thanks Peter. interplanetary means: long delays and disruptions. Earth to Mars one way delay = 4-22 minutes. So a messaging/protocol should not be "interactive" by having all kind of updates which are not real messages. Moreover, the transport has to be compatible. TCP won't work with this use case, so we are using a space profiled QUIC. So we would need XMPP over QUIC, which AFAIK is not active.
Possibly worth noting that XMPP already operates (quite nicely, even) over comparatively high delay networks in various non-internet settings; it might be very useful to look into this and improve it further based on this work. After all, if we can operate better on 4-22 minute delays, then operating over 30s latencies will be improved, too.
Dave.