Advertising Proxy for DNS-SD Service Registration Protocol

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Last updated 2020-07-13
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DNSSD                                                        S. Cheshire
Internet-Draft                                                  T. Lemon
Intended status: Standards Track                              Apple Inc.
Expires: 14 January 2021                                    13 July 2020

       Advertising Proxy for DNS-SD Service Registration Protocol


   An Advertising Proxy allows a device that accepts service registra-
   tions using Service Registration Protocol (SRP) to make those regis-
   trations visible to legacy clients that only implement Multicast DNS.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 14 January 2021.

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1.  Introduction

   DNS-Based Service Discovery [RFC6763] [ROADMAP] was designed to
   facilitate Zero Configuration IP Networking [RFC6760] [ZC].
   When used with Multicast DNS [RFC6762] with ".local" domain names
   [RFC6761] this works well on a single link (a single broadcast

   There is also a desire to have DNS-Based Service Discovery work
   between multiple links that aren't part of the same broadcast domain
   [RFC7558].  Even within a single Wi-Fi broadcast domain it is
   beneficial to reduce multicast traffic, because, in comparison to
   Wi-Fi unicast traffic, Wi-Fi multicast is inefficient, slow, and
   unreliable [MCAST].

   There are three variant ways that this move to greater use of unicast
   is achieved.

   One variant is pure end-to-end unicast, with services using unicast
   Service Registration Protocol [SRP] to register with a service
   registry, and clients using unicast DNS Push Notifications [RFC8765]
   over DNS Stateful Operations [RFC8490] to communicate with the
   service registry to discover and track changes to those registered

   A second variant is a hybrid approach that facilitates legacy devices
   that only implement link-local Multicast DNS (like your ten-year-old
   network laser printer) having their services discovered by remote
   clients, using a unicast DNS Push Notifications session to a
   Discovery Proxy [RFC8766].

   The third variant, documented here, is a logical complement to the
   second variant.  It enables legacy clients (that only implement link-
   local Multicast DNS) to discover services registered (using unicast)
   with a service registry.  The service registry accepts service
   registrations using unicast Service Registration Protocol [SRP], and
   makes those service registrations visible, both to remote clients
   using unicast DNS Push Notifications [RFC8765] and, using the
   Advertising Proxy mechanism documented here, to local clients using
   Multicast DNS [RFC6762].

1.1.  Conventions and Terminology Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.

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2.  Advertising Proxy

   An Advertising Proxy can be a component of any DNS authoritative
   server, though it logically makes most sense as a component of a
   service registry (a DNS authoritative server that implements Service
   Registration Protocol [SRP]).  A client can send registration
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