draft-ietf-dnssd-push-13.txt   draft-ietf-dnssd-push-14.txt 
Internet Engineering Task Force T. Pusateri Internet Engineering Task Force T. Pusateri
Internet-Draft Unaffiliated Internet-Draft Unaffiliated
Intended status: Standards Track S. Cheshire Intended status: Standards Track S. Cheshire
Expires: May 2, 2018 Apple Inc. Expires: September 19, 2018 Apple Inc.
October 29, 2017 March 18, 2018
DNS Push Notifications DNS Push Notifications
draft-ietf-dnssd-push-13 draft-ietf-dnssd-push-14
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 are 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, as long as the polling rate is not the updated results when polled, as long as the polling rate is not
too high. But there exists no mechanism for a client to be too high. But there exists no mechanism for a client to be
asynchronously notified when these changes occur. This document asynchronously notified when these changes occur. This document
defines a mechanism for a client to be notified of such changes to defines a mechanism for a client to be notified of such changes to
DNS records, called DNS Push Notifications. DNS records, called DNS Push Notifications.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 2, 2018. This Internet-Draft will expire on September 19, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. State Considerations . . . . . . . . . . . . . . . . . . . . 7 5. State Considerations . . . . . . . . . . . . . . . . . . . . 8
6. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 8 6. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 9
6.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2. DNS Push Notification SUBSCRIBE . . . . . . . . . . . . . 12 6.2. DNS Push Notification SUBSCRIBE . . . . . . . . . . . . . 13
6.2.1. SUBSCRIBE Request . . . . . . . . . . . . . . . . . . 13 6.2.1. SUBSCRIBE Request . . . . . . . . . . . . . . . . . . 13
6.2.2. SUBSCRIBE Response . . . . . . . . . . . . . . . . . 16 6.2.2. SUBSCRIBE Response . . . . . . . . . . . . . . . . . 16
6.3. DNS Push Notification Updates . . . . . . . . . . . . . . 19 6.3. DNS Push Notification Updates . . . . . . . . . . . . . . 19
6.3.1. PUSH Message . . . . . . . . . . . . . . . . . . . . 20 6.3.1. PUSH Message . . . . . . . . . . . . . . . . . . . . 19
6.3.2. PUSH Response . . . . . . . . . . . . . . . . . . . . 23 6.4. DNS Push Notification UNSUBSCRIBE . . . . . . . . . . . . 22
6.4. DNS Push Notification UNSUBSCRIBE . . . . . . . . . . . . 24 6.4.1. UNSUBSCRIBE Request . . . . . . . . . . . . . . . . . 22
6.4.1. UNSUBSCRIBE Request . . . . . . . . . . . . . . . . . 25 6.5. DNS Push Notification RECONFIRM . . . . . . . . . . . . . 24
6.4.2. UNSUBSCRIBE Response . . . . . . . . . . . . . . . . 27 6.5.1. RECONFIRM Request . . . . . . . . . . . . . . . . . . 24
6.5. DNS Push Notification RECONFIRM . . . . . . . . . . . . . 29 6.5.2. RECONFIRM Response . . . . . . . . . . . . . . . . . 26
6.5.1. RECONFIRM Request . . . . . . . . . . . . . . . . . . 30 6.6. Client-Initiated Termination . . . . . . . . . . . . . . 28
6.5.2. RECONFIRM Response . . . . . . . . . . . . . . . . . 32 7. Security Considerations . . . . . . . . . . . . . . . . . . . 29
6.6. Client-Initiated Termination . . . . . . . . . . . . . . 34 7.1. Security Services . . . . . . . . . . . . . . . . . . . . 29
7. Security Considerations . . . . . . . . . . . . . . . . . . . 35 7.2. TLS Name Authentication . . . . . . . . . . . . . . . . . 29
7.1. Security Services . . . . . . . . . . . . . . . . . . . . 35 7.3. TLS Compression . . . . . . . . . . . . . . . . . . . . . 30
7.2. TLS Name Authentication . . . . . . . . . . . . . . . . . 35 7.4. TLS Session Resumption . . . . . . . . . . . . . . . . . 30
7.3. TLS Compression . . . . . . . . . . . . . . . . . . . . . 36 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
7.4. TLS Session Resumption . . . . . . . . . . . . . . . . . 36 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 31
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 37 10.1. Normative References . . . . . . . . . . . . . . . . . . 31
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 37 10.2. Informative References . . . . . . . . . . . . . . . . . 33
10.1. Normative References . . . . . . . . . . . . . . . . . . 37 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
10.2. Informative References . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction 1. Introduction
DNS records may be updated using DNS Update [RFC2136]. Other Domain Name System (DNS) records may be updated using DNS Update
mechanisms such as a Discovery Proxy [DisProx] can also generate [RFC2136]. Other mechanisms such as a Discovery Proxy [DisProx] can
changes to a DNS zone. This document specifies a protocol for DNS also generate changes to a DNS zone. This document specifies a
clients to subscribe to receive asynchronous notifications of changes protocol for DNS clients to subscribe to receive asynchronous
to RRSets of interest. It is immediately relevant in the case of DNS notifications of changes to RRSets of interest. It is immediately
Service Discovery [RFC6763] but is not limited to that use case, and relevant in the case of DNS Service Discovery [RFC6763] but is not
provides a general DNS mechanism for DNS record change notifications. limited to that use case, and provides a general DNS mechanism for
Familiarity with the DNS protocol and DNS packet formats is assumed DNS record change notifications. Familiarity with the DNS protocol
[RFC1034] [RFC1035] [RFC6895]. and DNS packet formats is assumed [RFC1034] [RFC1035] [RFC6895].
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY",
"OPTIONAL" in this document are to be interpreted as described in and "OPTIONAL" in this document are to be interpreted as described
"Key words for use in RFCs to Indicate Requirement Levels" [RFC2119]. in "Key words for use in RFCs to Indicate Requirement Levels",
when, and only when, they appear in all capitals, as shown here
[RFC2119] [RFC8174].
2. Motivation 2. Motivation
As the domain name system continues to adapt to new uses and changes As the domain name system continues to adapt to new uses and changes
in deployment, polling has the potential to burden DNS servers at in deployment, polling has the potential to burden DNS servers at
many levels throughout the network. Other network protocols have many levels throughout the network. Other network protocols have
successfully deployed a publish/subscribe model to state changes successfully deployed a publish/subscribe model following the
following the Observer design pattern [obs]. XMPP Publish-Subscribe Observer design pattern [obs]. XMPP Publish-Subscribe [XEP0060] and
[XEP0060] and Atom [RFC4287] are examples. While DNS servers are Atom [RFC4287] are examples. While DNS servers are generally highly
generally highly tuned and capable of a high rate of query/response tuned and capable of a high rate of query/response traffic, adding a
traffic, adding a publish/subscribe model for tracking changes to DNS publish/subscribe model for tracking changes to DNS records can
records can result in more timely notification of changes with deliver more timely notification of changes with reduced CPU usage
reduced CPU usage and lower network traffic. and lower network traffic.
Multicast DNS [RFC6762] implementations always listen on a well known Multicast DNS [RFC6762] implementations always listen on a well known
link-local IP multicast group, and new services and updates are sent link-local IP multicast group, and record changes are sent to that
for all group members to receive. Therefore, Multicast DNS already multicast group address for all group members to receive. Therefore,
has asynchronous change notification capability. However, when DNS Multicast DNS already has asynchronous change notification
Service Discovery [RFC6763] is used across a wide area network using capability. However, when DNS Service Discovery [RFC6763] is used
Unicast DNS (possibly facilitated via a Discovery Proxy [DisProx]) it across a wide area network using Unicast DNS (possibly facilitated
would be beneficial to have an equivalent capability for Unicast DNS, via a Discovery Proxy [DisProx]) it would be beneficial to have an
to allow clients to learn about DNS record changes in a timely manner equivalent capability for Unicast DNS, to allow clients to learn
without polling. about DNS record changes in a timely manner without polling.
The DNS Long-Lived Queries (LLQ) [I-D.sekar-dns-llq] mechanism is an The DNS Long-Lived Queries (LLQ) mechanism [LLQ] is an existing
existing deployed solution to provide asynchronous change deployed solution to provide asynchronous change notifications, used
notifications, used by Apple's Back to My Mac Service [RFC6281] by Apple's Back to My Mac Service [RFC6281] introduced in Mac OS X
introduced in Mac OS X 10.5 Leopard in 2007. Back to My Mac was 10.5 Leopard in 2007. Back to My Mac was designed in an era when the
designed in an era when the data centre operations staff asserted data center operations staff asserted that it was impossible for a
that it was impossible for a server to handle large numbers of server to handle large numbers of mostly-idle TCP connections, so LLQ
mostly-idle TCP connections, so LLQ had to defined as a UDP-based was defined as a UDP-based protocol, effectively replicating much of
protocol, effectively replicating much of TCP's connection state TCP's connection state management logic in user space, and creating
management logic in user space, and creating its own poor imitations its own poor imitations of existing TCP features like the three-way
of existing TCP features like the three-way handshake, flow control, handshake, flow control, and reliability.
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 DNS Stateful Operations (DSO) [DSO] running over TLS over TCP, and
functionality. Using TCP also gives long-lived low-traffic therefore doesn't need to reinvent existing TCP functionality. Using
connections better longevity through NAT gateways without resorting TCP also gives long-lived low-traffic connections better longevity
to excessive keepalive traffic. Instead of inventing a new through NAT gateways without resorting to excessive keepalive
vocabulary of messages to communicate DNS zone changes as LLQ did, traffic. Instead of inventing a new vocabulary of messages to
this specification adopts the syntax and semantics of DNS Update communicate DNS zone changes as LLQ did, this specification borrows
messages [RFC2136]. the established syntax and semantics of DNS Update 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 receiving further 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 [RFC7719]. 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.
skipping to change at page 5, line 19 skipping to change at page 6, line 4
received with the RD bit set, matching records for names falling received with the RD bit set, matching records for names falling
within the server's zones should be returned with the RA (Recursion 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 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 zone, an error with RCODE NOTAUTH (Not Authoritative) should be
returned. 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 unilaterally informing a client of
records. changes to DNS 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". If messages are received for a class other than DNS class "IN". If messages are received for a class other than
"IN", and that class is not supported, an error with RCODE NOTIMPL "IN", and that class is not supported, an error with RCODE NOTIMPL
(Not Implemented) should be returned. (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. Specifically:
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
user) and the subscription SHOULD be cancelled as soon as the need
for that data ends (for example, when the user dismisses that
display). Implementations MAY want to implement idle timeouts, so
that if the user ceases interacting with the device, the display
showing the result of the DNS Push Notification subscription is
automatically dismissed after a certain period of inactivity. For
example, if a user presses the "Print" button on their smartphone,
and then leaves the phone showing the printer discovery screen until
the phone goes to sleep, then the printer discovery screen should be
automatically dismissed as the device goes to sleep. If the user
does still intend to print, this will require them to press the
"Print" button again when they wake their phone up.
A DNS Push Notification client must not routinely keep a DNS Push (a) A subscription should only be active when there is a valid reason
Notification subscription active 24 hours a day, 7 days a week, just to need live data (for example, an on-screen display is currently
to keep a list in memory up to date so that if the user does choose showing the results to the user) and the subscription SHOULD be
to bring up an on-screen display of that data, it can be displayed cancelled as soon as the need for that data ends (for example, when
really fast. DNS Push Notifications are designed to be fast enough the user dismisses that display). Implementations MAY want to
that there is no need to pre-load a "warm" list in memory just in implement idle timeouts, so that if the user ceases interacting with
case it might be needed later. the device, the display showing the result of the DNS Push
Notification subscription is automatically dismissed after a certain
period of inactivity. For example, if a user presses the "Print"
button on their smartphone, and then leaves the phone showing the
printer discovery screen until the phone goes to sleep, then the
printer discovery screen should be automatically dismissed as the
device goes to sleep. If the user does still intend to print, this
will require them to press the "Print" button again when they wake
their phone up.
(b) A DNS Push Notification client SHOULD NOT routinely keep a DNS
Push 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 bring up an on-screen display of that data, it can be
displayed 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 case it might be needed later.
Generally, as described in the DNS Stateful Operations specification Generally, as described in the DNS Stateful Operations specification
[StatefulOp], a client must not keep a connection to a server open [DSO], a client must not keep a session to a server open indefinitely
indefinitely if it has no subscriptions (or other operations) active if it has no subscriptions (or other operations) active on that
on that connection. A client MAY close a connection as soon as it session. A client MAY close a session as soon as it becomes idle,
becomes idle, and then if needed in the future, open a new connection and then if needed in the future, open a new session when required.
when required. Alternatively, a client MAY speculatively keep an Alternatively, a client MAY speculatively keep an idle session open
idle connection open for some time, subject to the constraint that it for some time, subject to the constraint that it MUST NOT keep a
MUST NOT keep a connection open that has been idle for more than the session open that has been idle for more than the session's idle
session's idle timeout (15 seconds by default). timeout (15 seconds by default).
4. Transport 4. Transport
Implementations of DNS Update [RFC2136] MAY use either User Datagram Other DNS operations like DNS Update [RFC2136] MAY use either User
Protocol (UDP) [RFC0768] or Transmission Control Protocol (TCP) Datagram Protocol (UDP) [RFC0768] or Transmission Control Protocol
[RFC0793] as the transport protocol, in keeping with the historical (TCP) [RFC0793] as the transport protocol, in keeping with the
precedent that DNS queries must first be sent over UDP [RFC1123]. historical precedent that DNS queries must first be sent over UDP
This requirement to use UDP has subsequently been relaxed [RFC7766]. [RFC1123]. 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 DNS
over TCP [RFC7858]. Stateful Operations (DSO) [DSO] running over TLS over TCP [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 [SYN] [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
current and future developments in TCP, such as Multipath TCP (MPTCP) current and future developments in TCP, such as Multipath TCP (MPTCP)
[RFC6824], TCP Fast Open (TFO) [RFC7413], Tail Loss Probe (TLP) [RFC6824], TCP Fast Open (TFO) [RFC7413], Tail Loss Probe (TLP)
[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, and message forgery. TLS is prevent eavesdropping, tampering, and 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.
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 session 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
connections to alternate DNS servers that support DNS Push sessions to alternate DNS servers that support DNS Push Notifications
Notifications for the zone and distribute subscriptions at its for the zone and distribute subscriptions at the client's discretion.
discretion. In this way, both clients and servers can react to In this way, both clients and servers can react to resource
resource constraints. Token bucket rate limiting schemes are also constraints. Token bucket rate limiting schemes are also effective
effective in providing fairness by a server across numerous client in providing fairness by a server across numerous client requests.
requests.
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 Stateful Operations [StatefulOp]. and makes use of DNS Stateful Operations (DSO) [DSO].
For details of the DNS Stateful Operations message format refer to For details of the DSO message format refer to the DNS Stateful
the DNS Stateful Operations specification [StatefulOp]. Those Operations specification [DSO]. Those details are not repeated here.
details are not repeated here.
DNS Push Notification clients and servers MUST support DNS Stateful DNS Push Notification clients and servers MUST support DSO, but (as
Operations, but the server SHOULD NOT issue any DNS Stateful stated in the DSO specification [DSO]) the server SHOULD NOT issue
Operations messages until after the client has first initiated a DNS any DSO messages until after the client has first initiated an
Stateful Operation of its own. A single server can support DNS acknowledged DSO message of its own. A single server can support DNS
Queries, DNS Updates, and DNS Push Notifications (using DNS Stateful Queries, DNS Updates, and DNS Push Notifications (using DSO) on the
Operations) on the same TCP port, and until the client has sent at same TCP port, and until the client has sent at least one DSO
least one DNS Stateful Operations message, the server does not know message, the server does not know what kind of client has connected
what kind of client has connected to it. Once the client has to it. Once the client has indicated willingness to use DSO by
indicated willingness to use DNS Stateful Operations by sending one sending one of its own, either side of the session may then initiate
of its own, either side of the connection may then initiate further further DSO messages at any time.
Stateful 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 DSO
Stateful Operations Keepalive operation to request a session timeout Keepalive operation to request a session timeout or keepalive
or keepalive interval longer than the the 15-second defaults, but interval longer than the the 15-second defaults, but this is not
this is not required. A DNS Push Notification client MAY issue other required. A DNS Push Notification client MAY issue other requests on
requests on the connection first, and only issue a DNS Stateful the session first, and only issue a DSO Keepalive operation later if
Operations Keepalive operation later if it determines that to be it determines that to be necessary.
necessary.
Once the connection is made, the client may then add and remove Push Once the session 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
situation where a Push Notification is in flight from server to situation where a Push Notification is in flight from server to
client while the client's UNSUBSCRIBE message cancelling that client while the client's UNSUBSCRIBE message cancelling that
subscription is simultaneously in flight from client to server. subscription is simultaneously in flight from client to server.
The exchange between client and server terminates when either end
closes the TCP connection with a TCP FIN or RST.
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 desired zone.
The client begins by opening a DNS Session to its normal configured The client begins by opening a DSO Session to its normal configured
DNS recursive resolver and requesting a Push Notification DNS recursive resolver and requesting a Push Notification
subscription. If this is successful, then the recursive resolver subscription. If this is successful, then the recursive resolver
will make appropriate Push Notification subscriptions on the client's will make appropriate Push Notification subscriptions on the client's
behalf, and the client will recieve appropriate results. If the behalf, and the client will receive appropriate results. If the
recursive resolver does not support Push Notification subscriptions, recursive resolver does not support Push Notification subscriptions,
then it will return an error code, and the client should proceed to then it will return an error code, and the client should proceed to
discover the appropriate server to talk to directly. The client MUST discover the appropriate server for direct communication. The client
also determine which TCP port on the server is listening for MUST also determine which TCP port on the server is listening for
connections, which need not be (and often is not) the typical TCP connections, which need not be (and often is not) the typical TCP
port 53 used for conventional DNS, or TCP port 853 used for DNS over port 53 used for conventional DNS, or TCP port 853 used for DNS over
TLS [RFC7858]. TLS [RFC7858].
The algorithm described here is an iterative algorithm, which starts
with the full name of the record to which the client wishes to
subscribe. Successive SOA queries are then issued, trimming one
label each time, until the closest enclosing authoritative server is
discovered. There is also an optimization to enable the client to
take a "short cut" directly to the SOA record of the closest
enclosing authoritative server in many cases.
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 record to local resolver, with record type SOA [RFC1035] for the record
which it wishes to subscribe. As an example, if it wishes to name to which it wishes to subscribe. As an example, suppose the
subscribe to PTR records with the name client wishes to subscribe to PTR records with the name
_printers._tcp.foo.example.com, it sends an SOA query for _ipp._tcp.foo.example.com (to discover Internet Printing Protocol
_printers._tcp.foo.example.com. The goal is to determine the (IPP) printers [RFC8010] [RFC8011] being advertised at
authoritative server for _printers._tcp.foo.example.com. "foo.example.com"). The client begins by sending an SOA query
for _ipp._tcp.foo.example.com to the local recursive resolver.
The goal is to determine the server authoritative for the name
_ipp._tcp.foo.example.com. The DNS zone containing the name
_ipp._tcp.foo.example.com could be example.com, or
foo.example.com, or _tcp.foo.example.com, or even
_ipp._tcp.foo.example.com. The client does not know in advance
where the closest enclosing zone cut occurs, which is why it uses
the procedure described here to discover this information.
2. If the SOA record exists as exactly specified in the query, it is 2. If the requested SOA record exists, it will be returned in the
expected to be returned in the Answer section with a NOERROR Answer section with a NOERROR response code, and the client has
response code. If the exact SOA record does not exist, the succeeded in discovering the information it needs. (This text is
client may get back a NOERROR/NODATA response or it may get back not placing any new requirements on DNS recursive resolvers. It
a NXDOMAIN/Name Error response. This depends on the resolver is merely describing the existing operation of the DNS protocol
implementation and whether the domain exists. The client is [RFC1034] [RFC1035].)
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 or a
response containing no SOA record, 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. In the example above, if an SOA record query is sent for 3. If the requested SOA record does not exist, the client will get
_printers._tcp.foo.example.com and an NXDOMAIN/Name Error is back a NOERROR/NODATA response or an NXDOMAIN/Name Error
returned with an SOA record in the Authority section for response. In either case, the local resolver SHOULD include the
foo.example.com, the client should strip the leading label and SOA record for the zone of the requested name in the Authority
query an SOA record for _tcp.foo.example.com. If a NOERROR/ Section. If the SOA record is received in the Authority Section,
NODATA response is received with an SOA record in the Authority then the client has succeeded in discovering the information it
section for foo.example.com, this is sufficent. If an NXDOMAIN/ needs. (This text is not placing any new requirements on DNS
Name Error response is received, the client should again strip recursive resolvers. It is merely describing the existing
the leading label and query an SOA record for foo.example.com. operation of the DNS protocol regarding negative responses
If the foo.example.com domain exists, this should result in a [RFC2308].)
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. If a NOERROR/NODATA response is received but contains no SOA in 4. If the client receives a response containing no SOA record, then
the Authority section, the client could try stripping the leading it proceeds with the iterative approach. The client strips the
label and issuing another SOA query. Additional information leading label from the current query name and if the resulting
about negative responses can be found in Section 2 of [RFC2308]. name has at least one label in it, the client sends a new SOA
query, and processing continues at step 2 above, repeating the
iterative search until either an SOA is received, or the query
name is empty. In the case of an empty name, this is a network
configuration error which should not happen and the client gives
up. The client may retry the operation at a later time, of the
client's choosing, such after a change in network attachment.
5. Once the SOA is known (either by virtue of being seen in the 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.
6. For implementors of this specification, an authoritative answer 6. If the zone in question does not offer DNS Push Notifications
for that SRV record, and only such an answer, will determine then SRV record MUST NOT exist, and the SRV query will return a
whether the zone supports DNS Push Notifications. negative answer. (The "_dns-push-tls._tcp" service type is
allocated by IANA for this purpose, and, like any allocated IANA
service type, MUST NOT be used for other services. Other
services that require an IANA service type should use a unique
service type allocated by IANA for that service [RFC6335][ST].)
7. If the SRV record does exist, the SRV "target" contains the name 7. If the zone in question is set up to offer DNS Push Notifications
of the server providing DNS Push Notifications for the zone. The then this SRV record MUST exist. (If this SRV record does not
port number on which to contact the server is in the SRV record exist then the zone is not correctly configured for DNS Push
"port" field. The address(es) of the target host MAY be included Notifications as specified in this document.) The SRV "target"
in the Additional Section, however, the address records SHOULD be contains the name of the server providing DNS Push Notifications
authenticated before use as described below in Section 7.2 and for the zone. The port number on which to contact the server is
[RFC7673]. in the SRV record "port" field. The address(es) of the target
host MAY be included in the Additional Section, however, the
address records SHOULD be authenticated before use as described
below in Section 7.2 and in the specification for using DANE TLSA
Records with SRV Records [RFC7673].
8. 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 willing to
is not willing to accept a subscription request, then a accept a subscription request, or is not reachable within a
subsequent server is to be contacted. reasonable time, as determined by the client, then a 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 session, it SHOULD repeat the discovery process in order to determine
determine the preferred DNS server for subscriptions at that time. the preferred DNS server for subscriptions at that time. However,
However, the client device MUST respect the DNS TTL values on records the client device MUST respect the DNS TTL values on records it
it receives, and store them in its local cache with this lifetime. receives, and store them in its local cache with this lifetime. This
This means that, as long as the DNS TTL values on the authoritative means that, as long as the DNS TTL values on the authoritative
records were set to reasonable values, repeated application of this records were set to reasonable values, repeated application of this
discovery process can be completed nearly instantaneously by the discovery process can be completed nearly instantaneously by the
client, using only locally-stored cached data. 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 DSO
connection to the server. A SUBSCRIBE request is encoded in a DNS session to the server. A SUBSCRIBE request is encoded in a DSO [DSO]
Stateful Operations [StatefulOp] message. This specification defines message. This specification defines a DSO TLV for DNS Push
a DNS Stateful Operations TLV for DNS Push Notification SUBSCRIBE Notification SUBSCRIBE Requests/Responses (tentatively DSO Type Code
Requests/Responses (tentatively Stateful Operations Type Code 0x40). 0x40).
The entity that initiates a SUBSCRIBE request is by definition the The entity that initiates a SUBSCRIBE request is by definition the
client. A server should not send a SUBSCRIBE request over an client. A server MUST NOT send a SUBSCRIBE request over an existing
existing connection from a client. If a server does send a SUBSCRIBE session from a client. If a server does send a SUBSCRIBE request
request over the connection initiated by a client, it is an error and over a DSO session initiated by a client, this is a fatal error and
the client should acknowledge the request with the error response the client should immediately abort the connection with a TCP RST (or
RCODE NOTAUTH (Not Authoritative). equivalent for other protocols).
6.2.1. SUBSCRIBE Request 6.2.1. SUBSCRIBE Request
A SUBSCRIBE request message begins with the standard DNS Stateful A SUBSCRIBE request begins with the standard DSO 12-byte header
Operations 12-byte header [StatefulOp], followed by the SUBSCRIBE [DSO], followed by the SUBSCRIBE TLV. A SUBSCRIBE request message is
TLV. A SUBSCRIBE request message is illustrated below: illustrated in Figure 1.
The MESSAGE ID field MUST be set to a unique value, that the client
is not using for any other active operation on this session. For the
purposes here, a MESSAGE ID is in use on this session if the client
has used it in a request for which it has not yet received a
response, or if the client has used it for a subscription which it
has not yet cancelled using UNSUBSCRIBE. In the SUBSCRIBE response
the server MUST echo back the MESSAGE ID value unchanged.
The other header fields MUST be set as described in the DSO
specification [DSO]. The DNS Opcode is the DSO Opcode (tentatively
6). The four count fields MUST be zero, and the corresponding four
sections MUST be empty (i.e., absent).
The DSO-TYPE is SUBSCRIBE (tentatively 0x40). The DSO-LENGTH is the
length of the DSO-DATA that follows, which specifies the name, type,
and class of the record(s) being sought.
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 | \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
|QR| Opcode | Z | RCODE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| QDCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER
| ANCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| NSCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| ARCOUNT (MUST BE ZERO) | /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
| DSO-TYPE = SUBSCRIBE (tentatively 0x40) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| MESSAGE ID | | DSO-LENGTH (number of octets in DSO-DATA) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode | Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 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 \ | \ NAME \ |
\ \ | \ \ |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > SSOP-DATA +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > DSO-DATA
| TYPE | | | TYPE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| CLASS | / | CLASS | /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
Figure 1 Figure 1: SUBSCRIBE Request
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
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
response, or if the client has used it for a subscription which it
has not yet cancelled using UNSUBSCRIBE. In the SUBSCRIBE response
the server MUST echo back the MESSAGE ID value unchanged.
The other header fields MUST be set as described in the DNS Stateful
Operations specification [StatefulOp]. The DNS Opcode is the
Stateful Operations Opcode (tentatively 6). The four count fields
MUST be zero, and the corresponding four sections MUST be empty
(i.e., absent).
The SSOP-TYPE is SUBSCRIBE (tentatively 0x40). The SSOP-LENGTH is
the length of the SSOP-DATA that follows, which specifies the name,
type, and class of the record(s) being sought.
The SSOP-DATA for a SUBSCRIBE request MUST contain exactly one The DSO-DATA for a SUBSCRIBE request MUST contain exactly one
question. The SSOP-DATA for a SUBSCRIBE request has no QDCOUNT field question. The DSO-DATA for a SUBSCRIBE request has no QDCOUNT field
to specify more than one question. Since SUBSCRIBE requests are sent to specify more than one question. Since SUBSCRIBE requests are sent
over TCP, multiple SUBSCRIBE request messages can be concatenated in over TCP, multiple SUBSCRIBE request messages can be concatenated in
a single TCP stream and packed efficiently into TCP segments. 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 DSO session
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 session MUST be unique. A client MUST
MUST NOT send a SUBSCRIBE message that duplicates the NAME, TYPE and NOT send a SUBSCRIBE message that duplicates the NAME, TYPE and CLASS
CLASS of an existing active subscription on that TLS/TCP connection. of an existing active subscription on that DSO session. For the
For the purpose of this matching, the established DNS case- purpose of this matching, the established DNS case-insensitivity for
insensitivity for US-ASCII letters applies (e.g., "example.com" and US-ASCII letters applies (e.g., "example.com" and "Example.com" are
"Example.com" are the same). If a server receives such a duplicate the same). If a server receives such a duplicate SUBSCRIBE message
SUBSCRIBE message this is an error and the server MUST immediately this is an error and the server MUST immediately terminate the
terminate the connection with a TCP RST (or equivalent for other connection with a TCP RST (or equivalent 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 16, line 10 skipping to change at page 16, line 10
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
Each SUBSCRIBE request generates exactly one SUBSCRIBE response from Each SUBSCRIBE request generates exactly one SUBSCRIBE response from
the server. the server.
A SUBSCRIBE response message begins with the standard DNS Stateful A SUBSCRIBE response message begins with the standard DSO 12-byte
Operations 12-byte header [StatefulOp], possibly followed by one or header [DSO], possibly followed by one or more optional TLVs, such as
more optional Modifier TLVs, such as a Retry Delay Modifier TLV. a Retry Delay 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
SUBSCRIBE request. This is how the client knows which request is SUBSCRIBE request. This is how the client knows which request is
being responded to. being responded to.
A SUBSCRIBE response message MUST NOT contain a Stateful Operations A SUBSCRIBE response message MUST NOT include a SUBSCRIBE TLV. If a
Operation TLV. The Stateful Operations Operation TLV is NOT copied client receives a SUBSCRIBE response message containing a SUBSCRIBE
from the SUBSCRIBE request. TLV then the response message is processed but the SUBSCRIBE TLV MUST
be silently ignored.
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 a | | SERVFAIL | 2 | Server failed to process request due to a |
| | | problem with the server. | | | | problem with the server. |
| NXDOMAIN | 3 | NOT APPLICABLE. DNS Push Notification | | NXDOMAIN | 3 | NOT APPLICABLE. DNS Push Notification servers |
| | | servers MUST NOT return NXDOMAIN errors in | | | | MUST NOT return NXDOMAIN errors in response |
| | | response to SUBSCRIBE requests. | | | | to SUBSCRIBE requests. |
| NOTIMP | 4 | Server does not recognize DNS Stateful | | NOTIMP | 4 | Server does not implement DSO. |
| | | Operations 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 requested |
| NOTAUTH | 9 | Server is not authoritative for the | | | | name. |
| | | requested name. | | DSOTYPENI | 11 | SUBSCRIBE operation not supported. |
| SSOPNOTIMP | 11 | SUBSCRIBE operation not supported. | +-----------+-------+-----------------------------------------------+
+------------+-------+----------------------------------------------+
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, that
the client is (at least partially) misconfigured, the server means (a) the client is (at least partially) misconfigured, (b) the
resources are exhausted, or there is some other unknown failure on server resources are exhausted, or (c) there is some other unknown
the server. In any case, the client shouldn't retry the subscription failure on the server. In any case, the client shouldn't retry the
right away. Either end can terminate the connection, but the client subscription right away. Either end can terminate the session, but
may want to try this subscription again, or it may have other the client may want to try this subscription again, or it may have
successful subscriptions that it doesn't want to abandon. If the other successful subscriptions that it doesn't want to abandon. If
server sends a nonzero RCODE then it SHOULD append a Retry Delay the server sends a nonzero RCODE then it SHOULD append a Retry Delay
Modifier TLV [StatefulOp] to the response specifying a delay before TLV [DSO] to the response specifying a delay before the client
the client attempts this operation again. Recommended values for the attempts this operation again. Recommended values for the delay for
delay for different RCODE values are given below: different RCODE values are given below. These recommended values
apply both to the default values a server should place in the Retry
Delay TLV, and the default values a client should assume if the
server provides no Retry Delay TLV.
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) the delay should be chosen according to For RCODE = 2 (SERVFAIL) the delay should be chosen according to
the level of server overload and the anticipated duration of that the level of server overload and the anticipated duration of that
overload. By default, a value of one minute is RECOMMENDED. If a overload. By default, a value of one minute is RECOMMENDED. If a
more serious server failure occurs, the delay may be longer in more serious server failure occurs, the delay may be longer in
accordance with the specific problem encountered. 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 Stateful Operations [StatefulOp], it is unlikely implement DSO [DSO], it is unlikely that the server will begin
that the server will begin supporting DNS Stateful Operations in supporting DSO in the next few minutes, so the retry delay SHOULD
the next few minutes, so the retry delay SHOULD be one hour. be one hour. Note that in such a case, a server that doesn't
implement DSO is unlikely to place a Retry Delay TLV in its
response, so this recommended value in particular applies to what
a client should assume by default.
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.
This is a misconfiguration, since this server is listed in a This is a misconfiguration, since this server is listed in a
"_dns-push-tls._tcp.<zone>" SRV record, but the server itself is "_dns-push-tls._tcp.<zone>" SRV record, but the server itself is
not currently configured to support DNS Push Notifications. Since not currently configured to support DNS Push Notifications. Since
it is possible that the misconfiguration may be repaired at any it is possible that the misconfiguration may be repaired at any
time, the retry delay should not be set too high. By default, a time, the retry delay should not be set too high. By default, a
skipping to change at page 18, line 21 skipping to change at page 18, line 28
For other RCODE values, the retry delay should be set by the For other RCODE values, the retry delay should be set by the
server as appropriate for that error condition. By default, a server as appropriate for that error condition. By default, a
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 session to
to remain open, or MAY send a DNS Push Notification Retry Delay remain open, or MAY send a DNS Push Notification Retry Delay
Operation TLV instructing the client to close the TCP connection, as Operation TLV instructing the client to close the session, as
described in the DNS Stateful Operations specification [StatefulOp]. described in the DSO specification [DSO]. Clients MUST correctly
Clients MUST correctly handle both cases. 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 Stateful Operations A PUSH message begins with the standard DSO 12-byte header [DSO],
12-byte header [StatefulOp], followed by the PUSH TLV. A PUSH followed by the PUSH TLV. A PUSH message is illustrated in Figure 2.
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 zero. There is no client response to a
is not currently using for any other active outgoing request that it PUSH message.
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 ID in any of the client subscriptions it may relate to. In
the PUSH response the client MUST echo back the MESSAGE ID value
unchanged.
The other header fields MUST be set as described in the DNS Stateful The other header fields MUST be set as described in the DSO
Operations specification [StatefulOp]. The DNS Opcode is the specification [DSO]. The DNS Opcode is the DSO Opcode (tentatively
Stateful Operations Opcode (tentatively 6). The four count fields 6). The four count fields MUST be zero, and the corresponding four
MUST be zero, and the corresponding four sections MUST be empty sections MUST be empty (i.e., absent).
(i.e., absent).
The SSOP-TYPE is PUSH (tentatively 0x41). The SSOP-LENGTH is the The DSO-TYPE is PUSH (tentatively 0x41). The DSO-LENGTH is the
length of the SSOP-DATA that follows, which specifies the changes length of the DSO-DATA that follows, which specifies the changes
being communicated. being communicated.
The SSOP-DATA contains one or more Update records. A PUSH Message The DSO-DATA contains one or more Update records. A PUSH Message
MUST contain at least one Update record. If a PUSH Message is MUST contain at least one Update record. If a PUSH Message is
received that contains no Update records, this is a fatal error, and received that contains no Update records, this is a fatal error, and
the receiver MUST immediately terminate the connection with a TCP RST the receiver MUST immediately terminate the connection with a TCP RST
(or equivalent for other protocols). The Update records are (or equivalent for other protocols). The Update records are
formatted in the customary way for Resource Records in DNS messages formatted in the customary way for Resource Records in DNS messages.
with the stipulation that DNS name compression is not permitted in Update records in a PUSH Message are interpreted according to the
DNS Stateful Operations TLVs. Update records in a PUSH Message are same rules as for DNS Update [RFC2136] messages, namely:
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;
TYPE, RDLENGTH and RDATA specifies the RR being deleted. TYPE, RDLENGTH and RDATA specifies the RR being deleted.
Add to an RRset: Add to an RRset:
TTL, CLASS, TYPE, RDLENGTH and RDATA specifies the RR being added. TTL, CLASS, TYPE, RDLENGTH and RDATA specifies the RR being added.
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) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER
| ANCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| NSCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| ARCOUNT (MUST BE ZERO) | /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
| DSO-TYPE = PUSH (tentatively 0x41) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| DSO-LENGTH (number of octets in DSO-DATA) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \
\ NAME \ \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| TYPE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| CLASS | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| TTL | |
| (32 bits) | > DSO-DATA
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| RDLEN | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
\ RDATA \ |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
: NAME, TYPE, CLASS, TTL, RDLEN, RDATA : |
: Repeated As Necessary : /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
Figure 2: PUSH Message
When processing the records received in a PUSH Message, the receiving When processing the records received in a PUSH Message, the receiving
client MUST validate that the records being added or deleted client MUST validate that the records being added or deleted
correspond with at least one currently active subscription on that correspond with at least one currently active subscription on that
connection. Specifically, the record name MUST match the name given session. Specifically, the record name MUST match the name given in
in the SUBSCRIBE request, subject to the usual established DNS case- the SUBSCRIBE request, subject to the usual established DNS case-
insensitivity for US-ASCII letters. If the TYPE in the SUBSCRIBE insensitivity for US-ASCII letters. If the TYPE in the SUBSCRIBE
request was not ANY (255) then the TYPE of the record must match the request was not ANY (255) then the TYPE of the record must match the
TYPE given in the SUBSCRIBE request. If the CLASS in the SUBSCRIBE TYPE given in the SUBSCRIBE request. If the CLASS in the SUBSCRIBE
request was not ANY (255) then the CLASS of the record must match the request was not ANY (255) then the CLASS of the record must match the
CLASS given in the SUBSCRIBE request. If a matching active CLASS given in the SUBSCRIBE request. If a matching active
subscription on that connection is not found, then that individual subscription on that session is not found, then that individual
record addition/deletion is silently ignored. Processing of other record addition/deletion is silently ignored. Processing of other
additions and deletions in this message is not affected. The TCP additions and deletions in this message is not affected. The DSO
connection is not closed. This is to allow for the unavoidable race session is not closed. This is to allow for the unavoidable race
condition where a client sends an outbound UNSUBSCRIBE while inbound condition where a client sends an outbound UNSUBSCRIBE while inbound
PUSH messages for that subscription from the server are still in PUSH messages for that subscription from the server are still in
flight. flight.
In the case where a single change affects more than one active In the case where a single change affects more than one active
subscription, only one PUSH message is sent. For example, a PUSH subscription, only one PUSH message is sent. For example, a PUSH
message adding a given record may match both a SUBSCRIBE request with message adding a given record may match both a SUBSCRIBE request with
the same TYPE and a different SUBSCRIBE request with TYPE=ANY. It is the same TYPE and a different SUBSCRIBE request with TYPE=ANY. It is
not the case that two PUSH messages are sent because the new record not the case that two PUSH messages are sent because the new record
matches two active subscriptions. matches two active subscriptions.
skipping to change at page 22, line 37 skipping to change at page 21, line 32
server SHOULD send a "delete an RRset from a name" PUSH message, not server SHOULD send a "delete an RRset from a name" PUSH message, not
three separate "delete an individual RR from a name" PUSH messages. three separate "delete an individual RR from a name" PUSH messages.
Similarly, when both an SRV and a TXT record are deleted from a given Similarly, when both an SRV and a TXT record are deleted from a given
name, and no other records of any kind exist for that name, the name, and no other records of any kind exist for that name, the
server SHOULD send a "delete all RRsets from a name" PUSH message, server SHOULD send a "delete all RRsets from a name" PUSH message,
not two separate "delete an RRset from a name" PUSH messages. not two separate "delete an RRset from a name" PUSH messages.
A server SHOULD combine multiple change notifications in a single A server SHOULD combine multiple change notifications in a single
PUSH message when possible, even if those change notifications apply PUSH message when possible, even if those change notifications apply
to different subscriptions. Conceptually, a PUSH message is a to different subscriptions. Conceptually, a PUSH message is a
connection-level mechanism, not a subscription-level mechanism. session-level mechanism, not a subscription-level mechanism.
Reception of a PUSH message by a client generates a PUSH response
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 DSO session being closed) record
record aging resumes and records are removed from the local cache aging resumes and records are removed from the local cache when their
when their TTL reaches zero. TTL reaches zero.
6.3.2. PUSH Response
Each PUSH message generates exactly one PUSH response from the
receiver.
A PUSH response message begins with the standard DNS Stateful
Operations 12-byte header [StatefulOp], possibly followed by one or
more optional Modifier TLVs.
The MESSAGE ID field MUST echo the value given in the ID field of the
PUSH message.
A PUSH response message MUST NOT contain a Stateful Operations
Operation TLV. The Stateful Operations Operation TLV is NOT copied
from the PUSH message.
In a PUSH response the RCODE MUST be zero. Receiving a PUSH response
with a nonzero RCODE is a fatal error, and the receiver MUST
immediately terminate the connection with a TCP RST (or equivalent
for other protocols).
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 DSO
connection, the client sends an UNSUBSCRIBE message over the session, the client sends an UNSUBSCRIBE message over the established
established TCP connection to the server. The UNSUBSCRIBE message is DSO session to the server. The UNSUBSCRIBE message is encoded in a
encoded in a DNS Stateful Operations [StatefulOp] message. This DSO [DSO] message. This specification defines a DSO TLV for DNS Push
specification defines a DNS Stateful Operations TLV for DNS Push Notification UNSUBSCRIBE Requests/Responses (tentatively DSO Type
Notification UNSUBSCRIBE Requests/Responses (tentatively Stateful Code 0x42).
Operations Type Code 0x42).
A server MUST NOT initiate an UNSUBSCRIBE request. If a server does A server MUST NOT initiate an UNSUBSCRIBE request. If a server does
send a UNSUBSCRIBE request over the connection initiated by a client, send an UNSUBSCRIBE request over a DSO session initiated by a client,
it is an error and the client should acknowledge the request with the this is a fatal error and the client should immediately abort the
error response RCODE NOTAUTH (Not Authoritative). connection with a TCP RST (or equivalent for other protocols).
6.4.1. UNSUBSCRIBE Request 6.4.1. UNSUBSCRIBE Request
An UNSUBSCRIBE request message begins with the standard DNS Stateful An UNSUBSCRIBE request begins with the standard DSO 12-byte header
Operations 12-byte header [StatefulOp], followed by the UNSUBSCRIBE [DSO], followed by the UNSUBSCRIBE TLV. An UNSUBSCRIBE request
TLV. message is illustrated in Figure 3.
1 1 1 1 1 1 The MESSAGE ID field MUST be zero. There is no server response to a
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 UNSUBSCRIBE message.
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| 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 The other header fields MUST be set as described in the DSO
specification [DSO]. The DNS Opcode is the DSO Opcode (tentatively
6). The four count fields MUST be zero, and the corresponding four
sections MUST be empty (i.e., absent).
In the UNSUBSCRIBE TLV the SSOP-TYPE is UNSUBSCRIBE (tentatively In the UNSUBSCRIBE TLV the DSO-TYPE is UNSUBSCRIBE (tentatively
0x42). The SSOP-LENGTH is 2 octets. 0x42). The DSO-LENGTH is 2 octets.
The SSOP-DATA contains the MESSAGE ID field of the value given in the The DSO-DATA contains the MESSAGE ID field of the value given in the
ID field of an active SUBSCRIBE request. This is how the server ID field of an active SUBSCRIBE request. This is how the server
knows which SUBSCRIBE request is being cancelled. After receipt of knows which SUBSCRIBE request is being cancelled. After receipt of
the UNSUBSCRIBE request, the SUBSCRIBE request is no longer active. the UNSUBSCRIBE request, the SUBSCRIBE request is no longer active.
If a server receives an UNSUBSCRIBE message where the MESSAGE ID does
not match the ID of an active SUBSCRIBE request the server MUST
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.
this is that if the client issues an UNSUBSCRIBE request for an as-
yet unacknowledged SUBSCRIBE request, and the SUBSCRIBE request is
subsequently unsuccessful for some reason, then when the UNSUBSCRIBE
request is eventually processed it will be an UNSUBSCRIBE request for
a nonexistent subscription, which will result NXDOMAIN response.
6.4.2. UNSUBSCRIBE Response
Each UNSUBSCRIBE request generates exactly one UNSUBSCRIBE response
from the server.
An UNSUBSCRIBE response message begins with the standard DNS Stateful
Operations 12-byte header [StatefulOp], possibly followed by one or
more 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
UNSUBSCRIBE request. This is how the client knows which request is
being responded to.
An UNSUBSCRIBE response message MUST NOT contain a Stateful
Operations Operation TLV. The Stateful Operations Operation TLV is
NOT copied from the UNSUBSCRIBE request.
In the UNSUBSCRIBE response the RCODE indicates whether or not the
unsubscribe request was successful. Supported RCODEs are as follows:
+------------+-------+----------------------------------------------+
| Mnemonic | Value | Description |
+------------+-------+----------------------------------------------+
| NOERROR | 0 | UNSUBSCRIBE successful. |
| FORMERR | 1 | Server failed to process request due to a |
| | | malformed request. |
| NXDOMAIN | 3 | Specified subscription does not exist. |
| NOTIMP | 4 | Server does not recognize DNS Stateful |
| | | Operations Opcode. |
| SSOPNOTIMP | 11 | UNSUBSCRIBE operation not supported. |
+------------+-------+----------------------------------------------+
UNSUBSCRIBE Response codes
This document specifies only these RCODE values for UNSUBSCRIBE
Responses. Servers sending UNSUBSCRIBE Responses SHOULD use one of
these values. However, future circumstances may create situations
where other RCODE values are appropriate in UNSUBSCRIBE Responses, so
clients MUST be prepared to accept UNSUBSCRIBE Responses with any
RCODE value.
Having being successfully revoked with a correctly-formatted
UNSUBSCRIBE message (resulting in a response with RCODE NOERROR) the
previously referenced subscription is no longer active and the server
MAY discard the state associated with it immediately, or later, at
the server's discretion.
Nonzero RCODE values signal some kind of error.
RCODE value FORMERR indicates a message format error.
RCODE value NXDOMAIN indicates a MESSAGE ID that does not correspond
to any active subscription.
RCODE values NOTIMP and SSOPNOTIMP should not occur in practice.
A server would only generate NOTIMP if it did not support Stateful
Operations, and if the server does not support Stateful Operations
then it should not be possible for a client to have an active
subscription to cancel.
Similarly, a server would only generate SSOPNOTIMP if it did not 1 1 1 1 1 1
support Push Notifications, and if the server does not support Push 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
Notifications then it should not be possible for a client to have an +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \
active subscription to cancel. | MESSAGE ID | \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
|QR| Opcode | Z | RCODE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| QDCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER
| ANCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| NSCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| ARCOUNT (MUST BE ZERO) | /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
| DSO-TYPE = UNSUBSCRIBE (tentatively 0x42) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| DSO-LENGTH (2 octets) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \
| SUBSCRIBE MESSAGE ID | > DSO-DATA
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
Nonzero RCODE values other than NXDOMAIN indicate a serious problem Figure 3: UNSUBSCRIBE Request
with the client. After sending an error response other than
NXDOMAIN, the server SHOULD send a DNS Stateful Operations Retry
Delay Operation TLV and then close the TCP connection, as described
in the DNS Stateful Operations specification [StatefulOp].
6.5. DNS Push Notification RECONFIRM 6.5. DNS Push Notification RECONFIRM
Sometimes, particularly when used with a Discovery Proxy [DisProx], a Sometimes, particularly when used with a Discovery Proxy [DisProx], a
DNS Zone may contain stale data. When a client encounters data that DNS Zone may contain stale data. When a client encounters data that
it believe may be stale (e.g., an SRV record referencing a target it believe may be stale (e.g., an SRV record referencing a target
host+port that is not responding to connection requests) the client host+port that is not responding to connection requests) the client
can send a RECONFIRM request to ask the server to re-verify that the can send a RECONFIRM request to ask the server to re-verify that the
data is still valid. For a Discovery Proxy, this causes it to issue data is still valid. For a Discovery Proxy, this causes it to issue
new Multicast DNS requests to ascertain whether the target device is new Multicast DNS requests to ascertain whether the target device is
skipping to change at page 30, line 7 skipping to change at page 24, line 32
If, after receiving a valid RECONFIRM request, the server determines If, after receiving a valid RECONFIRM request, the server determines
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 Stateful A RECONFIRM request begins with the standard DSO 12-byte header
Operations 12-byte header [StatefulOp], followed by the RECONFIRM [DSO], followed by the RECONFIRM TLV. A RECONFIRM request message is
TLV. A RECONFIRM request message is illustrated below: illustrated in Figure 4.
The MESSAGE ID field MUST be set to a unique value, that the client
is not using for any other active operation on this DSO session. For
the purposes here, a MESSAGE ID is in use on this session if the
client has used it in a request for which it has not yet received a
response, or if the client has used it for a subscription which it
has not yet cancelled using UNSUBSCRIBE. In the RECONFIRM response
the server MUST echo back the MESSAGE ID value unchanged.
The other header fields MUST be set as described in the DSO
specification [DSO]. The DNS Opcode is the DSO Opcode (tentatively
6). The four count fields MUST be zero, and the corresponding four
sections MUST be empty (i.e., absent).
The DSO-TYPE is RECONFIRM (tentatively 0x43). The DSO-LENGTH is the
length of the data that follows, which specifies the name, type,
class, and content of the record being disputed.
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 | \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
|QR| Opcode | Z | RCODE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| QDCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER
| ANCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| NSCOUNT (MUST BE ZERO) | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| ARCOUNT (MUST BE ZERO) | /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
| DSO-TYPE = RECONFIRM (tentatively 0x43) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| MESSAGE ID | | DSO-LENGTH (number of octets in DSO-DATA) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode | Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT (MUST BE ZERO) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-TYPE = RECONFIRM (tentatively 0x43) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| SSOP-LENGTH (number of octets in SSOP-DATA) |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \
\ NAME \ \ \ NAME \ \
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| TYPE | | | TYPE | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > DSO-DATA
| CLASS | > SSOP-DATA | CLASS | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| RDLEN | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
\ RDATA \ / \ RDATA \ /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ /
Figure 4 Figure 4: RECONFIRM Request
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
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
response, or if the client has used it for a subscription which it
has not yet cancelled using UNSUBSCRIBE. In the RECONFIRM response
the server MUST echo back the MESSAGE ID value unchanged.
The other header fields MUST be set as described in the DNS Stateful
Operations specification [StatefulOp]. The DNS Opcode is the
Stateful Operations Opcode (tentatively 6). The four count fields
MUST be zero, and the corresponding four sections MUST be empty
(i.e., absent).
The SSOP-TYPE is RECONFIRM (tentatively 0x43). The SSOP-LENGTH is
the length of the data that follows, which specifies the name, type,
class, and content of the record being disputed.
The SSOP-DATA for a RECONFIRM request MUST contain exactly one The DSO-DATA for a RECONFIRM request MUST contain exactly one record.
record. The SSOP-DATA for a RECONFIRM request has no count field to The DSO-DATA for a RECONFIRM request has no count field to specify
specify more than one record. Since RECONFIRM requests are sent over more than one record. Since RECONFIRM requests are sent over TCP,
TCP, multiple RECONFIRM request messages can be concatenated in a multiple RECONFIRM request messages can be concatenated in a single
single TCP stream and packed efficiently into TCP segments. 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.
6.5.2. RECONFIRM Response 6.5.2. RECONFIRM Response
Each RECONFIRM request generates exactly one RECONFIRM response from Each RECONFIRM request generates exactly one RECONFIRM response from
the server. the server.
A RECONFIRM response message begins with the standard DNS Stateful A RECONFIRM response message begins with the standard DSO 12-byte
Operations 12-byte header [StatefulOp], possibly followed by one or header [DSO], possibly followed by one or more optional TLVs, such as
more optional Modifier TLVs, such as a Retry Delay Modifier TLV. a Retry Delay TLV. For suggested values for the Retry Delay TLV, see
Section 6.2.2.
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
RECONFIRM request. This is how the client knows which request is RECONFIRM request. This is how the client knows which request is
being responded to. being responded to.
A RECONFIRM response message MUST NOT contain a Stateful Operations A RECONFIRM response message MUST NOT include a DSO RECONFIRM TLV.
Operation TLV. The Stateful Operations Operation TLV is NOT copied If a client receives a RECONFIRM response message containing a
from the RECONFIRM request. RECONFIRM TLV then the response message is processed but the
RECONFIRM TLV MUST be silently ignored.
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 a | | SERVFAIL | 2 | Server failed to process request due to a |
| | | problem with the server. | | | | problem with the server. |
| NXDOMAIN | 3 | NOT APPLICABLE. DNS Push Notification | | NXDOMAIN | 3 | NOT APPLICABLE. DNS Push Notification servers |
| | | servers MUST NOT return NXDOMAIN errors in | | | | MUST NOT return NXDOMAIN errors in response |
| | | response to RECONFIRM requests. | | | | to RECONFIRM requests. |
| NOTIMP | 4 | Server does not recognize DNS Stateful | | NOTIMP | 4 | Server does not implement DSO. |
| | | Operations 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 requested |
| NOTAUTH | 9 | Server is not authoritative for the | | | | name. |
| | | requested name. | | DSOTYPENI | 11 | RECONFIRM operation not supported. |
| SSOPNOTIMP | 11 | RECONFIRM operation not supported. | +-----------+-------+-----------------------------------------------+
+------------+-------+----------------------------------------------+
RECONFIRM Response codes RECONFIRM Response codes
This document specifies only these RCODE values for RECONFIRM This document specifies only these RCODE values for RECONFIRM
Responses. Servers sending RECONFIRM Responses SHOULD use one of Responses. Servers sending RECONFIRM 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 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 has exhausted its RCODE value SERVFAIL indicates that the server has exhausted its
resources or other serious problem occurred. 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 DSO,
Stateful Operations, and Stateful Operations is required for and DSO is required for RECONFIRM requests.
RECONFIRM 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
for the requested name, and can do nothing to remedy the apparent for the requested name, and can do nothing to remedy the apparent
error. Note that there may be future cases in which a server is able error. Note that there may be future cases in which a server is able
to pass on the RECONFIRM request to the ultimate source of the to pass on the RECONFIRM request to the ultimate source of the
information, and in these cases the server should return NOERROR. information, and in these cases the server should return NOERROR.
RCODE value SSOPNOTIMP indicates that the server does not support RCODE value DSOTYPENI indicates that the server does not support
RECONFIRM requests. RECONFIRM requests.
Nonzero RCODE values SERVFAIL, REFUSED and SSOPNOTIMP are benign from Nonzero RCODE values SERVFAIL, REFUSED and DSOTYPENI are benign from
the client's point of view. The client may log them to aid in the client's point of view. The client may log them to aid in
debugging, but otherwise they require no special action. debugging, but otherwise they require no special action.
Nonzero RCODE values other than these three indicate a serious Nonzero RCODE values other than these three indicate a serious
problem with the client. After sending an error response other than problem with the client. After sending an error response other than
one of these three, the server SHOULD send a DNS Stateful Operations one of these three, the server SHOULD send a DSO Retry Delay TLV to
Retry Delay Operation TLV and then close the TCP connection, as end the DSO session, as described in the DSO specification [DSO].
described in the DNS Stateful Operations specification [StatefulOp].
6.6. Client-Initiated Termination 6.6. Client-Initiated Termination
An individual subscription is terminated by sending an UNSUBSCRIBE An individual subscription is terminated by sending an UNSUBSCRIBE
TLV for that specific subscription, or all subscriptions can be TLV for that specific subscription, or all subscriptions can be
cancelled at once by the client closing the connection. When a cancelled at once by the client closing the DSO session. When a
client terminates an individual subscription (via UNSUBSCRIBE) or all client terminates an individual subscription (via UNSUBSCRIBE) or all
subscriptions on that connection (by closing the connection) it is subscriptions on that DSO session (by ending the session) it is
signaling to the server that it is longer interested in receiving signaling to the server that it is longer interested in receiving
those particular updates. It is informing the server that the server those particular updates. It is informing the server that the server
may release any state information it has been keeping with regards to may release any state information it has been keeping with regards to
these particular subscriptions. these particular subscriptions.
After terminating its last subscription on a connection via After terminating its last subscription on a session via UNSUBSCRIBE,
UNSUBSCRIBE, a client MAY close the connection immediately, or it may a client MAY close the session immediately, or it may keep it open if
keep it open if it anticipates performing further operations on that it anticipates performing further operations on that session in the
connection in the future. If a client wishes to keep an idle future. If a client wishes to keep an idle session open, it MUST
connection open, it MUST respect the maximum idle time required by respect the maximum idle time required by the server [DSO].
the server [StatefulOp].
If a client plans to terminate one or more subscriptions on a If a client plans to terminate one or more subscriptions on a session
connection and doesn't intend to keep that connection open, then as and doesn't intend to keep that session open, then as an efficiency
an efficiency optimization it MAY instead choose to simply close the optimization it MAY instead choose to simply close the session, which
connection, which implicitly terminates all subscriptions on that implicitly terminates all subscriptions on that session. This may
connection. This may occur because the client computer is being shut occur because the client computer is being shut down, is going to
down, is going to sleep, the application requiring the subscriptions sleep, the application requiring the subscriptions has terminated, or
has terminated, or simply because the last active subscription on simply because the last active subscription on that session has been
that connection has been cancelled. cancelled.
When closing a connection, a client will generally do an abortive When closing a session, a client will generally do an abortive
disconnect, sending a TCP RST. This immediately discards all disconnect, sending a TCP RST. This immediately discards all
remaining inbound and outbound data, which is appropriate if the remaining inbound and outbound data, which is appropriate if the
client no longer has any interest in this data. In the BSD Sockets client no longer has any interest in this data. In the BSD Sockets
API, sending a TCP RST is achieved by setting the SO_LINGER option API, sending a TCP RST is achieved by setting the SO_LINGER option
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 session 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 TLS close_notify followed by a TCP FIN. (In
FIN is achieved by calling "shutdown(s,SHUT_WR)" and keeping the the BSD Sockets API, sending a TCP FIN is achieved by calling
socket open until all remaining data has been read from it. "shutdown(s,SHUT_WR)" and keeping the socket open until all remaining
data has been read from it.)
7. Security Considerations 7. Security Considerations
The Strict Privacy Usage Profile for DNS over TLS is strongly The Strict Privacy Usage Profile for DNS over TLS is strongly
recommended for DNS Push Notifications as defined in Authentication recommended for DNS Push Notifications as defined in "Authentication
and (D)TLS Profile for DNS-over-(D)TLS and (D)TLS Profile for DNS-over-(D)TLS"
[I-D.ietf-dprive-dtls-and-tls-profiles]. The Opportunistic Privacy [I-D.ietf-dprive-dtls-and-tls-profiles]. The Opportunistic Privacy
Usage Profile is permissible as a way to support incremental Usage Profile is permissible as a way to support incremental
deployment of security capabilities. Cleartext connections for DNS deployment of security capabilities. Cleartext connections for DNS
Push Notifications are not permissible. Push Notifications are not permissible.
DNSSEC is RECOMMENDED for the authentication of DNS Push Notification DNSSEC is RECOMMENDED for the authentication of DNS Push Notification
servers. TLS alone does not provide complete security. TLS servers. TLS alone does not provide complete security. TLS
certificate verification can provide reasonable assurance that the certificate verification can provide reasonable assurance that the
client is really talking to the server associated with the desired client is really talking to the server associated with the desired
host name, but since the desired host name is learned via a DNS SRV host name, but since the desired host name is learned via a DNS SRV
skipping to change at page 36, line 34 skipping to change at page 30, line 34
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
servers. The server may keep TLS state with Session IDs [RFC5246] or servers. The server may keep TLS state with Session IDs [RFC5246] or
operate in stateless mode by sending a Session Ticket [RFC5077] to operate in stateless mode by sending a Session Ticket [RFC5077] to
the client for it to store. However, once the connection is closed, the client for it to store. However, once the DSO session is closed,
any existing subscriptions will be dropped. When the TLS session is any existing subscriptions will be dropped. When the TLS session is
resumed, the DNS Push Notification server will not have any resumed, the DNS Push Notification server will not have any
subscription state and will proceed as with any other new connection. subscription state and will proceed as with any other new DSO
Use of TLS Session Resumption allows a new TLS connection to be set session. Use of TLS Session Resumption allows a new TLS connection
up more quickly, but the client will still have to recreate any to be set up more quickly, but the client will still have to recreate
desired subscriptions. any 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 Registry Service Types
[RFC6335][SN]. [RFC6335][ST].
This document defines four DNS Stateful Operations TLV types: This document defines four DNS Stateful Operations TLV types:
SUBSCRIBE with (tentative) value 0x40 (64), PUSH with (tentative) SUBSCRIBE with (tentative) value 0x40 (64), PUSH with (tentative)
value 0x41 (65), UNSUBSCRIBE with (tentative) value 0x42 (66), and value 0x41 (65), UNSUBSCRIBE with (tentative) value 0x42 (66), and
RECONFIRM with (tentative) value 0x43 (67). RECONFIRM 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, Soraia Zlatkovic, Sara Shankar Rao, Markus Stenberg, Dave Thaler, Soraia Zlatkovic, Sara
Dickinson, and Andrew Sullivan. Dickinson, and Andrew Sullivan.
10. References 10. References
10.1. Normative References 10.1. Normative References
[DSO] Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S.,
Mankin, A., and T. Pusateri, "DNS Stateful Operations",
draft-ietf-dnsop-session-signal-05 (work in progress),
January 2018.
[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-tls13-21 (work in progress), Version 1.3", draft-ietf-tls-tls13-26 (work in progress),
July 2017. March 2018.
[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, <https://www.rfc- DOI 10.17487/RFC0768, August 1980,
editor.org/info/rfc768>. <https://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,
<https://www.rfc-editor.org/info/rfc793>. <https://www.rfc-editor.org/info/rfc793>.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>. <https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>. November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC1123] Braden, R., Ed., "Requirements for Internet Hosts - [RFC1123] Braden, R., Ed., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123, Application and Support", STD 3, RFC 1123,
DOI 10.17487/RFC1123, October 1989, <https://www.rfc- DOI 10.17487/RFC1123, October 1989,
editor.org/info/rfc1123>. <https://www.rfc-editor.org/info/rfc1123>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc- DOI 10.17487/RFC2119, March 1997,
editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)", "Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997, RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/info/rfc2136>. <https://www.rfc-editor.org/info/rfc2136>.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782, specifying the location of services (DNS SRV)", RFC 2782,
DOI 10.17487/RFC2782, February 2000, <https://www.rfc- DOI 10.17487/RFC2782, February 2000,
editor.org/info/rfc2782>. <https://www.rfc-editor.org/info/rfc2782>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, <https://www.rfc- DOI 10.17487/RFC5246, August 2008,
editor.org/info/rfc5246>. <https://www.rfc-editor.org/info/rfc5246>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS) [RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066, Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011, <https://www.rfc- DOI 10.17487/RFC6066, January 2011,
editor.org/info/rfc6066>. <https://www.rfc-editor.org/info/rfc6066>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA) Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165, Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011, RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>. <https://www.rfc-editor.org/info/rfc6335>.
[RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA [RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA
Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895, Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895,
skipping to change at page 38, line 46 skipping to change at page 33, line 5
[RFC7673] Finch, T., Miller, M., and P. Saint-Andre, "Using DNS- [RFC7673] Finch, T., Miller, M., and P. Saint-Andre, "Using DNS-
Based Authentication of Named Entities (DANE) TLSA Records Based Authentication of Named Entities (DANE) TLSA Records
with SRV Records", RFC 7673, DOI 10.17487/RFC7673, October with SRV Records", RFC 7673, DOI 10.17487/RFC7673, October
2015, <https://www.rfc-editor.org/info/rfc7673>. 2015, <https://www.rfc-editor.org/info/rfc7673>.
[RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and [RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and
D. Wessels, "DNS Transport over TCP - Implementation D. Wessels, "DNS Transport over TCP - Implementation
Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016, Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016,
<https://www.rfc-editor.org/info/rfc7766>. <https://www.rfc-editor.org/info/rfc7766>.
[SN] "Service Name and Transport Protocol Port Number [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>.
[ST] "Service Name and Transport Protocol Port Number
Registry", <http://www.iana.org/assignments/ Registry", <http://www.iana.org/assignments/
service-names-port-numbers/>. service-names-port-numbers/>.
[StatefulOp]
Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S.,
Mankin, A., and T. Pusateri, "DNS Stateful Operations",
draft-ietf-dnsop-session-signal-04 (work in progress),
September 2017.
10.2. Informative References 10.2. Informative References
[DisProx] Cheshire, S., "Hybrid Unicast/Multicast DNS-Based Service [DisProx] Cheshire, S., "Discovery Proxy for Multicast DNS-Based
Discovery", draft-ietf-dnssd-hybrid-07 (work in progress), Service Discovery", draft-ietf-dnssd-hybrid-08 (work in
September 2017. progress), March 2018.
[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] [I-D.ietf-dprive-dtls-and-tls-profiles]
Dickinson, S., Gillmor, D., and T. Reddy, "Usage and Dickinson, S., Gillmor, D., and T. Reddy, "Usage and
(D)TLS Profiles for DNS-over-(D)TLS", draft-ietf-dprive- (D)TLS Profiles for DNS-over-(D)TLS", draft-ietf-dprive-
dtls-and-tls-profiles-11 (work in progress), September dtls-and-tls-profiles-11 (work in progress), September
2017. 2017.
[I-D.sekar-dns-llq] [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] [obs] "Observer Pattern",
Eddy, W., "Defenses Against TCP SYN Flooding Attacks", The <https://en.wikipedia.org/wiki/Observer_pattern>.
Internet Protocol Journal, Cisco Systems, Volume 9,
Number 4, December 2006.
[obs] "Observer Pattern", <https://en.wikipedia.org/wiki/
Observer_pattern>.
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
<https://www.rfc-editor.org/info/rfc2308>. <https://www.rfc-editor.org/info/rfc2308>.
[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, <https://www.rfc-editor.org/info/rfc4287>. December 2005, <https://www.rfc-editor.org/info/rfc4287>.
[RFC4953] Touch, J., "Defending TCP Against Spoofing Attacks", [RFC4953] Touch, J., "Defending TCP Against Spoofing Attacks",
skipping to change at page 40, line 16 skipping to change at page 34, line 11
"Transport Layer Security (TLS) Session Resumption without "Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, DOI 10.17487/RFC5077, Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
January 2008, <https://www.rfc-editor.org/info/rfc5077>. January 2008, <https://www.rfc-editor.org/info/rfc5077>.
[RFC6281] Cheshire, S., Zhu, Z., Wakikawa, R., and L. Zhang, [RFC6281] Cheshire, S., Zhu, Z., Wakikawa, R., and L. Zhang,
"Understanding Apple's Back to My Mac (BTMM) Service", "Understanding Apple's Back to My Mac (BTMM) Service",
RFC 6281, DOI 10.17487/RFC6281, June 2011, RFC 6281, DOI 10.17487/RFC6281, June 2011,
<https://www.rfc-editor.org/info/rfc6281>. <https://www.rfc-editor.org/info/rfc6281>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013, <https://www.rfc- DOI 10.17487/RFC6762, February 2013,
editor.org/info/rfc6762>. <https://www.rfc-editor.org/info/rfc6762>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/info/rfc6763>. <https://www.rfc-editor.org/info/rfc6763>.
[RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
"TCP Extensions for Multipath Operation with Multiple "TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013, Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,
<https://www.rfc-editor.org/info/rfc6824>. <https://www.rfc-editor.org/info/rfc6824>.
skipping to change at page 40, line 47 skipping to change at page 34, line 42
[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS [RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", RFC 7719, DOI 10.17487/RFC7719, December Terminology", RFC 7719, DOI 10.17487/RFC7719, December
2015, <https://www.rfc-editor.org/info/rfc7719>. 2015, <https://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, <https://www.rfc-editor.org/info/rfc7858>. 2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC8010] Sweet, M. and I. McDonald, "Internet Printing
Protocol/1.1: Encoding and Transport", RFC 8010,
DOI 10.17487/RFC8010, January 2017,
<https://www.rfc-editor.org/info/rfc8010>.
[RFC8011] Sweet, M. and I. McDonald, "Internet Printing
Protocol/1.1: Model and Semantics", RFC 8011,
DOI 10.17487/RFC8011, January 2017,
<https://www.rfc-editor.org/info/rfc8011>.
[SYN] Eddy, W., "Defenses Against TCP SYN Flooding Attacks", The
Internet Protocol Journal, Cisco Systems, Volume 9,
Number 4, December 2006.
[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
Tom Pusateri Tom Pusateri
Unaffiliated Unaffiliated
Raleigh, NC 27608 Raleigh, NC 27608
USA USA
 End of changes. 121 change blocks. 
680 lines changed or deleted 593 lines changed or added

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