Abstract: An instance of a consensus protocol in initiated by a processor initiating an application program interface to submit a value and obtaining the value. The processor sends a message including the value to one or more hardware components communicatively coupled to the processor. Logic in the hardware components obtains the message and appends the message with a sequence number, where the sequence number identifies the instance. Logic in the hardware accepts the value and supplies the value to the processor. The processor replicates the value for the instance and returns the value to the application via a callback.

Abstract: An instance of a consensus protocol in initiated by a processor initiating an application program interface to submit a value and obtaining the value. The processor sends a message including the value to one or more hardware components communicatively coupled to the processor. Logic in the hardware components obtains the message and appends the message with a sequence number, where the sequence number identifies the instance. Logic in the hardware accepts the value and supplies the value to the processor. The processor replicates the value for the instance and returns the value to the application via a callback.

Abstract: A method of validating an e-ticket includes the step of sending the e-ticket from an initial receiving server Si to a plurality of servers including Si. Each server returns an answer indicative of whether that server previously answered an inquiry for the e-ticket. A conflict mode of validation is selected if at least one selected server of a majority of servers answered a previous inquiry for the e-ticket. A conflict-free mode of validation is selected if none of the majority of servers has answered any previous inquiry for the e-ticket.

Abstract: A method and distributed computing system for validation of service requests includes determining in first and second processes that a request for service has not been previously validated; transmitting from the first and second processes messages having information indicative of the transmitting from the first or second process and the request for service; storing the information in the first and second processes; and accepting the request for service in the first or second process after the message is transmitted and message related information is different from the information stored in the respective first or second process.

Abstract: A method for ensuring consistent message reception among a plurality of nodes in a distributed system includes the step of causing nodes with outgoing messages to send the messages to all of the nodes. Each of the nodes then re-sends whatever messages it has received to all of the nodes after each of the nodes has received at least one message. The sequence of received messages in each of the nodes is then determined. If the sequence is not the same for all of the nodes, then each of the nodes re-sends what it has received until each node receives the same sequence of messages. A distributed system with a weak atomic broadcast module in each node to ensure consistent message reception while the nodes operate asynchronously is also described.

Abstract: A distributed data center system protocol is provided which includes providing a client having a failure detector, a primary data center, and a backup data center operatively interconnected. A transaction operation is provided from the client to the primary database server in the primary data center and the backup database server for execution. If the client detects a failure or suspects a failure of the primary database server, the transaction operation is provided to the backup database server, which becomes the new primary database server. The database server executing the transaction operation returns the executed transaction operation to the client. If the primary data center suffers a disaster, the backup data center takes over control.

Abstract: A hierarchical method is provided for fault tolerance in a distributed computer system. A plurality of data centers is provided having a plurality of objects in each of the plurality of data centers. A local sub-protocol is used for dissemination of messages within a data center in the plurality of data centers and the local sub-protocol is activated from another data center of the plurality of data centers in a single round-trip message in the absence of faults.

Abstract: Methods of processing transactions in a multi-tier network of at least one database client and a plurality of database servers including a primary and a backup database server are described. One method includes the step of concurrently executing a plurality of transactions including a selected transaction on a first database server during an epoch exclusively identifying the first database server as a primary. The selected transaction is committed on the first database server in response to a commit request, if the commit request is encountered before the epoch is changed. The selected transaction is broadcast to a second database server for non-concurrent execution. The selected transaction is committed on the second database server if execution is completed and the epoch has not changed.

Abstract: A method for ensuring consistent message reception among a plurality of nodes in a distributed system includes the step of causing nodes with outgoing messages to send the messages to all of the nodes. Each of the nodes then re-sends whatever messages it has received to all of the nodes after each of the nodes has received at least one message. The sequence of received messages in each of the nodes is then determined. If the sequence is not the same for all of the nodes, then each of the nodes re-sends what it has received until each node receives the same sequence of messages. A distributed system with a weak atomic broadcast module in each node to ensure consistent message reception while the nodes operate asynchronously is also described.

Abstract: A method and distributed computing system for validation of service requests includes determining in first and second processes that a request for service has not been previously validated; transmitting from the first and second processes messages having information indicative of the transmitting from the first or second process and the request for service; storing the information in the first and second processes; and accepting the request for service in the first or second process after the message is transmitted and message related information is different from the information stored in the respective first or second process.

Abstract: A distributed data center system protocol is provided which includes providing a client having a failure detector, a primary data center, and a backup data center operatively interconnected. A transaction operation is provided from the client to the primary database server in the primary data center and the backup database server for execution. If the client detects a failure or suspects a failure of the primary database server, the transaction operation is provided to the backup database server, which becomes the new primary database server. The database server executing the transaction operation returns the executed transaction operation to the client. If the primary data center suffers a disaster, the backup data center takes over control.

Abstract: A hierarchical method is provided for fault tolerance in a distributed computer system. A plurality of data centers is provided having a plurality of objects in each of the plurality of data centers. A local sub-protocol is used for dissemination of messages within a data center in the plurality of data centers and the local sub-protocol is activated from another data center of the plurality of data centers in a single round-trip message in the absence of faults.

Abstract: A method of validating an e-ticket includes the step of sending the e-ticket from an initial receiving server Si to a plurality of servers including Si. Each server returns an answer indicative of whether that server previously answered an inquiry for the e-ticket. A conflict mode of validation is selected if at least one selected server of a majority of servers answered a previous inquiry for the e-ticket. A conflict-free mode of validation is selected if none of the majority of servers has answered any previous inquiry for the e-ticket.

Abstract: Methods of processing transactions in a multi-tier network of at least one database client and a plurality of database servers including a primary and a backup database server are described. One method includes the step of concurrently executing a plurality of transactions including a selected transaction on a first database server during an epoch exclusively identifying the first database server as a primary. The selected transaction is committed on the first database server in response to a commit request, if the commit request is encountered before the epoch is changed. The selected transaction is broadcast to a second database server for non-concurrent execution. The selected transaction is committed on the second database server if execution is completed and the epoch has not changed.