Transparent access to network attached devices

• US 6,601,101 B1
• Filed: 03/15/2000
• Issued: 07/29/2003
• Est. Priority Date: 03/15/2000
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Lee, David C., Wang, Peter S. S., OʼConnell, Anne G.
• Primary Examiner(s): Barot, Bharat
• Application Number:
  US09/525,965
• Time in Patent Office: 1,231 Days
• Field of Search: 709/202-203, 709/220, 709/223-224, 709/226-230, 709/236-240
• US Class Current: 709/227
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1008 based on parameters of servers, e.g. available memory or workload monitoring of computer activity G06F11/30
• CPC Class Codes: H04L 67/1017 based on a round robin mechanism
• CPC Class Codes: H04L 67/1034 Reaction to server failures by a load balancer
• CPC Class Codes: H04L 67/1036 Load balancing of requests to servers for services different from user content provisioning, e.g. load balancing across domain name servers

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.

Claims

1. A method for handing off TCP sessions in a system including a client in communication with a switch and two or more devices also in communication with the switch, the method comprising the steps of:

determining in a first device which is participating with a client in a TCP session that a different device should take over the TCP session;

identifying a second device which should take over the TCP session;

sending one or more hand-off messages from the first device to the second device;

receiving in the first device an acknowledgment from the second device;

reporting to the switch that the second device is participating with the client in the TCP session; and

acknowledging by the switch that the second device is participating with the client in the TCP session.

2. The method of claim 1, wherein the first and second devices are disk drives including file systems.

3. The method of claim 1, wherein the first and second devices are web servers.

4. The method of claim 1, wherein the first and second device are database servers.

5. The method of claim 1, wherein the first and second device are networked computing clusters.

6. The method of claim 1, wherein the first and second device are load balancing servers.

7. The method of claim 1, wherein the determining step includes evaluating the location of the data being processed in the TCP session.

8. The method of claim 1, wherein the determining step includes evaluating whether the data being returned to the client from a location other than the first device has reached a predetermined threshold.

9. The method of claim 1, wherein the determining step includes evaluating whether the data being returned to the client from another device has reached a predetermined threshold.

10. The method of claim 1, wherein the determining step includes evaluating the relative amount of data being returned to the client from the first device and one or more other devices coupled with the switch.

11. The method of claim 1, wherein the determining step includes evaluating the workload of the first device and one or more other devices coupled with the switch.

12. The method of claim 1, wherein the determining step includes evaluating the location of data being processed in more than one TCP session involving the first device.

13. The method of claim 1, wherein the first device is a disk drive equipped with a file system including a virtual root directory for the first device and other disk drive devices and the identifying step includes responding to a file request from the client by using the virtual root directory to identify the second device.

14. The method of claim 1, wherein the first device is a database server equipped with a table of database objects associated with the first device and other database server devices and the identifying step includes responding to a data object request from the client by using the table of database objects to identify the second device.

15. The method of claim 1, wherein the first device is a database server equipped with a table of transaction types associated with the first device and other database server devices and the identifying step includes responding to a transaction request from the client by using the table of transaction types to identify the second device.

16. The method of claim 1, wherein the first device is a database server equipped with a table of database subsystems associated with the first device and other database server devices and the identifying step includes responding to a request from the client by using the table of database subsystems to identify the second device.

17. The method of claim 1, wherein the first device is a load sharing server equipped with resources to monitor and analyze traffic through the switch and the identifying step includes responding to a request from the client by using the resources to monitor and analyze traffic to identify the second device.

18. The method of claim 1, wherein the first device is a load sharing server equipped with resources to receive availability messages from other load sharing devices and the identifying step includes responding to a request from the client by using the resources to receive availability messages to identify the second device.

19. The method of claim 1, wherein the first device is a load sharing server equipped with resources to interpret the requests from the client and the identifying step includes responding to a request from the client by using the resources to interpret the request from the client to identify the second device.

20. The method of claim 1, wherein a third device is equipped with a file system including a virtual root directory for the first device and other disk drive devices and the identifying step includes an inquiry from the first device and a response by the third device identifying the second device.

21. The method of claim 1, wherein a third device is equipped with a table of database objects associated with the first device and other database server devices and the identifying step includes an inquiry from the first device and a response by the third device identifying the second device.

22. The method of claim 1, wherein a third device is equipped with a table of transaction types associated with the first device and other database server devices and the identifying step includes an inquiry from the first device and a response by the third device identifying the second device.

23. The method of claim 1, wherein a third device is equipped with a table of database subsystems associated with the first device and other database server devices and the identifying step includes an inquiry from the first device and a response by the third device identifying the second device.

24. The method of claim 1, wherein a third device is equipped with resources to monitor and analyze traffic through the switch and the identifying step includes an inquiry from the first device and a response by the third device identifying the second device.

25. The method of claim 1, wherein a third device is equipped with resources to receive availability messages from load sharing devices and the identifying step includes an inquiry from the first device and a response by the third device identifying the second device.

26. The method of claim 1, wherein a third device is equipped with resources to interpret the requests from the client and the identifying step includes an inquiry from the first device and a response by the third device identifying the second device.

27. A method for handing off TCP sessions in a system including a client in communication with a switch and two or more devices also in communication with the switch, the method comprising the steps of:

sending one or more hand-off messages from the first device to the second device, wherein one of the handoff messages includes a kind field, a client port identification and a client IP address field;

receiving in the first device an acknowledgment from the second device;

reporting to the switch that the second device is participating with the client in the TCP session;

acknowledging by the switch that the second device is participating with the client in the TCP session.

28. A method according to claim 27 wherein the kind field, client port identification and client IP address fields appear in a TCP option.

29. A method according to claim 27 wherein the kind field, client port identification and client IP address fields appear in a IP option.

30. A method according to claim 27 wherein the kind field, client port identification and client IP address fields appear in a data field.

31. A method according to claim 27 wherein one of the handoff messages further includes a sequence number field and an acknowledgment number field.

32. A method for handing off TCP sessions in a system including a client in communication with a switch and two or more devices also in communication with the switch each having a TCP state machine, the method comprising the steps of:

sending one or more hand-off messages from a first device to a second device;

receiving in the first device an acknowledgment from the second device;

reporting to the switch that the second device is participating with the client in the TCP session;

acknowledging by the switch that the second device is participating with the client in the TCP session.

33. A method according to claim 32 wherein one or more handoff messages include TCP state information.

34. A method according to claim 32 wherein the first and second devices run an application program and one or more handoff messages include application program state information.

35. A method according to claim 32, wherein one of the handoff messages includes a Set flag, sending the Set flag causes the first device to transition from an Established state into a Set sent state and receipt of the Set flag causes the second device to transition from an Established state into a Set received state.

36. A method acccording to claim 32 wherein the handoff request messages indicate that the second device will send messages to the client and the first device will continue to receive messages from the client.

37. A method according to claim 32 wherein the handoff request messages specify that the second device will receive messages from the client and the first device will continue to send messages to the client.

38. A method according to claim 32 wherein the handoff request messages specify that the second device will send messages to the client and the first device will continue to receive messages from the client.

39. A method for handing off TCP sessions in a system including a client in communication with a switch and two or more devices also in communication with the switch each having a TCP state machine, the method comprising the steps of:

sending one or more hand-off preparation messages from a first device to one or more other devices;

receiving in the first device acknowledgments from the other devices;

determining in the first device to proceed with a handoff;

identifying a second device to receive the handoff from among the other devices which have acknowledged a handoff preparation message;

sending one or more hand-off messages from the first device to the second device;

receiving in the first device an acknowledgment from the second device;

reporting to the switch that the second device is participating with the client in the TCP session;

acknowledging by the switch that the second device is participating with the client in the TCP session.

40. A method according to claim 39 wherein one or more handoff messages include TCP state information.

41. A method according to claim 39 wherein the first and second devices run an application program and one or more handoff messages include application program state information.

42. A device capable of handing off TCP sessions including a client in communication with a switch and plurality of more devices also in communication with the switch, the device comprising:

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 of messages and to confirm that 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 the switch to reprogram its routing of messages;

wherein the a 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.

43. The device of claim 42, wherein the first and second devices are disk drives.

44. The device of claim 42, wherein the first and second devices are web servers.

45. The device of claim 42, wherein the first and second devices are database servers.

46. The method of claim 42, wherein the first and second device are networked computing clusters.

47. The method of claim 42, wherein the first and second device are load balancing servers.

48. The device of claim 42, wherein the logic to determine when to handoff a TCP session is based on evaluating the location of the data being processed in the TCP session.

49. The device of claim 42, wherein the logic to determine when to handoff a TCP session is based on evaluating whether the data being returned to the client from a location other than the first device has reached a predetermined threshold.

50. The device of claim 42, wherein the logic to determine when to handoff a TCP session is based on whether the data being returned to the client from an other device has reached a predetermined threshold.

51. The device of claim 42, wherein the logic to determine when to handoff a TCP session is based on evaluating the relative amount of data being returned to the client from the first device and one or more other devices in communication with the switch.

52. The device of claim 42, wherein the logic to determine when to handoff a TCP session is based on evaluating the workload of the first device and one or more other devices in communication with the switch.

53. The device of claim 42, wherein the logic to determine when to handoff a TCP session is based on evaluating the location of data being processed in more than one TCP session involving the first device.