DNS over Dedicated QUIC Connections
draft-ietf-dprive-dnsoquic-07
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9250.
|
|
|---|---|---|---|
| Authors | Christian Huitema , Sara Dickinson , Allison Mankin | ||
| Last updated | 2021-12-09 (Latest revision 2021-12-01) | ||
| Replaces | draft-huitema-dprive-dnsoquic | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
TSVART Last Call review
(of
-08)
by Brian Trammell
Ready w/nits
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Brian Haberman | ||
| Shepherd write-up | Show Last changed 2021-12-08 | ||
| IESG | IESG state | Became RFC 9250 (Proposed Standard) | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Éric Vyncke | ||
| Send notices to | brian@innovationslab.net, dns-privacy@ietf.org |
draft-ietf-dprive-dnsoquic-07
Network Working Group C. Huitema
Internet-Draft Private Octopus Inc.
Intended status: Standards Track S. Dickinson
Expires: 4 June 2022 Sinodun IT
A. Mankin
Salesforce
1 December 2021
DNS over Dedicated QUIC Connections
draft-ietf-dprive-dnsoquic-07
Abstract
This document describes the use of QUIC to provide transport privacy
for DNS. The encryption provided by QUIC has similar properties to
that provided by TLS, while QUIC transport eliminates the head-of-
line blocking issues inherent with TCP and provides more efficient
packet loss recovery than UDP. DNS over QUIC (DoQ) has privacy
properties similar to DNS over TLS (DoT) specified in RFC7858, and
latency characteristics similar to classic DNS over UDP.
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 4 June 2022.
Copyright Notice
Copyright (c) 2021 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
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and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Document work via GitHub . . . . . . . . . . . . . . . . . . 5
4. Design Considerations . . . . . . . . . . . . . . . . . . . . 5
4.1. Provide DNS Privacy . . . . . . . . . . . . . . . . . . . 5
4.2. Design for Minimum Latency . . . . . . . . . . . . . . . 5
4.3. Middlebox Considerations . . . . . . . . . . . . . . . . 6
4.4. No Server Initiated Transactions . . . . . . . . . . . . 6
5. Specifications . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Connection Establishment . . . . . . . . . . . . . . . . 6
5.1.1. Draft Version Identification . . . . . . . . . . . . 7
5.1.2. Port Selection . . . . . . . . . . . . . . . . . . . 7
5.2. Stream Mapping and Usage . . . . . . . . . . . . . . . . 7
5.2.1. DNS Message IDs . . . . . . . . . . . . . . . . . . . 8
5.3. DoQ Error Codes . . . . . . . . . . . . . . . . . . . . . 9
5.3.1. Transaction Cancellation . . . . . . . . . . . . . . 9
5.3.2. Transaction Errors . . . . . . . . . . . . . . . . . 10
5.3.3. Protocol Errors . . . . . . . . . . . . . . . . . . . 10
5.3.4. Alternative error codes . . . . . . . . . . . . . . . 11
5.4. Connection Management . . . . . . . . . . . . . . . . . . 11
5.5. Session Resumption and 0-RTT . . . . . . . . . . . . . . 12
5.6. Message Sizes . . . . . . . . . . . . . . . . . . . . . . 13
6. Implementation Requirements . . . . . . . . . . . . . . . . . 13
6.1. Authentication . . . . . . . . . . . . . . . . . . . . . 13
6.2. Fallback to Other Protocols on Connection Failure . . . . 14
6.3. Address Validation . . . . . . . . . . . . . . . . . . . 14
6.4. Padding . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.5. Connection Handling . . . . . . . . . . . . . . . . . . . 15
6.5.1. Connection Reuse . . . . . . . . . . . . . . . . . . 15
6.5.2. Resource Management . . . . . . . . . . . . . . . . . 15
6.5.3. Using 0-RTT and Session Resumption . . . . . . . . . 16
6.5.4. Controlling Connection Migration For Privacy . . . . 17
6.6. Processing Queries in Parallel . . . . . . . . . . . . . 17
6.7. Zone transfer . . . . . . . . . . . . . . . . . . . . . . 17
6.8. Flow Control Mechanisms . . . . . . . . . . . . . . . . . 18
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 18
7.1. Performance Measurements . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 20
9.1. Privacy Issues With 0-RTT data . . . . . . . . . . . . . 20
9.2. Privacy Issues With Session Resumption . . . . . . . . . 21
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9.3. Privacy Issues With Address Validation Tokens . . . . . . 22
9.4. Privacy Issues With Long Duration Sessions . . . . . . . 22
9.5. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 23
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
10.1. Registration of DoQ Identification String . . . . . . . 23
10.2. Reservation of Dedicated Port . . . . . . . . . . . . . 23
10.2.1. Port number 784 for experimentations . . . . . . . . 24
10.3. Reservation of Extended DNS Error Code Too Early . . . . 24
10.4. DNS over QUIC Error Codes Registry . . . . . . . . . . . 24
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
12.1. Normative References . . . . . . . . . . . . . . . . . . 26
12.2. Informative References . . . . . . . . . . . . . . . . . 29
Appendix A. The NOTIFY Service . . . . . . . . . . . . . . . . . 30
Appendix B. Notable Changes From Previous Versions . . . . . . . 30
B.1. Stream Mapping Incompatibility With Draft-02 . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction
Domain Name System (DNS) concepts are specified in "Domain names -
concepts and facilities" [RFC1034]. The transmission of DNS queries
and responses over UDP and TCP is specified in "Domain names -
implementation and specification" [RFC1035].
This document presents a mapping of the DNS protocol over the QUIC
transport [RFC9000] [RFC9001]. DNS over QUIC is referred here as
DoQ, in line with "DNS Terminology" [I-D.ietf-dnsop-rfc8499bis].
The goals of the DoQ mapping are:
1. Provide the same DNS privacy protection as DNS over TLS (DoT)
[RFC7858]. This includes an option for the client to
authenticate the server by means of an authentication domain name
as specified in "Usage Profiles for DNS over TLS and DNS over
DTLS" [RFC8310].
2. Provide an improved level of source address validation for DNS
servers compared to classic DNS over UDP.
3. Provide a transport that is not constrained by path MTU
limitations on the size of DNS responses it can send.
In order to achieve these goals, and to support ongoing work on
encryption of DNS, the scope of this document includes
* the "stub to recursive resolver" scenario
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* the "recursive resolver to authoritative nameserver" scenario and
* the "nameserver to nameserver" scenario (mainly used for zone
transfers (XFR) [RFC1995], [RFC5936]).
In other words, this document is intended to specify QUIC as a
general purpose transport for DNS.
The specific non-goals of this document are:
1. No attempt is made to evade potential blocking of DNS over QUIC
traffic by middleboxes.
2. No attempt to support server initiated transactions, which are
used only in DNS Stateful Operations (DSO) [RFC8490].
Specifying the transmission of an application over QUIC requires
specifying how the application's messages are mapped to QUIC streams,
and generally how the application will use QUIC. This is done for
HTTP in "Hypertext Transfer Protocol Version 3
(HTTP/3)"[I-D.ietf-quic-http]. The purpose of this document is to
define the way DNS messages can be transmitted over QUIC.
DNS over HTTP [RFC8484] can be used with HTTP/3 to get some of the
benefits of QUIC. However, a lightweight direct mapping for DNS over
QUIC can be regarded as a more natural fit for both the recursive to
authoritative and zone transfer scenarios which rarely involve
intermediaries. In these scenarios, the additional overhead of HTTP
is not offset by, e.g., benefits of HTTP proxying and caching
behavior.
In this document, Section 4 presents the reasoning that guided the
proposed design. Section 5 specifies the actual mapping of DoQ.
Section 6 presents guidelines on the implementation, usage and
deployment of DoQ.
2. Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14 [RFC8174].
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3. Document work via GitHub
(RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION)The
Github repository for this document is at https://github.com/huitema/
dnsoquic. Proposed text and editorial changes are very much welcomed
there, but any functional changes should always first be discussed on
the IETF DPRIVE WG (dns-privacy) mailing list.
4. Design Considerations
This section and its subsections present the design guidelines that
were used for DoQ. This section is informative in nature.
4.1. Provide DNS Privacy
DoT [RFC7858] defines how to mitigate some of the issues described in
"DNS Privacy Considerations" [RFC9076] by specifying how to transmit
DNS messages over TLS. The "Usage Profiles for DNS over TLS and DNS
over DTLS" [RFC8310] specify Strict and Opportunistic Usage Profiles
for DoT including how stub resolvers can authenticate recursive
resolvers.
QUIC connection setup includes the negotiation of security parameters
using TLS, as specified in "Using TLS to Secure QUIC" [RFC9001],
enabling encryption of the QUIC transport. Transmitting DNS messages
over QUIC will provide essentially the same privacy protections as
DoT [RFC7858] including Strict and Opportunistic Usage Profiles
[RFC8310]. Further discussion on this is provided in Section 9.
4.2. Design for Minimum Latency
QUIC is specifically designed to reduce protocol-induced delays, with
features such as:
1. Support for 0-RTT data during session resumption.
2. Support for advanced packet loss recovery procedures as specified
in "QUIC Loss Detection and Congestion Control" [RFC9002].
3. Mitigation of head-of-line blocking by allowing parallel delivery
of data on multiple streams.
This mapping of DNS to QUIC will take advantage of these features in
three ways:
1. Optional support for sending 0-RTT data during session resumption
(the security and privacy implications of this are discussed in
later sections).
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2. Long-lived QUIC connections over which multiple DNS transactions
are performed, generating the sustained traffic required to
benefit from advanced recovery features.
3. Mapping of each DNS Query/Response transaction to a separate
stream, to mitigate head-of-line blocking. This enables servers
to respond to queries "out of order". It also enables clients to
process responses as soon as they arrive, without having to wait
for in order delivery of responses previously posted by the
server.
These considerations are reflected in the mapping of DNS traffic to
QUIC streams in Section 5.2.
4.3. Middlebox Considerations
Using QUIC might allow a protocol to disguise its purpose from
devices on the network path using encryption and traffic analysis
resistance techniques like padding. This specification does not
include any measures that are designed to avoid such classification.
Consequently, firewalls and other middleboxes might be able to
distinguish DoQ from other protocols that use QUIC, like HTTP, and
apply different treatment.
The lack of measures in this specification to avoid protocol
classification is not an endorsement of such practices.
4.4. No Server Initiated Transactions
As stated in Section 1, this document does not specify support for
server initiated transactions within established DoQ connections.
That is, only the initiator of the DoQ connection may send queries
over the connection.
DSO does support server-initiated transactions within existing
connections. However DoQ as defined here does not meet the criteria
for an applicable transport for DSO because it does not guarantee in-
order delivery of messages, see Section 4.2 of [RFC8490].
5. Specifications
5.1. Connection Establishment
DoQ connections are established as described in the QUIC transport
specification [RFC9000]. During connection establishment, DoQ
support is indicated by selecting the ALPN token "doq" in the crypto
handshake.
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5.1.1. Draft Version Identification
(RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION) Only
implementations of the final, published RFC can identify themselves
as "doq". Until such an RFC exists, implementations MUST NOT
identify themselves using this string.
Implementations of draft versions of the protocol MUST add the string
"-" and the corresponding draft number to the identifier. For
example, draft-ietf-dprive-dnsoquic-00 is identified using the string
"doq-i00".
5.1.2. Port Selection
By default, a DNS server that supports DoQ MUST listen for and accept
QUIC connections on the dedicated UDP port TBD (number to be defined
in Section 10), unless there is a mutual agreement to use another
port.
By default, a DNS client desiring to use DoQ with a particular server
MUST establish a QUIC connection to UDP port TBD on the server,
unless there is a mutual agreement to use another port.
In order to use a port other than TBD, both clients and servers would
need a configuration option in their software.
DoQ connections MUST NOT use UDP port 53. This recommendation
against use of port 53 for DoQ is to avoid confusion between DoQ and
the use of DNS over UDP [RFC1035].
In the stub to recursive scenario, the use of port 443 as a mutually
agreed alternative port can be operationally beneficial, since port
443 is less likely to be blocked than other ports. Several
mechanisms for stubs to discover recursives offering encrypted
transports, including the use of custom ports, are the subject of
ongoing work.
5.2. Stream Mapping and Usage
The mapping of DNS traffic over QUIC streams takes advantage of the
QUIC stream features detailed in Section 2 of [RFC9000], the QUIC
transport specification.
DNS traffic follows a simple pattern in which the client sends a
query, and the server provides one or more responses (multiple
responses can occur in zone transfers).
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The mapping specified here requires that the client selects a
separate QUIC stream for each query. The server then uses the same
stream to provide all the response messages for that query. In order
that multiple responses can be parsed, a 2-octet length field is used
in exactly the same way as the 2-octet length field defined for DNS
over TCP [RFC1035]. The practical result of this is that the content
of each QUIC stream is exactly the same as the content of a TCP
connection that would manage exactly one query.
All DNS messages (queries and responses) sent over DoQ connections
MUST be encoded as a 2-octet length field followed by the message
content as specified in [RFC1035].
The client MUST select the next available client-initiated
bidirectional stream for each subsequent query on a QUIC connection,
in conformance with the QUIC transport specification [RFC9000].
The client MUST send the DNS query over the selected stream, and MUST
indicate through the STREAM FIN mechanism that no further data will
be sent on that stream.
The server MUST send the response(s) on the same stream and MUST
indicate, after the last response, through the STREAM FIN mechanism
that no further data will be sent on that stream.
Therefore, a single client initiated DNS transaction consumes a
single stream. This means that the client's first query occurs on
QUIC stream 0, the second on 4, and so on.
Servers MAY defer processing of a query until the STREAM FIN has been
indicated on the stream selected by the client. Servers and clients
MAY monitor the number of "dangling" streams for which the expected
queries or responses have been received but not the STREAM FIN.
Implementations MAY impose a limit on the number of such dangling
streams. If limits are encountered, implementations MAY close the
connection.
5.2.1. DNS Message IDs
When sending queries over a QUIC connection, the DNS Message ID MUST
be set to zero. The stream mapping for DoQ allows for unambiguous
correlation of queries and responses and so the Message ID field is
not required.
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This has implications for proxying DoQ message to and from other
transports. For example, proxies may have to manage the fact that
DoQ can support a larger number of outstanding queries on a single
connection than e.g., DNS over TCP because DoQ is not limited by the
Message ID space. This issue already exists for DoH, where a Message
ID of 0 is recommended.
When forwarding a DNS message from DoQ over another transport, a DNS
Message ID MUST be generated according to the rules of the protocol
that is in use. When forwarding a DNS message from another transport
over DoQ, the Message ID MUST be set to zero.
5.3. DoQ Error Codes
The following error codes are defined for use when abruptly
terminating streams, aborting reading of streams, or immediately
closing connections:
DOQ_NO_ERROR (0x0): No error. This is used when the connection or
stream needs to be closed, but there is no error to signal.
DOQ_INTERNAL_ERROR (0x1): The DoQ implementation encountered an
internal error and is incapable of pursuing the transaction or the
connection.
DOQ_PROTOCOL_ERROR (0x2): The DoQ implementation encountered an
protocol error and is forcibly aborting the connection.
DOQ_REQUEST_CANCELLED (0x3): A DoQ client uses this to signal that
it wants to cancel an outstanding transaction.
DOQ_EXCESSIVE_LOAD (0x4): A DoQ implementation uses this to signal
when closing a connection due to excessive load.
DOQ_ERROR_RESERVED (0xd098ea5e): Alternative error code used for
tests.
See Section 10.4 for details on registering new error codes.
5.3.1. Transaction Cancellation
In QUIC, sending STOP_SENDING requests that a peer cease transmission
on a stream. If a DoQ client wishes to cancel an outstanding
request, it MUST issue a QUIC Stop Sending with error code
DOQ_REQUEST_CANCELLED. This may be sent at any time but will be
ignored if the server has already sent the response. The
corresponding DNS transaction MUST be abandoned.
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Servers that receive STOP_SENDING act in accordance with Section 3.5
of [RFC9000]. Servers MAY impose implementation limits on the total
number or rate of request cancellations. If limits are encountered,
servers MAY close the connection. In this case, servers wanting to
help client debugging MAY use the error code DOQ_EXCESSIVE_LOAD.
There is always a trade-off between helping good faith clients debug
issues and allowing denial-of-service attackers to test server
defenses, so depending on circumstances servers might very well chose
to send different error codes.
Note that this mechanism provides a way for secondaries to cancel a
single zone transfer occurring on a given stream without having to
close the QUIC connection.
5.3.2. Transaction Errors
Servers normally complete transactions by sending a DNS response (or
responses) on the transaction's stream, including cases where the DNS
response indicates a DNS error. For example, a Server Failure
(SERVFAIL, [RFC1035]) SHOULD be notified to the client by sending
back a response with the Response Code set to SERVFAIL.
If a server is incapable of sending a DNS response due to an internal
error, it SHOULD issue a QUIC Stream Reset. The error code SHOULD be
set to DOQ_INTERNAL_ERROR. The corresponding DNS transaction MUST be
abandoned. Clients MAY limit the number of unsolicited QUIC Stream
Resets received on a connection before choosing to close the
connection.
Note that this mechanism provides a way for primaries to abort a
single zone transfer occurring on a given stream without having to
close the QUIC connection.
5.3.3. Protocol Errors
Other error scenarios can occur due to malformed, incomplete or
unexpected messages during a transaction. These include (but are not
limited to)
* a client or server receives a message with a non-zero Message ID
* a client or server receives a STREAM FIN before receiving all the
bytes for a message indicated in the 2-octet length field
* a client receives a STREAM FIN before receiving all the expected
responses
* a server receives more than one query on a stream
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* a client receives a different number of responses on a stream than
expected (e.g. multiple responses to a query for an A record)
* a client receives a STOP_SENDING request
* the client or server does not indicate the expected STREAM FIN
after sending requests or responses (see Section 5.2).
* an implementation receives a message containing the edns-tcp-
keepalive EDNS(0) Option [RFC7828] (see Section 6.5.2)
* a client or a server attempts to open an unidirectional QUIC
stream
* a server attempts to open a server-initiated bidirectional QUIC
stream
If a peer encounters such an error condition it is considered a fatal
error. It SHOULD forcibly abort the connection using QUIC's
CONNECTION_CLOSE mechanism, and SHOULD use the DoQ error code
DOQ_PROTOCOL_ERROR.
It is noted that the restrictions on use of the above EDNS(0) options
has implications for proxying message from TCP/DoT/DoH over DoQ.
5.3.4. Alternative error codes
This specification suggests specific error codes Section 5.3.1,
Section 5.3.2, and Section 5.3.3. These error codes are meant to
facilitate investigation of failures and other incidents. New error
codes may be defined in future versions of DoQ, or registered as
specified in Section 10.4.
Because new error codes can be defined without negotiation, use of an
error code in an unexpected context or receipt of an unknown error
code MUST be treated as equivalent to DOQ_NO_ERROR.
Implementations MAY wish to test the support for the error code
extension mechanism by using error codes not listed in this document,
or they MAY use DOQ_ERROR_RESERVED.
5.4. Connection Management
Section 10 of [RFC9000], the QUIC transport specification, specifies
that connections can be closed in three ways:
* idle timeout
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* immediate close
* stateless reset
Clients and servers implementing DoQ SHOULD negotiate use of the idle
timeout. Closing on idle timeout is done without any packet
exchange, which minimizes protocol overhead. Per Section 10.1 of
[RFC9000], the QUIC transport specification, the effective value of
the idle timeout is computed as the minimum of the values advertised
by the two endpoints. Practical considerations on setting the idle
timeout are discussed in Section 6.5.2.
Clients SHOULD monitor the idle time incurred on their connection to
the server, defined by the time spent since the last packet from the
server has been received. When a client prepares to send a new DNS
query to the server, it will check whether the idle time is
sufficient lower than the idle timer. If it is, the client will send
the DNS query over the existing connection. If not, the client will
establish a new connection and send the query over that connection.
Clients MAY discard their connections to the server before the idle
timeout expires. A client that has outstanding queries SHOULD close
the connection explicitly using QUIC's CONNECTION_CLOSE mechanism and
the DoQ error code DOQ_NO_ERROR.
Clients and servers MAY close the connection for a variety of other
reasons, indicated using QUIC's CONNECTION_CLOSE. Client and servers
that send packets over a connection discarded by their peer MAY
receive a stateless reset indication. If a connection fails, all the
in progress transaction on that connection MUST be abandoned.
5.5. Session Resumption and 0-RTT
A client MAY take advantage of the session resumption mechanisms
supported by QUIC transport [RFC9000] and QUIC TLS [RFC9001].
Clients SHOULD consider potential privacy issues associated with
session resumption before deciding to use this mechanism. These
privacy issues are detailed in Section 9.2 and Section 9.1, and the
implementation considerations are discussed in Section 6.5.3.
The 0-RTT mechanism SHOULD NOT be used to send DNS requests that are
not "replayable" transactions. In this specification, only
transactions that have an OPCODE of QUERY or NOTIFY are considered
replayable and MAY be sent in 0-RTT data. See Appendix A for a
detailed discussion of why NOTIFY is included here.
Servers MUST NOT execute non replayable transactions received in
0-RTT data. Servers MUST adopt one of the following behaviors:
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* Queue the offending transaction and only execute it after the QUIC
handshake has been completed, as defined in Section 4.1.1 of
[RFC9001].
* Reply to the offending transaction with a response code REFUSED
and an Extended DNS Error Code (EDE) "Too Early", see
Section 10.3.
* Close the connection with the error code DOQ_PROTOCOL_ERROR.
5.6. Message Sizes
DoQ Queries and Responses are sent on QUIC streams, which in theory
can carry up to 2^62 bytes. However, DNS messages are restricted in
practice to a maximum size of 65535 bytes. This maximum size is
enforced by the use of a two-octet message length field in DNS over
TCP [RFC1035] and DNS over TLS [RFC7858], and by the definition of
the "application/dns-message" for DNS over HTTP [RFC8484]. DoQ
enforces the same restriction.
The Extension Mechanisms for DNS (EDNS) [RFC6891] allow peers to
specify the UDP message size. This parameter is ignored by DoQ. DoQ
implementations always assume that the maximum message size is 65535
bytes.
6. Implementation Requirements
6.1. Authentication
For the stub to recursive resolver scenario, the authentication
requirements are the same as described in DoT [RFC7858] and "Usage
Profiles for DNS over TLS and DNS over DTLS" [RFC8310]. [RFC8932]
states that DNS privacy services SHOULD provide credentials that
clients can use to authenticate the server. Given this, and to align
with the authentication model for DoH, DoQ stubs SHOULD use a Strict
authentication profile. Client authentication for the encrypted stub
to recursive scenario is not described in any DNS RFC.
For zone transfer, the requirements are the same as described in
[RFC9103].
For the recursive resolver to authoritative nameserver scenario,
authentication requirements are unspecified at the time of writing
and are the subject on ongoing work in the DPRIVE WG.
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6.2. Fallback to Other Protocols on Connection Failure
If the establishment of the DoQ connection fails, clients MAY attempt
to fall back to DoT and then potentially clear text, as specified in
DoT [RFC7858] and "Usage Profiles for DNS over TLS and DNS over DTLS"
[RFC8310], depending on their privacy profile.
DNS clients SHOULD remember server IP addresses that don't support
DoQ. Timeouts, connection refusals, and QUIC handshake failures are
valid indicators that a server does not support DoQ. Clients SHOULD
NOT attempt DoQ queries to a server that does not support DoQ for a
reasonable period (such as one hour per server). DNS clients
following an out-of-band key-pinned privacy profile ([RFC7858]) MAY
be more aggressive about retrying DoQ connection failures.
6.3. Address Validation
Section 8 of [RFC9000], the QUIC transport specification, defines
Address Validation procedures to avoid servers being used in address
amplification attacks. DoQ implementations MUST conform to this
specification, which limits the worst case amplification to a factor
3.
DoQ implementations SHOULD consider configuring servers to use the
Address Validation using Retry Packets procedure defined in
Section 8.1.2 of [RFC9000], the QUIC transport specification. This
procedure imposes a 1-RTT delay for verifying the return routability
of the source address of a client, similar to the DNS Cookies
mechanism [RFC7873].
DoQ implementations that configure Address Validation using Retry
Packets SHOULD implement the Address Validation for Future
Connections procedure defined in Section 8.1.3 of [RFC9000], the QUIC
transport specification. This defines how servers can send NEW_TOKEN
frames to clients after the client address is validated, in order to
avoid the 1-RTT penalty during subsequent connections by the client
from the same address.
6.4. Padding
Implementations SHOULD protect against the traffic analysis attacks
described in Section 9.5 by the judicious injection of padding. This
could be done either by padding individual DNS messages using the
EDNS(0) Padding Option [RFC7830] and by padding QUIC packets (see
Section 8.6 of [RFC9000], the QUIC transport specification.
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In theory, padding at the QUIC level could result in better
performance for the equivalent protection, because the amount of
padding can take into account non-DNS frames such as acknowledgeemnts
or flow control updates, and also because QUIC packets can carry
multiple DNS messages. However, applications can only control the
amount of padding in QUIC packets if the implementation of QUIC
exposes adequate APIs. This leads to the following recommendation:
* if the implementation of QUIC exposes APIs to set a padding
policy, DNS over QUIC SHOULD use that API to align the packet
length to a small set of fixed sizes, aligned with the
recommendations of the "Padding Policies for Extension Mechanisms
for DNS (EDNS(0))" [RFC8467].
* if padding at the QUIC level is not available or not used, DNS
over QUIC MUST ensure that all DNS queries and responses are
padded to a small set of fixed sizes, using the EDNS padding
extension as specified in "Padding Policies for Extension
Mechanisms for DNS (EDNS(0))" [RFC8467].
6.5. Connection Handling
"DNS Transport over TCP - Implementation Requirements" [RFC7766]
provides updated guidance on DNS over TCP, some of which is
applicable to DoQ. This section provides similar advice on
connection handling for DoQ.
6.5.1. Connection Reuse
Historic implementations of DNS clients are known to open and close
TCP connections for each DNS query. To amortise connection setup
costs, both clients and servers SHOULD support connection reuse by
sending multiple queries and responses over a single persistent QUIC
connection.
In order to achieve performance on par with UDP, DNS clients SHOULD
send their queries concurrently over the QUIC streams on a QUIC
connection. That is, when a DNS client sends multiple queries to a
server over a QUIC connection, it SHOULD NOT wait for an outstanding
reply before sending the next query.
6.5.2. Resource Management
Proper management of established and idle connections is important to
the healthy operation of a DNS server.
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An implementation of DoQ SHOULD follow best practices similar to
those specified for DNS over TCP [RFC7766], in particular with regard
to:
* Concurrent Connections (Section 6.2.2 of [RFC7766], updated by
Section 6.4 of [RFC9103])
* Security Considerations (Section 10 of [RFC7766])
Failure to do so may lead to resource exhaustion and denial of
service.
Clients that want to maintain long duration DoQ connections SHOULD
use the idle timeout mechanisms defined in Section 10.1 of [RFC9000],
the QUIC transport specification. Clients and servers MUST NOT send
the edns-tcp-keepalive EDNS(0) Option [RFC7828] in any messages sent
on a DoQ connection (because it is specific to the use of TCP/TLS as
a transport).
This document does not make specific recommendations for timeout
values on idle connections. Clients and servers should reuse and/or
close connections depending on the level of available resources.
Timeouts may be longer during periods of low activity and shorter
during periods of high activity.
6.5.3. Using 0-RTT and Session Resumption
Using 0-RTT for DNS over QUIC has many compelling advantages.
Clients can establish connections and send queries without incurring
a connection delay. Servers can thus negotiate low values of the
connection timers, which reduces the total number of connections that
they need to manage. They can do that because the clients that use
0-RTT will not incur latency penalties if new connections are
required for a query.
Session resumption and 0-RTT data transmission create privacy risks
detailed in detailed in Section 9.2 and Section 9.1. The following
recommendations are meant to reduce the privacy risks while enjoying
the performance benefits of 0-RTT data, with the restriction
specified in Section 5.5.
Clients SHOULD use resumption tickets only once, as specified in
Appendix C.4 to [RFC8446]. By default, clients SHOULD NOT use
session resumption if the client's connectivity has changed.
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Clients could receive address validation tokens from the server using
the NEW_TOKEN mechanism; see Section 8 of [RFC9000]. The associated
tracking risks are mentioned in Section 9.3. Clients SHOULD only use
the address validation tokens when they are also using session
resumption, thus avoiding additional tracking risks.
Servers SHOULD issue session resumption tickets with a sufficiently
long life time (e.g., 6 hours), so that clients are not tempted to
either keep connection alive or frequently poll the server to renew
session resumption tickets. Servers SHOULD implement the anti-replay
mechanisms specified in Section 8 of [RFC8446].
6.5.4. Controlling Connection Migration For Privacy
DoQ implementation might consider using the connection migration
features defined in Section 9 of [RFC9000]. These features enable
connections to continue operating as the client's connectivity
changes. As detailed in Section 9.4, these features trade off
privacy for latency. By default, clients SHOULD be configured to
prioritise privacy and start new sessions if their connectivity
changes.
6.6. Processing Queries in Parallel
As specified in Section 7 of [RFC7766] "DNS Transport over TCP -
Implementation Requirements", resolvers are RECOMMENDED to support
the preparing of responses in parallel and sending them out of order.
In DoQ, they do that by sending responses on their specific stream as
soon as possible, without waiting for availability of responses for
previously opened streams.
6.7. Zone transfer
[RFC9103] specifies zone transfer over TLS (XoT) and includes updates
to [RFC1995] (IXFR), [RFC5936] (AXFR) and [RFC7766]. Considerations
relating to the re-use of XoT connections described there apply
analogously to zone transfers performed using DoQ connections. For
example:
* DoQ servers MUST be able to handle multiple concurrent IXFR
requests on a single QUIC connection
* DoQ servers MUST be able to handle multiple concurrent AXFR
requests on a single QUIC connection
* DoQ implementations SHOULD
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- use the same QUIC connection for both AXFR and IXFR requests to
the same primary
- pipeline such requests (if they pipeline XFR requests in
general) and MAY intermingle them
- send the response(s) for each request as soon as they are
available i.e. responses MAY be sent intermingled
6.8. Flow Control Mechanisms
Servers and Clients manage flow control using the mechanisms defined
in Section 4 of [RFC9000]. These mechanisms allow clients and
servers to specify how many streams can be created, how much data can
be sent on a stream, and how much data can be sent on the union of
all streams. For DNS over QUIC, controlling how many streams are
created allows servers to control how many new requests the client
can send on a given connection.
Flow control exists to protect endpoint resources. For servers,
global and per-stream flow control limits control how much data can
be sent by clients. The same mechanisms allow clients to control how
much data can be sent by servers. Values that are too small will
unnecessarily limit performance. Values that are too large might
expose endpoints to overload or memory exhaustion. Implementations
or deployments will need to adjust flow control limits to balance
these concerns. In particular, zone transfer implementations will
need to control these limits carefully to ensure both large and
concurrent zone transfers are well managed.
Initial values of parameters control how many requests and how much
data can be sent by clients and servers at the beginning of the
connection. These values are specified in transport parameters
exchanged during the connection handshake. The parameter values
received in the initial connection also control how many requests and
how much data can be sent by clients using 0-RTT data in a resumed
connection. Using too small values of these initial parameters would
restrict the usefulness of allowing 0-RTT data.
7. Implementation Status
(RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION) This
section records the status of known implementations of the protocol
defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
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1. AdGuard launched a DoQ recursive resolver service in December
2020. They have released a suite of open source tools that
support DoQ:
1. AdGuard C++ DNS libraries (https://github.com/AdguardTeam/
DnsLibs) A DNS proxy library that supports all existing DNS
protocols including DNS-over-TLS, DNS-over-HTTPS, DNSCrypt
and DNS-over-QUIC (experimental).
2. DNS Proxy (https://github.com/AdguardTeam/dnsproxy) A simple
DNS proxy server that supports all existing DNS protocols
including DNS-over-TLS, DNS-over-HTTPS, DNSCrypt, and DNS-
over-QUIC. Moreover, it can work as a DNS-over-HTTPS, DNS-
over-TLS or DNS-over-QUIC server.
3. CoreDNS fork for AdGuard DNS (https://github.com/AdguardTeam/
coredns) Includes DNS-over-QUIC server-side support.
4. dnslookup (https://github.com/ameshkov/dnslookup) Simple
command line utility to make DNS lookups. Supports all known
DNS protocols: plain DNS, DoH, DoT, DoQ, DNSCrypt.
2. Quicdoq (https://github.com/private-octopus/quicdoq) Quicdoq is a
simple open source implementation of DoQ. It is written in C,
based on Picoquic (https://github.com/private-octopus/picoquic).
3. Flamethrower (https://github.com/DNS-OARC/flamethrower/tree/dns-
over-quic) is an open source DNS performance and functional
testing utility written in C++ that has an experimental
implementation of DoQ.
4. aioquic (https://github.com/aiortc/aioquic) is an implementation
of QUIC in Python. It includes example client and server for
DoQ.
7.1. Performance Measurements
To our knowledge, no benchmarking studies comparing DoT, DoH and DoQ
are published yet. However anecdotal evidence from the AdGuard DoQ
recursive resolver deployment (https://adguard.com/en/blog/dns-over-
quic.html) indicates that it performs well compared to the other
encrypted protocols, particularly in mobile environments. Reasons
given for this include that DoQ
* Uses less bandwidth due to a more efficient handshake (and due to
less per message overhead when compared to DoH).
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* Performs better in mobile environments due to the increased
resilience to packet loss
* Can maintain connections as users move between mobile networks via
its connection management
8. Security Considerations
The security considerations of DoQ should be comparable to those of
DoT [RFC7858].
9. Privacy Considerations
The general considerations of encrypted transports provided in "DNS
Privacy Considerations" [RFC9076] apply to DoQ. The specific
considerations provided there do not differ between DoT and DoQ, and
are not discussed further here. Similarly, "Recommendations for DNS
Privacy Service Operators" [RFC8932] (which covers operational,
policy, and security considerations for DNS privacy services) is also
applicable to DoQ services.
QUIC incorporates the mechanisms of TLS 1.3 [RFC8446] and this
enables QUIC transmission of "0-RTT" data. This can provide
interesting latency gains, but it raises two concerns:
1. Adversaries could replay the 0-RTT data and infer its content
from the behavior of the receiving server.
2. The 0-RTT mechanism relies on TLS session resumption, which can
provide linkability between successive client sessions.
These issues are developed in Section 9.1 and Section 9.2.
9.1. Privacy Issues With 0-RTT data
The 0-RTT data can be replayed by adversaries. That data may trigger
queries by a recursive resolver to authoritative resolvers.
Adversaries may be able to pick a time at which the recursive
resolver outgoing traffic is observable, and thus find out what name
was queried for in the 0-RTT data.
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This risk is in fact a subset of the general problem of observing the
behavior of the recursive resolver discussed in "DNS Privacy
Considerations" [RFC9076]. The attack is partially mitigated by
reducing the observability of this traffic. The mandatory replay
protection mechanisms in TLS 1.3 [RFC8446] limit but do not eliminate
the risk of replay. 0-RTT packets can only be replayed within a
narrow window, which is only wide enough to account for variations in
clock skew and network transmission.
The recommendation for TLS 1.3 [RFC8446] is that the capability to
use 0-RTT data should be turned off by default, and only enabled if
the user clearly understands the associated risks. In our case,
allowing 0-RTT data provides significant performance gains, and we
are concerned that a recommendation to not use it would simply be
ignored. Instead, we provide a set of practical recommendations in
Section 5.5 and Section 6.5.3.
The prevention on allowing replayable transactions in 0-RTT data
expressed in Section 5.5 blocks the most obvious risks of replay
attacks, as it only allows for transactions that will not change the
long term state of the server.
The attacks described above apply to the stub resolver to recursive
resolver scenario, but similar attacks might be envisaged in the
recursive resolver to authoritative resolver scenario, and the same
mitigations apply.
9.2. Privacy Issues With Session Resumption
The QUIC session resumption mechanism reduces the cost of re-
establishing sessions and enables 0-RTT data. There is a linkability
issue associated with session resumption, if the same resumption
token is used several times. Attackers on path between client and
server could observe repeated usage of the token and use that to
track the client over time or over multiple locations.
The session resumption mechanism allows servers to correlate the
resumed sessions with the initial sessions, and thus to track the
client. This creates a virtual long duration session. The series of
queries in that session can be used by the server to identify the
client. Servers can most probably do that already if the client
address remains constant, but session resumption tickets also enable
tracking after changes of the client's address.
The recommendations in Section 6.5.3 are designed to mitigate these
risks. Using session tickets only once mitigates the risk of
tracking by third parties. Refusing to resume a session if addresses
change mitigates the risk of tracking by the server.
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The privacy trade-offs here may be context specific. Stub resolvers
will have a strong motivation to prefer privacy over latency since
they often change location. However, recursive resolvers that use a
small set of static IP addresses are more likely to prefer the
reduced latency provided by session resumption and may consider this
a valid reason to use resumption tickets even if the IP address
changed between sessions.
Encrypted zone transfer (RFC9103) explicitly does not attempt to hide
the identity of the parties involved in the transfer, but at the same
time such transfers are not particularly latency sensitive. This
means that applications supporting zone transfers may decide to apply
the same protections as stub to recursive applications.
9.3. Privacy Issues With Address Validation Tokens
QUIC specifies address validation mechanisms in Section 8 of
[RFC9000]. Use of an address validation token allows QUIC servers to
avoid an extra RTT for new connections. Address validation tokens
are typically tied to an IP address. QUIC clients normally only use
these tokens when setting a new connection from a previously used
address. However, due to the prevalence of NAT, clients are not
always aware that they are using a new address. There is a
linkability risk if clients mistakenly use address validation tokens
after unknowingly moving to a new location.
The recommendations in Section 6.5.3 mitigates this risk by tying the
usage of the NEW_TOKEN to that of session resumption.
9.4. Privacy Issues With Long Duration Sessions
A potential alternative to session resumption is the use of long
duration sessions: if a session remains open for a long time, new
queries can be sent without incurring connection establishment
delays. It is worth pointing out that the two solutions have similar
privacy characteristics. Session resumption may allow servers to
keep track of the IP addresses of clients, but long duration sessions
have the same effect.
In particular, a DoQ implementation might take advantage of the
connection migration features of QUIC to maintain a session even if
the client's connectivity changes, for example if the client migrates
from a Wi-Fi connection to a cellular network connection, and then to
another Wi-Fi connection. The server would be able to track the
client location by monitoring the succession of IP addresses used by
the long duration connection.
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The recommendation in Section 6.5.4 mitigates the privacy concerns
related to long duration sessions using multiple client addresses.
9.5. Traffic Analysis
Even though QUIC packets are encrypted, adversaries can gain
information from observing packet lengths, in both queries and
responses, as well as packet timing. Many DNS requests are emitted
by web browsers. Loading a specific web page may require resolving
dozen of DNS names. If an application adopts a simple mapping of one
query or response per packet, or "one QUIC STREAM frame per packet",
then the succession of packet lengths may provide enough information
to identify the requested site.
Implementations SHOULD use the mechanisms defined in Section 6.4 to
mitigate this attack.
10. IANA Considerations
10.1. Registration of DoQ Identification String
This document creates a new registration for the identification of
DoQ in the "Application Layer Protocol Negotiation (ALPN) Protocol
IDs" registry [RFC7301].
The "doq" string identifies DoQ:
Protocol: DoQ
Identification Sequence: 0x64 0x6F 0x71 ("doq")
Specification: This document
10.2. Reservation of Dedicated Port
Port 853 is currently reserved for 'DNS query-response protocol run
over TLS/DTLS' [RFC7858]. However, the specification for DNS over
DTLS (DoD) [RFC8094] is experimental, limited to stub to resolver,
and no implementations or deployments currently exist to our
knowledge (even though several years have passed since the
specification was published).
This specification proposes to additionally reserve the use of port
853 for DoQ. QUIC was designed to be able to co-exist with other
protocols on the same port, including DTLS , see Section 17.2 of
[RFC9000].
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IANA is requested to add the following value to the "Service Name and
Transport Protocol Port Number Registry" in the System Range. The
registry for that range requires IETF Review or IESG Approval
[RFC6335].
Service Name: dns-over-quic
Port Number: 853
Transport Protocol(s): UDP
Assignee: IESG
Contact: IETF Chair
Description: DNS query-response protocol run over QUIC
Reference: This document
10.2.1. Port number 784 for experimentations
(RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION)
Early experiments MAY use port 784. This port is marked in the IANA
registry as unassigned.
(Note that version in -02 of this draft experiments were directed to
use port 8853.)
10.3. Reservation of Extended DNS Error Code Too Early
IANA is requested to add the following value to the Extended DNS
Error Codes registry [RFC8914]:
INFO-CODE: TBD
Purpose: Too Early
Reference: This document
10.4. DNS over QUIC Error Codes Registry
IANA [SHALL add/has added] a registry for "DNS over QUIC Error Codes"
on the "Domain Name System (DNS) Parameters" web page.
The "DNS over QUIC Error Codes" registry governs a 62-bit space.
This space is split into three regions that are governed by different
policies:
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* Permanent registrations for values between 0x00 and 0x3f (in
hexadecimal; inclusive), which are assigned using Standards Action
or IESG Approval as defined in Section 4.9 and Section 4.10 of
[RFC8126]
* Permanent registrations for values larger than 0x3f, which are
assigned using the Specification Required policy ([RFC8126])
* Provisonal registrations for values larger than 0x3f, which
require Expert Review, as defined in Section 4.5 of [RFC8126].
Provisional reservations share the range of values larger than 0x3f
with some permanent registrations. This is by design, to enable
conversion of provisional registrations into permanent registrations
without requiring changes in deployed systems. (This design is
aligned with the principles set in Section 22 of [RFC9000].)
Registrations in this registry MUST include the following fields:
Value: The assigned codepoint.
Status: "Permanent" or "Provisional".
Contact: Contact details for the registrant.
Notes: Supplementary notes about the registration.
In addition, permanent registrations MUST include:
Error: A short mnemonic for the parameter.
Specification: A reference to a publicly available specification for
the value (optional for provisional registrations).
Description: A brief description of the error code semantics, which
MAY be a summary if a specification reference is provided.
Provisional registrations of codepoints are intended to allow for
private use and experimentation with extensions to DNS over QUIC.
However, provisional registrations could be reclaimed and reassigned
for another purpose. In addition to the parameters listed above,
provisional registrations MUST include:
Date: The date of last update to the registration.
A request to update the date on any provisional registration can be
made without review from the designated expert(s).
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The initial contents of this registry are shown in Table 1.
+==========+=======================+================+===============+
|Value | Error |Description | Specification |
+==========+=======================+================+===============+
|0x0 | DOQ_NO_ERROR |No error | Section 5.3 |
+----------+-----------------------+----------------+---------------+
|0x1 | DOQ_INTERNAL_ERROR |Implementation | Section 5.3 |
| | |error | |
+----------+-----------------------+----------------+---------------+
|0x2 | DOQ_PROTOCOL_ERROR |Generic protocol| Section 5.3 |
| | |violation | |
+----------+-----------------------+----------------+---------------+
|0x3 | DOQ_REQUEST_CANCELLED |Request | Section 5.3 |
| | |cancelled by | |
| | |client | |
+----------+-----------------------+----------------+---------------+
|0x4 | DOQ_EXCESSIVE_LOAD |Closing a | Section 5.3 |
| | |connection for | |
| | |excessive load | |
+----------+-----------------------+----------------+---------------+
|0xd098ea5e| DOQ_ERROR_RESERVED |Alternative | Section 5.3 |
| | |error code used | |
| | |for tests | |
+----------+-----------------------+----------------+---------------+
Table 1: Initial DNS over QUIC Error Codes Entries
11. Acknowledgements
This document liberally borrows text from the HTTP-3 specification
[I-D.ietf-quic-http] edited by Mike Bishop, and from the DoT
specification [RFC7858] authored by Zi Hu, Liang Zhu, John Heidemann,
Allison Mankin, Duane Wessels, and Paul Hoffman.
The privacy issue with 0-RTT data and session resumption were
analyzed by Daniel Kahn Gillmor (DKG) in a message to the IETF
"DPRIVE" working group [DNS0RTT].
Thanks to Tony Finch for an extensive review of the initial version
of this draft, and to Robert Evans for the discussion of 0-RTT
privacy issues. Reviews by Paul Hoffman and Martin Thomson and
interoperability tests conducted by Stephane Bortzmeyer helped
improve the definition of the protocol.
12. References
12.1. Normative References
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[I-D.ietf-dnsop-rfc8499bis]
Hoffman, P. and K. Fujiwara, "DNS Terminology", Work in
Progress, Internet-Draft, draft-ietf-dnsop-rfc8499bis-03,
28 September 2021, <https://www.ietf.org/archive/id/draft-
ietf-dnsop-rfc8499bis-03.txt>.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[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>.
[RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
DOI 10.17487/RFC1995, August 1996,
<https://www.rfc-editor.org/info/rfc1995>.
[RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol
(AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010,
<https://www.rfc-editor.org/info/rfc5936>.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891,
DOI 10.17487/RFC6891, April 2013,
<https://www.rfc-editor.org/info/rfc6891>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and
D. Wessels, "DNS Transport over TCP - Implementation
Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016,
<https://www.rfc-editor.org/info/rfc7766>.
[RFC7828] Wouters, P., Abley, J., Dickinson, S., and R. Bellis, "The
edns-tcp-keepalive EDNS0 Option", RFC 7828,
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>.
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[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>.
[RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS)
Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016,
<https://www.rfc-editor.org/info/rfc7873>.
[RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
Transport Layer Security (DTLS)", RFC 8094,
DOI 10.17487/RFC8094, February 2017,
<https://www.rfc-editor.org/info/rfc8094>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
[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,
<https://www.rfc-editor.org/info/rfc8310>.
[RFC8467] Mayrhofer, A., "Padding Policies for Extension Mechanisms
for DNS (EDNS(0))", RFC 8467, DOI 10.17487/RFC8467,
October 2018, <https://www.rfc-editor.org/info/rfc8467>.
[RFC8914] Kumari, W., Hunt, E., Arends, R., Hardaker, W., and D.
Lawrence, "Extended DNS Errors", RFC 8914,
DOI 10.17487/RFC8914, October 2020,
<https://www.rfc-editor.org/info/rfc8914>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
[RFC9001] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
<https://www.rfc-editor.org/info/rfc9001>.
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[RFC9103] Toorop, W., Dickinson, S., Sahib, S., Aras, P., and A.
Mankin, "DNS Zone Transfer over TLS", RFC 9103,
DOI 10.17487/RFC9103, August 2021,
<https://www.rfc-editor.org/info/rfc9103>.
12.2. Informative References
[DNS0RTT] Kahn Gillmor, D., "DNS + 0-RTT", Message to DNS-Privacy WG
mailing list, 6 April 2016, <https://www.ietf.org/mail-
archive/web/dns-privacy/current/msg01276.html>.
[I-D.ietf-quic-http]
Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-34, 2 February 2021,
<https://www.ietf.org/archive/id/draft-ietf-quic-http-
34.txt>.
[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
August 1996, <https://www.rfc-editor.org/info/rfc1996>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[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>.
[RFC8490] Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S.,
Lemon, T., and T. Pusateri, "DNS Stateful Operations",
RFC 8490, DOI 10.17487/RFC8490, March 2019,
<https://www.rfc-editor.org/info/rfc8490>.
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[RFC8932] Dickinson, S., Overeinder, B., van Rijswijk-Deij, R., and
A. Mankin, "Recommendations for DNS Privacy Service
Operators", BCP 232, RFC 8932, DOI 10.17487/RFC8932,
October 2020, <https://www.rfc-editor.org/info/rfc8932>.
[RFC9002] Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
and Congestion Control", RFC 9002, DOI 10.17487/RFC9002,
May 2021, <https://www.rfc-editor.org/info/rfc9002>.
[RFC9076] Wicinski, T., Ed., "DNS Privacy Considerations", RFC 9076,
DOI 10.17487/RFC9076, July 2021,
<https://www.rfc-editor.org/info/rfc9076>.
Appendix A. The NOTIFY Service
This appendix discusses why it is considered acceptable to send
NOTIFY (see [RFC1996]) in 0-RTT data.
Section 5.5 says "The 0-RTT mechanism SHOULD NOT be used to send DNS
requests that are not "replayable" transactions". This specification
supports sending a NOTIFY in 0-RTT data because although a NOTIFY
technically changes the state of the receiving server, the effect of
replaying NOTIFYs has negligible impact in practice.
NOTIFY messages prompt a secondary to either send an SOA query or an
XFR request to the primary on the basis that a newer version of the
zone is available. It has long been recognized that NOTIFYs can be
forged and, in theory, used to cause a secondary to send repeated
unnecessary requests to the primary. For this reason, most
implementations have some form of throttling of the SOA/XFR queries
triggered by the receipt of one or more NOTIFYs.
[RFC9103] describes the privacy risks associated with both NOTIFY and
SOA queries and does not include addressing those risks within the
scope of encrypting zone transfers. Given this, the privacy benefit
of using DoQ for NOTIFY is not clear - but for the same reason,
sending NOTIFY as 0-RTT data has no privacy risk above that of
sending it using cleartext DNS.
Appendix B. Notable Changes From Previous Versions
(RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION)
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B.1. Stream Mapping Incompatibility With Draft-02
Versions prior to -02 of this specification proposed a simpler
mapping scheme of queries and responses to QUIc stream, which omitted
the 2 byte length field and supported only a single response on a
given stream. The more complex mapping in Section 5.2 was adopted to
specifically cater for XFR support, however it breaks compatibility
with earlier versions.
Authors' Addresses
Christian Huitema
Private Octopus Inc.
427 Golfcourse Rd
Friday Harbor, WA 98250
United States of America
Email: huitema@huitema.net
Sara Dickinson
Sinodun IT
Oxford Science Park
Oxford
OX4 4GA
United Kingdom
Email: sara@sinodun.com
Allison Mankin
Salesforce
Email: allison.mankin@gmail.com
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