The receive-instantiation procedure is called from the receive procedure when a new peer is discovered. It initializes the peer variables and mobilizes the association. If the message is from a peer operating in client mode (3), the host mode is set to server mode (4); otherwise, it is set to symmetric passive mode (2). The authentication variables are used only if the authentication mechanism described in Appendix C is implemented. If implemented, only properly authenticated non-configured peers can become the synchronization source.