DNS Push Notifications
RFC 8765

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Internet Engineering Task Force (IETF)                       T. Pusateri
Request for Comments: 8765                                  Unaffiliated
Category: Standards Track                                    S. Cheshire
ISSN: 2070-1721                                               Apple Inc.
                                                               June 2020

                         DNS Push Notifications

Abstract

   The Domain Name System (DNS) was designed to return matching records
   efficiently for queries for data that are relatively static.  When
   those records change frequently, DNS is still efficient at returning
   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
   asynchronously notified when these changes occur.  This document
   defines a mechanism for a client to be notified of such changes to
   DNS records, called DNS Push Notifications.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8765.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
     1.1.  Requirements Language
     1.2.  Fatal Errors
   2.  Motivation
   3.  Overview
   4.  State Considerations
   5.  Transport
   6.  Protocol Operation
     6.1.  Discovery
     6.2.  DNS Push Notification SUBSCRIBE
       6.2.1.  SUBSCRIBE Request
       6.2.2.  SUBSCRIBE Response
     6.3.  DNS Push Notification Updates
       6.3.1.  PUSH Message
     6.4.  DNS Push Notification UNSUBSCRIBE
       6.4.1.  UNSUBSCRIBE Message
     6.5.  DNS Push Notification RECONFIRM
       6.5.1.  RECONFIRM Message
     6.6.  DNS Stateful Operations TLV Context Summary
     6.7.  Client-Initiated Termination
     6.8.  Client Fallback to Polling
   7.  Security Considerations
     7.1.  Security Services
     7.2.  TLS Name Authentication
     7.3.  TLS Early Data
     7.4.  TLS Session Resumption
   8.  IANA Considerations
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

   Domain Name System (DNS) records may be updated using DNS Update
   [RFC2136].  Other mechanisms such as a Discovery Proxy [RFC8766] can
   also generate changes to a DNS zone.  This document specifies a
   protocol for DNS clients to subscribe to receive asynchronous
   notifications of changes to RRsets of interest.  It is immediately
   relevant in the case of DNS-based Service Discovery [RFC6763] but is
   not limited to that use case; it provides a general DNS mechanism for
   DNS record change notifications.  Familiarity with the DNS protocol
   and DNS packet formats is assumed [RFC1034] [RFC1035] [RFC6895].

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

1.2.  Fatal Errors

   Certain invalid situations are described in this specification, such
   as a server sending a Push Notification subscription request to a
   client, or a client sending a Push Notification response to a server.
   These should never occur with a correctly implemented client and
   server, and if they do occur, then they indicate a serious
   implementation error.  In these extreme cases, there is no reasonable
   expectation of a graceful recovery, and the recipient detecting the
   error should respond by unilaterally aborting the session without
   regard for data loss.  Such cases are addressed by having an engineer
   investigate the cause of the failure and fixing the problem in the
   software.

   Where this specification says "forcibly abort", it means sending a