Patent ID: 7599303

Claim:
A method of determining path availability comprising: providing an accumulator, the accumulator counting intermediate hops; populating a maximum number of hops, the maximum number of hops and accumulator initially having a common value; transmitting a message packet over a pseudowire, the pseudowire defined by a set of intermediate hops terminated by ultimate nodes, the message packet adapted to commence at any of the intermediate hops, the message packet including the accumulator and the maximum number of hops, the accumulator decrementing at each hop along a path to an ultimate node so as to provide a traversed number of incremental hops, the ultimate node responsive to the transmitted message packet with a return message having a number of return hops computable from the accumulator and the maximum number, such that the number of return hops can be decremented at each of the intermediate hops, wherein transmitting the message packet further comprises: sending the return message the number of return hops from at least one of the ultimate nodes and the intermediate hops, the accumulator and the maximum number of hops indicating the number of return hops back to the originating node; computing a difference between the traversed number of incremental hops and the maximum number of hops; setting the number of return hops in a return message to the computed difference; identifying when the number of return hops is reached by the return message, which includes (i) decrementing the set number of return hops for each hop traversed by the return message and (ii) concluding the originating node has been reached when the number of return hops decrements to zero, wherein the step of identifying further comprises: for each of the hops, appending time stamps, the time stamps differentiate processing time and transmission time for a packet at the respective hops; and observing incoming message traffic for the return message by identifying the return message having a return hop decremented to zero.