Patent ID: 7061858
Filing Date: 2006-06-13
Classification: H04L

Abstract:
1. In an intermediate network device having at least one line card defining a plurality of ports for receiving and forwarding messages and two or more supervisors, each supervisor configured to run one or more applications to facilitate message handling by the network device, a method for continuing operation of at least one application despite a crash or failure, the method comprising the steps of: designating a first supervisor to be an active supervisor and a second supervisor to be a standby supervisor for the network device; executing the at least one application at the active supervisor; holding the at least one application at the standby supervisor in a dormant state; transmitting state information generated during execution of the at least one application from the active supervisor to the standby supervisor; storing the state information at the standby supervisor; in response to the standby supervisor detecting a crash or failure at the active supervisor, carrying on execution of the at least one application at the standby supervisor based upon at least some of the stored state information; generating a sequence number for use in instructing the at least one line card to change operating condition; sending the sequence number to the at least one line card with the instruction; storing the sequence number at the at least one line card; sending the sequence number to the standby supervisor; storing the sequence number at the standby supervisor; and in response to the standby supervisor detecting the crash or failure of the active supervisor, comparing the sequence number stored at the standby supervisor with the sequence number at the at least one line card.