Advertising Proxy for DNS-SD Service Registration Protocol
draft-sctl-advertising-proxy-00

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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
                    draft-sctl-advertising-proxy-00

Abstract

   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

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 14 January 2021.

Copyright Notice

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   provided without warranty as described in the Simplified BSD License.

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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
   domain).

   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
   services.

   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",
   "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.

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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