The Mercure Protocol

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Last updated 2019-01-09
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Network Working Group                                         K. Dunglas
Intended status: Informational                            9 January 2019
Expires: 13 July 2019

                          The Mercure Protocol


   Mercure is a protocol enabling the pushing of data updates to web
   browsers and other HTTP clients in a fast, reliable and battery-
   efficient way.  It is especially useful for publishing real-time
   updates of resources served through web APIs to reactive web and
   mobile apps.

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
   Task Force (IETF).  Note that other groups may also distribute
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 13 July 2019.

Copyright Notice

   Copyright (c) 2019 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
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Terminology
   2.  Discovery
   3.  Subscriptions
   4.  Publication
   5.  Authorization
       5.1.  Publishers
       5.2.  Subscribers
   6.  Reconnection and State Reconciliation
   7.  Encryption
   8.  Security Considerations
   9.1.  Normative References
   9.2.  Informative References
   Author's Address

1.  Terminology

   *SHOULD NOT*, RECOMMENDED, MAY, and OPTIONAL, when they appear in
   this document, are to be interpreted as described in [RFC2119].

   *  Topic: An HTTP [RFC7230] or HTTPS [RFC2818] topic URL.  The unit
      to which one can subscribe to changes.

   *  Publisher: An owner of a topic.  Notifies the hub when the topic
      feed has been updated.  As in almost all pubsub systems, the
      publisher is unaware of the subscribers, if any.  Other pubsub
      systems might call the publisher the "source".  Typically a
      website or a web API, but can also be a web browser.

   *  Subscriber: A client application that subscribes to real-time
      updates of topics.  Typically a Progressive Web App or a Mobile
      App, but can also be a server.

   *  Target: A subscriber, or a group of subscribers.  A publisher is
      able to securely dispatch updates to specific targets.  Using an
      HTTP [RFC7230] or HTTPS [RFC2818] URL to identify targets is

   *  Hub: A server that handles subscription requests and distributes
      the content to subscribers when the corresponding topics have been
      updated (a hub implementation is provided in this repository).
      Any hub MAY implement its own policies on who can use it.

2.  Discovery

   If the publisher is a server, it SHOULD advertise the URL of one or
   more hubs to the subscriber, allowing it to receive live updates when
   topics are updated.  If more than one hub URL is specified, it is
   RECOMMENDED that the publisher notifies each hub, so the subscriber
   MAY subscribe to one or more of them.

   The publisher SHOULD include at least one Link Header [RFC5988] with
   "rel=mercure" (a hub link header).  The target URL of these links
   MUST be a hub implementing the Mercure protocol.

   Note: this relation type has not been registered yet [RFC5988].  In
   the meantime, the relation type "" MAY be used

   The publisher MAY provide the following target attributes in the Link

   *  "last-event-id": the globally unique identifier of the last event
      dispatched by the publisher at the time of the generation of this
      resource.  If provided, it MUST be passed to the hub through a
      query parameter called "Last-Event-ID" and will be used to ensure
      that possible updates having been made during between the resource
      generation time and the connection to the hub are not lost.  See
      section #Re-Connection-and-State-Reconciliation.  If this
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