Should a client only have got a sequence number at file entries which the client modified by itself or should it be over all changes (including received ones)?
Is there some deduplication or do all clients tell each other one (once because later there is the delta index exchange) their whole index? Assuming a client assigns each received change a sequence number: Does he send this changes back to the sender with the new sequence number?
Every device sends information about every file / directory they have, with a locally assigned sequence number. So if you tell me about a new revision of a file, I’ll grab the pieces to get it somehow, then send an update for it sequenced by me.
Every device gets the full index from everyone else on first connect, then just the deltas.