if an active router master control processor fails , a backup mcp switches over without interrupting peer network router connections , because all previously established connection parameters are replicated on both mcps . once the mcp programs line cards , the packet forwarding modules and embedded system function without further involvement of the mcp until the next programming update . messages flow through the backup mcp and then through the active mcp , which outputs messages through the backup mcp . thus the backup mcp captures state changes before and after the active mcp . both mcps maintain replicated queues in which they store replicated messages awaiting processing or retransmission . if acknowledgment of receiving a transmitted message is received from a destination peer router , that message is deleted from both mcps . if acknowledgment is not received within a predetermined interval , the stored message is retransmitted . message splicing prevents lost and partially transmitted messages during and after switchovers .