Transferring messages between nodes in a network

• US 5,167,035 A
• Filed: 02/13/1992
• Issued: 11/24/1992
• Est. Priority Date: 09/08/1988
• Status: Expired due to Fees

• Current Assignee: Digital Equipment Corporation (HP Inc.)
• Original Assignee: Digital Equipment Corporation (HP Inc.)
• Inventors: Mann, Bruce E., Saether, Christian D., Wells, Philip J.
• Primary Examiner(s): Chan, Eddie P.
• Application Number:
  US07/836,197
• Time in Patent Office: 285 Days
• Field of Search: 395/200, 395/800, 395/575, 364/DIG. 1, 370/32, 370/60, 370/85.1, 370/94.1, 340/825.06, 340/825.3, 340/825.53, 375/121, 371/33
• US Class Current: 714/4.1
• CPC Class Codes: H04L 69/00 Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass networks security protocols H04L9/40; wireless communication networks H04W

Abstract

A message transfer arrangement includes a client node and a server node interconnected by a data link. The client node sequentially receives requests from user applications and generates, in response to each request, command messages for transmission by the interface. Each command message includes a command, a transmit slot identifier identifying the request in the sequence of requests received by the request receiver, and a transmit sequence identifier identifying the channel message in the sequence of command relating to the request. The selection of whether to transmit a command message related to one request or to a subsequent request is based on a received slot identifier and a received sequence identifier in a response message. The server node receives command messages from, and transmits response messages to, the client node over the data link. It selectively executes the command contained in each command message and generates, in response thereto, a response message including a response slot identifier and response sequence identifier corresponding to the commanmd slot identifier and command sequence identifier. The determination of whether to execute a command in a command message is based on the command slot identifier and command sequence identifier of the received command message and the command slot identifier and command sequence identifier of the command message containing the previously executed command.

Claims

1. A system that includes a client node and a server node for exchanging messages over a communication link, comprising

said client node including

a message generator for generating command messages and iteratively transmitting said command messages to said server node on said communication link each of said command messages including a sequence number that identifies said command message,

a receiver for receiving corresponding response messages from said server node on said communication link, and

said message generator including means for retransmitting another iteration of each said command message unless said receiver receives a response message that corresponds to said command message within a predetermined time interval, said message generator including means for changing the sequence number of the retransmitted command message to indicate that said retransmitted command message is another iteration of said command message,

said server node including

a processor for executing said command messages received from said client node via said communication link and generating said corresponding response messages, each said response message including a sequence number that corresponds to the sequence number of the iteration of the command message to which the response message corresponds,

said receiver comprising means for comparing the sequence number included in each received response message with the sequence number included in a most recently transmitted command message, and determining to discard said response message unless said comparison indicates that said response message corresponds to the most recently transmitted iteration of said command message.

2. The system of claim 1 wherein said means for comparing determines to utilize said response message if said sequence number included in said received response message matches said sequence number of said most recently transmitted iteration of said command message.

3. The system of claim 2 wherein said command messages and said response messages relate to requests made by a user of said client node, each command message identifying said related request,

said means for comparing determining to utilize a response message related to one of said requests if said sequence number of the response message matches the sequence number of the most recently transmitted command message related to said request.

4. The system of claim 1 wherein causing each of said command messages to be iteratively transmitted until said receiver receives a response message corresponding thereto from said server node, and for incrementing said sequence number of said command message in each iteration, and

said means for comparing determining to utilize said response message if said sequence numbers match.

5. The system of claim 4 wherein said controller includes a timer for determining a time interval between said iterative transmissions of said command message, said controller transmitting an iteration of said command message unless said receiver receives a response message having said matching sequence number within said time interval.

6. The system of claim 5 wherein said processor includes

a response timer for determining if a response to one of said command messages will require longer than said time interval, and

a resynchronizer responsive to said response timer for transmitting a resynchronization response message that includes the sequence number of said command message to said client node to cause said controller to extend said time interval to temporarily prevent transmission of another iteration of said command message.

7. The system of claim 4 wherein each one of said command messages includes a field that identifies a command for execution by said processor to produce a result, at least some of said commands having a characteristic that iterative execution thereof does not change said result.

8. The system of claim 7 wherein at least some of said series of command messages include commands execution of which are commutative with execution of commands of other command messages of said series.

9. The system of claim 1 wherein said client node is adapted to receive multiple requests from a user, said message generator generating said series of command messages in response to said requests, each said command message being related to one of said requests and including:

a request field that identifies said related request; and

a sequence field that identifies said sequence number of said command message,

said message generator comprising a controller for causing each of said command messages for each one of said requests to be iteratively transmitted until said receiver receives a response message corresponding to said request from said server node, said controller incrementing said sequence number in said sequence field in each iteration.

10. The system of claim 9 wherein said processor includes in each said response message:

a request field that identifies the request to which the corresponding command message is related; and

a sequence field that identifies the sequence number of said command message;

said means for comparing relating each said response message to one of said requests based on the request field thereof, and for comparing the sequence number identified by said sequence field with the sequence number of the previously transmitted command message for said request, said means for comparing determining to utilize said response message if said sequence numbers match.

11. The system of claim 10 wherein at least some of said response messages comprise a plurality of message segments,

said processor additionally including in each response message segment a segment field that identifies said message segment in said plurality of message segments,

said means for comparing monitoring said message segment field of received response message segments as a basis for determining whether a complete response message has been received.

12. A system that includes a client node and a server node for exchanging messages over a communication link comprising

said client node including

a message generator for generating command messages and iteratively transmitting said command messages to said server node on said communication link, each of said command messages including a sequence number that identifies said command message,

a receiver for receiving corresponding response messages from said server node on said communication link, and

said message generator including means for retransmitting another iteration of each said command message unless said receiver receives a response message that corresponds to said command message within a predetermined time interval, said message generator including means for changing the sequence number of the retransmitted command message to indicate that said retransmitted command message is another iteration of said command message,

said server node including

a processor for executing said command messages received form said client node via said communication link and generating said corresponding response messages, each said response message including a sequence number that corresponds to the sequence number of the iteration of the command message to which the response message corresponds, and

an execution enabler for comparing the sequence number included in each command messages received by said server node with the sequence number included in a command message previously processed by said processor, and selectively enabling said processor to execute said command message when said comparison of said sequence number indicates that said command message received by said server node is not a previous iteration of said command message previously processed by said processor.

13. The system of claim 12 wherein

said message generator comprises a controller for causing each of said command messages to be iteratively transmitted until said receiver receives a response message corresponding thereto from said server node, and for incrementing said sequence number of said command message in each iteration, and

said execution enabler enabling said processor to execute said received command message if said sequence number of said received command message is greater than the sequence number of said most recent iteration.

14. The system of claim 13 wherein said execution enabler determines to execute said received command message if the sequence number of said received command message is within a predetermined range of sequence numbers greater than the sequence number of said previously executed command message.

15. The system of claim 13 wherein said controller includes a timer for determining a time interval between said iterative transmissions of said command message, said controller transmitting an iteration of said command message unless said receiver receives a response message having said matching sequence number within said time interval, and

said processor includes a response timer for determining if a response to one of said command messages will require longer than said time interval, and a resynchronizer responsive to said response timer for transmitting a resynchronization response message that includes the sequence number of said command message to said client node to cause said controller to extend said time interval to temporarily prevent transmission of another iteration of said command message.

16. The system of claim 12 wherein said command messages relate to requests made by a user of said client node, each command message identifying said related request, said message generator incrementing the sequence numbers of successive command messages for each request, and

said execution enabler determining to utilize said received command message if said sequence number of said received command message is greater than the sequence number of said most recently executed command message.

17. The system of claim 12 wherein said client node is adapted to receive multiple requests from a user, said message generator generating said series of command messages in response to said requests, each said command message being related to one of said requests and including:

a request field that identifies said related request; and

a sequence field that identifies said sequence number of said command message,

said message generator comprising a controller for causing, each of said command messages for each one of said requests to be iteratively transmitted until said receiver receives a response message corresponding to said request from said serve node, said controller incrementing said sequence number in said sequence field in each iteration.

18. The system of claim 17 wherein said execution enabler compares the sequence number identified by said request field with the sequence number of the command message for said request that has most recently been executed by said processor, and determines to utilize said received command message if said sequence number of said received command message is greater than the sequence number of said most recently executed command message.

19. The system of claim 18 wherein said controller increments said sequence number over a predetermined range, said execution enabler determining to utilize said received command message if said sequence number of said received command message is greater than the sequence number of said most recently executed command message by up to a predetermined amount within said range.

20. The system of claim 19 wherein at least some of said command messages comprise a plurality of message segments and include a segment field that identifies each message segment in said plurality of message segments,

said execution enabler monitors said message segment field of each received command message segment as a basis for determining whether a complete command message has been received.

21. The system of claim 12 wherein each one of said command messages includes a field that identifies a command for execution by said processor to produce a result, at least some of said commands having a characteristic that iterative execution thereof does not change said result.

22. The system of claim 21 wherein at least some of said series of command messages include commands execution of which are commutative with execution of commands of other command messages of said series.

23. A system that includes a client node and a server node for exchanging messages over a communication link, comprising

said client node including

a message generator for generating command messages and iteratively transmitting said command messages to said server node on said communication link, each of said command messages including a sequence number that identifies said command message,

a receiver for receiving corresponding response messages from said server node on said communication link, and

said message generator including means for retransmitting another iteration of each said command message unless said receiver receives a response message that corresponds to said command message within a predetermined time interval, said message generator including means for changing the sequence number of the retransmitted command message to indicate that said retransmitted command message is another iteration of said command message,

said server node including

a processor for executing said command messages received from said client node via said communication link and generating said corresponding response messages, each said response message including a sequence number that corresponds to the sequence number of the iteration of the command message to which the response message corresponds, and

an execution enabler for comparing the sequence number included in each command message received by said server node with the sequence number included in a command message previously processed by said processor, and selectively enabling said processor to execute said command message when said comparison of said sequence numbers indicates that said command message received by said server node is not a previous iteration of said command message previously processed by said processor,

said receiver comprising means for comparing the sequence number included in each received response message with the sequence number included in a most recently transmitted command message, and determining to discard said response message unless said comparison indicates that said response message corresponds to the most recently transmitted iteration of said command message.

24. The system of claim 23 wherein said communication link includes a plurality of physical connections between said client node and said server node,

said client node further comprising an interface for transmitting different ones of said series of command messages to said server node over different ones of said physical connections, and receiving different ones of said response messages from said server node over different ones of said physical connections, and

said server node further comprising an interface for receiving said different command messages over said physical connections, and for transmitting said different response messages over said different physical connections.

25. The system of claim 23 further comprising a plurality of said client nodes and a plurality of said server nodes, the message generator of each one of said client does including in each said command message a destination field that identifies the server node to which said command message is being transmitted.

26. The system of claim 25 wherein said one of said server nodes is adapted to provide at least one data processing service for users of said client nodes,

each one of said server nodes further comprising a service message generator for broadcasting to said client nodes over said communication link a service message that identifies the at least one service provided by said server node,

each one of said message generators of said client nodes determining contents of said destination field based at least in part on the service messages from said server nodes.

27. The system of claim 23 wherein each one of said command messages includes a field that identifies a command for execution by said processor to produce a result, at least some of said commands having a characteristic that iterative execution thereof does not change said result.

28. The system of claim 27 wherein at least some of said series of command messages include commands execution of which are commutative with execution of commands of other command messages of said series.

29. A client node for use in a system in which one or more client nodes and at least one server node exchange messages over a communication link, said client node including

a message generator for generating command messages and iteratively transmitting said command messages on said communication link, each of said command messages including a sequence number that identifies said command message,

said message generator including means for retransmitting another iteration of each said command message when said client node does not receive a response message that corresponds to said command message within a predetermined time interval, said message generator including means for changing the sequence number of the retransmitted command message to indicate that said retransmitted command message is another iteration of said command message, and

a receiver for receiving corresponding response messages from said server node via said communication link, each said response message including a sequence number that corresponds to the sequence number of the iteration of the command message with which said response message corresponds,

said receiver comprising means for comparing the sequence number included in each received response message with the sequence number included in a most recently transmitted command message, and determining to discard said response message when said comparison indicates that said response message does not correspond to the most recently transmitted iteration of said command message.

30. A server node for use in a system in which at least one client node and one or more server nodes exchange messages over a communication link, said server node including

a processor for executing command messages received from said client node via said communication link, each of said command messages including a sequence number that identifies said command message, said client node including means for retransmitting an iteration of each said command message when said client node does not receive a response message from said server node that corresponds to said command message within a predetermined time interval, and means for changing the sequence number of the retransmitted command message to indicate that said retransmitted command message is an iteration of said command message,

said processor generating corresponding response messages and transmitting said response messages to said client node via said communication link, and including in each said response message a sequence number that corresponds to the sequence number of the iteration of the command message to which said response message corresponds, and

an execution enabler for comparing the sequence number included in each command message received by said server node with the sequence number included in a command message previously processed by said processor, and selectively enabling said processor to execute said command message when said comparison of said sequence numbers indicates that said command message received by said server node is not a previously iteration of said command message previously processed by said processor.

31. A method of exchanging messages between a client node and a server node over a communication link, comprising

said client node;

(1) generating command messages and iteratively transmitting said command messages to said server node on said communication link, each of said command messages including a sequence number that identifies said command message, (2) receiving corresponding response messages from said server node on said communication link, and (3) retransmitting another iteration of each said command message when said client node receives a response message that does not correspond to said command message within a predetermined tim interval, said client node changing the sequence number of the retransmitted command message to indicate that said retransmitted command message is another iteration of said command message,

said server node processing said command messages received from said client node via said communication link and generating said corresponding response messages, each said response message including a sequence number that corresponds to the sequence number of the iteration of the command message to which the response message corresponds, and

said client node comparing the sequence number included in each received response message with the sequence number included in a most recently transmitted command message, and determining to discard said response message when said comparison indicates that said response messages does not correspond to the most recently transmitted iteration of said command message.

32. The method of claim 31 wherein said step of determining includes utilizing said response message if said sequence numbers match.

33. The method of claim 32 wherein said command messages and said response messages relate to requests made by a user of said client node, each command message identifying said related request,

said step of determining including utilizing a response message related to one of said requests if said sequence number of the response message matches the sequence number of the most recently transmitted command message related to said request.

34. The method of claim 31 further comprising

said client node incrementing said sequence number of said command message in each iteration, and

said step of determining comprises utilizing said response message if said sequence numbers match.

35. The method of claim 34 further comprising transmitting an iteration of said command message unless said client node receives a response message having said matching sequence number within a predetermined time interval.

36. The method of claim 35 further comprising said server node determining if a response to one of said command messages will require longer than said time interval, and, if so, transmitting a resynchronization response message that includes the sequence number of said command message to said client node to cause said client node to extend said time interval to temporarily prevent transmission of another iteration of said command message.

37. The method of claim 34 wherein each one of said command messages includes a field that identifies a command for execution by said processor to produce a result, at least some of said commands having a characteristic that iterative execution thereof does not change said result.

38. The method of claim 37 wherein at least some of said series of command messages include commands execution of which are commutative with execution of commands of other command messages of said series.

39. The method of claim 31 wherein said client node receives multiple requests from a user and generates said series of command messages in response to said requests, each said command message being related to one of said requests and including:

a request field that identifies said related request; and

a sequence field that identifies said sequence number of said command message,

said client node iteratively transmitting each of said command messages for each one of said requests until said client node receives a response message corresponding to said request from said server node, and incrementing said sequence number in said sequence field in each iteration.

40. The method of claim 39 wherein said server node includes in each said response message:

a request field that identifies that the request to which the corresponding command message is related; and

a sequence field that identifies the sequence number of said command message,

said client node related each said response message to one of said requests based on the request field thereof, comparing the sequence number identified by said sequence field with the sequence number of the previously transmitted command message for said request, and determining to utilize said response message if said sequence numbers match.

41. The method of claim 40 wherein at least some of said response messages comprise a plurality of message segments, and further comprising

said server node including in each response message segment a segment field that identifies said message segment in said plurality of message segments, and

said client node monitoring said message segment field of received response message segments as a basis for determining whether a complete response message has been received.

42. A method of exchanging messages between a client node and a server node over a communication link, comprising

said client node:

(1) generating command messages and iteratively transmitting said command messages to said server node on said communication link, each of said command messages including a sequence number that identifies aid command message, (2) receiving corresponding response messages from said server node on said communication link, and (3) retransmitting another iteration of each said command message when said client node does not receive a response message that corresponds to said command message within a predetermined time interval, said client node changing the sequence number of the retransmitted command message to indicate that said retransmitted command message is another iteration of said command message,

said server node processing said command messages received from said client node via said communication link and generating said corresponding response messages, each said response message including a sequence number that corresponds to the sequence number of the iteration of the command message to which the response message corresponds, and

said server node comparing the sequence number included in each command message received by said server node with the sequence number included in a command message previously processed by said processor, and selectively enabling said processing of each said command message when said comparison of said sequence numbers indicates that said command message received by said server node is not a previous iteration of said command message previously processed by said processor.

43. The method of claim 42 further comprising

said client node incrementing said sequence number of said command message in each iteration, and

said serve node utilizing said received command message if said sequence number of said received command message is greater than the sequence number of said most recent iteration.

44. The method of claim 43 further comprising determining to execute said received command message if the sequence number of said received command message is within a predetermined range of sequence numbers greater than the sequence number of said previously executed command message.

45. The method of claim 43 further comprising

said client node transmitting an iteration of said command message unless said client node receives a response message having said matching sequence number with in a predetermined time interval, and

said server node determining if a response to one of said command messages will require longer than said time interval, and, if so, transmitting a resynchronization response message that includes the sequence number of said command message to cause said client node to extend said time interval to temporarily prevent transmission of another iteration of said command message.

46. The method of claim 42 wherein said command messages relate to requests made by a user of said client node, each command message identifying said related request, and further comprising

said client node incrementing the sequence numbers of successive command messages for each request, and

said server node comparing the sequence number of a received command message related to one of said requests t the sequence number of the command message for said request that has most recently been executed, and utilizing said received command message if said sequence number of said received command message is greater than the sequence number of said most recently executed command message.

47. The method of claim 42 wherein said client node receives multiple requests from a user and generates said series of command messages in response to said requests, each said command message being related to one of said request and including:

a request field that identifies said related request; and

a sequence field that identifies said sequence number of said command message,

said client node iteratively transmitting each of said command messages for each one of said requests until said client node receives a response message corresponding to said request from said server node, and incrementing said sequence number in said sequence field in each iteration.

48. The method of claim 47 further comprising the steps of

said server node relating each received command message to one of said requests based on the request field thereof, comparing the sequence number identified by said request field with the sequence number of the command message for said request that has most recently been executed, and utilizing said received command message if said sequence number of said received command message is greater than the sequence number of said most recently executed command message.

49. The method of claim 48 wherein said client node increments said sequence number over a predetermined range, said serve node determining to utilize said received command message if said sequence number of said received command message is greater than the sequence number of said most recently executed command message by up to a predetermined amount within said range.

50. The method of claim 49 wherein at least some of said command messages comprise a plurality of message segments and include a segment field that identifies each message segment in said plurality of message segments, and further comprising

said server node monitoring said message segment field of each received command message segment as a basis for determining whether a complete command message has been received.

51. The method of claim 42 wherein each one of said command messages includes a field that identifies a command for execution by said processor to produce a result, at least some of said commands having a characteristic that iterative execution thereof does not change said result.

52. The method of claim 51 wherein at least some of said series of command messages include commands execution of which are commutative with execution of commands of other command messages of said series.

53. A method of exchanging messages between a client node and a server node over a communication link, comprising

said client node;

(1) generating command messages and iteratively transmitting said command messages to said server node on said communication link, each of said command messages including a sequence number that identifies said command message, (2) receiving corresponding response messages from said server node on said communication line, and (3) retransmitting another iteration of each said command message when said client node does not receive a response message that corresponds to said command message within a predetermined time interval, said client node changing the sequence number of the retransmitted command message to indicate that said retransmitted command message is another iteration of said command message,

said server node processing said command messages received from said client node via said communication link and generating said corresponding response messages, each said response message including a sequence number that corresponds to the sequence number of the iteration of the command message to which the response message corresponds,

said server node comparing the sequence number included in each command message received by said server node with the sequence number included in a command message previously processed by said processor, said selectively enabling said processing of each said command message when said comparison indicates that said command message received by said server node is not a previous iteration of said command message previously processed by said processor,

said client node comparing the sequence number included in each received response message with the sequence number included in a most recently transmitted command message, and determining to discard said responses message when said comparison indicates that said response message does not correspond to the most recently transmitted iteration of said command message.