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Requirements of Interoperable Messaging

Document Type Active Internet-Draft (individual)
Author Travis Ralston
Last updated 2023-03-13
RFC stream (None)
Intended RFC status (None)
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
On agenda mimi at IETF-116
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IESG IESG state I-D Exists
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More Instant Messaging Interoperability                       T. Ralston
Internet-Draft                          The Foundation C.I.C.
Intended status: Informational                             13 March 2023
Expires: 14 September 2023

                Requirements of Interoperable Messaging


   This document describes a set of requirements for messaging services
   to interoperate.

   These requirements are independent of any particular protocol or
   messaging service, describing the set of features an interoperable
   messaging service should support.  Services should expect to go
   beyond the requirements listed here, as MIMI's future content format

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at
   ralston-mimi-messaging-requirements.html.  Status information for
   this document may be found at

   Discussion of this document takes place on the More Instant Messaging
   Interoperability Working Group mailing list (,
   which is archived at
   Subscribe at

   Source for this draft and an issue tracker can be found at

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   This Internet-Draft will expire on 14 September 2023.

Copyright Notice

   Copyright (c) 2023 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 Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Minimum Feature Set . . . . . . . . . . . . . . . . . . . . .   3
   3.  Maximum Feature Set . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Moderation and Personal Safety Functionality  . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   MIMI's charter seeks to establish an extensible set of messaging
   features which make use of a future content format published by MIMI.
   The charter also states that MIMI will use End-to-End Encryption
   (E2EE), and that the content format must support E2EE.

   This document describes a possible set of features that messaging
   services should support.  By extension, it also includes what MIMI
   should support in its future content format.  This document also
   explores extensibility by contrasting a minimum and maximum feature
   set for interoperability over MIMI.

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2.  Minimum Feature Set

   The following are the minimum features for an interoperable messaging
   service.  We consider group communication on the basis that 1:1
   communication can typically be modelled as a subset of group

   *  Encryption, as required by MIMI's charter, and all associated
      features (device tracking, etc).

   *  Reliable synchronisation of messages between messaging services,
      avoiding gaps.

   *  Text and rich text to represent nearly all features persisted to
      the conversation history.

   *  Ability to redact, remove, or delete a message, both as an
      individual and as a room moderator.

   *  Invite, kick, ban, and leave membership states within a

   *  Display names and avatars for users, to allow for personalization
      beyond their identifier or username.

   *  Direct messaging, or conversations of exactly 2 users.  The
      underlying protocol might choose to treat DMs no different from
      multi-user conversations, though messaging services might apply
      semantics to represent DMs usefully to users.

   *  Differentiation between users and their abilities.  For example,
      roles for Moderators, Admins, etc.

3.  Maximum Feature Set

   This list is not exhaustive, but outlines some examples for what the
   content format should be capable of supporting.  The features that
   messaging services currently support are:

   *  Names, topics/descriptions, and avatars for conversations for
      personalization.  Messaging services which don't support these
      aesthetic features would ignore them.

   *  Read receipts/indicators when others in the room have read the
      message.  If a messaging service doesn't support them, that
      service would not produce receipts and ignore received receipts.
      This is a safe failure mode for the feature.

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   *  Typing notifications when others in the room are writing a
      message.  Like read receipts, services have the same safe failure

   *  Presence or online state.  Like read receipts or typing
      notifications, presence has the same safe fallback mode.

   *  Ability to reliably synchronize visible conversation history
      between messaging services.

   *  Ability to port conversation history between messaging services.

   *  Images, videos, files, and audio in messages.  The content format
      would specify a fallback to (rich) text to support messaging
      services that are primarily text-based, such as by specifying a
      URL for users to click on to view the relevant media.

   *  Voice messages are semantically distinct from file transfers, but
      can be represented as audio file uploads with minor decoration
      metadata in the content format.

   *  Replies (also called "rich quoting") to reference specific
      messages or parts of messages.  A content format specification
      might define a fallback format to ensure messaging services that
      do not support replies can still render something which looks
      vaguely like a reply.

   *  Threads to organize a conversation.  A content format
      specification might define a fallback to Replies to keep a
      reader's context in tact when using a messaging service that
      doesn't support threads.

   *  1:1 VoIP.  Messaging services which don't support VoIP could be
      asked to say "a call is happening, but you can't join on this
      device" under a content format, or, if the conference protocol
      allows, a link for the user to click and join the call externally.

   *  Multi-party VoIP.

   *  Message editing.  A content format could define a fallback which
      references the edited message with a reply and using a difference
      syntax to highlight applicable changes.

   *  Reactions.  A content format might decide to provide a fallback by
      using replies to associate an emoji or textual reaction to a given
      message, or simply ignore it.

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   As implied above, a future content format document would be
   responsible for describing the exact details of how features fall
   back, if at all.  This document offers non-binding suggestions.

3.1.  Moderation and Personal Safety Functionality

   Currently out of scope for MIMI, moderation, anti-spam, etc
   functionality would likely be considered part of the "Maximum Feature
   Set".  A suitable protocol could support functionality such as
   ignoring or blocking individual users, "who can send invites to me"
   controls, and similar features without needing to have a specific
   content format specification necessarily.  For example, preventing
   invites from being received could simply be a rejected action over
   the delivery and transport layer.

4.  Security Considerations

   Security considerations for these features would be handled by other
   documents, such as a content format document.

5.  IANA Considerations

   This document has no IANA actions.

Author's Address

   Travis Ralston
   The Foundation C.I.C.

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