The IETF is getting serious about interoperability among messaging services (this might have had something to do with it). The charter for the Messaging Layer Security Working Group (MLS) specifically excluded interoperability, though the group organized a draft that addressed the basic concepts that would allow MLS-compatible systems to federate. In early 2023, a new Working Group - More Instant Messaging Interoperability (MIMI) - was chartered to expand on the MLS federation work. Given IETF’s relatively long and somewhat checkered history with messaging, the Working Group’s charter included this reminder to itself:
Numerous prior attempts have been made to address messaging interoperability, including the IETF's extensive prior work on XMPP, SIP/SIMPLE, and their related messaging formats. The MIMI working group will draw lessons from these prior attempts, seek to avoid re-hashing old debates, and will focus on the minimal standards suite necessary to facilitate interoperability given the feature set of modern messaging applications.
Thus, its remit had some strict limits:
The More Instant Messaging Interoperability (MIMI) working group will specify the minimal set of mechanisms required to make modern Internet messaging services interoperable.
…minimum being the operative word. So, what’s in scope?
- messaging interoperability
- user discovery
- messaging content format
- (an appropriate) MLS profile
- message delivery service and transport mechanisms
- establishment of end-to-end cryptographic identity
- identifier naming conventions
Specifically out of scope are:
- metadata processing to manage spam and abuse
- interoperable mechanisms for group administration or moderation across systems
- extensions to the MLS protocol (if needed, requirements will be referred to the MLS working group or other relevant working groups in the security area)
- definition of completely new identity formats or protocols
- extensions to SIP, SDP, MSRP, or WebRTC
- development of anti-spam or anti-abuse algorithms
- oracle or look-up services that reveal the list of messaging services associated with a given user identity without the user’s permission
This being the first formal meeting after group charter, discussions are still at the stage where defining what in scope means is still open, as are the most basic tenets of the technical mechanisms to implement the required features. Grab your popcorn!