System and method for transparent takeover of TCP connections between servers

• US 7,076,555 B1
• Filed: 01/23/2002
• Issued: 07/11/2006
• Est. Priority Date: 01/23/2002
• Status: Active Grant

• Current Assignee: Micro Focus Software, Inc. (Open Text Corporation)
• Original Assignee: Novell Incorporated (Open Text Corporation)
• Inventors: Mahdavi, Jamshid, Davis, Howard Rollin, Orman, Hilarie
• Primary Examiner(s): Follansbee, John
• Assistant Examiner(s): Lee, Philip C.
• Application Number:
  US10/055,865
• Time in Patent Office: 1,630 Days
• Field of Search: 714/4, 370/217, 364/187, 713/201, 709/227, 709/231
• US Class Current: 709/227
• CPC Class Codes: G06F 11/203 using migration
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1034 Reaction to server failures by a load balancer
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/163 In-band adaptation of TCP data exchange; In-band control procedures
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06

Abstract

A system and a method for transparent takeover (or failover) of a remote client TCP connection from a first server in a cluster of interconnected servers to a second server provides the storing of shared state information relative to the connection on each involved server and using of the shared state information to reestablish the connection on the second server. A message using a sequence number to refer to a previously transmitted data element (such as a byte) is sent by the second server and a received client acknowledgement (ACK) of that sequence number, or a higher one, is used to synchronize the server'"'"'s data packet transmission sequence number with the ACK-transmitted sequence number. If synchronization is successful, then the connection is restarted on the second server from the point of termination/failure on the first server.

Claims

1. A method for takeover of a Transport Control Protocol (TCP) connection by a second server from a first server comprising:

generating shared state information with respect to the connection for access by the first server and the second server, wherein the shared state information includes an identification of an application layer protocol being used for communication of an application;

comparing a received data byte sequence number from an acknowledgement byte received by the second server with a sequence number related to the shared state information;

recreating the connection within the second server based upon the compared sequence numbers;

performing a connection checkpoint with an application program interface (API) so as to communicate with each of a plurality of protocols in the first server and so as to cause each of the plurality of protocols to append relevant state information to a data block passed to each of the plurality of protocols with respect to the connection, and to thereby provide the relevant state information to the shared state information; and

relating, by the API, the compared sequence numbers in conjunction with the ready signal to a byte sequence number in an object referenced in the shared state information.

2. The method as set forth in claim 1 in which the relating includes resuming sending the data associated with an object over the restarted TCP connection.