draft-ietf-doh-dns-over-https-07.txt   draft-ietf-doh-dns-over-https-08.txt 
Network Working Group P. Hoffman Network Working Group P. Hoffman
Internet-Draft ICANN Internet-Draft ICANN
Intended status: Standards Track P. McManus Intended status: Standards Track P. McManus
Expires: October 13, 2018 Mozilla Expires: November 17, 2018 Mozilla
April 11, 2018 May 16, 2018
DNS Queries over HTTPS DNS Queries over HTTPS (DOH)
draft-ietf-doh-dns-over-https-07 draft-ietf-doh-dns-over-https-08
Abstract Abstract
This document describes how to run DNS service over HTTP (DOH) using This document describes how to make DNS queries over HTTPS.
https:// URIs.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://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 October 13, 2018. This Internet-Draft will expire on November 17, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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
skipping to change at page 2, line 11 skipping to change at page 2, line 11
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. Protocol Requirements . . . . . . . . . . . . . . . . . . . . 3 3. Protocol Requirements . . . . . . . . . . . . . . . . . . . . 3
3.1. Non-requirements . . . . . . . . . . . . . . . . . . . . 4 3.1. Non-requirements . . . . . . . . . . . . . . . . . . . . 4
4. The HTTP Exchange . . . . . . . . . . . . . . . . . . . . . . 4 4. Selection of DNS API Server . . . . . . . . . . . . . . . . . 4
4.1. The HTTP Request . . . . . . . . . . . . . . . . . . . . 4 5. The HTTP Exchange . . . . . . . . . . . . . . . . . . . . . . 4
4.1.1. HTTP Request Examples . . . . . . . . . . . . . . . . 5 5.1. The HTTP Request . . . . . . . . . . . . . . . . . . . . 4
4.2. The HTTP Response . . . . . . . . . . . . . . . . . . . . 6 5.1.1. HTTP Request Examples . . . . . . . . . . . . . . . . 5
4.2.1. HTTP Response Example . . . . . . . . . . . . . . . . 7 5.2. The HTTP Response . . . . . . . . . . . . . . . . . . . . 6
5. HTTP Integration . . . . . . . . . . . . . . . . . . . . . . 7 5.2.1. HTTP Response Example . . . . . . . . . . . . . . . . 7
5.1. Cache Interaction . . . . . . . . . . . . . . . . . . . . 7 6. HTTP Integration . . . . . . . . . . . . . . . . . . . . . . 8
5.2. HTTP/2 . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Cache Interaction . . . . . . . . . . . . . . . . . . . . 8
5.3. Server Push . . . . . . . . . . . . . . . . . . . . . . . 9 6.2. HTTP/2 . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.4. Content Negotiation . . . . . . . . . . . . . . . . . . . 9 6.3. Server Push . . . . . . . . . . . . . . . . . . . . . . . 10
6. DNS Wire Format . . . . . . . . . . . . . . . . . . . . . . . 9 6.4. Content Negotiation . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. DNS Wire Format . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Registration of application/dns-message Media Type . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 8.1. Registration of application/dns-message Media Type . . . 11
9. Operational Considerations . . . . . . . . . . . . . . . . . 13 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 10. Operational Considerations . . . . . . . . . . . . . . . . . 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative References . . . . . . . . . . . . . . . . . . 14 11.1. Normative References . . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . 15 11.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Previous Work on DNS over HTTP or in Other Formats . 16 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Previous Work on DNS over HTTP or in Other Formats . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
This document defines a specific protocol for sending DNS [RFC1035] This document defines a specific protocol for sending DNS [RFC1035]
queries and getting DNS responses over HTTP [RFC7540] using https:// queries and getting DNS responses over HTTP [RFC7540] using https
(and therefore TLS [RFC5246] security for integrity and URIs (and therefore TLS [RFC5246] security for integrity and
confidentiality). Each DNS query-response pair is mapped into a HTTP confidentiality). Each DNS query-response pair is mapped into a HTTP
exchange. exchange.
The described approach is more than a tunnel over HTTP. It The described approach is more than a tunnel over HTTP. It
establishes default media formatting types for requests and responses establishes default media formatting types for requests and responses
but uses normal HTTP content negotiation mechanisms for selecting but uses normal HTTP content negotiation mechanisms for selecting
alternatives that endpoints may prefer in anticipation of serving new alternatives that endpoints may prefer in anticipation of serving new
use cases. In addition to this media type negotiation, it aligns use cases. In addition to this media type negotiation, it aligns
itself with HTTP features such as caching, redirection, proxying, itself with HTTP features such as caching, redirection, proxying,
authentication, and compression. authentication, and compression.
The integration with HTTP provides a transport suitable for both The integration with HTTP provides a transport suitable for both
traditional DNS clients and native web applications seeking access to existing DNS clients and native web applications seeking access to
the DNS. the DNS.
Two primary uses cases were considered during this protocol's Two primary uses cases were considered during this protocol's
development. They included preventing on-path devices from development. They included preventing on-path devices from
interfering with DNS operations and allowing web applications to interfering with DNS operations and allowing web applications to
access DNS information via existing browser APIs in a safe way access DNS information via existing browser APIs in a safe way
consistent with Cross Origin Resource Sharing (CORS) [CORS]. There consistent with Cross Origin Resource Sharing (CORS) [CORS]. No
are certainly other uses for this work. special effort has been taken to enable or prevent application to
other use cases. This document focuses on communication between DNS
clients (such as operating system stub resolvers) and recursive
resolvers.
2. Terminology 2. Terminology
A server that supports this protocol on one or more URIs is called a A server that supports this protocol is called a "DNS API server" to
"DNS API server" to differentiate it from a "DNS server" (one that differentiate it from a "DNS server" (one that only provides DNS
uses the regular DNS protocol). Similarly, a client that supports service over one or more of the other transport protocols
this protocol is called a "DNS API client". standardized for DNS). Similarly, a client that supports this
protocol is called a "DNS API client".
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14, RFC8174 [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Protocol Requirements 3. Protocol Requirements
[[ RFC Editor: Please remove this entire section before publication.
]]
The protocol described here bases its design on the following The protocol described here bases its design on the following
protocol requirements: protocol requirements:
o The protocol must use normal HTTP semantics. o The protocol must use normal HTTP semantics.
o The queries and responses must be able to be flexible enough to o The queries and responses must be able to be flexible enough to
express every DNS query that would normally be sent in DNS over express every DNS query that would normally be sent in DNS over
UDP (including queries and responses that use DNS extensions, but UDP (including queries and responses that use DNS extensions, but
not those that require multiple responses). not those that require multiple responses).
skipping to change at page 4, line 14 skipping to change at page 4, line 17
3.1. Non-requirements 3.1. Non-requirements
o Supporting network-specific DNS64 [RFC6147] o Supporting network-specific DNS64 [RFC6147]
o Supporting other network-specific inferences from plaintext DNS o Supporting other network-specific inferences from plaintext DNS
queries queries
o Supporting insecure HTTP o Supporting insecure HTTP
4. The HTTP Exchange 4. Selection of DNS API Server
4.1. The HTTP Request Before using a DNS API server for DNS resolution, the client MUST
establish that the HTTP request URI is a trusted service for the DOH
query, in other words, a DNS API client MUST only use a DNS API
server that is configured as trustworthy.
A client MUST NOT use a DNS API server simply because it was
discovered, or because the client was told to use the DNS API server
by an untrusted party.
This specification does not extend DNS resolution privileges to URIs
that are not recognized by the DNS API client as trusted DNS API
servers. As such, use of untrusted servers is out of scope of this
document.
5. The HTTP Exchange
5.1. The HTTP Request
A DNS API client encodes a single DNS query into an HTTP request A DNS API client encodes a single DNS query into an HTTP request
using either the HTTP GET or POST method and the other requirements using either the HTTP GET or POST method and the other requirements
of this section. The DNS API server defines the URI used by the of this section. The DNS API server defines the URI used by the
request through the use of a URI Template [RFC6570]. Configuration request through the use of a URI Template [RFC6570].
and discovery of the URI Template is done out of band from this
protocol. Configuration and discovery of the URI Template is done out of band
from this protocol. DNS API Servers MAY support more than one URI.
This allows the different endpoints to have different properties such
as different authentication requirements or service level guarantees.
The URI Template defined in this document is processed without any The URI Template defined in this document is processed without any
variables when the HTTP method is POST. When the HTTP method is GET variables when the HTTP method is POST. When the HTTP method is GET
the single variable "dns" is defined as the content of the DNS the single variable "dns" is defined as the content of the DNS
request (as described in Section 6), encoded with base64url request (as described in Section 7), encoded with base64url
[RFC4648]. [RFC4648].
Future specifications for new media types MUST define the variables Future specifications for new media types MUST define the variables
used for URI Template processing with this protocol. used for URI Template processing with this protocol.
DNS API servers MUST implement both the POST and GET methods. DNS API servers MUST implement both the POST and GET methods.
When using the POST method the DNS query is included as the message When using the POST method the DNS query is included as the message
body of the HTTP request and the Content-Type request header body of the HTTP request and the Content-Type request header
indicates the media type of the message. POST-ed requests are indicates the media type of the message. POST-ed requests are
smaller than their GET equivalents. smaller than their GET equivalents.
Using the GET method is friendlier to many HTTP cache Using the GET method is friendlier to many HTTP cache
implementations. implementations.
The DNS API client SHOULD include an HTTP "Accept" request header to The DNS API client SHOULD include an HTTP "Accept" request header to
indicate what type of content can be understood in response. indicate what type of content can be understood in response.
Irrespective of the value of the Accept request header, the client Irrespective of the value of the Accept request header, the client
MUST be prepared to process "application/dns-message" (as described MUST be prepared to process "application/dns-message" (as described
in Section 6) responses but MAY also process any other type it in Section 7) responses but MAY also process any other type it
receives. receives.
In order to maximize cache friendliness, DNS API clients using media In order to maximize cache friendliness, DNS API clients using media
formats that include DNS ID, such as application/dns-message, SHOULD formats that include DNS ID, such as application/dns-message, SHOULD
use a DNS ID of 0 in every DNS request. HTTP correlates the request use a DNS ID of 0 in every DNS request. HTTP correlates the request
and response, thus eliminating the need for the ID in a media type and response, thus eliminating the need for the ID in a media type
such as application/dns-message. The use of a varying DNS ID can such as application/dns-message. The use of a varying DNS ID can
cause semantically equivalent DNS queries to be cached separately. cause semantically equivalent DNS queries to be cached separately.
DNS API clients can use HTTP/2 padding and compression in the same DNS API clients can use HTTP/2 padding and compression in the same
way that other HTTP/2 clients use (or don't use) them. way that other HTTP/2 clients use (or don't use) them.
4.1.1. HTTP Request Examples 5.1.1. HTTP Request Examples
These examples use HTTP/2 style formatting from [RFC7540]. These examples use HTTP/2 style formatting from [RFC7540].
These examples use a DNS API service with a URI Template of These examples use a DNS API service with a URI Template of
"https://dnsserver.example.net/dns-query{?dns}" to resolve IN A "https://dnsserver.example.net/dns-query{?dns}" to resolve IN A
records. records.
The requests are represented as application/dns-message typed bodies. The requests are represented as application/dns-message typed bodies.
The first example request uses GET to request www.example.com The first example request uses GET to request www.example.com
skipping to change at page 6, line 20 skipping to change at page 6, line 43
:method = GET :method = GET
:scheme = https :scheme = https
:authority = dnsserver.example.net :authority = dnsserver.example.net
:path = /dns-query? (no space or CR) :path = /dns-query? (no space or CR)
dns=AAABAAABAAAAAAAAAWE-NjJjaGFyYWN0ZXJsYWJl (no space or CR) dns=AAABAAABAAAAAAAAAWE-NjJjaGFyYWN0ZXJsYWJl (no space or CR)
bC1tYWtlcy1iYXNlNjR1cmwtZGlzdGluY3QtZnJvbS1z (no space or CR) bC1tYWtlcy1iYXNlNjR1cmwtZGlzdGluY3QtZnJvbS1z (no space or CR)
dGFuZGFyZC1iYXNlNjQHZXhhbXBsZQNjb20AAAEAAQ dGFuZGFyZC1iYXNlNjQHZXhhbXBsZQNjb20AAAEAAQ
accept = application/dns-message accept = application/dns-message
4.2. The HTTP Response 5.2. The HTTP Response
An HTTP response with a 2xx status code ([RFC7231] Section 6.3) An HTTP response with a 2xx status code ([RFC7231] Section 6.3)
indicates a valid DNS response to the query made in the HTTP request. indicates a valid DNS response to the query made in the HTTP request.
A valid DNS response includes both success and failure responses. A valid DNS response includes both success and failure responses.
For example, a DNS failure response such as SERVFAIL or NXDOMAIN will For example, a DNS failure response such as SERVFAIL or NXDOMAIN will
be the message in a successful 2xx HTTP response even though there be the message in a successful 2xx HTTP response even though there
was a failure at the DNS layer. Responses with non-successful HTTP was a failure at the DNS layer. Responses with non-successful HTTP
status codes do not contain DNS answers to the question in the status codes do not contain DNS answers to the question in the
corresponding request. Some of these non-successful HTTP responses corresponding request. Some of these non-successful HTTP responses
(e.g., redirects or authentication failures) could allow clients to (e.g., redirects or authentication failures) could mean that clients
make new requests to satisfy the original question. need to make new requests to satisfy the original question.
Different response media types will provide more or less information Different response media types will provide more or less information
from a DNS response. For example, one response type might include from a DNS response. For example, one response type might include
the information from the DNS header bytes while another might omit the information from the DNS header bytes while another might omit
it. The amount and type of information that a media type gives is it. The amount and type of information that a media type gives is
solely up to the format, and not defined in this protocol. solely up to the format, and not defined in this protocol.
At the time this is published, the response types are works in The only response type defined in this document is "application/dns-
progress. The only response type defined in this document is message", but it is possible that other response formats will be
"application/dns-message", but it is possible that other response defined in the future.
formats will be defined in the future.
The DNS response for "application/dns-message" in Section 6 MAY have The DNS response for "application/dns-message" in Section 7 MAY have
one or more EDNS options, depending on the extension definition of one or more EDNS options [RFC6891], depending on the extension
the extensions given in the DNS request. definition of the extensions given in the DNS request.
Each DNS request-response pair is matched to one HTTP exchange. The Each DNS request-response pair is matched to one HTTP exchange. The
responses may be processed and transported in any order using HTTP's responses may be processed and transported in any order using HTTP's
multi-streaming functionality ([RFC7540] Section 5). multi-streaming functionality ([RFC7540] Section 5).
Section 5.1 discusses the relationship between DNS and HTTP response Section 6.1 discusses the relationship between DNS and HTTP response
caching. caching.
A DNS API server MUST be able to process application/dns-message A DNS API server MUST be able to process application/dns-message
request messages. request messages.
A DNS API server SHOULD respond with HTTP status code 415 A DNS API server SHOULD respond with HTTP status code 415
(Unsupported Media Type) upon receiving a media type it is unable to (Unsupported Media Type) upon receiving a media type it is unable to
process. process.
4.2.1. HTTP Response Example 5.2.1. HTTP Response Example
This is an example response for a query for the IN A records for This is an example response for a query for the IN A records for
"www.example.com" with recursion turned on. The response bears one "www.example.com" with recursion turned on. The response bears one
record with an address of 192.0.2.1 and a TTL of 128 seconds. record with an address of 192.0.2.1 and a TTL of 128 seconds.
:status = 200 :status = 200
content-type = application/dns-message content-type = application/dns-message
content-length = 64 content-length = 64
cache-control = max-age=128 cache-control = max-age=128
<64 bytes represented by the following hex encoding> <64 bytes represented by the following hex encoding>
00 00 81 80 00 01 00 01 00 00 00 00 03 77 77 77 00 00 81 80 00 01 00 01 00 00 00 00 03 77 77 77
07 65 78 61 6d 70 6c 65 03 63 6f 6d 00 00 01 00 07 65 78 61 6d 70 6c 65 03 63 6f 6d 00 00 01 00
01 03 77 77 77 07 65 78 61 6d 70 6c 65 03 63 6f 01 03 77 77 77 07 65 78 61 6d 70 6c 65 03 63 6f
6d 00 00 01 00 01 00 00 00 80 00 04 C0 00 02 01 6d 00 00 01 00 01 00 00 00 80 00 04 C0 00 02 01
5. HTTP Integration 6. HTTP Integration
This protocol MUST be used with the https scheme URI [RFC7230]. This protocol MUST be used with the https scheme URI [RFC7230].
5.1. Cache Interaction 6.1. Cache Interaction
A DNS API client may utilize a hierarchy of caches that include both A DOH exchange can pass through a hierarchy of caches that include
HTTP and DNS specific caches. HTTP cache entries may be bypassed both HTTP and DNS specific caches. These caches may exist beteen the
with HTTP mechanisms such as the "Cache-Control no-cache" directive; DNS API server and client, or on the DNS API client itself. HTTP
however DNS caches do not have a similar mechanism. caches are by design generic; that is, they do not understand this
protocol. Even if a DNS API client has modified its cache
implementation to be aware of DOH semantics, it does not follow that
all upstream caches (for example, inline proxies, server-side
gateways and Content Delivery Networks) will be.
The Answer section of a DNS response can contain zero or more RRsets. As a result, DNS API servers need to carefully consider the HTTP
(RRsets are defined in [RFC7719].) According to [RFC2181], each caching metadata they send in response to GET requests (POST requests
resource record in an RRset has Time To Live (TTL) freshness are not cacheable unless specific response headers are sent; this is
information. Different RRsets in the Answer section can have not widely implemented, and not advised for DOH).
different TTLs, although it is only possible for the HTTP response to
have a single freshness lifetime. The HTTP response freshness In particular, DNS API servers SHOULD assign an explicit freshness
lifetime ([RFC7234] Section 4.2) should be coordinated with the RRset lifetime ([RFC7234] Section 4.2) so that the DNS API client is more
with the smallest TTL in the Answer section of the response. likely to use fresh DNS data. This requirement is due to HTTP caches
Specifically, the HTTP freshness lifetime SHOULD be set to expire at being able to assign their own heuristic freshness (such as that
the same time any of the DNS resource records in the Answer section described in [RFC7234] Section 4.2.2), which would take control of
reach a 0 TTL. The response freshness lifetime MUST NOT be greater the cache contents out of the hands of the DNS API server.
than that indicated by the DNS resoruce record with the smallest TTL
in the response. The assigned freshness lifetime of a DOH HTTP response SHOULD be the
smallest TTL in the Answer section of the DNS response. For example,
if a HTTP response carries three RRsets with TTLs of 30, 600, and
300, the HTTP freshness lifetime should be 30 seconds (which could be
specified as "Cache-Control: max-age=30"). The assigned freshness
lifetime MUST NOT be greater than the smallest TTL in the Answer
section of the DNS response. This requirement helps assure that none
of the RRsets contained in a DNS response are served stale from an
HTTP cache.
If the DNS response has no records in the Answer section, and the DNS If the DNS response has no records in the Answer section, and the DNS
response has an SOA record in the Authority section, the response response has an SOA record in the Authority section, the response
freshness lifetime MUST NOT be greater than the MINIMUM field from freshness lifetime MUST NOT be greater than the MINIMUM field from
that SOA record. (See [RFC2308].) Otherwise, the HTTP response MUST that SOA record (see [RFC2308]).
set a freshness lifetime ([RFC7234] Section 4.2) of 0 by using a
mechanism such as "Cache-Control: no-cache" ([RFC7234]
Section 5.2.1.4).
A DNS API client that receives a response without an explicit The stale-while-revalidate and stale-if-error Cache-Control
freshness lifetime MUST NOT assign that response a heuristic directives ([RFC5861]) could be well suited to a DOH implementation
freshness ([RFC7234] Section 4.2.2.) greater than that indicated by when allowed by server policy. Those mechanisms allow a client, at
the DNS Record with the smallest TTL in the response. the server's discretion, to reuse a cache entry that is no longer
fresh. In such a case, the client reuses all of a cached entry, or
none of it.
A DOH response that was previously stored in an HTTP cache will DNS API servers also need to consider caching when generating
contain the [RFC7234] Age response header indicating the elapsed time responses that are not globally valid. For instance, if a DNS API
between when the entry was placed in the HTTP cache and the current server customizes a response based on the client's identity, it would
DOH response. DNS API clients should subtract this time from the DNS not want to allow global reuse of that response. This could be
TTL if they are re-sharing the information in a non HTTP context accomplished through a variety of HTTP techniques such as a Cache-
(e.g., their own DNS cache) to determine the remaining time to live Control max-age of 0, or by using the Vary response header ([RFC7231]
of the DNS record. Section 7.1.4) to establish a secondary cache key ([RFC7234]
Section 4.1).
HTTP revalidation (e.g., via If-None-Match request headers) of cached DNS API clients MUST account for the Age response header's value
DNS information may be of limited value to DOH as revalidation ([RFC7234]) when calculating the DNS TTL of a response. For example,
provides only a bandwidth benefit and DNS transactions are normally if a RRset is received with a DNS TTL of 600, but the Age header
latency bound. Furthermore, the HTTP response headers that enable indicates that the response has been cached for 250 seconds, the
revalidation (such as "Last-Modified" and "Etag") are often fairly remaining lifetime of the RRset is 350 seconds.
large when compared to the overall DNS response size, and have a
variable nature that creates constant pressure on the HTTP/2
compression dictionary [RFC7541]. Other types of DNS data, such as
zone transfers, may be larger and benefit more from revalidation.
DNS API servers may wish to consider whether providing these
validation enabling response headers is worthwhile.
The stale-while-revalidate and stale-if-error cache control DNS API clients can request an uncached copy of a response by using
directives may be well suited to a DOH implementation when allowed by the "no-cache" request cache control directive ([RFC7234],
server policy. Those mechanisms allow a client, at the server's Section 5.2.1.4) and similar controls. Note that some caches might
discretion, to reuse a cache entry that is no longer fresh under some not honor these directives, either due to configuration or
extenuating circumstances defined in [RFC5861]. interaction with traditional DNS caches that do not have such a
mechanism.
All HTTP servers, including DNS API servers, need to consider cache HTTP conditional requests ([RFC7232]) may be of limited value to DOH,
interaction when they generate responses that are not globally valid. as revalidation provides only a bandwidth benefit and DNS
For instance, if a DNS API server customized a response based on the transactions are normally latency bound. Furthermore, the HTTP
client's identity then it would not want to globally allow reuse of response headers that enable revalidation (such as "Last-Modified"
that response. This could be accomplished through a variety of HTTP and "Etag") are often fairly large when compared to the overall DNS
techniques such as a Cache-Control max-age of 0, or perhaps by the response size, and have a variable nature that creates constant
Vary response header. pressure on the HTTP/2 compression dictionary [RFC7541]. Other types
of DNS data, such as zone transfers, may be larger and benefit more
from revalidation.
5.2. HTTP/2 6.2. HTTP/2
The minimum version of HTTP used by DOH SHOULD be HTTP/2 [RFC7540]. HTTP/2 [RFC7540] is the minimum RECOMMENDED version of HTTP for use
with DOH.
The messages in classic UDP based DNS [RFC1035] are inherently The messages in classic UDP based DNS [RFC1035] are inherently
unordered and have low overhead. A competitive HTTP transport needs unordered and have low overhead. A competitive HTTP transport needs
to support reordering, parallelism, priority, and header compression to support reordering, parallelism, priority, and header compression
to achieve similar performance. Those features were introduced to to achieve similar performance. Those features were introduced to
HTTP in HTTP/2 [RFC7540]. Earlier versions of HTTP are capable of HTTP in HTTP/2 [RFC7540]. Earlier versions of HTTP are capable of
conveying the semantic requirements of DOH but may result in very conveying the semantic requirements of DOH but may result in very
poor performance. poor performance.
5.3. Server Push 6.3. Server Push
Before using DOH response data for DNS resolution, the client MUST Before using DOH response data for DNS resolution, the client MUST
establish that the HTTP request URI is a trusted service for the DOH establish that the HTTP request URI may be used for the DOH query.
query. For HTTP requests initiated by the DNS API client this trust For HTTP requests initiated by the DNS API client this is implicit in
is implicit in the selection of URI. For HTTP server push ([RFC7540] the selection of URI. For HTTP server push ([RFC7540] Section 8.2)
Section 8.2) extra care must be taken to ensure that the pushed URI extra care must be taken to ensure that the pushed URI is one that
is one that the client would have directed the same query to if the the client would have directed the same query to if the client had
client had initiated the request. This specification does not extend initiated the request.
DNS resolution privileges to URIs that are not recognized by the
client as trusted DNS API servers.
5.4. Content Negotiation 6.4. Content Negotiation
In order to maximize interoperability, DNS API clients and DNS API In order to maximize interoperability, DNS API clients and DNS API
servers MUST support the "application/dns-message" media type. Other servers MUST support the "application/dns-message" media type. Other
media types MAY be used as defined by HTTP Content Negotiation media types MAY be used as defined by HTTP Content Negotiation
([RFC7231] Section 3.4). ([RFC7231] Section 3.4). Those media types MUST be flexible enough
to express every DNS query that would normally be sent in DNS over
UDP (including queries and responses that use DNS extensions, but not
those that require multiple responses).
6. DNS Wire Format 7. DNS Wire Format
The data payload is the DNS on-the-wire format defined in [RFC1035]. The data payload is the DNS on-the-wire format defined in [RFC1035].
The format is for DNS over UDP. Note that this is different than the The format is for DNS over UDP. Note that this is different than the
wire format used in [RFC7858]. Also note that while [RFC1035] says wire format used in [RFC7858]. Also note that while [RFC1035] says
"Messages carried by UDP are restricted to 512 bytes", that was later "Messages carried by UDP are restricted to 512 bytes", that was later
updated by [RFC6891], and this protocol allows DNS on-the-wire format updated by [RFC6891]. This protocol allows DNS on-the-wire format
payloads of any size. payloads of any size.
When using the GET method, the data payload MUST be encoded with When using the GET method, the data payload MUST be encoded with
base64url [RFC4648] and then provided as a variable named "dns" to base64url [RFC4648] and then provided as a variable named "dns" to
the URI Template expansion. Padding characters for base64url MUST the URI Template expansion. Padding characters for base64url MUST
NOT be included. NOT be included.
When using the POST method, the data payload MUST NOT be encoded and When using the POST method, the data payload MUST NOT be encoded and
is used directly as the HTTP message body. is used directly as the HTTP message body.
DNS API clients using the DNS wire format MAY have one or more EDNS DNS API clients using the DNS wire format MAY have one or more EDNS
options [RFC6891] in the request. options [RFC6891] in the request.
The media type is "application/dns-message". The media type is "application/dns-message".
7. IANA Considerations 8. IANA Considerations
7.1. Registration of application/dns-message Media Type 8.1. Registration of application/dns-message Media Type
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of MIME media type Subject: Registration of MIME media type
application/dns-message application/dns-message
MIME media type name: application MIME media type name: application
MIME subtype name: dns-message MIME subtype name: dns-message
Required parameters: n/a Required parameters: n/a
skipping to change at page 12, line 5 skipping to change at page 13, line 5
Paul Hoffman, paul.hoffman@icann.org Paul Hoffman, paul.hoffman@icann.org
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: n/a Restrictions on usage: n/a
Author: Paul Hoffman, paul.hoffman@icann.org Author: Paul Hoffman, paul.hoffman@icann.org
Change controller: IESG Change controller: IESG
8. Security Considerations 9. Security Considerations
Running DNS over HTTPS relies on the security of the underlying HTTP Running DNS over HTTPS relies on the security of the underlying HTTP
transport. This mitigates classic amplification attacks for UDP- transport. This mitigates classic amplification attacks for UDP-
based DNS. Implementations utilizing HTTP/2 benefit from the TLS based DNS. Implementations utilizing HTTP/2 benefit from the TLS
profile defined in [RFC7540] Section 9.2. profile defined in [RFC7540] Section 9.2.
Session level encryption has well known weaknesses with respect to Session level encryption has well known weaknesses with respect to
traffic analysis which might be particularly acute when dealing with traffic analysis which might be particularly acute when dealing with
DNS queries. HTTP/2 provides further advice about the use of DNS queries. HTTP/2 provides further advice about the use of
compression (Section 10.6 of [RFC7540]) and padding (Section 10.7 of compression ([RFC7540] Section 10.6) and padding ([RFC7540]
[RFC7540]). Section 10.7 ). DNS API Servers can also add DNS padding [RFC7830]
if the DNS API requests it in the DNS query.
The HTTPS connection provides transport security for the interaction The HTTPS connection provides transport security for the interaction
between the DNS API server and client, but does not inherently ensure between the DNS API server and client, but does not provide the
the authenticity of DNS data. A DNS API client may also perform full response integrity of DNS data provided by DNSSEC. DNSSEC and DOH
DNSSEC validation of answers received from a DNS API server or it may are independent and fully compatible protocols, each solving
choose to trust answers from a particular DNS API server, much as a different problems. The use of one does not diminish the need nor
DNS client might choose to trust answers from its recursive DNS the usefulness of the other. It is the choice of a client to either
resolver. This capability might be affected by the response media perform full DNSSEC validation of answers or to trust the DNS API
type. server to do DNSSEC validation and inspect the AD (Authentic Data)
bit in the returned message to determine whether an answer was
authentic or not. As noted in Section 5.2, different response media
types will provide more or less information from a DNS response so
this choice may be affected by the response media type.
Section 5.1 describes the interaction of this protocol with HTTP Section 6.1 describes the interaction of this protocol with HTTP
caching. An adversary that can control the cache used by the client caching. An adversary that can control the cache used by the client
can affect that client's view of the DNS. This is no different than can affect that client's view of the DNS. This is no different than
the security implications of HTTP caching for other protocols that the security implications of HTTP caching for other protocols that
use HTTP. use HTTP.
A server that is acting both as a normal web server and a DNS API In the absence of DNSSEC information, a DNS API server can give a
server is in a position to choose which DNS names it forces a client client invalid data in response to a DNS query. A client MUST NOT
to resolve (through its web service) and also be the one to answer use arbitrary DNS API servers. Instead, a client MUST only use DNS
those queries (through its DNS API service). An untrusted DNS API API servers specified using mechanisms such as explicit
server can thus easily cause damage by poisoning a client's cache configuration. This does not guarantee protection against invalid
with names that the DNS API server chooses to poison. A client MUST data but reduces the risk.
NOT trust a DNS API server simply because it was discovered, or
because the client was told to trust the DNS API server by an
untrusted party. Instead, a client MUST only trust DNS API server
that is configured as trustworthy.
A client can use DNS over HTTPS as one of multiple mechanisms to A client can use DNS over HTTPS as one of multiple mechanisms to
obtain DNS data. If a client of this protocol encounters an HTTP obtain DNS data. If a client of this protocol encounters an HTTP
error after sending a DNS query, and then falls back to a different error after sending a DNS query, and then falls back to a different
DNS retrieval mechanism, doing so can weaken the privacy and DNS retrieval mechanism, doing so can weaken the privacy and
authenticity expected by the user of the client. authenticity expected by the user of the client.
9. Operational Considerations 10. Operational Considerations
Local policy considerations and similar factors mean different DNS Local policy considerations and similar factors mean different DNS
servers may provide different results to the same query: for instance servers may provide different results to the same query: for instance
in split DNS configurations [RFC6950]. It logically follows that the in split DNS configurations [RFC6950]. It logically follows that the
server which is queried can influence the end result. Therefore a server which is queried can influence the end result. Therefore a
client's choice of DNS server may affect the responses it gets to its client's choice of DNS server may affect the responses it gets to its
queries. For example, in the case of DNS64 [RFC6147], the choice queries. For example, in the case of DNS64 [RFC6147], the choice
could affect whether IPv6/IPv4 translation will work at all. could affect whether IPv6/IPv4 translation will work at all.
The HTTPS channel used by this specification establishes secure two The HTTPS channel used by this specification establishes secure two
skipping to change at page 13, line 33 skipping to change at page 14, line 33
procedure and the check itself requires DNS resolution to connect to procedure and the check itself requires DNS resolution to connect to
the third party a deadlock can occur. The use of OCSP [RFC6960] the third party a deadlock can occur. The use of OCSP [RFC6960]
servers or AIA for CRL fetching ([RFC5280] Section 4.2.2.1) are servers or AIA for CRL fetching ([RFC5280] Section 4.2.2.1) are
examples of how this deadlock can happen. To mitigate the examples of how this deadlock can happen. To mitigate the
possibility of deadlock, DNS API servers SHOULD NOT rely on DNS based possibility of deadlock, DNS API servers SHOULD NOT rely on DNS based
references to external resources in the TLS handshake. For OCSP the references to external resources in the TLS handshake. For OCSP the
server can bundle the certificate status as part of the handshake server can bundle the certificate status as part of the handshake
using a mechanism appropriate to the version of TLS, such as using using a mechanism appropriate to the version of TLS, such as using
[RFC6066] Section 8 for TLS version 1.2. AIA deadlocks can be [RFC6066] Section 8 for TLS version 1.2. AIA deadlocks can be
avoided by providing intermediate certificates that might otherwise avoided by providing intermediate certificates that might otherwise
be obtained through additional requests. be obtained through additional requests. Note that these deadlocks
also need to be considered for server that a DNS API server might
redirect to.
A DNS API client may face a similar bootstrapping problem when the A DNS API client may face a similar bootstrapping problem when the
HTTP request needs to resolve the hostname portion of the DNS URI. HTTP request needs to resolve the hostname portion of the DNS URI.
Just as the address of a traditional DNS nameserver cannot be Just as the address of a traditional DNS nameserver cannot be
originally determined from that same server, a DNS API client cannot originally determined from that same server, a DNS API client cannot
use its DNS API server to initially resolve the server's host name use its DNS API server to initially resolve the server's host name
into an address. Alternative strategies a client might employ into an address. Alternative strategies a client might employ
include making the initial resolution part of the configuration, IP include making the initial resolution part of the configuration, IP
based URIs and corresponding IP based certificates for HTTPS, or based URIs and corresponding IP based certificates for HTTPS, or
resolving the DNS API server's hostname via traditional DNS or resolving the DNS API server's hostname via traditional DNS or
another DNS API server while still authenticating the resulting another DNS API server while still authenticating the resulting
connection via HTTPS. connection via HTTPS.
HTTP [RFC7230] is a stateless application level protocol and HTTP [RFC7230] is a stateless application level protocol and
therefore DOH implementations do not provide stateful ordering therefore DOH implementations do not provide stateful ordering
guarantees between different requests. DOH cannot be used as a guarantees between different requests. DOH cannot be used as a
transport for other protocols that require strict ordering. transport for other protocols that require strict ordering.
If a DNS API server responds to a DNS API client with a DNS message A DNS API server is allowed to answer queries with any valid DNS
that has the TC (truncation) bit set in the header, that indicates response. For example, a valid DNS response might have the TC
that the DNS API server was not able to retrieve a full answer for (truncation) bit set in the DNS header to indicate that the server
the query and is providing the best answer it could get. This was not able to retrieve a full answer for the query but is providing
protocol does not require that a DNS API server that cannot get an the best answer it could get. A DNS API server can reply to queries
untruncated answer send back such an answer; it can instead send back with an HTTP error for queries that it cannot fulfill. In this same
an HTTP error to indicate that it cannot give a useful answer. example, a DNS API server could use an HTTP error instead of a non-
error response that has the TC bit set.
10. Acknowledgments
This work required a high level of cooperation between experts in Many extensions to DNS, using [RFC6891], have been defined over the
different technologies. Thank you Ray Bellis, Stephane Bortzmeyer, years. Extensions that are specific to the choice of transport, such
Manu Bretelle, Tony Finch, Daniel Kahn Gilmor, Olafur Guomundsson, as [RFC7828], are not applicable to DOH.
Wes Hardaker, Rory Hewitt, Joe Hildebrand, David Lawrence, Eliot
Lear, John Mattson, Alex Mayrhofer, Mark Nottingham, Jim Reid, Adam
Roach, Ben Schwartz, Davey Song, Daniel Stenberg, Andrew Sullivan,
Martin Thomson, and Sam Weiler.
11. References 11. References
11.1. Normative References 11.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/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>.
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
<https://www.rfc-editor.org/info/rfc2308>. <https://www.rfc-editor.org/info/rfc2308>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>. <https://www.rfc-editor.org/info/rfc4648>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
skipping to change at page 15, line 10 skipping to change at page 16, line 10
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>. <https://www.rfc-editor.org/info/rfc7230>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>. <https://www.rfc-editor.org/info/rfc7231>.
[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Conditional Requests", RFC 7232,
DOI 10.17487/RFC7232, June 2014,
<https://www.rfc-editor.org/info/rfc7232>.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching", Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, DOI 10.17487/RFC7234, June 2014, RFC 7234, DOI 10.17487/RFC7234, June 2014,
<https://www.rfc-editor.org/info/rfc7234>. <https://www.rfc-editor.org/info/rfc7234>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540, Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015, DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>. <https://www.rfc-editor.org/info/rfc7540>.
skipping to change at page 15, line 33 skipping to change at page 16, line 38
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References 11.2. Informative References
[CORS] "Cross-Origin Resource Sharing", n.d., [CORS] "Cross-Origin Resource Sharing", n.d.,
<https://fetch.spec.whatwg.org/#http-cors-protocol>. <https://fetch.spec.whatwg.org/#http-cors-protocol>.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
<https://www.rfc-editor.org/info/rfc2181>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
[RFC5861] Nottingham, M., "HTTP Cache-Control Extensions for Stale [RFC5861] Nottingham, M., "HTTP Cache-Control Extensions for Stale
Content", RFC 5861, DOI 10.17487/RFC5861, May 2010, Content", RFC 5861, DOI 10.17487/RFC5861, May 2010,
<https://www.rfc-editor.org/info/rfc5861>. <https://www.rfc-editor.org/info/rfc5861>.
skipping to change at page 16, line 27 skipping to change at page 17, line 27
"Architectural Considerations on Application Features in "Architectural Considerations on Application Features in
the DNS", RFC 6950, DOI 10.17487/RFC6950, October 2013, the DNS", RFC 6950, DOI 10.17487/RFC6950, October 2013,
<https://www.rfc-editor.org/info/rfc6950>. <https://www.rfc-editor.org/info/rfc6950>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A., [RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP", Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013, RFC 6960, DOI 10.17487/RFC6960, June 2013,
<https://www.rfc-editor.org/info/rfc6960>. <https://www.rfc-editor.org/info/rfc6960>.
[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS [RFC7828] Wouters, P., Abley, J., Dickinson, S., and R. Bellis, "The
Terminology", RFC 7719, DOI 10.17487/RFC7719, December edns-tcp-keepalive EDNS0 Option", RFC 7828,
2015, <https://www.rfc-editor.org/info/rfc7719>. DOI 10.17487/RFC7828, April 2016,
<https://www.rfc-editor.org/info/rfc7828>.
[RFC7830] Mayrhofer, A., "The EDNS(0) Padding Option", RFC 7830,
DOI 10.17487/RFC7830, May 2016,
<https://www.rfc-editor.org/info/rfc7830>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D., [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>. 2016, <https://www.rfc-editor.org/info/rfc7858>.
Appendix A. Previous Work on DNS over HTTP or in Other Formats Acknowledgments
This work required a high level of cooperation between experts in
different technologies. Thank you Ray Bellis, Stephane Bortzmeyer,
Manu Bretelle, Sara Dickinson, Tony Finch, Daniel Kahn Gilmor, Olafur
Guomundsson, Wes Hardaker, Rory Hewitt, Joe Hildebrand, David
Lawrence, Eliot Lear, John Mattson, Alex Mayrhofer, Mark Nottingham,
Jim Reid, Adam Roach, Ben Schwartz, Davey Song, Daniel Stenberg,
Andrew Sullivan, Martin Thomson, and Sam Weiler.
Previous Work on DNS over HTTP or in Other Formats
The following is an incomplete list of earlier work that related to The following is an incomplete list of earlier work that related to
DNS over HTTP/1 or representing DNS data in other formats. DNS over HTTP/1 or representing DNS data in other formats.
The list includes links to the tools.ietf.org site (because these The list includes links to the tools.ietf.org site (because these
documents are all expired) and web sites of software. documents are all expired) and web sites of software.
o https://tools.ietf.org/html/draft-mohan-dns-query-xml o https://tools.ietf.org/html/draft-mohan-dns-query-xml
o https://tools.ietf.org/html/draft-daley-dnsxml o https://tools.ietf.org/html/draft-daley-dnsxml
 End of changes. 57 change blocks. 
179 lines changed or deleted 234 lines changed or added

This html diff was produced by rfcdiff 1.46. The latest version is available from http://tools.ietf.org/tools/rfcdiff/