Importance

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Abstract

The present invention relates to transparent access to network attached devices, such as network attached storage devices, Web servers or database servers. In particular, the present invention provides hand-off protocols that are transparent to a network client, with the advantage that physical devices can be added to, replaced on or removed from a network without reconfiguring network clients or applications running applications at levels above the network clients. One aspect the present invention is a method for handing off TCP sessions in a system including a client in communication with a switch and to or more devices. This method includes determining in the first device that a handoff should take place, identifying a second device to take over the session, sending handoff messages to and receiving an acknowledgment from the second device, and reporting the handoff to and receiving an acknowledgment from the switch. The devices applying this method may be disk drives, Web servers, database servers or any other device that benefits from being clustered. A device according to the present invention may comprise: a switch including logic for routing messages among a client and a plurality of devices and logic responsive to an instruction to reprogram its routing messages and to confirm the road reprogramming is complete; a first device including logic to determine when a TCP session should be handed off to another device, logic to instruct a second device to accept a handoff, and logic to instruct a switch to reprogram its routing of messages; wherein the second device is in communication with the switch and includes logic responsive to an instruction to accept a handoff and to confirm acceptance of the handoff. The first and second devices may be disk drives, Web servers, database servers or any other device that benefits from being clustered. Logic may be included to determine when to handoff a TCP session and to identify a second device to receive the handoff, consistent with the method of present invention.

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First Claim