draft-ietf-dnssd-push-10.txt   draft-ietf-dnssd-push-11.txt 
Internet Engineering Task Force T. Pusateri Internet Engineering Task Force T. Pusateri
Internet-Draft Seeking affiliation Internet-Draft Seeking affiliation
Intended status: Standards Track S. Cheshire Intended status: Standards Track S. Cheshire
Expires: September 14, 2017 Apple Inc. Expires: December 19, 2017 Apple Inc.
March 13, 2017 June 17, 2017
DNS Push Notifications DNS Push Notifications
draft-ietf-dnssd-push-10 draft-ietf-dnssd-push-11
Abstract Abstract
The Domain Name System (DNS) was designed to return matching records The Domain Name System (DNS) was designed to return matching records
efficiently for queries for data that is relatively static. When efficiently for queries for data that is relatively static. When
those records change frequently, DNS is still efficient at returning those records change frequently, DNS is still efficient at returning
the updated results when polled. But there exists no mechanism the updated results when polled. But there exists no mechanism
for a client to be asynchronously notified when these changes occur. for a client to be asynchronously notified when these changes occur.
This document defines a mechanism for a client to be notified This document defines a mechanism for a client to be notified
of such changes to DNS records, called DNS Push Notifications. of such changes to DNS records, called DNS Push Notifications.
skipping to change at page 1, line 37 skipping to change at page 1, line 37
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 14, 2017. This Internet-Draft will expire on December 19, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. State Considerations . . . . . . . . . . . . . . . . . . . . 8 5. State Considerations . . . . . . . . . . . . . . . . . . . . 7
6. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 9 6. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 8
6.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 9
6.2. DNS Push Notification SUBSCRIBE . . . . . . . . . . . . . 12 6.2. DNS Push Notification SUBSCRIBE . . . . . . . . . . . . . 11
6.2.1. SUBSCRIBE Request . . . . . . . . . . . . . . . . . . 13 6.2.1. SUBSCRIBE Request . . . . . . . . . . . . . . . . . . 12
6.2.2. SUBSCRIBE Response . . . . . . . . . . . . . . . . . 15 6.2.2. SUBSCRIBE Response . . . . . . . . . . . . . . . . . 15
6.3. DNS Push Notification Updates . . . . . . . . . . . . . . 18 6.3. DNS Push Notification Updates . . . . . . . . . . . . . . 18
6.3.1. PUSH Message . . . . . . . . . . . . . . . . . . . . 19 6.3.1. PUSH Message . . . . . . . . . . . . . . . . . . . . 19
6.3.2. PUSH Response . . . . . . . . . . . . . . . . . . . . 21 6.3.2. PUSH Response . . . . . . . . . . . . . . . . . . . . 22
6.4. DNS Push Notification UNSUBSCRIBE . . . . . . . . . . . . 22 6.4. DNS Push Notification UNSUBSCRIBE . . . . . . . . . . . . 23
6.4.1. UNSUBSCRIBE Request . . . . . . . . . . . . . . . . . 23 6.4.1. UNSUBSCRIBE Request . . . . . . . . . . . . . . . . . 24
6.4.2. UNSUBSCRIBE Response . . . . . . . . . . . . . . . . 24 6.4.2. UNSUBSCRIBE Response . . . . . . . . . . . . . . . . 26
6.5. DNS Push Notification RECONFIRM . . . . . . . . . . . . . 26 6.5. DNS Push Notification RECONFIRM . . . . . . . . . . . . . 28
6.5.1. RECONFIRM Request . . . . . . . . . . . . . . . . . . 26 6.5.1. RECONFIRM Request . . . . . . . . . . . . . . . . . . 29
6.5.2. RECONFIRM Response . . . . . . . . . . . . . . . . . 28 6.5.2. RECONFIRM Response . . . . . . . . . . . . . . . . . 31
6.6. Client-Initiated Termination . . . . . . . . . . . . . . 30 6.6. Client-Initiated Termination . . . . . . . . . . . . . . 33
7. Security Considerations . . . . . . . . . . . . . . . . . . . 31 7. Security Considerations . . . . . . . . . . . . . . . . . . . 34
7.1. Security Services . . . . . . . . . . . . . . . . . . . . 31 7.1. Security Services . . . . . . . . . . . . . . . . . . . . 34
7.2. TLS Name Authentication . . . . . . . . . . . . . . . . . 31 7.2. TLS Name Authentication . . . . . . . . . . . . . . . . . 34
7.3. TLS Compression . . . . . . . . . . . . . . . . . . . . . 32 7.3. TLS Compression . . . . . . . . . . . . . . . . . . . . . 35
7.4. TLS Session Resumption . . . . . . . . . . . . . . . . . 32 7.4. TLS Session Resumption . . . . . . . . . . . . . . . . . 35
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 32 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
10.1. Normative References . . . . . . . . . . . . . . . . . . 33 10.1. Normative References . . . . . . . . . . . . . . . . . . 36
10.2. Informative References . . . . . . . . . . . . . . . . . 34 10.2. Informative References . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40
1. Introduction 1. Introduction
DNS records may be updated using DNS Update [RFC2136]. Other DNS records may be updated using DNS Update [RFC2136]. Other
mechanisms such as a Discovery Proxy [DisProx] can also generate mechanisms such as a Discovery Proxy [DisProx] can also generate
changes to a DNS zone. This document specifies a protocol for DNS changes to a DNS zone. This document specifies a protocol for DNS
clients to subscribe to receive asynchronous notifications of changes clients to subscribe to receive asynchronous notifications of changes
to RRSets of interest. It is immediately relevant in the case of DNS to RRSets of interest. It is immediately relevant in the case of DNS
Service Discovery [RFC6763] but is not limited to that use case, and Service Discovery [RFC6763] but is not limited to that use case, and
provides a general DNS mechanism for DNS record change notifications. provides a general DNS mechanism for DNS record change notifications.
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UDP-based protocol, effectively replicating much of TCP's connection UDP-based protocol, effectively replicating much of TCP's connection
state management logic in user space, and creating its own poor state management logic in user space, and creating its own poor
imitations of existing TCP features like the three-way handshake, imitations of existing TCP features like the three-way handshake,
flow control, and reliability. flow control, and reliability.
This document builds on experience gained with the LLQ protocol, with This document builds on experience gained with the LLQ protocol, with
an improved design. Instead of using UDP, this specification uses an improved design. Instead of using UDP, this specification uses
TCP, and therefore doesn't need to reinvent existing TCP TCP, and therefore doesn't need to reinvent existing TCP
functionality. Using TCP also gives long-lived low-traffic functionality. Using TCP also gives long-lived low-traffic
connections better longevity through NAT gateways without resorting connections better longevity through NAT gateways without resorting
to excessive keepalive traffic [SessSig]. Instead of inventing a new to excessive keepalive traffic. Instead of inventing a new
vocabulary of messages to communicate DNS zone changes as LLQ did, vocabulary of messages to communicate DNS zone changes as LLQ did,
this specification adopts the syntax and semantics of DNS Update this specification adopts the syntax and semantics of DNS Update
messages [RFC2136]. messages [RFC2136].
3. Overview 3. Overview
The existing DNS Update protocol [RFC2136] provides a mechanism for The existing DNS Update protocol [RFC2136] provides a mechanism for
clients to add or delete individual resource records (RRs) or entire clients to add or delete individual resource records (RRs) or entire
resource record sets (RRSets) on the zone's server. resource record sets (RRSets) on the zone's server.
This specification adopts a simplified subset of these existing This specification adopts a simplified subset of these existing
syntax and semantics, and uses them for DNS Push Notification syntax and semantics, and uses them for DNS Push Notification
messages going in the opposite direction, from server to client, to messages going in the opposite direction, from server to client, to
communicate changes to a zone. The client subscribes for Push communicate changes to a zone. The client subscribes for Push
Notifications by connecting to the server and sending DNS message(s) Notifications by connecting to the server and sending DNS message(s)
indicating the RRSet(s) of interest. When the client loses interest indicating the RRSet(s) of interest. When the client loses interest
in updates to these records, it unsubscribes. in updates to these records, it unsubscribes.
The DNS Push Notification server for a zone is any server capable The DNS Push Notification server for a zone is any server capable
of generating the correct change notifications for a name. of generating the correct change notifications for a name.
It may be a master, slave, or stealth name server [RFC1996]. It may be a master, slave, or stealth name server [RFC7719].
Consequently, the "_dns-push-tls._tcp.<zone>" SRV record for a Consequently, the "_dns-push-tls._tcp.<zone>" SRV record for a
zone MAY reference the same target host and port as that zone's zone MAY reference the same target host and port as that zone's
"_dns-update-tls._tcp.<zone>" SRV record. When the same target host "_dns-update-tls._tcp.<zone>" SRV record. When the same target host
and port is offered for both DNS Updates and DNS Push Notifications, and port is offered for both DNS Updates and DNS Push Notifications,
a client MAY use a single TCP connection to that server for both DNS a client MAY use a single TCP connection to that server for both DNS
Updates and DNS Push Notification Queries. Updates and DNS Push Notification Queries.
Supporting DNS Updates and DNS Push Notifications on the same server Supporting DNS Updates and DNS Push Notifications on the same server
is OPTIONAL. A DNS Push Notification server does NOT also have to is OPTIONAL. A DNS Push Notification server does NOT also have to
support DNS Update. support DNS Update.
DNS Updates and DNS Push Notifications may be handled on different DNS Updates and DNS Push Notifications may be handled on different
ports on the same target host, in which case they are not considered ports on the same target host, in which case they are not considered
to be the "same server" for the purposes of this specification, and to be the "same server" for the purposes of this specification, and
communications with these two ports are handled independently. communications with these two ports are handled independently.
Standard DNS Queries MAY be sent over a DNS Push Notification Standard DNS Queries MAY be sent over a DNS Push Notification
connection, provided that these are queries for names falling within connection, provided that these are queries for names falling within
the server's zone (the <zone> in the "_dns-push-tls._tcp.<zone>" SRV the server's zone (the <zone> in the "_dns-push-tls._tcp.<zone>" SRV
record). The RD (Recursion Desired) bit MUST be zero. record). The RD (Recursion Desired) bit MUST be zero. If a query is
received with the RD bit set, matching records for names falling
within the server's zones should be returned with the RA (Recursion
Available) bit clear. If the query is for a name not in the server's
zone, an error with RCODE NOTAUTH (Not Authoritative) should be
returned.
DNS Push Notification clients are NOT required to implement DNS DNS Push Notification clients are NOT required to implement DNS
Update Prerequisite processing. Prerequisites are used to perform Update Prerequisite processing. Prerequisites are used to perform
tentative atomic test-and-set type operations when a client updates tentative atomic test-and-set type operations when a client updates
records on a server, and that concept has no applicability when it records on a server, and that concept has no applicability when it
comes to an authoritative server informing a client of changes to DNS comes to an authoritative server informing a client of changes to DNS
records. records.
This DNS Push Notification specification includes support for DNS This DNS Push Notification specification includes support for DNS
classes, for completeness. However, in practice, it is anticipated classes, for completeness. However, in practice, it is anticipated
that for the foreseeable future the only DNS class in use will be DNS that for the foreseeable future the only DNS class in use will be DNS
class "IN", as is the reality today with existing DNS servers and class "IN", as is the reality today with existing DNS servers and
clients. A DNS Push Notification server MAY choose to implement only clients. A DNS Push Notification server MAY choose to implement only
DNS class "IN". DNS class "IN". If messages are received for a class other than
"IN", and that class is not supported, an error with RCODE NOTIMPL
(Not Implemented) should be returned.
DNS Push Notifications impose less load on the responding server than DNS Push Notifications impose less load on the responding server than
rapid polling would, but Push Notifications do still have a cost, so rapid polling would, but Push Notifications do still have a cost, so
DNS Push Notification clients MUST NOT recklessly create an excessive DNS Push Notification clients must not recklessly create an excessive
number of Push Notification subscriptions. A subscription SHOULD number of Push Notification subscriptions. A subscription should
only be active when there is a valid reason to need live data (for only be active when there is a valid reason to need live data (for
example, an on-screen display is currently showing the results to the example, an on-screen display is currently showing the results to the
user) and the subscription SHOULD be cancelled as soon as the need user) and the subscription SHOULD be cancelled as soon as the need
for that data ends (for example, when the user dismisses that for that data ends (for example, when the user dismisses that
display). Implementations MAY want to implement idle timeouts, so display). Implementations MAY want to implement idle timeouts, so
that if the user ceases interacting with the device, the display that if the user ceases interacting with the device, the display
showing the result of the DNS Push Notification subscription is showing the result of the DNS Push Notification subscription is
automatically dismissed after a certain period of inactivity. For automatically dismissed after a certain period of inactivity. For
example, if a user presses the "Print" button on their smartphone, example, if a user presses the "Print" button on their smartphone,
and then leaves the phone showing the printer discovery screen until and then leaves the phone showing the printer discovery screen until
the phone goes to sleep, then the printer discovery screen should be the phone goes to sleep, then the printer discovery screen should be
automatically dismissed as the device goes to sleep. If the user automatically dismissed as the device goes to sleep. If the user
does still intend to print, this will require them to press the does still intend to print, this will require them to press the
"Print" button again when they wake their phone up. "Print" button again when they wake their phone up.
A DNS Push Notification client MUST NOT routinely keep a DNS Push A DNS Push Notification client must not routinely keep a DNS Push
Notification subscription active 24 hours a day, 7 days a week, just Notification subscription active 24 hours a day, 7 days a week, just
to keep a list in memory up to date so that if the user does choose to keep a list in memory up to date so that if the user does choose
to bring up an on-screen display of that data, it can be displayed to bring up an on-screen display of that data, it can be displayed
really fast. DNS Push Notifications are designed to be fast enough really fast. DNS Push Notifications are designed to be fast enough
that there is no need to pre-load a "warm" list in memory just in that there is no need to pre-load a "warm" list in memory just in
case it might be needed later. case it might be needed later.
Generally, as described in the DNS Session Signaling specification Generally, as described in the DNS Session Signaling specification
[SessSig], a client MUST NOT keep a connection to a server open [SessSig], a client must not keep a connection to a server open
indefinitely if it has no subscriptions (or other operations) active indefinitely if it has no subscriptions (or other operations) active
on that connection. A client MAY close a connection as soon as it on that connection. A client MAY close a connection as soon as it
becomes idle, and then if needed in the future, open a new connection becomes idle, and then if needed in the future, open a new connection
when required. Alternatively, a client MAY speculatively keep an when required. Alternatively, a client MAY speculatively keep an
idle connection open for some time, subject to the constraint that it idle connection open for some time, subject to the constraint that it
MUST NOT keep a connection open that has been idle for more than the MUST NOT keep a connection open that has been idle for more than the
session's idle timeout (15 seconds by default). session's idle timeout (15 seconds by default).
4. Transport 4. Transport
Implementations of DNS Update [RFC2136] MAY use either User Datagram Implementations of DNS Update [RFC2136] MAY use either User Datagram
Protocol (UDP) [RFC0768] or Transmission Control Protocol (TCP) Protocol (UDP) [RFC0768] or Transmission Control Protocol (TCP)
[RFC0793] as the transport protocol, in keeping with the historical [RFC0793] as the transport protocol, in keeping with the historical
precedent that DNS queries must first be sent over UDP [RFC1123]. precedent that DNS queries must first be sent over UDP [RFC1123].
This requirement to use UDP has subsequently been relaxed [RFC7766]. This requirement to use UDP has subsequently been relaxed [RFC7766].
In keeping with the more recent precedent, DNS Push Notification is In keeping with the more recent precedent, DNS Push Notification is
defined only for TCP. DNS Push Notification clients MUST use TLS defined only for TCP. DNS Push Notification clients MUST use TLS
over TCP. over TCP, see RFC 7858 [RFC7858].
Connection setup over TCP ensures return reachability and alleviates Connection setup over TCP ensures return reachability and alleviates
concerns of state overload at the server through anonymous concerns of state overload at the server through anonymous
subscriptions. All subscribers are guaranteed to be reachable by the subscriptions. All subscribers are guaranteed to be reachable by the
server by virtue of the TCP three-way handshake. Flooding attacks server by virtue of the TCP three-way handshake. Flooding attacks
are possible with any protocol, and a benefit of TCP is that there are possible with any protocol, and a benefit of TCP is that there
are already established industry best practices to guard against SYN are already established industry best practices to guard against SYN
flooding and similar attacks [IPJ.9-4-TCPSYN] [RFC4953]. flooding and similar attacks [IPJ.9-4-TCPSYN] [RFC4953].
Use of TCP also allows DNS Push Notifications to take advantage of Use of TCP also allows DNS Push Notifications to take advantage of
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[I-D.dukkipati-tcpm-tcp-loss-probe], and so on. [I-D.dukkipati-tcpm-tcp-loss-probe], and so on.
Transport Layer Security (TLS) [RFC5246] is well understood and Transport Layer Security (TLS) [RFC5246] is well understood and
deployed across many protocols running over TCP. It is designed to deployed across many protocols running over TCP. It is designed to
prevent eavesdropping, tampering, or message forgery. TLS is prevent eavesdropping, tampering, or message forgery. TLS is
REQUIRED for every connection between a client subscriber and server REQUIRED for every connection between a client subscriber and server
in this protocol specification. Additional security measures such as in this protocol specification. Additional security measures such as
client authentication during TLS negotiation MAY also be employed to client authentication during TLS negotiation MAY also be employed to
increase the trust relationship between client and server. increase the trust relationship between client and server.
Additional authentication of the SRV target using DNSSEC verification
and DANE TLSA records [RFC7673] is strongly encouraged. See below in
Section 7.2 for details.
5. State Considerations 5. State Considerations
Each DNS Push Notification server is capable of handling some finite Each DNS Push Notification server is capable of handling some finite
number of Push Notification subscriptions. This number will vary number of Push Notification subscriptions. This number will vary
from server to server and is based on physical machine from server to server and is based on physical machine
characteristics, network bandwidth, and operating system resource characteristics, network bandwidth, and operating system resource
allocation. After a client establishes a connection to a DNS server, allocation. After a client establishes a connection to a DNS server,
each subscription is individually accepted or rejected. Servers may each subscription is individually accepted or rejected. Servers may
employ various techniques to limit subscriptions to a manageable employ various techniques to limit subscriptions to a manageable
level. Correspondingly, the client is free to establish simultaneous level. Correspondingly, the client is free to establish simultaneous
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6. Protocol Operation 6. Protocol Operation
The DNS Push Notification protocol is a session-oriented protocol, The DNS Push Notification protocol is a session-oriented protocol,
and makes use of DNS Session Signaling [SessSig]. and makes use of DNS Session Signaling [SessSig].
For details of the DNS Session Signaling message format refer to the For details of the DNS Session Signaling message format refer to the
DNS Session Signaling specification [SessSig]. Those details are not DNS Session Signaling specification [SessSig]. Those details are not
repeated here. repeated here.
DNS Push Notification clients and servers MUST support DNS Session DNS Push Notification clients and servers MUST support DNS Session
Signaling, but the server MUST NOT issue any DNS Session Signaling Signaling, but the server SHOULD NOT issue any DNS Session Signaling
operations until after the client has first initiated a DNS Session operations until after the client has first initiated a DNS Session
Signaling operation of its own. A single server can support DNS Signaling operation of its own. A single server can support DNS
Queries, DNS Updates, and DNS Push Notifications (using DNS Session Queries, DNS Updates, and DNS Push Notifications (using DNS Session
Signaling) on the same TCP port, and until the client has sent at Signaling) on the same TCP port, and until the client has sent at
least one DNS Session Signaling operation the server does not know least one DNS Session Signaling operation the server does not know
what kind of client has connected to it. Once the client has what kind of client has connected to it. Once the client has
indicated willingness to use DNS Session Signaling operations by indicated willingness to use DNS Session Signaling operations by
sending one of its own, either side of the connection may then sending one of its own, either side of the connection may then
initiate further Session Signaling operations at any time. initiate further Session Signaling operations at any time.
A DNS Push Notification exchange begins with the client discovering A DNS Push Notification exchange begins with the client discovering
the appropriate server, using the procedure described in Section 6.1, the appropriate server, using the procedure described in Section 6.1,
and then making a TLS/TCP connection to it. and then making a TLS/TCP connection to it.
A typical DNS Push Notification client will immediately issue a DNS A typical DNS Push Notification client will immediately issue a DNS
Session Signaling Keepalive operation to request a session timeout or Session Signaling Keepalive operation to request a session timeout or
keepalive interval longer than the the 15-second defaults, but this keepalive interval longer than the the 15-second defaults, but this
is NOT REQUIRED. A DNS Push Notification client MAY issue other is not required. A DNS Push Notification client MAY issue other
requests on the connection first, and only issue a DNS Session requests on the connection first, and only issue a DNS Session
Signaling Keepalive operation later if it determines that to be Signaling Keepalive operation later if it determines that to be
necessary. necessary.
Once the connection is made, the client may then add and remove Push Once the connection is made, the client may then add and remove Push
Notification subscriptions. In accordance with the current set of Notification subscriptions. In accordance with the current set of
active subscriptions the server sends relevant asynchronous Push active subscriptions the server sends relevant asynchronous Push
Notifications to the client. Note that a client MUST be prepared to Notifications to the client. Note that a client MUST be prepared to
receive (and silently ignore) Push Notifications for subscriptions it receive (and silently ignore) Push Notifications for subscriptions it
has previously removed, since there is no way to prevent the has previously removed, since there is no way to prevent the
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6.1. Discovery 6.1. Discovery
The first step in DNS Push Notification subscription is to discover The first step in DNS Push Notification subscription is to discover
an appropriate DNS server that supports DNS Push Notifications for an appropriate DNS server that supports DNS Push Notifications for
the desired zone. The client MUST also determine which TCP port on the desired zone. The client MUST also determine which TCP port on
the server is listening for connections, which need not be (and often the server is listening for connections, which need not be (and often
is not) the typical TCP port 53 used for conventional DNS, or TCP is not) the typical TCP port 53 used for conventional DNS, or TCP
port 853 used for DNS over TLS [RFC7858]. port 853 used for DNS over TLS [RFC7858].
1. The client begins the discovery by sending a DNS query to its 1. The client begins the discovery by sending a DNS query to its
local resolver, with record type SOA [RFC1035], for the domain local resolver, with record type SOA [RFC1035] for the record to
name to which it wishes to subscribe. which it wishes to subscribe. As an example, if it wishes to
subscribe to PTR records with the name
_printers._tcp.foo.example.com, it sends an SOA query for
_printers._tcp.foo.example.com. The goal is to determine the
authoritative server for foo.example.com.
2. If the SOA record exists, it MUST be returned in the Answer 2. If the SOA record exists as exactly specified in the query, it is
Section of the response. If not, the local resolver SHOULD expected to be returned in the Answer section with a NOERROR
include the SOA record for the zone of the requested name in the response code. If the exact SOA record does not exist, the
Authority Section. client may get back a NOERROR/NODATA response or it may get back
a NXDOMAIN/Name Error response. This depends on the resolver
implementation and whether the domain exists. The client is
looking for an SOA record to be returned in either the Answer
section or the Authority section with a NOERROR response code.
If the client receives an NXDOMAIN/Name Error response code, it
should strip the leading label from the query name and if the
resulting name has at least one label in it, the client should
send a new SOA query, repeating this until a NOERROR response
code is received or the query name is empty. In the case of an
empty name, the client may retry the operation at a later time,
of the client's choosing, such after a change in network
attachment.
3. If no SOA record is returned, the client then strips off the 3. In the example above, if an SOA record query is sent for
leading label from the requested name. If the resulting name has _printers._tcp.foo.example.com and an NXDOMAIN/Name Error is
at least one label in it, the client sends a new SOA query and returned with an SOA record in the Authority section for
processing continues at step 2 above. If the resulting name is foo.example.com, the client should strip the leading label and
empty (the root label) then this is a network configuration error query an SOA record for _tcp.foo.example.com. If a NOERROR/
and the client gives up. The client MAY retry the operation at a NODATA response is received with an SOA record in the Authority
later time, of the client's choosing, such after a change in section for foo.example.com, this is sufficent. If an NXDOMAIN/
network attachment. Name Error response is received, the client should again strip
the leading label and query an SOA record for foo.example.com.
If the foo.example.com domain exists, this should result in a
NOERROR response with the SOA record in the Answer section. If
the domain foo.example.com does not exist, the response will
likely be an NXDOMAIN/Name Error with an SOA record for
example.com in the Authority section. This means the subdomain
foo.example.com has not been properly delegated by example.com.
4. Once the SOA is known (either by virtue of being seen in the 4. If a NOERROR/NODATA response is received but contains no SOA in
the Authority section, the client could try stripping the leading
label and issuing another SOA query. Additional information
about negative responses can be found in Section 2 of [RFC2308].
5. Once the SOA is known (either by virtue of being seen in the
Answer Section, or in the Authority Section), the client sends a Answer Section, or in the Authority Section), the client sends a
DNS query with type SRV [RFC2782] for the record name DNS query with type SRV [RFC2782] for the record name
"_dns-push-tls._tcp.<zone>", where <zone> is the owner name of "_dns-push-tls._tcp.<zone>", where <zone> is the owner name of
the discovered SOA record. the discovered SOA record.
5. If the zone in question does not offer DNS Push Notifications 6. For implementors of this specification, an authoritative answer
then SRV record MUST NOT exist and the SRV query will return a for that SRV record, and only such an answer, will determine
negative answer. whether the zone supports DNS Push Notifications.
6. If the zone in question is set up to offer DNS Push Notifications 7. If the SRV record does exist, the SRV "target" contains the name
then this SRV record MUST exist. The SRV "target" contains the of the server providing DNS Push Notifications for the zone. The
name of the server providing DNS Push Notifications for the zone. port number on which to contact the server is in the SRV record
The port number on which to contact the server is in the SRV "port" field. The address(es) of the target host MAY be included
record "port" field. The address(es) of the target host MAY be in the Additional Section, however, the address records SHOULD be
included in the Additional Section, however, the address records authenticated before use as described below in Section 7.2 and
SHOULD be authenticated before use as described below in [RFC7673].
Section 7.2 [RFC7673].
7. More than one SRV record may be returned. In this case, the 8. More than one SRV record may be returned. In this case, the
"priority" and "weight" values in the returned SRV records are "priority" and "weight" values in the returned SRV records are
used to determine the order in which to contact the servers for used to determine the order in which to contact the servers for
subscription requests. As described in the SRV specification subscription requests. As described in the SRV specification
[RFC2782], the server with the lowest "priority" is first [RFC2782], the server with the lowest "priority" is first
contacted. If more than one server has the same "priority", the contacted. If more than one server has the same "priority", the
"weight" indicates the weighted probability that the client "weight" indicates the weighted probability that the client
should contact that server. Higher weights have higher should contact that server. Higher weights have higher
probabilities of being selected. If a server is not reachable or probabilities of being selected. If a server is not reachable or
is not willing to accept a subscription request, then a is not willing to accept a subscription request, then a
subsequent server is to be contacted. subsequent server is to be contacted.
Each time a client makes a new DNS Push Notification subscription Each time a client makes a new DNS Push Notification subscription
connection, it SHOULD repeat the discovery process in order to connection, it SHOULD repeat the discovery process in order to
determine the preferred DNS server for subscriptions at that time. determine the preferred DNS server for subscriptions at that time.
However, the client device MUST respect the DNS TTL values on records
Note that this repeated discovery step is typically very fast and it receives, and store them in its local cache with this lifetime.
typically results in no queries on the network. The client device This means that, as long as the DNS TTL values on the authoritative
MUST respect the DNS TTL values on records it receives, and store records were set to reasonable values, repeated application of this
them in its local cache with this lifetime. This means that, as long discovery process can be completed nearly instantaneously by the
as the DNS TTL values on the authoritative records were set to client, using only locally-stored cached data.
reasonable values, repeated application of this discovery process can
be completed nearly instantaneously by the client, using only
locally-stored cached data.
6.2. DNS Push Notification SUBSCRIBE 6.2. DNS Push Notification SUBSCRIBE
After connecting, and requesting a longer idle timeout and/or After connecting, and requesting a longer idle timeout and/or
keepalive interval if necessary, a DNS Push Notification client then keepalive interval if necessary, a DNS Push Notification client then
indicates its desire to receive DNS Push Notifications for a given indicates its desire to receive DNS Push Notifications for a given
domain name by sending a SUBSCRIBE request over the established TLS domain name by sending a SUBSCRIBE request over the established TLS
connection to the server. A SUBSCRIBE request is encoded in a DNS connection to the server. A SUBSCRIBE request is encoded in a DNS
Session Signaling [SessSig] message. This specification defines a Session Signaling [SessSig] message. This specification defines a
DNS Session Signaling TLV for DNS Push Notification SUBSCRIBE DNS Session Signaling TLV for DNS Push Notification SUBSCRIBE
Requests/Responses (tentatively Session Signaling Type Code 0x40). Requests/Responses (tentatively Session Signaling Type Code 0x40).
A server MUST NOT initiate a SUBSCRIBE request. The entity that initiates a SUBSCRIBE request is by definition the
client. A server should not send a SUBSCRIBE request over an
existing connection from a client. If a server does send a SUBSCRIBE
request over the connection initiated by a client, it is an error and
the client should acknowledge the request with the error response
RCODE NOTAUTH (Not Authoritative).
6.2.1. SUBSCRIBE Request 6.2.1. SUBSCRIBE Request
A SUBSCRIBE request message begins with the standard DNS Session A SUBSCRIBE request message begins with the standard DNS Session
Signaling 12-byte header [SessSig], followed by the SUBSCRIBE TLV. Signaling 12-byte header [SessSig], followed by the SUBSCRIBE TLV. A
The SSOP-DATA for the the SUBSCRIBE TLV is as follows: SUBSCRIBE request message is illustrated below:
1 1 1 1 1 1 1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | MESSAGE ID |
\ NAME \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
\ \ |QR| Opcode | Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TYPE | | QDCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| CLASS | | ANCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-TYPE = SUBSCRIBE (tentatively 0x40) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-LENGTH (number of octets in SSOP-DATA) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \
| | \
\ NAME \ |
\ \ |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > SSOP-DATA
| TYPE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| CLASS | /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
Figure 1 Figure 1
The MESSAGE ID field MUST be set to a unique value, that the client The MESSAGE ID field MUST be set to a unique value, that the client
is not using for any other active operation on this connection. For is not using for any other active operation on this connection. For
the purposes here, a MESSAGE ID is in use on this connection if the the purposes here, a MESSAGE ID is in use on this connection if the
client has used it in a request for which it has not yet received a client has used it in a request for which it has not yet received a
response, or if if the client has used it for a subscription which it response, or if the client has used it for a subscription which it
has not yet cancelled using UNSUBSCRIBE. In the SUBSCRIBE response has not yet cancelled using UNSUBSCRIBE. In the SUBSCRIBE response
the server MUST echo back the MESSAGE ID value unchanged. the server MUST echo back the MESSAGE ID value unchanged.
In the SUBSCRIBE TLV the SSOP-TYPE is SUBSCRIBE (tentatively 0x40). The other header fields MUST be set as described in the DNS Session
The SSOP-LENGTH is the length of the SSOP-DATA that follows, which Signaling specification [SessSig]. The DNS Opcode is the Session
specifies the name, type, and class of the record(s) being sought. Signaling Opcode (tentatively 6). The four count fields MUST be
empty, and the corresponding four sections MUST be empty (i.e.,
absent).
A SUBSCRIBE request MUST contain exactly one question. The SUBSCRIBE The SSOP-TYPE is SUBSCRIBE (tentatively 0x40). The SSOP-LENGTH is
TLV has no QDCOUNT field to specify more than one question. Since the length of the SSOP-DATA that follows, which specifies the name,
SUBSCRIBE requests are sent over TCP, multiple SUBSCRIBE request type, and class of the record(s) being sought.
messages can be concatenated in a single TCP stream and packed
efficiently into TCP segments. The SSOP-DATA for a SUBSCRIBE request MUST contain exactly one
question. The SSOP-DATA for a SUBSCRIBE request has no QDCOUNT field
to specify more than one question. Since SUBSCRIBE requests are sent
over TCP, multiple SUBSCRIBE request messages can be concatenated in
a single TCP stream and packed efficiently into TCP segments.
If accepted, the subscription will stay in effect until the client If accepted, the subscription will stay in effect until the client
cancels the subscription using UNSUBSCRIBE or until the connection cancels the subscription using UNSUBSCRIBE or until the connection
between the client and the server is closed. between the client and the server is closed.
SUBSCRIBE requests on a given connection MUST be unique. A client SUBSCRIBE requests on a given connection MUST be unique. A client
MUST NOT send a SUBSCRIBE message that duplicates the NAME, TYPE and MUST NOT send a SUBSCRIBE message that duplicates the NAME, TYPE and
CLASS of an existing active subscription on that TLS/TCP connection. CLASS of an existing active subscription on that TLS/TCP connection.
For the purpose of this matching, the established DNS case- For the purpose of this matching, the established DNS case-
insensitivity for US-ASCII letters applies (e.g., "foo.com" and insensitivity for US-ASCII letters applies (e.g., "foo.com" and
"Foo.com" are the same). If a server receives such a duplicate "Foo.com" are the same). If a server receives such a duplicate
SUBSCRIBE message this is an error and the server MUST immediately SUBSCRIBE message this is an error and the server MUST immediately
immediately terminate the connection with a TCP RST (or equivalent terminate the connection with a TCP RST (or equivalent for other
for other protocols). protocols).
DNS wildcarding is not supported. That is, a wildcard ("*") in a DNS wildcarding is not supported. That is, a wildcard ("*") in a
SUBSCRIBE message matches only a literal wildcard character ("*") in SUBSCRIBE message matches only a literal wildcard character ("*") in
the zone, and nothing else. the zone, and nothing else.
Aliasing is not supported. That is, a CNAME in a SUBSCRIBE message Aliasing is not supported. That is, a CNAME in a SUBSCRIBE message
matches only a literal CNAME record in the zone, and nothing else. matches only a literal CNAME record in the zone, and nothing else.
A client may SUBSCRIBE to records that are unknown to the server at A client may SUBSCRIBE to records that are unknown to the server at
the time of the request (providing that the name falls within one of the time of the request (providing that the name falls within one of
skipping to change at page 14, line 30 skipping to change at page 14, line 9
If neither TYPE nor CLASS are ANY (255) then this is a specific If neither TYPE nor CLASS are ANY (255) then this is a specific
subscription to changes for the given NAME, TYPE and CLASS. If one subscription to changes for the given NAME, TYPE and CLASS. If one
or both of TYPE or CLASS are ANY (255) then this subscription matches or both of TYPE or CLASS are ANY (255) then this subscription matches
any type and/or any class, as appropriate. any type and/or any class, as appropriate.
NOTE: A little-known quirk of DNS is that in DNS QUERY requests, NOTE: A little-known quirk of DNS is that in DNS QUERY requests,
QTYPE and QCLASS 255 mean "ANY" not "ALL". They indicate that the QTYPE and QCLASS 255 mean "ANY" not "ALL". They indicate that the
server should respond with ANY matching records of its choosing, not server should respond with ANY matching records of its choosing, not
necessarily ALL matching records. This can lead to some surprising necessarily ALL matching records. This can lead to some surprising
and unexpected results, were a query returns some valid answers but and unexpected results, where a query returns some valid answers but
not all of them, and makes QTYPE=ANY queries less useful than people not all of them, and makes QTYPE=ANY queries less useful than people
sometimes imagine. sometimes imagine.
When used in conjunction with SUBSCRIBE, TYPE and CLASS 255 should be When used in conjunction with SUBSCRIBE, TYPE and CLASS 255 should be
interpreted to mean "ALL", not "ANY". After accepting a subscription interpreted to mean "ALL", not "ANY". After accepting a subscription
where one or both of TYPE or CLASS are 255, the server MUST send Push where one or both of TYPE or CLASS are 255, the server MUST send Push
Notification Updates for ALL record changes that match the Notification Updates for ALL record changes that match the
subscription, not just some of them. subscription, not just some of them.
6.2.2. SUBSCRIBE Response 6.2.2. SUBSCRIBE Response
skipping to change at page 15, line 31 skipping to change at page 15, line 31
In the SUBSCRIBE response the RCODE indicates whether or not the In the SUBSCRIBE response the RCODE indicates whether or not the
subscription was accepted. Supported RCODEs are as follows: subscription was accepted. Supported RCODEs are as follows:
+------------+-------+----------------------------------------------+ +------------+-------+----------------------------------------------+
| Mnemonic | Value | Description | | Mnemonic | Value | Description |
+------------+-------+----------------------------------------------+ +------------+-------+----------------------------------------------+
| NOERROR | 0 | SUBSCRIBE successful. | | NOERROR | 0 | SUBSCRIBE successful. |
| FORMERR | 1 | Server failed to process request due to a | | FORMERR | 1 | Server failed to process request due to a |
| | | malformed request. | | | | malformed request. |
| SERVFAIL | 2 | Server failed to process request due to | | SERVFAIL | 2 | Server failed to process request due to a |
| | | resource exhaustion. | | | | problem with the server. |
| NXDOMAIN | 3 | NOT APPLICABLE. DNS Push Notification | | NXDOMAIN | 3 | NOT APPLICABLE. DNS Push Notification |
| | | servers MUST NOT return NXDOMAIN errors in | | | | servers MUST NOT return NXDOMAIN errors in |
| | | response to SUBSCRIBE requests. | | | | response to SUBSCRIBE requests. |
| NOTIMP | 4 | Server does not recognize DNS Session | | NOTIMP | 4 | Server does not recognize DNS Session |
| | | Signaling Opcode. | | | | Signaling Opcode. |
| REFUSED | 5 | Server refuses to process request for policy | | REFUSED | 5 | Server refuses to process request for policy |
| | | or security reasons. | | | | or security reasons. |
| NOTAUTH | 9 | Server is not authoritative for the | | NOTAUTH | 9 | Server is not authoritative for the |
| | | requested name. | | | | requested name. |
| SSOPNOTIMP | 11 | SUBSCRIBE operation not supported. | | SSOPNOTIMP | 11 | SUBSCRIBE operation not supported. |
skipping to change at page 16, line 6 skipping to change at page 16, line 6
SUBSCRIBE Response codes SUBSCRIBE Response codes
This document specifies only these RCODE values for SUBSCRIBE This document specifies only these RCODE values for SUBSCRIBE
Responses. Servers sending SUBSCRIBE Responses SHOULD use one of Responses. Servers sending SUBSCRIBE Responses SHOULD use one of
these values. However, future circumstances may create situations these values. However, future circumstances may create situations
where other RCODE values are appropriate in SUBSCRIBE Responses, so where other RCODE values are appropriate in SUBSCRIBE Responses, so
clients MUST be prepared to accept SUBSCRIBE Responses with any RCODE clients MUST be prepared to accept SUBSCRIBE Responses with any RCODE
value. value.
If the server sends a nonzero RCODE in the SUBSCRIBE response, either If the server sends a nonzero RCODE in the SUBSCRIBE response, either
the client is (at least partially) misconfigured or the server the client is (at least partially) misconfigured, the server
resources are exhausted. In either case, the client shouldn't retry resources are exhausted, or there is some other unknown failure on
the subscription right away. Either end can terminate the the server. In any case, the client shouldn't retry the subscription
connection, but the client may want to try this subscription again or right away. Either end can terminate the connection, but the client
it may have other successful subscriptions that it doesn't want to may want to try this subscription again or it may have other
abandon. If the server sends a nonzero RCODE then it SHOULD append a successful subscriptions that it doesn't want to abandon. If the
Retry Delay Modifier TLV [SessSig] to the response specifying a delay server sends a nonzero RCODE then it SHOULD append a Retry Delay
before the client attempts this operation again. Recommended values Modifier TLV [SessSig] to the response specifying a delay before the
for the delay for different RCODE values are given below: client attempts this operation again. Recommended values for the
delay for different RCODE values are given below:
For RCODE = 1 (FORMERR) the delay may be any value selected by the For RCODE = 1 (FORMERR) the delay may be any value selected by the
implementer. A value of five minutes is RECOMMENDED, to reduce implementer. A value of five minutes is RECOMMENDED, to reduce
the risk of high load from defective clients. the risk of high load from defective clients.
For RCODE = 2 (SERVFAIL), which occurs due to resource exhaustion, For RCODE = 2 (SERVFAIL) the delay should be chosen according to
the delay should be chosen according to the level of server the level of server overload and the anticipated duration of that
overload and the anticipated duration of that overload. By overload. By default, a value of one minute is RECOMMENDED. If a
default, a value of one minute is RECOMMENDED. more serious server failure occurs, the delay may be longer in
accordance with the specific problem encountered.
For RCODE = 4 (NOTIMP), which occurs on a server that doesn't For RCODE = 4 (NOTIMP), which occurs on a server that doesn't
implement DNS Session Signaling [SessSig], it is unlikely that the implement DNS Session Signaling [SessSig], it is unlikely that the
server will begin supporting DNS Session Signaling in the next few server will begin supporting DNS Session Signaling in the next few
minutes, so the retry delay SHOULD be one hour. minutes, so the retry delay SHOULD be one hour.
For RCODE = 5 (REFUSED), which occurs on a server that implements For RCODE = 5 (REFUSED), which occurs on a server that implements
DNS Push Notifications, but is currently configured to disallow DNS Push Notifications, but is currently configured to disallow
DNS Push Notifications, the retry delay may be any value selected DNS Push Notifications, the retry delay may be any value selected
by the implementer and/or configured by the operator. by the implementer and/or configured by the operator.
skipping to change at page 17, line 23 skipping to change at page 17, line 23
value of 5 minutes is RECOMMENDED. value of 5 minutes is RECOMMENDED.
For RCODE = 9 (NOTAUTH), the time delay applies to requests for other For RCODE = 9 (NOTAUTH), the time delay applies to requests for other
names falling within the same zone. Requests for names falling names falling within the same zone. Requests for names falling
within other zones are not subject to the delay. For all other within other zones are not subject to the delay. For all other
RCODEs the time delay applies to all subsequent requests to this RCODEs the time delay applies to all subsequent requests to this
server. server.
After sending an error response the server MAY allow the connection After sending an error response the server MAY allow the connection
to remain open, or MAY send a DNS Push Notification Retry Delay to remain open, or MAY send a DNS Push Notification Retry Delay
Operation TLV and then close the TCP connection, as described in the Operation TLV asserting the client close the TCP connection, as
DNS Session Signaling specification [SessSig]. Clients MUST described in the DNS Session Signaling specification [SessSig].
correctly handle both cases. Clients MUST correctly handle both cases.
6.3. DNS Push Notification Updates 6.3. DNS Push Notification Updates
Once a subscription has been successfully established, the server Once a subscription has been successfully established, the server
generates PUSH messages to send to the client as appropriate. In the generates PUSH messages to send to the client as appropriate. In the
case that the answer set was non-empty at the moment the subscription case that the answer set was non-empty at the moment the subscription
was established, an initial PUSH message will be sent immediately was established, an initial PUSH message will be sent immediately
following the SUBSCRIBE Response. Subsequent changes to the answer following the SUBSCRIBE Response. Subsequent changes to the answer
set are then communicated to the client in subsequent PUSH messages. set are then communicated to the client in subsequent PUSH messages.
6.3.1. PUSH Message 6.3.1. PUSH Message
A PUSH message begins with the standard DNS Session Signaling 12-byte A PUSH message begins with the standard DNS Session Signaling 12-byte
header [SessSig], followed by the PUSH TLV. header [SessSig], followed by the PUSH TLV. A PUSH message is
illustrated below:
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| MESSAGE ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode | Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-TYPE = PUSH (tentatively 0x42) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-LENGTH (number of octets in SSOP-DATA) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \
\ NAME \ \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| TYPE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| CLASS | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| RDLEN | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
\ RDATA \ |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > SSOP-DATA
\ NAME \ |
+--+--+--+--+--+--+- | |
| TYPE Repeated | |
+--+--+--+--+--+--+- | |
| CLASS As | |
+--+--+--+--+--+--+- | |
| RDLEN Necessary | |
+--+--+--+--+--+--+- | |
\ RDATA \ /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
Figure 2
The MESSAGE ID field MUST be set to a unique value, that the server The MESSAGE ID field MUST be set to a unique value, that the server
is not currently using for any other active outgoing request that it is not currently using for any other active outgoing request that it
has sent on this connection. The MESSAGE ID in the outgoing PUSH has sent on this connection. The MESSAGE ID in the outgoing PUSH
message is selected by the server and has no relationship to the message is selected by the server and has no relationship to the
MESSAGE ID in any of the client subscriptions it may relate to. In MESSAGE ID in any of the client subscriptions it may relate to. In
the PUSH response the client MUST echo back the MESSAGE ID value the PUSH response the client MUST echo back the MESSAGE ID value
unchanged. unchanged.
In the PUSH TLV the SSOP-TYPE is PUSH (tentatively 0x41). The SSOP- The other header fields MUST be set as described in the DNS Session
LENGTH is the length of the SSOP-DATA that follows, which specifies Signaling specification [SessSig]. The DNS Opcode is the Session
the changes being communicated. Signaling Opcode (tentatively 6). The four count fields MUST be
empty, and the corresponding four sections MUST be empty (i.e.,
absent).
The SSOP-DATA contains one or more Update records, in customary The SSOP-TYPE is PUSH (tentatively 0x41). The SSOP-LENGTH is the
Resource Record format, as used in DNS Update [RFC2136] messages. A length of the SSOP-DATA that follows, which specifies the changes
PUSH Message MUST contain at least one Update record. If a PUSH being communicated.
Message is received that contains no Update records this is a fatal
error, and the receiver MUST immediately terminate the connection
with a TCP RST (or equivalent for other protocols).
The SSOP-DATA contains the relevant change information for the The SSOP-DATA contains one or more Update records. A PUSH Message
client, formatted identically to a DNS Update [RFC2136]. To recap: MUST contain at least one Update record. If a PUSH Message is
received that contains no Update records, this is a fatal error, and
the receiver MUST immediately terminate the connection with a TCP RST
(or equivalent for other protocols). The Update records are
formatted in the customary way for Resource Records in DNS messages
with the stipulation that DNS name compression is not permitted in
DNS Session Signaling TLVs. Update records in a PUSH Message are
interpreted according to the same rules as for DNS Update [RFC2136]
messages, namely:
Delete all RRsets from a name: Delete all RRsets from a name:
TTL=0, CLASS=ANY, RDLENGTH=0, TYPE=ANY. TTL=0, CLASS=ANY, RDLENGTH=0, TYPE=ANY.
Delete an RRset from a name: Delete an RRset from a name:
TTL=0, CLASS=ANY, RDLENGTH=0; TTL=0, CLASS=ANY, RDLENGTH=0;
TYPE specifies the RRset being deleted. TYPE specifies the RRset being deleted.
Delete an individual RR from a name: Delete an individual RR from a name:
TTL=0, CLASS=NONE; TTL=0, CLASS=NONE;
skipping to change at page 20, line 48 skipping to change at page 21, line 50
back to the server. back to the server.
The TTL of an added record is stored by the client and decremented as The TTL of an added record is stored by the client and decremented as
time passes, with the caveat that for as long as a relevant time passes, with the caveat that for as long as a relevant
subscription is active, the TTL does not decrement below 1 second. subscription is active, the TTL does not decrement below 1 second.
For as long as a relevant subscription remains active, the client For as long as a relevant subscription remains active, the client
SHOULD assume that when a record goes away the server will notify it SHOULD assume that when a record goes away the server will notify it
of that fact. Consequently, a client does not have to poll to verify of that fact. Consequently, a client does not have to poll to verify
that the record is still there. Once a subscription is cancelled that the record is still there. Once a subscription is cancelled
(individually, or as a result of the TCP connection being closed) (individually, or as a result of the TCP connection being closed)
record ageing resumes and records are removed from the local cache record aging resumes and records are removed from the local cache
when their TTL reaches zero. when their TTL reaches zero.
6.3.2. PUSH Response 6.3.2. PUSH Response
Each PUSH message generates exactly one PUSH response from the Each PUSH message generates exactly one PUSH response from the
receiver. receiver.
A PUSH response message begins with the standard DNS Session A PUSH response message begins with the standard DNS Session
Signaling 12-byte header [SessSig], possibly followed by one or more Signaling 12-byte header [SessSig], possibly followed by one or more
optional Modifier TLVs, such as a Retry Delay Modifier TLV. optional Modifier TLVs, such as a Retry Delay Modifier TLV.
skipping to change at page 22, line 15 skipping to change at page 23, line 15
6.4. DNS Push Notification UNSUBSCRIBE 6.4. DNS Push Notification UNSUBSCRIBE
To cancel an individual subscription without closing the entire To cancel an individual subscription without closing the entire
connection, the client sends an UNSUBSCRIBE message over the connection, the client sends an UNSUBSCRIBE message over the
established TCP connection to the server. The UNSUBSCRIBE message is established TCP connection to the server. The UNSUBSCRIBE message is
encoded in a DNS Session Signaling [SessSig] message. This encoded in a DNS Session Signaling [SessSig] message. This
specification defines a DNS Session Signaling TLV for DNS Push specification defines a DNS Session Signaling TLV for DNS Push
Notification UNSUBSCRIBE Requests/Responses (tentatively Session Notification UNSUBSCRIBE Requests/Responses (tentatively Session
Signaling Type Code 0x42). Signaling Type Code 0x42).
A server MUST NOT initiate an UNSUBSCRIBE request. A server MUST NOT initiate an UNSUBSCRIBE request. If a server does
send a UNSUBSCRIBE request over the connection initiated by a client,
it is an error and the client should acknowledge the request with the
error response RCODE NOTAUTH (Not Authoritative).
6.4.1. UNSUBSCRIBE Request 6.4.1. UNSUBSCRIBE Request
An UNSUBSCRIBE request message begins with the standard DNS Session An UNSUBSCRIBE request message begins with the standard DNS Session
Signaling 12-byte header [SessSig], followed by the UNSUBSCRIBE TLV. Signaling 12-byte header [SessSig], followed by the UNSUBSCRIBE TLV.
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| MESSAGE ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode | Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-TYPE = UNSUBSCRIBE (tentatively 0x42) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-LENGTH (2 octets) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SUBSCRIBE MESSAGE ID | SSOP-DATA
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Figure 3
In the UNSUBSCRIBE TLV the SSOP-TYPE is UNSUBSCRIBE (tentatively In the UNSUBSCRIBE TLV the SSOP-TYPE is UNSUBSCRIBE (tentatively
0x42). The SSOP-LENGTH is zero. There is no SSOP-DATA for 0x42). The SSOP-LENGTH is 2 octets.
UNSUBSCRIBE.
The MESSAGE ID field MUST match the value given in the ID field of an The SSOP-DATA contains the MESSAGE ID field of the value given in the
active SUBSCRIBE request. This is how the server knows which ID field of an active SUBSCRIBE request. This is how the server
SUBSCRIBE request is being cancelled. After receipt of the knows which SUBSCRIBE request is being cancelled. After receipt of
UNSUBSCRIBE request, the SUBSCRIBE request is no longer active. If a the UNSUBSCRIBE request, the SUBSCRIBE request is no longer active.
server receives an UNSUBSCRIBE message where the MESSAGE ID does not If a server receives an UNSUBSCRIBE message where the MESSAGE ID does
match the ID of an active SUBSCRIBE request the server MUST return a not match the ID of an active SUBSCRIBE request the server MUST
response containing RCODE = 3 (NXDOMAIN). return a response containing RCODE = 3 (NXDOMAIN).
It is allowable for the client to issue an UNSUBSCRIBE request for a It is allowable for the client to issue an UNSUBSCRIBE request for a
previous SUBSCRIBE request for which the client has not yet received previous SUBSCRIBE request for which the client has not yet received
a SUBSCRIBE response. This is to allow for the case where a client a SUBSCRIBE response. This is to allow for the case where a client
starts and stops a subscription in less than the round-trip time to starts and stops a subscription in less than the round-trip time to
the server. The client is NOT required to wait for the SUBSCRIBE the server. The client is NOT required to wait for the SUBSCRIBE
response before issuing the UNSUBSCRIBE request. A consequence of response before issuing the UNSUBSCRIBE request. A consequence of
this is that if the client issues an UNSUBSCRIBE request for an as- this is that if the client issues an UNSUBSCRIBE request for an as-
yet unacknowledged SUBSCRIBE request, and the SUBSCRIBE request is yet unacknowledged SUBSCRIBE request, and the SUBSCRIBE request is
subsequently unsuccessful for some reason, then when the UNSUBSCRIBE subsequently unsuccessful for some reason, then when the UNSUBSCRIBE
request is eventually processed it will be an UNSUBSCRIBE request for request is eventually processed it will be an UNSUBSCRIBE request for
a nonexistent subscription, which will result NXDOMAIN response. a nonexistent subscription, which will result NXDOMAIN response.
Note that when the client issues an UNSUBSCRIBE request for an as-yet
unacknowledged SUBSCRIBE request, at that moment the client will have
two outstanding DNS Session Signaling operations with same MESSAGE
ID, a SUBSCRIBE request and an UNSUBSCRIBE request, which will both
receive responses, in that order. When the client has multiple
outstanding DNS Session Signaling operations with same MESSAGE ID,
care should be taken that when a DNS Session Signaling response
message is received for that MESSAGE ID, it is associated with the
*first* unacknowledged request.
6.4.2. UNSUBSCRIBE Response 6.4.2. UNSUBSCRIBE Response
Each UNSUBSCRIBE request generates exactly one UNSUBSCRIBE response Each UNSUBSCRIBE request generates exactly one UNSUBSCRIBE response
from the server. from the server.
An UNSUBSCRIBE response message begins with the standard DNS Session An UNSUBSCRIBE response message begins with the standard DNS Session
Signaling 12-byte header [SessSig], possibly followed by one or more Signaling 12-byte header [SessSig], possibly followed by one or more
optional Modifier TLVs, such as a Retry Delay Modifier TLV. optional Modifier TLVs, such as a Retry Delay Modifier TLV.
The MESSAGE ID field MUST echo the value given in the ID field of the The MESSAGE ID field MUST echo the value given in the ID field of the
skipping to change at page 26, line 33 skipping to change at page 29, line 8
that the disputed records are in fact no longer valid, then that the disputed records are in fact no longer valid, then
subsequent DNS PUSH Messages will be generated to inform interested subsequent DNS PUSH Messages will be generated to inform interested
clients. Thus, one client discovering that a previously-advertised clients. Thus, one client discovering that a previously-advertised
device (like a network printer) is no longer present has the side device (like a network printer) is no longer present has the side
effect of informing all other interested clients that the device in effect of informing all other interested clients that the device in
question is now gone. question is now gone.
6.5.1. RECONFIRM Request 6.5.1. RECONFIRM Request
A RECONFIRM request message begins with the standard DNS Session A RECONFIRM request message begins with the standard DNS Session
Signaling 12-byte header [SessSig], followed by the RECONFIRM TLV. Signaling 12-byte header [SessSig], followed by the RECONFIRM TLV. A
The SSOP-DATA for the the RECONFIRM TLV is as follows: RECONFIRM request message is illustrated below:
1 1 1 1 1 1 1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | MESSAGE ID |
\ NAME \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
\ \ |QR| Opcode | Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| TYPE | | QDCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| CLASS | | ANCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| RDLEN | | NSCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | ARCOUNT (MUST BE ZERO) |
\ RDATA \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
\ \ | SSOP-TYPE = RECONFIRM (tentatively 0x43) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-LENGTH (number of octets in SSOP-DATA) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \
\ NAME \ \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| TYPE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| CLASS | > SSOP-DATA
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| RDLEN | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
\ RDATA \ /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
Figure 2 Figure 4
The MESSAGE ID field MUST be set to a unique value, that the client The MESSAGE ID field MUST be set to a unique value, that the client
is not using for any other active operation on this connection. For is not using for any other active operation on this connection. For
the purposes here, a MESSAGE ID is in use on this connection if the the purposes here, a MESSAGE ID is in use on this connection if the
client has used it in a request for which it has not yet received a client has used it in a request for which it has not yet received a
response, or if if the client has used it for a subscription which it response, or if the client has used it for a subscription which it
has not yet cancelled using UNSUBSCRIBE. In the RECONFIRM response has not yet cancelled using UNSUBSCRIBE. In the RECONFIRM response
the server MUST echo back the MESSAGE ID value unchanged. the server MUST echo back the MESSAGE ID value unchanged.
In the RECONFIRM TLV the SSOP-TYPE is RECONFIRM (tentatively 0x43). The other header fields MUST be set as described in the DNS Session
The SSOP-LENGTH is the length of the data that follows, which Signaling specification [SessSig]. The DNS Opcode is the Session
specifies the name, type, class, and content of the record being Signaling Opcode (tentatively 6). The four count fields MUST be
disputed. empty, and the corresponding four sections MUST be empty (i.e.,
absent).
A RECONFIRM request MUST contain exactly one record. The RECONFIRM The SSOP-TYPE is RECONFIRM (tentatively 0x43). The SSOP-LENGTH is
TLV has no count field to specify more than one record. Since the length of the data that follows, which specifies the name, type,
RECONFIRM requests are sent over TCP, multiple RECONFIRM request class, and content of the record being disputed.
messages can be concatenated in a single TCP stream and packed
efficiently into TCP segments. The SSOP-DATA for a RECONFIRM request MUST contain exactly one
record. The SSOP-DATA for a RECONFIRM request has no count field to
specify more than one record. Since RECONFIRM requests are sent over
TCP, multiple RECONFIRM request messages can be concatenated in a
single TCP stream and packed efficiently into TCP segments.
TYPE MUST NOT be the value ANY (255) and CLASS MUST NOT be the value TYPE MUST NOT be the value ANY (255) and CLASS MUST NOT be the value
ANY (255). ANY (255).
DNS wildcarding is not supported. That is, a wildcard ("*") in a DNS wildcarding is not supported. That is, a wildcard ("*") in a
RECONFIRM message matches only a literal wildcard character ("*") in RECONFIRM message matches only a literal wildcard character ("*") in
the zone, and nothing else. the zone, and nothing else.
Aliasing is not supported. That is, a CNAME in a RECONFIRM message Aliasing is not supported. That is, a CNAME in a RECONFIRM message
matches only a literal CNAME record in the zone, and nothing else. matches only a literal CNAME record in the zone, and nothing else.
skipping to change at page 28, line 31 skipping to change at page 31, line 31
In the RECONFIRM response the RCODE confirms receipt of the In the RECONFIRM response the RCODE confirms receipt of the
reconfirmation request. Supported RCODEs are as follows: reconfirmation request. Supported RCODEs are as follows:
+------------+-------+----------------------------------------------+ +------------+-------+----------------------------------------------+
| Mnemonic | Value | Description | | Mnemonic | Value | Description |
+------------+-------+----------------------------------------------+ +------------+-------+----------------------------------------------+
| NOERROR | 0 | RECONFIRM accepted. | | NOERROR | 0 | RECONFIRM accepted. |
| FORMERR | 1 | Server failed to process request due to a | | FORMERR | 1 | Server failed to process request due to a |
| | | malformed request. | | | | malformed request. |
| SERVFAIL | 2 | Server failed to process request due to | | SERVFAIL | 2 | Server failed to process request due to a |
| | | resource exhaustion. | | | | problem with the server. |
| NXDOMAIN | 3 | NOT APPLICABLE. DNS Push Notification | | NXDOMAIN | 3 | NOT APPLICABLE. DNS Push Notification |
| | | servers MUST NOT return NXDOMAIN errors in | | | | servers MUST NOT return NXDOMAIN errors in |
| | | response to RECONFIRM requests. | | | | response to RECONFIRM requests. |
| NOTIMP | 4 | Server does not recognize DNS Session | | NOTIMP | 4 | Server does not recognize DNS Session |
| | | Signaling Opcode. | | | | Signaling Opcode. |
| REFUSED | 5 | Server refuses to process request for policy | | REFUSED | 5 | Server refuses to process request for policy |
| | | or security reasons. | | | | or security reasons. |
| NOTAUTH | 9 | Server is not authoritative for the | | NOTAUTH | 9 | Server is not authoritative for the |
| | | requested name. | | | | requested name. |
| SSOPNOTIMP | 11 | RECONFIRM operation not supported. | | SSOPNOTIMP | 11 | RECONFIRM operation not supported. |
skipping to change at page 29, line 10 skipping to change at page 32, line 10
these values. However, future circumstances may create situations these values. However, future circumstances may create situations
where other RCODE values are appropriate in RECONFIRM Responses, so where other RCODE values are appropriate in RECONFIRM Responses, so
clients MUST be prepared to accept RECONFIRM Responses with any RCODE clients MUST be prepared to accept RECONFIRM Responses with any RCODE
value. value.
Nonzero RCODE values signal some kind of error. Nonzero RCODE values signal some kind of error.
RCODE value FORMERR indicates a message format error, for example RCODE value FORMERR indicates a message format error, for example
TYPE or CLASS being ANY (255). TYPE or CLASS being ANY (255).
RCODE value SERVFAIL indicates that the server is overloaded. RCODE value SERVFAIL indicates that the server has exhausted its
resources or other serious problem occurred.
RCODE values NOTIMP indicates that the server does not support RCODE values NOTIMP indicates that the server does not support
Session Signaling, and Session Signaling is required for RECONFIRM Session Signaling, and Session Signaling is required for RECONFIRM
requests. requests.
RCODE value REFUSED indicates that the server supports RECONFIRM RCODE value REFUSED indicates that the server supports RECONFIRM
requests but is currently not configured to accept them from this requests but is currently not configured to accept them from this
client. client.
RCODE value NOTAUTH indicates that the server is not authoritative RCODE value NOTAUTH indicates that the server is not authoritative
skipping to change at page 31, line 7 skipping to change at page 34, line 7
with a time of 0 seconds and then closing the socket. with a time of 0 seconds and then closing the socket.
If a client has performed operations on this connection that it would If a client has performed operations on this connection that it would
not want lost (like DNS updates) then the client SHOULD do an orderly not want lost (like DNS updates) then the client SHOULD do an orderly
disconnect, sending a TCP FIN. In the BSD Sockets API, sending a TCP disconnect, sending a TCP FIN. In the BSD Sockets API, sending a TCP
FIN is achieved by calling "shutdown(s,SHUT_WR)" and keeping the FIN is achieved by calling "shutdown(s,SHUT_WR)" and keeping the
socket open until all remaining data has been read from it. socket open until all remaining data has been read from it.
7. Security Considerations 7. Security Considerations
TLS support is REQUIRED in DNS Push Notifications. There is no The Strict Privacy Usage Profile for DNS over TLS is strongly
provision for opportunistic encryption using a mechanism like recommended for DNS Push Notifications as defined in Authentication
"STARTTLS". and (D)TLS Profile for DNS-over-(D)TLS
[I-D.ietf-dprive-dtls-and-tls-profiles]. The Opportunistic Privacy
Usage Profile is permissible as a way to support incremental
deployment of security capabilities. Cleartext connections for DNS
Push Notifications are not permissible.
DNSSEC is RECOMMENDED for DNS Push Notifications. TLS alone does not DNSSEC is RECOMMENDED for the authentication of DNS Push Notification
provide complete security. TLS certificate verification can provide servers. TLS alone does not provide complete security. TLS
reasonable assurance that the client is really talking to the server certificate verification can provide reasonable assurance that the
associated with the desired host name, but since the desired host client is really talking to the server associated with the desired
name is learned via a DNS SRV query, if the SRV query is subverted host name, but since the desired host name is learned via a DNS SRV
then the client may have a secure connection to a rogue server. query, if the SRV query is subverted then the client may have a
DNSSEC can provided added confidence that the SRV query has not been secure connection to a rogue server. DNSSEC can provided added
subverted. confidence that the SRV query has not been subverted.
7.1. Security Services 7.1. Security Services
It is the goal of using TLS to provide the following security It is the goal of using TLS to provide the following security
services: services:
Confidentiality: All application-layer communication is encrypted Confidentiality: All application-layer communication is encrypted
with the goal that no party should be able to decrypt it except with the goal that no party should be able to decrypt it except
the intended receiver. the intended receiver.
skipping to change at page 32, line 4 skipping to change at page 35, line 8
As described in Section 6.1, the client discovers the DNS Push As described in Section 6.1, the client discovers the DNS Push
Notification server using an SRV lookup for the record name Notification server using an SRV lookup for the record name
"_dns-push-tls._tcp.<zone>". The server connection endpoint SHOULD "_dns-push-tls._tcp.<zone>". The server connection endpoint SHOULD
then be authenticated using DANE TLSA records for the associated SRV then be authenticated using DANE TLSA records for the associated SRV
record. This associates the target's name and port number with a record. This associates the target's name and port number with a
trusted TLS certificate [RFC7673]. This procedure uses the TLS Sever trusted TLS certificate [RFC7673]. This procedure uses the TLS Sever
Name Indication (SNI) extension [RFC6066] to inform the server of the Name Indication (SNI) extension [RFC6066] to inform the server of the
name the client has authenticated through the use of TLSA records. name the client has authenticated through the use of TLSA records.
Therefore, if the SRV record passes DNSSEC validation and a TLSA Therefore, if the SRV record passes DNSSEC validation and a TLSA
record matching the target name is useable, an SNI extension MUST be record matching the target name is useable, an SNI extension must be
used for the target name to ensure the client is connecting to the used for the target name to ensure the client is connecting to the
server it has authenticated. If the target name does not have a server it has authenticated. If the target name does not have a
usable TLSA record, then the use of the SNI extension is optional. usable TLSA record, then the use of the SNI extension is optional.
See Authentication and (D)TLS Profile for DNS-over-(D)TLS
[I-D.ietf-dprive-dtls-and-tls-profiles] for more information on
authenticating domain names. Also note that a DNS Push server is an
authoritative server and a DNS Push client is a standard DNS client.
While the terminology in Authentication and (D)TLS Profile for DNS-
over-(D)TLS [I-D.ietf-dprive-dtls-and-tls-profiles] explicitly states
it does not apply to authoritative servers, it does in this case
apply to DNS Push Notification clients and servers.
7.3. TLS Compression 7.3. TLS Compression
In order to reduce the chances of compression-related attacks, TLS- In order to reduce the chances of compression-related attacks, TLS-
level compression SHOULD be disabled when using TLS versions 1.2 and level compression SHOULD be disabled when using TLS versions 1.2 and
earlier. In the draft version of TLS 1.3 [I-D.ietf-tls-tls13], TLS- earlier. In the draft version of TLS 1.3 [I-D.ietf-tls-tls13], TLS-
level compression has been removed completely. level compression has been removed completely.
7.4. TLS Session Resumption 7.4. TLS Session Resumption
TLS Session Resumption is permissible on DNS Push Notification TLS Session Resumption is permissible on DNS Push Notification
skipping to change at page 32, line 36 skipping to change at page 35, line 49
up more quickly, but the client will still have to recreate any up more quickly, but the client will still have to recreate any
desired subscriptions. desired subscriptions.
8. IANA Considerations 8. IANA Considerations
This document defines the service name: "_dns-push-tls._tcp". This document defines the service name: "_dns-push-tls._tcp".
It is only applicable for the TCP protocol. It is only applicable for the TCP protocol.
This name is to be published in the IANA Service Name Registry This name is to be published in the IANA Service Name Registry
[RFC6335][SN]. [RFC6335][SN].
This document defines three DNS Session Signaling TLV types: This document defines four DNS Session Signaling TLV types: SUBSCRIBE
SUBSCRIBE with (tentative) value 0x40 (64), PUSH with (tentative) with (tentative) value 0x40 (64), PUSH with (tentative) value 0x41
value 0x41 (65), UNSUBSCRIBE with (tentative) value 0x42 (66), and (65), UNSUBSCRIBE with (tentative) value 0x42 (66), and RECONFIRM
RECONFIRM with (tentative) value 0x43 (67). with (tentative) value 0x43 (67).
9. Acknowledgements 9. Acknowledgements
The authors would like to thank Kiren Sekar and Marc Krochmal for The authors would like to thank Kiren Sekar and Marc Krochmal for
previous work completed in this field. previous work completed in this field.
This draft has been improved due to comments from Ran Atkinson, Tim This draft has been improved due to comments from Ran Atkinson, Tim
Chown, Mark Delany, Ralph Droms, Bernie Volz, Jan Komissar, Manju Chown, Mark Delany, Ralph Droms, Bernie Volz, Jan Komissar, Manju
Shankar Rao, Markus Stenberg, Dave Thaler, and Soraia Zlatkovic. Shankar Rao, Markus Stenberg, Dave Thaler, Soraia Zlatkovic, Sara
Dickinson, and Andrew Sullivan.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-tls-tls13] [I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-18 (work in progress), Version 1.3", draft-ietf-tls-tls13-20 (work in progress),
October 2016. April 2017.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980, DOI 10.17487/RFC0768, August 1980,
<http://www.rfc-editor.org/info/rfc768>. <http://www.rfc-editor.org/info/rfc768>.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981, RFC 793, DOI 10.17487/RFC0793, September 1981,
<http://www.rfc-editor.org/info/rfc793>. <http://www.rfc-editor.org/info/rfc793>.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
skipping to change at page 35, line 11 skipping to change at page 38, line 21
[DisProx] Cheshire, S., "Hybrid Unicast/Multicast DNS-Based Service [DisProx] Cheshire, S., "Hybrid Unicast/Multicast DNS-Based Service
Discovery", draft-ietf-dnssd-hybrid-06 (work in progress), Discovery", draft-ietf-dnssd-hybrid-06 (work in progress),
March 2017. March 2017.
[I-D.dukkipati-tcpm-tcp-loss-probe] [I-D.dukkipati-tcpm-tcp-loss-probe]
Dukkipati, N., Cardwell, N., Cheng, Y., and M. Mathis, Dukkipati, N., Cardwell, N., Cheng, Y., and M. Mathis,
"Tail Loss Probe (TLP): An Algorithm for Fast Recovery of "Tail Loss Probe (TLP): An Algorithm for Fast Recovery of
Tail Losses", draft-dukkipati-tcpm-tcp-loss-probe-01 (work Tail Losses", draft-dukkipati-tcpm-tcp-loss-probe-01 (work
in progress), February 2013. in progress), February 2013.
[I-D.ietf-dprive-dtls-and-tls-profiles]
Dickinson, S., Gillmor, D., and T. Reddy, "Usage and
(D)TLS Profiles for DNS-over-(D)TLS", draft-ietf-dprive-
dtls-and-tls-profiles-10 (work in progress), June 2017.
[I-D.sekar-dns-llq] [I-D.sekar-dns-llq]
Sekar, K., "DNS Long-Lived Queries", draft-sekar-dns- Sekar, K., "DNS Long-Lived Queries", draft-sekar-dns-
llq-01 (work in progress), August 2006. llq-01 (work in progress), August 2006.
[IPJ.9-4-TCPSYN] [IPJ.9-4-TCPSYN]
Eddy, W., "Defenses Against TCP SYN Flooding Attacks", The Eddy, W., "Defenses Against TCP SYN Flooding Attacks", The
Internet Protocol Journal, Cisco Systems, Volume 9, Internet Protocol Journal, Cisco Systems, Volume 9,
Number 4, December 2006. Number 4, December 2006.
[obs] "Observer Pattern", <https://en.wikipedia.org/wiki/ [obs] "Observer Pattern", <https://en.wikipedia.org/wiki/
Observer_pattern>. Observer_pattern>.
[RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996, NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
August 1996, <http://www.rfc-editor.org/info/rfc1996>. <http://www.rfc-editor.org/info/rfc2308>.
[RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom [RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
Syndication Format", RFC 4287, DOI 10.17487/RFC4287, Syndication Format", RFC 4287, DOI 10.17487/RFC4287,
December 2005, <http://www.rfc-editor.org/info/rfc4287>. December 2005, <http://www.rfc-editor.org/info/rfc4287>.
[RFC4953] Touch, J., "Defending TCP Against Spoofing Attacks", [RFC4953] Touch, J., "Defending TCP Against Spoofing Attacks",
RFC 4953, DOI 10.17487/RFC4953, July 2007, RFC 4953, DOI 10.17487/RFC4953, July 2007,
<http://www.rfc-editor.org/info/rfc4953>. <http://www.rfc-editor.org/info/rfc4953>.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
skipping to change at page 36, line 20 skipping to change at page 39, line 38
[RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP [RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP
Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014,
<http://www.rfc-editor.org/info/rfc7413>. <http://www.rfc-editor.org/info/rfc7413>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>. 2015, <http://www.rfc-editor.org/info/rfc7525>.
[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", RFC 7719, DOI 10.17487/RFC7719, December
2015, <http://www.rfc-editor.org/info/rfc7719>.
[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, <http://www.rfc-editor.org/info/rfc7858>. 2016, <http://www.rfc-editor.org/info/rfc7858>.
[XEP0060] Millard, P., Saint-Andre, P., and R. Meijer, "Publish- [XEP0060] Millard, P., Saint-Andre, P., and R. Meijer, "Publish-
Subscribe", XSF XEP 0060, July 2010. Subscribe", XSF XEP 0060, July 2010.
Authors' Addresses Authors' Addresses
 End of changes. 64 change blocks. 
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