Patent ID: 7660236

Claim:
An automatic protection switching system comprising: a local node for transmitting a first data stream to be protected; and a redundant protection pair of nodes comprising: a first remote node coupled to said local node, said first remote node receiving said first data stream from said local node, and a second remote node coupled to said local node and said first remote node, said second remote node receiving said first data stream from said local node; a first control link that sends periodic liveliness messages from the first remote node to the second remote node; a second control link that sends periodic liveliness messages from the second remote node to the first remote node; a first data link that couples the local node to the first remote node; and a second data link that couples the local node to the second remote node; wherein each periodic liveliness message sent on the first control link to said second remote node comprises an I Heard You (IHY) message, the IHY message indicating whether the first remote node received within a duration of a single liveliness message cycle a previously transmitted periodic liveliness message from the second remote node on the second control link, and wherein a protection switching behavior of the second remote node is triggered within substantially a single liveliness message cycle, depends upon the IHY message sent to the second remote node, and prevents duplication of data on the first data link and the second data link by deactivating one of the data links.