transport are the type of transport
that is DNS, DoT or DoH as well as the necessary parameters to
establish the session. This may include specific TLS parameters for
DoT and DoH as well as specific HTTP versions and URI template for
DoH. These parameters are expected to be identified in a standard
way.
5.3. DNS Service related Information
Parameters associated to the resolving service include for example,
the presence of filtering services, the associated authoritative
domains.
6. Architecture Overview
DRDP can be used by a resolver or a DNS client (REQ1), which share
DNS as a common protocol. In addition, the ability to deploy
incrementally DRDP over legacy DNS client (REQ9) makes DNS a good
candidate for DRDP.
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DNS based Service Discovery (DNS-SD) [RFC6763] is a discovery
protocol for services based on DNS messages.
DNS-SD provides the ability to display user-friendly names in UTF-8
and uses a combination of DNS RRsets of type PTR, SRV and TXT. The
current document is largely inspired from this long time and already
existing protocol. However, DRDP differs from DNS SD in that DNS-SD
discovers services within a specific domain (such as .local or
.home.arpa for example) while DRDP needs to discover the resolving
domain as well as the resolving services associated to this domain.
In addition, DRDP is taking advantage of the latests development of
SRVCB RRsets [I-D.ietf-dnsop-svcb-httpssvc] which, among other
things, enables to combine the SRV and TXT Rsets. While nothing
prevents DRDP to use SRV and TXT RRsets, DRDP uses instead SVCB RRset
as web browser are more likely to implement SVBC.
The overall procedure is performed as described below: 1. Discovery
of the global and local available resolving domains 2. Discovery of
the resolving services within a resolving domain.
7. Domain Discovery with DRDP
7.1. Global Domain
The mechanism involves the creation of a special domain name
rdns.arpa that lists the various resolving domains. This mechanism
remains valid as long as the list of resolving domain name remains
relatively limited. The number of resolving domain that can fit into
a payload will depend on the length of the various resolving domain.
That said, a UDP packet of 4096 bytes is expected to contain a
significant amount of resolvers. The number of open resolver is not
expected to reach that limit and if so the list can be retrieved
through TCP.
The zone file below is inspired from DNS-SD where b indicates a
browsing domain, _dns indicates the DNS resolving service and
rdns.arpa. indicates the special domain. dns domain_0, nds_domain_n
indicates the various resolving domains. The order of the resolving
domains is irrelevant, and the zone administrator SHOULD regularly
reorder them. The RRsets MUST be signed with DNSSEC.
b._dns.rdns.arpa PTR <resolving_domain_0>
[...]
b._dns.rdns.arpa PTR <resolving_domain_n>
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7.2. Local Domain
The resolving domains that are local needs to be provisioned or
advertised by the network. With that resolving domain the DNS client
could proceed to its resolving service selection.
Resolving service are currently configured or advertised via IP
addresses rather than a FQDN as a DNS resolution would be needed to
resolve the IP address. More specifically, networks usually
advertise the resolving service via a Recursive Name Server option
[RFC3646] that contains an IP address. Similarly application usually
configures their resolving services with IP addresses (8.8.8.8,
1.1.1.1, 9.9.9.9,...). As a result, this section indicates a
mechanism that would enable a DNS client to derive a resolving domain
of a resolver from an IP address of an advertised resolver. The
mechanism described here is expected to be used as an hint.
The resolving domain will be derived from the IP address by:
1. performing a reverse resolution
2. assume the resulting FQDN is composed of a hostname appended to
the resolving domain. For example, if resolver.example.com is
the resulting FQDN from the reverse resolution, then the rdns
domain will be example.com.
In most cases local resolving services uses global IP address which
does not limit the reverse resolution to an associated local
resolver. However the zone associated to the resolving domain might
not be available globally and instead be restricted to the local
network. As a result, DNS client SHOULD perform DNS resolution
associated to the local resolving domain using the local resolver,
and resolver operator SHOULD publish the resolving domain zone to the
global Internet.
Legacy DNS client will not be impacted. Upon receiving the IP
address they will send their DNS queries to that IP address. DRDP
aware DNS client will derive the resolving domain and attempt to
perform a discovery within the resolving domain.
If other mechanisms as used to advertise the resolving domains such
as those described in [I-D.btw-add-home], and the resolving domain
are different, the DNS client should perform DRDP with both resolving
domains.
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8. Resolving Service Discovery
8.1. Discovery of all service instances
Given a resolving domain example.com, a DNS client MAY request all
possible resolving service instances with a query of type SVCB with
the service _dns.
The example below presents the use of an AliasForm followed by a
ServiceForm which allows an indirection. The Alias form is not
madatory and instead only ServiceForm associated to _dn.example.com
could have been used instead.
The SvcFieldPriority indicates the preference of the resolving
service instance.
The SvcParamKey alpn MUST be present when TLS is used as its presence
and value indicates the DNS transport. The absence of the alpn
SvcParamKey indicates Do53, alpn set to dot indicates DoT is served
while h* indicates DoH is served. Note that the port value (53, 853,
443) is not used to determine teh DNS transport as non standard port
MAY be used. The example below uses an non standard port 5353 for
illustrative purpose.
The SvcParamField ux is optional is provides an UTF-8 string that is
expected to be displayed to the end user if needed.
The RRsets MUST be protected with DNSSEC and when alpn is provided a
TLSA RRset SHOULD be present. These RRsets have been omitted for
clarity.
## Discovery of all service instances
_dns.example.com. 7200 IN SVCB 0 svc.example.com.
svc.example.com. 7200 IN SVCB 12 ( svc0.example.net.
port="5353" ux="Legacy Resolver" )
svc.example.com. 7200 IN SVCB 1 ( svc1.example.net. alpn="dot"
port="5353" esniconfig="..."
ux="Preferred Example's Choice" )
svc.example.com. 7200 IN SVCB 3 ( svc2.example.net. alpn="h2"
port="5353" esniconfig="..." ux= )
svc.example.com. 7200 IN SVCB 2 ( svc3.example.net. alpn="h3"
port="5353" esniconfig="..." ux= )
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8.2. Discovery of specific service instances
To reduce the size of the messages, the DNS client MAY also prefer to
query information of resolvers using a specific transport (DNS, DoT,
DoH) that are designated as sub sets. A DNS client MAY list the the
different subsets of that resolving domain with a PTR query. This
document defines the following subsets _53._dns for DNS, _853._dns
for DoT and _443.__dns for DoH. Other subsets MAY be defined in the
future. A DNS client that does not understand a subset SHOULD ignore
it and maybe proceed to the discovery as defined in Section 8.1.
All subsets MUST share the same resolving domain and be listed with a
PTR RRsets. The DNS client MAY NOT performed a DNS query of type
PTR, for example, if it has a previous knowledge of the existence of
the subset or if indicated by its policy. In this it MAY directly
proceed to the SRVCB resolution.
The same restrictions as defined in section Section 8.1 apply.
Note that while the SvcFieldPriority indicates the priority within a
subservice, this field MUST have a coherence across subservices. The
priority provided SHOULD be coherent with the case of a _dns SRVCB
query of section Section 8.1.
The figure below illustrates an example of zone file. RRSIG and TLSA
have been omited for the purpose of clarity.
### Definition of the resolving service subsets
_dns.example.com PTR _53._dns.example.com
_dns.example.com PTR _853._dns.example.com
_dns.example.com PTR _443._dns.example.com
### services instances per service subset
_53._dns.example.com. 7200 IN SVCB 0 svc0.example.com.
svc0.example.com. 7200 IN SVCB 12 ( svc0.example.net.
port="5353" ux="Legacy Resolver" )
_853._dns.example.com. 7200 IN SVCB 0 svc1.example.com.
svc1.example.com. 7200 IN SVCB 1 ( svc1.example.net. alpn="dot"
port="5353" esniconfig="..."
ux="Preferred Example's Choice" )
_443_dns.example.com. 7200 IN SVCB 0 svc4.example.net.
svc4.example.com. 7200 IN SVCB 3 ( svc2.example.net. alpn="h2"
port="5353" esniconfig="..." ux= )
svc4.example.com. 7200 IN SVCB 2 ( svc3.example.net. alpn="h3"
port="5353" esniconfig="..."
ux="Testing QUIC")
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Some notes:
1. _domain uses SVCB but does not have TLS. While SVCB has been
created essentially for TLS based service, this does not appear
to be mandatory.
2. Should we have some constraints regarding the SvcDomainName and
QNAME ?
9. Resolver advertising other service sub type
A resolver receiving a DNS request over a service sub type MAY be
willing to advertise the DNS client that other sub service type are
available. This is especially useful, when, for example, a resolver
wants that the DNS resolver switches to other service sub types that
are more secure.
In order to do so the resolver MAY provide in the additional data
field the _dns SRVCB of ServiceForm.
10. Migration to service sub types
The principle of the discovery mechanism is that the resolver
indicates the available service sub types and let the DNS client
chose which sub type it prefers. On the other hand, the resolver MAY
also indicate a preference using the priority and weight fields.
However, there is no mechanisms that could permit an indirection from
one service sub type to another service sub type. This document
specifies that weight needs to be considered across sub types.
Redirection MAY especially be needed when a DNS client is using the
Do53 and the resolver would like to upgrade the DNS client session to
a more secure session. This MAY require a specific ERROR code that
will request the DNS client to perform service discovery.
It is expected that DRDP MUST always be available via Do53. However,
this does not mean that a resolver is expected to implement the Do53
sub type service for a resolving service. If a resolving service
provider chooses not to provide a resolving service using Do53, that
service MUST NOT be pointed by the _53._dns.example.com search and
MUST NOT provide _dns.example.com SRVCB RRsets with no SvcParamKey
alpn.
11. Security Considerations
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11.1. Use of protected channel is RECOMMENDED
When available, it is recommended to chose a protected version of the
rdns service. More specifically, the use of end-to-end protection
ensures that the DNS client is connected to the expected platform and
that its traffic cannot be intercepted on path. Typically, the
selection of resolver on the Internet (and not on your ISP network)
and the use of a non protected channel enables an attacker to monitor
your DNS traffic. The similar observation remains true if you are
connected to the resolver of your ISP. It is commonly believed that
trusting your ISP (that is your first hop) makes encryption
unecessary. Trusting your ISP is mandatory in any case, but the
associated level of trust with an protected channel is restricted to
the operation of the DNS platform. With non protected channel the
trust is extended to any segment between the DNS client and the
resolver, which is consequently larger. The use of a protected
channel is recommended as it will prevent anyone on path to monitor
your traffic.
11.2. DNSSEC is RECOMMENDED
The exchanges SHOULD be protected with DNSSEC to ensure integrity of
the information between the authoritative servers and the DNS client.
Without DNSSEC protection, DNS messages may be tampered typically
when they are transmitted over an unprotected channel either between
the DNS client and the resolver or between the resolver and the
authoritative servers. The messages may be tampered by an online
attacker intercepting the messages or by the intermediary devices.
It is important to realize that protection provided by TLS is limited
to the channel between the DNS client and the resolver. There are a
number of cases were the trust in the resolver is not sufficient
which justify the generalization of the use of DNSSEC. The following
examples are illustrative and are intended to be exhaustive.
First, the discovery exchanges may happen over an unprotected
channel, in which case, the messages exchanged may be tampered by
anyone on-path between the DNS client and the resolver as well as
between the resolver and the authoritative servers - including the
resolver. When TLS is used between the DNS client and the resolver,
this does not necessarily mean the DNS client trusts the resolver.
Typically, the TLS session may be established with a self-signed
certificate in which case the session is basically protected by a
proof-of-ownership. In other cases, the session may be established
based on Certificate Authorities (CA) that have been configured into
the TLS client, but that are not necessarily trusted by the DNS
client. In such cases, the connected resolver may be used to
discover resolvers from another domain. In this case, the resolver
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is probably interacting with authoritative servers using untrusted
and unprotected channels. Integrity protection relies on DNSSEC.
11.3. TLSA is RECOMMENDED
When TLS is used to protect the DNS exchanges, certificates or
fingerprint SHOULD be provided to implement trust into the
communication between the DNS client and the resolver. The TLS
session and the association of the private key to a specific identity
can be based on two different trust model. The Web PKI that will
rely on CA provisioned in the TLS library or the TA provided to the
DNS client. A DNS client SHOULD be able to validate the trust of a
TLS session based on the DNSSEC trust model using DANE.
When the DNS client is protecting its session to the resolver via
TLS, the DNS client may initiate an TLS session that is not validated
by a CA or a TLSA RRsets. The DNS client MUST proceed to the
discovery process and validate the certificate match the TLSA RRset.
In case of mismatch the DNS client MUST abort the session.
12. Privacy Considerations
When the discovery protocol is performed using a resolver that
belongs to one domain for another domain, or over an unprotected
channel, the DNS client must be conscious that its is revealing to
the resolver its intention to use another resolver. More
specifically, suppose an resolver is complying some legal
requirements that DNS traffic must be unencrypted. Using this
resolver to perform a resolver discovery reveals the intention of
potentially using alternative resolvers. Alternatively, narrowing
down the discovery over a specific sub type of resolver (DoT, or DoH)
may reveal to that resolver the type of communication. As result,
when performing a discovery over a domain that differs to the domain
the resolver belongs to, it is RECOMMENDED to request the SRV RRsets
associated to all different sub type of proposed services.
The absence of traffic that results from switching completely to a
newly discovered resolver right after the discovery process provides
an indication to the resolver the DNS client is switching to. It is
hard to make that switch unnoticed to the initial resolver and the
DNS resolver MUST assume this will be noticed. The information of
switching may be limited by sharing the traffic between different
resolvers, however, the traffic pattern associated to each resolver
may also reveal the switch. In addition, when the initial resolver
is provided by the ISP, the ISP is also able to monitor the IP
traffic and infer the switch. As a result, the DNS client SHOULD
assume the switch will be detected.
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With DoT or DoH, the selection of port 443 will make the traffic
indistinguishable from HTTPS traffic. This means that an observer
will not be able to tell whether the traffic carries web traffic or
DNS traffic. Note that it presents an interest if the server offers
both a web service as well as a resolution service. Note that many
resolvers have a dedicated IP address for the resolution service, in
which case, the information will be inferred from the IP address.
Note also that traffic analysis may infer this as well. Typically
suppose an IP address hosts one or multiple web sites that are not
popular as well as a resolving service. If this IP address is
associated frequent short size exchanges, it is likely that these
exchanges will be DNS exchanges rather than Web traffic. The size of
the packet may also be used as well as many other patterns. As a
result, the use port 443 to hide the DNS traffic over web traffic
should be considered as providing limited privacy.
13. IANA Considerations
This document requests the IANA the creation of the following
underscored node names in the Underscored and Globally Scoped DNS
Node Names registry https://www.iana.org/assignments/dns-parameters/
dns-parameters.xhtml#dns-parameters-14
RR Type | _NODE NAME | Reference
--------+------------+----------
SRVCB | _dns | RFC-TBD
SvcParamKey | NAME | Meaning | Reference
------------+--------------+-----------------------------+-----------
7 | user-display | User friendly string (UTF8) | RFC-TBD
| | to represent the resolver |
| uri_template | URI template |
| auth_domain | Domains the resolving |
| | service is authoritative |
| filetring | Filetring services provided |
SvcParamValue for filetring
14. Acknowledgments
We would like thank Mirja Kuehlewind as well as the GSMA IG for their
comments. We also thank Ted Hardie and Paul Hoffman for their feed
backs regarding the dns schemes for DoT and DoH.
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15. References
15.1. Normative References
[I-D.ietf-dnsop-svcb-httpssvc]
Schwartz, B., Bishop, M., and E. Nygren, "Service binding
and parameter specification via the DNS (DNS SVCB and
HTTPSSVC)", draft-ietf-dnsop-svcb-httpssvc-02 (work in
progress), March 2020.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3646] Droms, R., Ed., "DNS Configuration options for Dynamic
Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
DOI 10.17487/RFC3646, December 2003,
<https://www.rfc-editor.org/info/rfc3646>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/info/rfc6763>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
15.2. Informative References
[I-D.btw-add-home]
Boucadair, M., Reddy.K, T., Wing, D., and N. Cook, "DNS-
over-HTTPS and DNS-over-TLS Server Discovery and
Deployment Considerations for Home and Mobile Networks",
draft-btw-add-home-04 (work in progress), March 2020.
Migault Expires September 25, 2020 [Page 14]
Internet-Draft DRDP March 2020
[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", RFC 7719, DOI 10.17487/RFC7719, December
2015, <https://www.rfc-editor.org/info/rfc7719>.
Author's Address
Daniel Migault
Ericsson
8275 Trans Canada Route
Saint Laurent, QC 4S 0B6
Canada
EMail: daniel.migault@ericsson.com
Migault Expires September 25, 2020 [Page 15]