US Patent 7706255 Communications apparatus with redundant switching or backpressure mechanism

A communications apparatus includes several functional modules for implementing an application, a pair of switch modules to provide redundant switching capability for transferring frames between the functional modules. Each functional module is connected to each switch module by a frame-based communication link. A redundancy logic unit at each functional module inserts sequence numbers into outgoing frames, replicates the outgoing frames for forwarding to each of said switch modules, and monitors incoming frames from each of the switch modules to select frames for forwarding to an application based on the sequence numbers. In this way, redundancy is maintained at all times, while duplicate frames are eliminated at the receiving module.