Live Contracts relies on message brokers to share event chains between nodes. The message broker MUST use the AMQP 0-9-1 to communicate and SHOULD be available over a secured connection.
New events on a chain are pushes to all nodes designated by the participating identities. Nodes may also request an event chain for instance when a user of the node is invited on a chain.
A message broker allows for asynchronous and decoupled data transfer. With a protocols like HTTP, an unresponsive node could slow down other nodes. With a message broker, messages to an unreachable node may be delivered as a later time.
Nodes MAY have an HTTP REST API which can be used to interface with the event chain service. Other node SHOULD NOT use the REST API. It's only intended for client applications hosted by the owner of the node.