P2P connections happen in the context of a NetStream, which is connected to a NetConnection. for traditional client-server NetStreams, if the controlling NetConnection closes, the NetStreams must also close. for Flash Player 10, we wanted to maintain as much of the programming paradigm and semantics as possible for the new P2P connections. while it would have been technically possible to continue P2P NetStreams after the controlling NetConnection was closed, we felt that that behavior would have been too drastic a departure from the previously-understood operation of NetStreams and NetConnections, and would have complicated the programming model. additionally, properties of your connection, such as your peerID, belong to the NetConnection, and allowing the peerID to continue beyond the life of the NetConnection's connection to a server (and especially allowing the same peerID to be re-used if you connected to a new server or reconnected to the old one) could compromise the strong uniqueness property that peerIDs have.
for purposes of peer-to-peer connections, an RTMFP server such as Stratus acts as a kind of name service and UDP hole punch helper for NAT traversal. specifically, it translates a peerID to one or more IP address+port for all of your directly attached network interfaces (IPv4 and IPv6), your NAT-translated address, and (if configured) your TURN proxy address, and forwards introduction packets to a destination peer to cause it to send UDP traffic toward the source peer (UDP hole punching). the RTMFP source peer then tries all available paths (directly connected interfaces, translated address, TURN proxy address, and UDP punched-hole) in parallel to try to bring up the best possible P2P session.