ADD M. Boucadair
Internet-Draft Orange
Intended status: Standards Track T. Reddy
Expires: September 17, 2020 McAfee
D. Wing
N. Cook
March 16, 2020

DNS-over-HTTPS and DNS-over-TLS Server Discovery and Deployment Considerations for Home and Mobile Networks


This document discusses DoT/DoH deployment considerations for home networks. It particularly sketches the required steps to use DoT/DoH capabilities provided by local networks.

One of the goals of this document is to assess to what extent existing tools can be used to provide a DoT/DoH service. As an outcome, new DHCP and Router Advertisement Options are specified in order to convey a DNS Authentication Domain Name.

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

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 17, 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 ( 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

Internet Service Providers (ISPs) traditionally provide DNS resolvers to their customers. Typically, ISPs deploy the following mechanisms to advertise a list of DNS Recursive DNS server(s) to their customers:

The communication between a customer's device (a.k.a., User Equipment (UE)) (possibly via Customer Premises Equipment (CPE)) and an ISP-supplied DNS resolver takes place by using cleartext DNS messages (Do53, [I-D.ietf-dnsop-terminology-ter]). Some examples are depicted in Figure 1. In the case of cellular networks, connectivity can be provided to a UE or to a CPE. Do53 mechanisms used within the Local Area Network (LAN) are similar in both fixed and cellular CPE-based broadband service offerings.

(a) Fixed Networks

           ,--,--,--.             ,--,--,--.
        ,-'   +--+  `-.       ,-'   ISP    `-. 
       ( LAN  |UE|    CPE----(    DNS Server  )
        `-.   +--+   ,-'       `-.          ,-' 
           `--'|-'--'             `--'--'--'    
               |                     |

(b) Cellular Networks

           ,--,-|,--.                      |
        ,-'   +--+   `-.               ,--,--,--.    
       ( LAN  |UE|     CPE------------+          \
        `-.   +--+   ,-'            ,'   ISP     `-. 
           `--'--'--'              (    DNS Server  )
                              +-----+-.          ,-'
               +--+           |        `--'--'--'  

Figure 1: Sample Legacy Deployments

ISPs use DNS to provide additional services such as (but not limited to) malware filtering, parental control, or VoD (Video on Demand) optimization. DNS is also a central component for mastering the quality of experience for current latency-sensitive services, but also emerging ones (such as those services that pertain to the Ultra Reliability and Low Latency Communications (uRLLC) or Enhanced Mobile Broadband (eMBB).

Relying upon local DNS resolvers will therefore contribute to meet the aforementioned service requirements. The use of external resolvers is likely to induce an extra service delay which exceeds by far the service target.

This document focuses on the support of DNS-over-HTTPS (DoH) [RFC8484] or DNS-over-TLS (DoT) [RFC7858] in local networks. In particular, the document describes how a local DoH/DoT server can be discovered and used by connected hosts. This document specifies options that allow DNS clients to discover local DoT/DoH servers. In particular, Section 4 describes DHCP, DHCPv6, and RA options to convey the Authentication Domain Name (ADN, defined in [RFC8310]).

Some ISPs rely upon external resolvers (e.g., outsourced service or public resolvers); these ISPs provide their customers with the IP addresses of these resolvers. These addresses are typically configured on CPEs using the same mechanisms listed above. Likewise, users can modify the default DNS configuration of their CPEs (e.g., supplied by their ISP) to configure their favorite DNS servers. This document permits such deployments.

Both managed and unmanaged CPEs are discussed in the document (Section 3) .

2. Terminology

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.

This document makes use of the terms defined in [RFC8499] and [I-D.ietf-dnsop-terminology-ter].

'DoH/DoT' refers to DNS-over-HTTPS and/or DNS-over-TLS.

3. Sample Deployment Scenarios

3.1. Managed CPEs

ISPs have developed an expertise in managing service-specific configuration information (e.g., CPE WAN Management Protocol [TR-069]). For example, these tools may be used to provision the authentication domain name information (ADN) to managed CPEs if DoH/DoT is supported by a local network similar to what is depicted in Figure 2.

DoH-capable (or DoT) clients establish the DoH (or DoT) session with the discovered DNS server.

If a DNS client supports both DoT and DoH, the client try to establish DoH/DoT sessions with the discovered DNS server to determine whether these servers support DoH and/or DoT (Section 6). Alternatively, the DNS client may discover whether the DNS server in the local network supports DoH/DoT by using the mechanism discussed in Section 7.

(a) Fixed Networks

           ,--,--,--.             ,--,--,--.
        ,-'   +--+  `-.       ,-'   ISP    `-. 
       ( LAN  |UE|    CPE----(    DNS Server  )
        `-.   +--+   ,-'       `-.         ,-' 
           `--'|-'--'             `--'--'--'    
               |                     |

(b) Cellular Networks    
           ,--,-|,--.                      |
        ,-'   +--+   `-.               ,--,--,--.    
       ( LAN  |UE|     CPE------------+          \
        `-.   +--+   ,-'            ,'   ISP     `-. 
           `--'--'--'              (    DNS Server  )
                              +-----+-.          ,-'
               +--+           |        `--'--'--'  

Figure 2: DoH/DoT in the WAN

Figure 2 shows the scenario where the CPE relays the list of DoT/DoH servers it learns for the network by using mechanisms like DHCP or a specific Router Advertisement message. In such context, direct DoH/DoT sessions will be established between a host serviced by a CPE and an ISP-supplied DoT/DoH server (see the example depicted in Figure 3 for a DoH/DoT-capable host).

                      ,--,--,--.             ,--,--,--.
                   ,-'          `-.       ,-'   ISP    `-.
            UE----(      LAN      CPE----(    DNS Server  )
             |     `-.          ,-'       `-.          ,-'
             |        `--'--'--'             `--'--'--'
             |                                   | 

Figure 3: Direct DoH/DoT Sessions

Figure 4 shows a deployment where the CPE embeds a caching DNS forwarder. The CPE advertises itself as the default DNS server to the hosts it serves. The CPE relies upon DHCP or RA to advertise itself to internal hosts as the default DoT/DoH/Do53 server. When receiving a DNS request it cannot handle locally, the CPE forwards the request to an upstream DoH/DoT/Do53 resolver. Such deployment is required for IPv4 service continuity purposes (e.g., [I-D.ietf-v6ops-rfc7084-bis]) or for supporting advanced services within the home (e.g., malware filtering, parental control, Manufacturer Usage Description (MUD, [RFC8520] to only allow intended communications to and from an IoT device)). When the CPE behaves as a DNS forwarder, DNS communications can be decomposed into two legs:

An ISP that offers DoH/DoT to its customers may enable DoH/DoT in both legs as shown in Figure 4. Additional considerations related to this deployment are discussed in Section 8.

                      ,--,--,--.             ,--,--,--.
                   ,-'          `-.       ,-'   ISP    `-.
            UE----(      LAN      CPE----(    DNS Server  )
             |     `-.          ,-'|      `-.          ,-'
             |        `--'--'--'   |         `--'--'--'
             |                     |             | 

Figure 4: Proxied DoH/DoT Sessions

3.2. Unmanaged CPEs

Customers may decide to deploy unmanaged CPEs (assuming the CPE is compliant with the network access technical specification that is usually published by ISPs). Upon attachment to the network, an unmanaged CPE receives from the network its service configuration (including the DNS information) by means of, e.g., DHCP. That DNS information is shared within the LAN following the same mechanisms as those discussed in Section 3.1. A host can thus establish DoH/DoT session with a DoH/DoT server similar to what is depicted in Figure 3.

Customers may also decide to deploy internal home routers (called hereafter, Internal CPEs) for a variety of reasons that are not detailed here. Absent any explicit configuration on the internal CPE to override the DNS configuration it receives from the ISP-supplied CPE, an Internal CPE relays the DNS information it receives via DHCP/RA from the ISP-supplied CPE to connected hosts. DoH/DoT sessions can be established by a host with the DoH/DoT servers of the ISP (see Figure 5).

          ,--,--,--.                    ,--,--,--.
       ,-'          Internal         ,-'    ISP   `-.
UE----(    Network#A   CPE----CPE---(    DNS Server   )
 |     `-.          ,-'              `-.          ,-'
 |        `--'--'--'                    `--'--'--'
 |                                          | 

Figure 5: Direct DoH/DoT Sessions with the ISP DNS Resolver (Internal CPE)

Similar to managed CPEs, a user may modify the default DNS configuration of an unmanaged CPE to use his/her favorite DNS servers instead. DoH/DoT sessions can be established directly between a host and a 3rd Party DNS server (see Figure 6).

         ,--,--,--.                  ,--,
       ,'         Internal        ,-'    '-     3rd Party
UE----(  Network#A  CPE----CPE---(   ISP   )--- DNS Server
 |     `.         ,-'             `-.    -'         |
 |       `-'--'--'                   `--'           |
 |                                                  | 

Figure 6: Direct DoH/DoT Sessions with a Third Party DNS Resolver

4. DNS Reference Identifier Option

This section describes how a DNS client can discover the ADN of local DoH/DoT server(s) using DHCP (Sections 4.1 and 4.2) and Neighbor Discovery protocol (Section 4.3).

As reported in Section 1.7.2 of [RFC6125]:

In order to allow for PKIX-based authentication between a DNS client and a DoH/DoT server while accommodating the current best practices for issuing certificates, this document allows for configuring an authentication domain name to be presented as a reference identifier for DNS authentication purposes.

The DNS client establishes a DoH/DoT session with the discovered DNS IP address(es) (Section 6) and uses the mechanism discussed in Section 8 of [RFC8310] to authenticate the DNS server certificate using the authentication domain name conveyed in the DNS Reference Identifier.

If the DNS Reference Identifier is discovered by a host using both RA and DHCP, the rules discussed in Section 5.3.1 of [RFC8106] MUST be followed.

4.1. DHCPv6 DNS Reference Identifier Option

The DHCPv6 DNS Reference Identifier option is used to configure an authentication domain name of the DoH/DoT server. The format of this option is shown in Figure 7.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |     OPTION_V6_DNS_RI          |         Option-length         |
   |                                                               |
   |                 Authentication Domain Name                    |
   |                                                               |

Figure 7: DHCPv6 DNS Reference Identifier Option

Figure 7 are as follows:

Figure 8. This example conveys the FQDN "".

      | 0x04 |   d  |   o  |   h  |  1   | 0x07 |   e  |   x  |   a  |
      |   m  |   p  |   l  |   e  | 0x03 |   c  |   o  |   m  | 0x00 |

Figure 8: An example of the authentication-domain-name Encoding

4.2. DHCP DNS Reference Identifier Option

The DHCP DNS Reference Identifier option is used to configure an authentication domain name of the DoH/DoT server. The format of this option is illustrated in Figure 9.

          Code  Length   Authentication Domain Name 
         |TBA2 |  n  |  s1 |  s2 |  s3 |  s4 | s5  |  ...

   The values s1, s2, s3, etc. represent the domain name labels in the
   domain name encoding.

Figure 9: DHCP DNS Reference Identifier Option

The fields of the option shown in Figure 9 are as follows:

4.3. RA DNS Reference Identifier Option

The IPv6 Router Advertisement (RA) DNS Reference Identifier option is used to configure an authentication domain name of the DoH/DoT server. The format of this option is illustrated in Figure 10.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     |     Type      |     Length    |           Reserved            |
     |                           Lifetime                            |
     |                                                               |
     :                  Authentication Domain Name                   :
     |                                                               |

Figure 10: RA DNS Reference Identifier Option

The fields of the option shown in Figure 10 are as follows:

5. DoH URI Templates

DoH servers may support more than one URI Template [RFC8484]. The following sub-sections discuss some candidate solutions for a DoH client to retrieve the list of supported templates by a DoH server. Also, if the resolver hosts several DoH services (e.g., no-filtering, blocking adult content, blocking malware), these services can be discovered as templates.

How a DoH client makes use of the configured DoH services is out of scope of this document.

5.1. Define a Dedicated DHCP/RA Option

This solution assumes that DHCP servers and access routers maintain an updated list of the templates used by DoH resolvers.

The following observations can be made:

RA/DHCP has the following advantages:

5.2. Retrieve the List Directly from the DoH Server

Upon discovery of a DoH resolver (Section 4), the DoH client contacts that DoH resolver to retrieve the list of supported DoH services (e.g., use of a well-known URI). That information is cached by the DoH client for a given period (e.g., 24h). DoH clients re-iterates that request regularly (e.g., 24h) to retrieve an updated list of supported DoH services. Note that a "push" mode can be considered using the mechanism defined in [I-D.ietf-dnssd-push].

This approach allows to avoid adherence of DoH servers with DHCP servers (or access routers) for (de)activating new DoH services.

6. Locating DoH/DoT Servers

A CPE or a host relies upon discovery mechanisms (such as PCO, DHCP, or RA) to retrieve DoH/DoT servers' reachability information. In the various scenarios sketched in Section 3, Do53, DoH, and DoT may terminate on the same IP address (or distinct IP addresses as depicted in Figure 12). Terminating Do53/DoH/DoT on the same or distinct IP addresses is deployment-specific.

                 Legacy Do53                       
                       |    {@1}    |       |
                       |            |       |
                       |======Do53 Query===>|
                       |            |       |   --,--,-
                      ,+-,--,--.    |       |,/  ISP   \.
                   ,-'          `-. |     ,-'            `-.
         DoH/DoT --(      LAN      CPE----( S (@1)         )
    capable client  `-.          ,-'|      `-.           ,-'
             |        `--'--'--'    |       | `--'--'--'
             |<========DHCP========>|       | 
             |       {RI, @1}       |       | 
             |                              | 

  * S: DNS server 
  * {@1}: IP address of S; returned in a DHCP 
    Domain Name Server option
  * RI: DNS Reference Identifier

Figure 11: Locating DoH/DoT/Do53 (Same DNS Server)

From an IP reachability standpoint, DoH/DoT servers SHOULD be located by their address literals rather than their names. This avoids adding a dependency on another server to resolve the DoH/DoT name. Concretely, if Do53/DoH/DoT terminate on same IP addresses, existing discovery mechanisms [RFC2132][RFC3646][RFC8106] can be leveraged to learn the IP addresses of DoT/DoH servers while an authentication domain name is supplied by one of the options discussed in Section 4. An example is depicted in Figure 11.

                 Legacy Do53                       
                       | {RI,@1,@2} |             |
                       |            |             |
                       |========Do53 Query=======>|
                       |            |           --,--,-
                      ,+-,--,--.    |        ,/  S1 (@1)\.
                   ,-'          `-. |     ,-'    ISP     `-.
         DoH/DoT --(      LAN      CPE----(                 )
    capable client  `-.          ,-'|      `-.   S2 (@2)  ,-'
             |        `--'--'--'    |         `--'--'--'
             |<=========RA==========|             | 
             |      {RI,@1,@2}      |             | 
             |                                    | 

  * S1: Do53 server
  * S2: DoH/DoT server
  * @1: IP address of S1
  * @1: IP address of S2
  * RI: DNS Reference Identifier

Figure 12: Locating DoH/DoT/Do53 (Distinct Servers)

The following sub-sections discusses the conditions under which discovered DoT/DoH server can be used.

6.1. DoT/DoH Auto-Upgrade

Additional considerations are discussed below for the use of DoH and DoT servers provided by local networks:

Such an auto-upgrade mechanism would be compatible with the Redirection method of Section 8.1.2, for managed CPEs hosting a DoT/DoH forwarder.


Some deployment options to securely configure hosts are discussed below. These options are provided for the sake of completeness.

7. DoT and DoH DNS-SD Considerations

As an alternative to probing discovered DNS servers in order to check (1) whether they support DoT and/or DoH, and (2) whether customized port numbers are used (instead of 443/853 port numbers), a DNS client MAY use DNS-based Service Discovery (DNS-SD) [RFC6763].

DNS-SD defines a set of naming rules for certain DNS record types that they use for advertising and discovering services. Section 4.1 of [RFC6763] specifies that a service instance name in DNS-SD has the following structure:

<Instance> . <Service> . <Domain>

The <Domain> portion specifies the authentication domain name (Section 4). The <Service> portion of the DNS service instance name MUST be "_domain-s._tcp" (Section 6 of [RFC7858]) or "_doh._tcp" (Section 10.4). If no DNS-SD records can be retrieved by the DNS client, it MUST wait a time period that is appropriate for the encountered error (e.g., NXDOMAIN, timeout, etc.).

8. Hosting DoH/DoT Forwarder in the CPE

8.1. Managed CPEs

The following mechanisms can be used to host a DoH/DoT forwarder in a managed CPE (Section 3.1).

8.1.1. ACME

If a CPE is co-located with security services (e.g., malware filtering, parental control, MUD), the ISP can assign a unique FQDN (e.g., and a domain-validated public certificate to the DoH/DoT forwarder hosted on the CPE. Automatic Certificate Management Environment (ACME) [RFC8555] can be used to automate certificate management functions such as domain validation procedure, certificate issuance and certificate revocation.

Alternatively, the security service provider can assign a unique FQDN to the managed CPE. DNS requests to the forwarder are sent to the internal IP address, not the external one. The DoH/DoT forwarder will act like a private DoT/DoH server only be accessible from within the home network.

8.1.2. Redirection

An ISP-managed CPE can be configured with the ISP's DoH resolver IP addresses and ADN, which it will communicate to internal hosts using DHCP/RA. Upon joining the network, a DoH client follows the procedure specified in Section 6.1 to upgrade to DoH.

Once the DoH session is established, the ISP DoH server uses HTTP redirection (Section 6.4.4 in [RFC7231]) to redirect the DNS client to the DoH forwarder hosted on the CPE (e.g., The DNS client either uses Do53 or opportunistic privacy profile (Section 7.2 of [RFC8310]) to resolve the domain name in the redirected URI and eventually establishes DoH session with the DoH forwarder in the CPE reachable on the LAN interface. A simplified example is illustrated in Figure 13.

PKIX authentication [RFC6125] based upon the domain name in the redirected URI will detect rogue DNS servers.

A DNS client that successfully connects to a redirected DoH server may choose to locally cache the server host IP addresses in order to not have to repeat the Do53 query.

                      ,+-,--,--.             ,/  ISP   \.
                   ,-'          `-.       ,-'            `-.
         DoH/DoT --(      LAN      CPE----( S (@1)          )
    capable client  `-.          ,-'|      `-.           ,-'
             |        `--'--'--'    |       | `--'--'--'
             |<========DHCP========>|       | 
             |       {RI, @1}       |       | 
             |                              | 
             |<------303 (See Other)--------| 
             |                              | 
             |-----Do53 Query------>| 
             |<----CPE's LAN @------|
             |                      |        
             |                      |     
  * S: DoH/DoT server
  * @1: IP address of S

Figure 13: A Simplified Example of Redirection to the DNS Forwarder in the CPE

8.2. Unmanaged CPEs

The approach specified in Section 8.1 does not apply for hosting a DNS forwarder in an unmanaged CPE.

The unmanaged CPE administrator (referred to as administrator) can host a DoH/DoT forwarder on the unmanaged CPE. This assumes the following:

Figure 14 illustrates an example of an unmanaged CPE hosting a forwarder which connects to a 3rd party DoH/DoT server. In this example, the DNS information received from the managed CPE (and therefore from the ISP) is ignored by the Internal CPE hosting the forwarder.

         ,--,--,--.                         ,--,
       ,'         Internal   Managed     ,-'    '-     3rd Party
UE----(  Network#A  CPE--------CPE------(   ISP   )--- DNS Server
 |     `.         ,-'|          |        `-.    -'       |
 |       `-'--'--'   |          |<==DHCP==>|`--'         |
 |                   |<==DHCP==>|          |             | 
 |<======DHCP=======>|          |                        |
 |     {RI, @i}      |                                   |

  * @i: IP address of the DNS forwarder hosted in the Internal

Figure 14: Example of an Internal CPE Hosting a Forwarder

9. Security Considerations

An attacker can get a domain name, domain-validated public certificate from a CA, host a DoT/DoH server and claim the best DNS privacy preservation policy. Also, an attacker within the home network can use the public IP address, get an 'IP address'-validated public certificate from a CA, host a DoT/DoH server and claim the best DNS privacy preservation policy.

Because DHCP/RA messages are not encrypted or protected against modification in any way, their content can be spoofed or modified by compromised devices within the home network. An attacker can spoof the DHCP/RA response to provide the attacker's DoT/DoH server. Note that such an attacker can launch other attacks as discussed in Section 22 of [RFC8415]. Furthermore, if the browser or the OS is pre-configured with a list of DNS servers and some of which perform malware filtering while others do not, an attacker can prevent contacting the preferred filtering DNS servers causing a downgrade attack to a non-filtering DNS server, which the attacker can leverage to deliver malware.

The primary attacks against the methods described in Section 7 are the ones that would lead to impersonation of a DNS server and spoofing the DNS response to indicate that the DNS server does not support DoH or DoT. To protect against DNS-vectored attacks, secured DNS (DNSSEC) can be used to ensure the validity of the received DNS records received. Impersonation of a DoH/DoT server is prevented by validating the certificate presented by the DoH/DoT server. If DHCP/RA conveys an ADN, but the DNS-SD lookup indicates that the DNS server does not support DoH/DoT, the DNS client can detect the DNS response is spoofed.

The use of DoH/DoT also depends on the user's policies. For example, the user may indicate his/her consent to use (or not) the locally- discovered DoH/DoT server or request to review human-readable privacy policy information of a selected DNS server and to assess whether that DNS server performs DNS-based content filtering (e.g., [I-D.reddy-dprive-dprive-privacy-policy]). The DNS client is assumed to adhere to these policies. This document does not make any assumption about the structure of such policies nor mandates specific requirements. Such policies and their handling is out of scope.

DoH/DoT servers discovered using insecure discovery mechanisms like DHCP/RA are used by a DNS client if the insecurely discovered DoH/DoT server is pre-configured in the OS or the browser. Section 6.1 identifies a set of deployment options under which DHCP/RA RI options can be used.

If the insecurely discovered DoH/DoT server is not pre-configured in the OS or browser, the client may validate the signatory (e.g., cryptographically attested by the ISP). However, as discussed above, the use of policies to select servers is out of scope of this document.

DoT/DoH sessions with rogue servers spoofing the IP address of a DNS server will fail because the DNS client will fail to authenticate that rogue server based upon PKIX authentication [RFC6125] based upon the authentication domain name in the Reference Identifier Option. DNS clients that ignore authentication failures and accept spoofed certificates will be subject to attacks (e.g., redirect to malicious servers, intercept sensitive data).

TCP connections received outside the home network MUST be discarded by the DoH/DoT forwarder in the CPE. This behavior adheres to REQ#8 in [RFC6092]; it MUST apply for both IPv4 and IPv6.

10. IANA Considerations

10.1. DHCPv6 Option

IANA is requested to assign the following new DHCPv6 Option Code in the registry maintained in:

Value Description Client ORO Singleton Option Reference
TBA1 OPTION_V6_DNS_RI Yes Yes [ThisDocument]

10.2. DHCP Option

IANA is requested to assign the following new DHCP Option Code in the registry maintained in:

| Tag  | Name             | Data  | Meaning        | Reference      |
|      |                  | Length|                |                |
| TBA2 | OPTION_V4_DNS_RI | N     | DoT/DoH server | [ThisDocument] |
|      |                  |       | authentication |                |
|      |                  |       | domain name    |                |

10.3. RA Option

IANA is requested to assign the following new IPv6 Neighbor Discovery Option type in the "IPv6 Neighbor Discovery Option Formats" sub-registry under the "Internet Control Message Protocol version 6 (ICMPv6) Parameters" registry maintained in

Type Description Reference
TBA3 DNS Reference Identifier Option [ThisDocument]

10.4. Service Name

IANA is requested to allocate the following service name from the registry available at:

     Service Name:            doh
     Port Number:             N/A
     Transport Protocol(s):   TCP
     Description:             DNS-over-HTTPS
     Assignee:                IESG <>
     Contact:                 IETF Chair <>
     Reference:               [ThisDocument]

11. Acknowledgements

Many thanks to Christian Jacquenet for the review.

Thanks to Tommy Jensen, Stephen Farrell, Martin Thomson, and Vittorio Bertola for the comments.

12. References

12.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997.
[RFC4861] Narten, T., Nordmark, E., Simpson, W. and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013.
[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.
[RFC8106] Jeong, J., Park, S., Beloeil, L. and S. Madanapalli, "IPv6 Router Advertisement Options for DNS Configuration", RFC 8106, DOI 10.17487/RFC8106, March 2017.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.
[RFC8310] Dickinson, S., Gillmor, D. and T. Reddy, "Usage Profiles for DNS over TLS and DNS over DTLS", RFC 8310, DOI 10.17487/RFC8310, March 2018.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., Richardson, M., Jiang, S., Lemon, T. and T. Winters, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 8415, DOI 10.17487/RFC8415, November 2018.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018.

12.2. Informative References

[Auto-upgrade] The Unicode Consortium, "DoH providers: criteria, process for Chrome"
[DPP] The Wi-Fi Alliance, "Device Provisioning Protocol Specification"
[I-D.ietf-dnsop-terminology-ter] Hoffman, P., "Terminology for DNS Transports and Location", Internet-Draft draft-ietf-dnsop-terminology-ter-01, February 2020.
[I-D.ietf-dnssd-push] Pusateri, T. and S. Cheshire, "DNS Push Notifications", Internet-Draft draft-ietf-dnssd-push-25, October 2019.
[I-D.ietf-v6ops-rfc7084-bis] Palet, J., "Basic Requirements for IPv6 Customer Edge Routers", Internet-Draft draft-ietf-v6ops-rfc7084-bis-04, June 2017.
[I-D.reddy-dprive-bootstrap-dns-server] Reddy.K, T., Wing, D., Richardson, M. and M. Boucadair, "A Bootstrapping Procedure to Discover and Authenticate DNS-over-TLS and DNS-over-HTTPS Servers", Internet-Draft draft-reddy-dprive-bootstrap-dns-server-08, March 2020.
[I-D.reddy-dprive-dprive-privacy-policy] Reddy.K, T., Wing, D., Richardson, M. and M. Boucadair, "DNS Server Privacy Statement and Filtering Policy with Assertion Token", Internet-Draft draft-reddy-dprive-dprive-privacy-policy-03, March 2020.
[RFC3646] Droms, R., "DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, DOI 10.17487/RFC3646, December 2003.
[RFC6092] Woodyatt, J., "Recommended Simple Security Capabilities in Customer Premises Equipment (CPE) for Providing Residential IPv6 Internet Service", RFC 6092, DOI 10.17487/RFC6092, January 2011.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March 2011.
[RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014.
[RFC7250] Wouters, P., Tschofenig, H., Gilmore, J., Weiler, S. and T. Kivinen, "Using Raw Public Keys in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, June 2014.
[RFC7969] Lemon, T. and T. Mrugalski, "Customizing DHCP Configuration on the Basis of Network Topology", RFC 7969, DOI 10.17487/RFC7969, October 2016.
[RFC8499] Hoffman, P., Sullivan, A. and K. Fujiwara, "DNS Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499, January 2019.
[RFC8520] Lear, E., Droms, R. and D. Romascanu, "Manufacturer Usage Description Specification", RFC 8520, DOI 10.17487/RFC8520, March 2019.
[RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D. and J. Kasten, "Automatic Certificate Management Environment (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019.
[TR-069] The Broadband Forum, "CPE WAN Management Protocol", December 2018.
[TS.24008] 3GPP, "Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 (Release 16)", December 2019.

Authors' Addresses

Mohamed Boucadair Orange Rennes, 35000 France EMail:
Tirumaleswar Reddy McAfee, Inc. Embassy Golf Link Business Park Bangalore, Karnataka 560071 India EMail:
Dan Wing Citrix Systems, Inc. USA EMail:
Neil Cook Open-Xchange UK EMail: