Patent ID: 7975173

Claim:
A method of providing fault tolerance to a primary instance, the method comprising: receiving a copy of a first input transmitted to the primary instance followed by a copy of a second input transmitted to the primary instance, wherein the order in which the first and second inputs were transmitted to the primary instance may be different than the order in which the copies of the first and second inputs are received; waiting, in response to the receiving of the copies of the first and second inputs, for the primary instance to transmit a next result; forwarding the copy of the first input to a backup instance operative to generate a first backup result based on the forwarded copy of the first input upon the transmission of the next result when the next result includes a first primary result generated by the primary instance based on the first input; forwarding the copy of the second input to the backup instance operative to generate a second backup result based on the forwarded copy of the second input upon the transmission of the next result when the next result includes a second primary result generated by the primary instance based on the second input.