Method and apparatus for transmitting data to a node in a distributed data processing system

• US 6,570,853 B1
• Filed: 10/04/2000
• Issued: 05/27/2003
• Est. Priority Date: 12/18/1998
• Status: Expired due to Term

• Current Assignee: NetApp, Inc.
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Johnson, Stephen M., Adams, John M., Hoglund, Timothy E., Weber, David M., Reber, Mark A.
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): NGUYEN, HANH N
• Application Number:
  US09/679,506
• Time in Patent Office: 965 Days
• Field of Search: 370/400, 370/428, 370/429, 370/235, 370/231, 370/230, 370/412, 370/413, 370/417, 370/236, 370/395, 370/410, 370/360, 370/395.2, 370/395.21, 370/236.1, 370/236.2, 370/411, 370/389, 370/392, 709/230-235
• US Class Current: 370/236
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/286 Time to live
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 47/39 Credit based
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]

Abstract

A method and apparatus in a source node for transmitting data to a target node. Responsive to a request to transmit data to the target node, a determination is made as to whether a selected period of time has passed without data transmitted from the source node being received by the target node. Responsive to detecting the selected period of time has passed without data transmitted from the source node being received by the target node, a determination is made as to whether space is available in the target node to receive the data. Responsive to a determination that space is unavailable in the target node, generating an indication that the target node is blocked is generated.

Claims

1. A method for transmitting data from a source to a target node, wherein the target node has a buffer, the method comprising:

detecting a request to transmit data from the source node to the target node;

responsive to detecting the request to transmit data to the target node, activating a timer;

responsive to detecting an expiration of the timer, determining whether the buffer is available to receive the data, and

responsive to determining whether the buffer is available, generating a buffer status signal.

2. The method of claim 1, wherein a buffer to buffer credit is used to transmit data and wherein the step of determining whether the buffer is available comprises:

responsive to detecting an expiration of the timer, determining whether buffer to buffer credit is present in the target node.

3. The method of claim 2, wherein the status signal is a blocked signal when a determination is made that the buffer is unavailable.

4. The method of claim 1 further comprising:

responsive to the buffer status signal being a blocked status signal, halting attempts to transmit data to the target node.

5. The method of claim 4, wherein the data is a first set of data and further comprising:

responsive to the blocked status signal, loading a second set of data into the memory for transmission to another target node, while retaining the first set of data in the memory.

6. The method of claim 1, wherein the request to transmit data comprises a request to send a frame of data to the target node.

7. The method of claim 1, wherein the source node is connected to the target node by a loop and wherein the request to transmit data comprises arbitrating for the loop.

8. The method of claim 1, wherein the source node is connected to the target node by a network.

9. The method of claim 1, wherein the source node is connected to the target node by a Fibre Channel fabric.

10. The method of claim 9, wherein the Fibre Channel fabric is an arbitrated loop.

11. The method of claim 9, wherein the Fibre Channel fabric is a switched fabric.

12. The method of claim 1, wherein the source node is a computer.

13. The method of claim 1, wherein the source node is an adapter.

14. A method for transmitting data from a source node to a target node, the method comprising:

responsive to detecting a request to transmit data to the target node, activating a timer;

responsive to detecting an expiration of the timer, determining whether space is available in the target node to receive the data; and

responsive to a determination that space is unavailable in the target node, generating an indication that the target node is blocked.

15. The method of claim 14, wherein the request to transmit data comprises a request to send a frame of data to the target node.

16. The method of claim 14, wherein the source node is connected to the target node by a loop and wherein the request to transmit data comprises arbitrating for the loop.

17. The method of claim 14, further comprising:

responsive to the indication, halting attempts to transmit data to the target node.

18. The method of claim 14, wherein a determination of determining whether space is available in the target node to receive the data is made by examining buffer to buffer credit from the target node.

19. A method in a source node for transmitting data to a target node, the method comprising:

detecting a request to transmit data from the source node to the target node;

responsive to detecting the request to transmit data to the target node, activating a timer;

monitoring the timer for an expiration of the timer;

responsive to detecting an expiration of the timer, determining whether a buffer to buffer credit is present in the target node; and

responsive to a determination that buffer to buffer credit is absent, generating a blocked signal.

20. An apparatus comprising:

a memory, wherein the memory is configured to hold data for transmission to target node;

a controller, wherein the controller controls transmission of data located in the memory to the target node;

an interface connected to the memory and configured to connection to a data channel,

wherein the interface has a plurality of modes of operation including;

a first mode of operation in which the interface monitors for a request to transmit data signal;

a second mode of operation, responsive to detecting a request to transmit data signal, in which the controller activates a timer and determines whether the timer expires;

a third mode of operation, responsive to detecting an expiration of the timer, determining whether space is available in the target node to receive the data; and

fourth mode of operation, responsive to a determination that space is unavailable in the target node, in which the controller generates an indication that the target node is blocked.

21. The apparatus of claim 20, wherein the memory is connected to the interface by a data framer, which creates frames from the data for the data transfer.

22. The method of claim 20, wherein the controller has a plurality of modes of operation including:

a first mode of operation in which the controller is idle and monitors for signals;

a second mode of operation, responsive to detecting a request to transmit data signal in the first mode of operation, in which the controller determines whether space is present in the memory and allocates a first buffer space in the memory for a first data transfer, loads a set of data corresponding the request into a buffer space in the memory, and begins the data transfer; and

a third mode of operation, responsive to generation of the blocked indication by the interface while a data transfer is occurring, in which the controller halts the data transfer, determines if another set of data is available for transfer and begins another data transfer using the another set of data.

23. The apparatus of claim 20, wherein other data is present in another buffer and wherein the controller further includes:

a fourth mode of operation, responsive to detecting a request to rescan in the first mode of operation, in which the controller selects the another buffer for transmission and begins transmission of the other data.

24. The apparatus of claim 20, wherein the data channel is a Fibre Channel arbitrated loop.

25. The apparatus of claim 20, wherein the data channel is a switched fabric.

26. A source node for transmitting data to a target node, wherein the target node has a buffer, the source node comprising:

detecting means for detecting a request to transmit data from the source node to the target node;

activating means, responsive to detecting the request to transmit data to the target node, for activating a timer;

determining means, responsive to detecting an expiration of the timer, for determining whether the buffer is available to receive the data; and

generating means, responsive to determining whether the buffer is available, for generating a buffer status signal.

27. The source node of claim 26, wherein a buffer to buffer credit is used to transmit data and wherein the determining means whether the buffer is available comprises:

determining means, responsive to detecting an expiration of the timer, for determining whether buffer to buffer credit is present in the target node.

28. The source node of claim 27, wherein the status signal is a blocked signal when a determination is made that the buffer is unavailable.

29. The source node of claim 26, further comprising:

halting means, responsive to the buffer status signal being a blocked status signal, for halting attempts to transmit data to the target node.

30. The source node of claim 29, wherein the data is a first set of data and further comprising:

loading means, responsive to the blocked status signal, for loading a second set of data into the memory for transmission to another target node, while retaining the first set of data in the memory.

31. The source node of claim 29, wherein the source node is a computer.

32. The source node of claim 29, wherein the source node is an adapter.

33. The source node of claim 26, wherein the request to transmit data comprises a request to send a frame of data to the target node.

34. The source node of claim 26, wherein the source node is connected to the target node by a loop and wherein the request to transmit data comprises arbitrating for the loop.

35. The source node of claim 26, wherein the source node is connected to the target node by a network.

36. The source node of claim 26, wherein the source node is connected to the target node by a Fibre Channel fabric.

37. The source node of claim 36, wherein the Fibre Channel fabric is an arbitrated loop.

38. The source node of claim 36, wherein the Fibre Channel fabric is a switched fabric.

39. A source node for transmitting data to a target node comprising

first determining means, responsive to detecting a request to transmit data to the target node, for activating a timer and detecting an expiration of the timer;

second determining means, responsive to detecting an expiration of the timer, for determining whether space is available in the target node to receive the data; and

generating means, responsive to a determination that space is unavailable in the target node, for generating an indication that the target node is blocked.

40. The source node of claim 39, wherein the request to transmit data comprises a request to send a frame of data to the target node.

41. The source node of claim 39, wherein the source node is connected to the target node by a loop and wherein the request to transmit data comprises arbitrating for the loop.

42. The source node of claim 39 further comprising:

halting means, responsive to the indication, for halting attempts to transmit data to the target node.

43. The source node of claim 39, wherein a determination of determining whether space is available in the target node to receive the data is made by examining buffer to buffer credit from the target node.

44. A source node comprising:

detecting means for detecting a request to transmit data from a source node to a target node;

activating means, responsive to detecting the request to transmit data to the target node, for activating a timer;

monitoring means for monitoring the timer for an expiration of the timer;

determining means, responsive to detecting an expiration of the timer, for determining whether a buffer to buffer credit is present in the target node; and

generating means, responsive to a determination that the buffer to buffer credit is absent, for generating a blocked signal.

45. A computer program product in a computer readable medium in a source node for transmitting data to a target node, wherein the target node has a buffer to buffer credit, the computer program product comprising:

first instructions for detecting a request to transmit data from the source node to a target node;

second instructions, responsive to detecting the request to transmit data to the target node, for activating a timer;

third instructions for monitoring the timer for an expiration of the timer;

fourth instructions, responsive to detecting an expiration of the timer, for determining whether buffer to buffer credit is present in the target node;

fifth instructions, responsive to a determination that buffer to buffer credit is absent, for generating a blocked signal.