Notification and verification of state changes in a data processing input/output system

• US 5,423,006 A
• Filed: 06/30/1993
• Issued: 06/06/1995
• Est. Priority Date: 08/31/1990
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Hoppe, Karl H., Brown, Paul J., Elliott, Joseph C., Sachs, Martin W., Lynch, Kenneth R.
• Primary Examiner(s): Harvey, Jack B.
• Assistant Examiner(s): Myers, Paul R.
• Application Number:
  US08/086,390
• Time in Patent Office: 706 Days
• Field of Search: 395/200, 370/58.1, 370/94.1, 370/94.3, 370/58.1, 370/94.1, 370/94.3, 370/60
• US Class Current: 710/19
• CPC Class Codes: G06F 13/4022 using switching circuits, e.g. switching matrix, connection or expansion network G06F13/4009 takes precedence

Abstract

A computer I/O system which includes a dynamic switch having a plurality of ports and a plurality of link-level facilities, with each link-level facility being attached to an individual one of the ports. Whenever the state of a port or its attached link-level facility is changed in such a way that the attached link-level facility'"'"'s ability to communicate with another link-level facility might be affected, this fact is recognized by a dynamic switch control unit which causes a state change notification (SCN) frame to be transmitted to all other link-level facilities which might be affected. The link-level facilities receiving such a state change notification then determine if any of the associations or potential associations with the link-level facility which caused the state change notification are affected.

Claims

1. In a computer I/O system including a plurality of link-level facilities and a dynamic switch having a plurality of ports, each link-level facility attached to an individual one of said ports, said dynamic switch for making point-to-point connections between any two of said ports such that communications may be established through said dynamic switch between any two link-level facilities connected to ports of the dynamic switch, each of said ports and link-level facilities being in one of several stats, some of said states affecting the ability of communication between link-level facilities, a state change notification mechanism comprising:

a dynamic-switch control unit connected to said dynamic switch, said dynamic-switch control unit having

a connection table means for storing a table of all the allowed connections between said link-level facilities

a state change initiative means for creating an initiative to report a state change of specific link-level facility on behalf of said specific link-level facility, and

a frame generator in aid dynamic switch for transmitting state change notification (SCN) frames responsive to said connection table means and said state change initiative means, one of said SCN frames being transmitted to each of said link-level facilities which has an allowed connection to said specific link-level facility in said connection table means, said frame generator comprising means for including within each of said SCN frames, an identification of said specific link-level facility on whose behalf the state change is being reported.

2. The state change notification mechanism of claim 1 wherein each link-level facility has one or more associations with other link-level facilities to which connections are allowed, each link-level facility further including

a receiver for receiving from said dynamic switch, a SCN frame containing said identification of said specific link-level facility,

association table means for storing a list of said associations, and

determining association means connected to said receiver and said association table means for determining that said identification of said specific link-level facility from said SCN frame received by said receiver is stored in said association table means.

3. The state change notification mechanism of claim 2 wherein each link-level facility includes a link-level frame generator for transmitting a SCN frame to said dynamic-switch, the SCN frame having a destination address which may be one of a target destination address to be passed through said dynamic switch to the link-level facility addressed by said target destination address or a to-whom-it-may-concern destination address, said dynamic-switch control unit being connected to said dynamic switch such that said dynamic-switch control unit receives each SCN frame having said to-whom-it-may-concern address.

4. The state change notification mechanism of claim 3 wherein the state change initiative means of said dynamic-switch control unit includes means to create an initiative reporting a state change on behalf of said specific link-level facility in response to one of:

the receipt by said dynamic-switch control unit of said SCN frame with a to-whom-it-may-concern destination address from the link-level frame generator of said specific link-level facility;

said specific link-level facility as requested that it be assigned a link-level facility identification;

the state of the port to which said specific link-level facility is connected changes to one of a link-failure state, an off-line state, or a static state; and

said connection table has been altered such that allowed connections to said specific link-level facility are changed.

5. The state change notification mechanism of claim 4 further comprising:

ACK sending means in each of said link-level frame generators for sending an ACK response frame to said dynamic-switch control unit upon receipt of one of said SCN frames from said dynamic-switch control unit;

retry means in said dynamic-switch control unit for retrying the sending of one of said SCN frames when an ACK frame is not received responsive to the sending by said dynamic-switch control unit of a previously sent one of said SCN frames; and

initiative discharging means in said state change initiative means for discharging said initiative to report a state change, said discharging being completed when one of the following occurs for each allowable connection to said specific link-level facility;

the receipt by said dynamic-switch control unit of an ACK response frame in response to one of said SCN frames previously sent by said dynamic-switch control unit;

the failure of said retry means to retry sending of one of said SCN frames by said dynamic-switch control unit; and

exhausting without success, a set number of retries by said retry means.

6. The state change mechanism of claim 5 wherein said state change initiative means includes means for preventing the creation of a new initiative on behalf of said specific link-level facility prior to the discharging of an earlier initiative by said discharging means.

7. The state change notification mechanism of claim 4 wherein said frame generator of said dynamic switch and said link-level frame generator of each of said link-level facilities include means for inserting into transmitted-frames transmitted therefrom an identification of the source of the transmitted-frame, and wherein each of said link-level facilities further includes response means in said link-level generator for transmitting a response-frame to the source of a transmitted-frame received by said receiver, said transmitted-frames including SCN frames.

8. The state change notification mechanism of claim 7 wherein said response frame is one of

a busy (BSY) frame indicating that the state of the link-level facility receiving said transmitted-frame is busy, or

an acknowledgment (ACK) frame indicating that the state of the link-level facility receiving said transmitted-frame is not busy.

9. The state change notification mechanism of claim 8 wherein each of said ports includes

a port receiver for receiving one of said transmitted-frames from the source identified therein, and

a port frame generator for transmitting a reject (RJT) frame or a port-BSY frame to the source of said transmitted-frame, said RJT frame reporting that the state of the port receiving said transmitted-frame is one of a port intervention or a port malfunction, and said port-BSY frame reporting that the state of the port receiving said transmitted-frame is busy.

10. The state change notification mechanism of claim 9 wherein said link-level generator of each of said link-level facilities includes retry means responsive to the receipt of a port-BSY frame or a RJT frame for retrying the sending of a SCN frame to to said dynamic-switch control unit upon receipt of a port-BSY frame or a RJT frame.

11. The state change notification mechanism of claim 9 wherein each of said determining association means includes means connected to said link-level frame generator for transmitting a test initialization (TIN) frame to said specific link-level facility after transmission of said ACK frame the source of said one of said SCN frames.

12. The state change notification mechanism of claim 11 wherein each of said determining association means includes TIN retry means for transmitting an additional TIN frame to said specific link-level facility upon receipt of a BSY frame or a port-BSY frame in response to a previously sent TIN frame.

13. The state change notification mechanism of claim 11 wherein:

each of said link-level frame generators includes means for inserting into said TIN frame, an identification of the link-level facility sending the TIN frame; and

each of said determining association means includes response means connected to said link-level frame generator for transmitting one of a test initiation response (TIR) frame or said BSY frame to the link-level facility identified in said TIN frame upon receipt of the TIN frame, and

each of said ports include means for transmitting one of said RJT frame or said port-BSY frame to the link-level facility identified in said TIN frame upon receipt of the TIN frame.

14. The state change notification mechanism of claim 13 wherein each of said determining association means includes table altering means for deleting from said association table means, the identification of said specific link-level facility upon receipt of said RJT frame sent in response to said TIN frame, and wherein said TIR frame sent in response to said TIN frame indicates that communication has been made with said specific link-level facility.

15. In a computer I/O system including a plurality of link-level facilities and a dynamic switch having a plurality of ports, each link-level facility being attached to an individual one of said ports, said dynamic switch for making point-to-point connection between any two of said ports such that communications may be established through said dynamic switch between any two link-level facilities connected to ports of the dynamic switch, each of said ports and said link-level facilities being on one state of several states, some of said states affecting the ability of communication between link-level facilities, a method of providing a state change notification comprising:

storing in said dynamic switch, a connection table of all allowed connections between said link-level facilities wherein said allowed connections are a selected subset of all possible connections between pairs of said link-level features;

a first transmitting step comprising transmitting an initial state change notification (SCN) frame having a to-whom-it-may concern destination address from a specific link-level facility to said dynamic switch, said initial SCN frame reporting a state change in said specific link-level facility;

a second transmitting step comprising transmitting from said dynamic switch to each link-level facility having an allowed connection to said specific link-level facility as recorded in said connection table, one of subsequent SCN frames on behalf of said specific link-level facility through said dynamic switch, thereby notifying each link-level facility which may be affected by said state change in said specific link-level facility,

said creating initiative step is in response to one of;

A. the receipt by a control unit controlling said dynamic switch of a SCN frame with a to-whom-it-may-concern destination address from said specific link-level facility;

B. said specific link-level facility has requested that it be assigned a link-level facility identification;

C. the port to which said specific link-level facility is attached enters one of the link-failure, off-line, or static states; and

D. entries in the connection table for the interconnection of ports with the port connected to said specific link-level facility have been altered,

transmitting within said second SCN frame, an identification of said specific link-level faciality on whose behalf the state change notification is being sent.

16. The method of claim 15 wherein each of said link level facilities includes an association table for storing therein a list of associated link-level facilities, said method further comprising:

storing in said association table means in one link-level facility of said link-level facilities, a list of other link-level facilities to which associations have been made on behalf of said one link-level facility,

receiving at said one link-level facility, one of said SCN frames transmitted in said second transmitting step,

searching the association table of said one link-level facility to determine if the identification of said specific link-level facility is stored therein, and

when said identification of said specific link-level facility is found in said association table, sending an association message from said one link-level facility to said specific link-level facility for determining if there is communication between said one link-level facility and said specific link-level facility.

17. The method of 16 further comprising before said sending an association message step:

transmitting from said one link-level facility a response frame to said dynamic switch, said response frame for showing whether or not one of said SCN frames transmitted in said second transmitting step was received by said one link-level facility.

18. The method of claim 17 wherein said response frame is one of

a busy (BSY) frame indicating to said dynamic switch that the state of said one link-level facility is busy, or

an acknowledgment (ACK) frame indicating to said dynamic switch that the state of said one link-level facility is not busy.

19. The method of claim 18 wherein said sending of said association message includes transmitting a test initialization (TIN) frame from said one link-level facility addressed to said specific link-level facility after transmission of said ACK frame from said one link-level facility to said dynamic switch.

20. The method of claim 19 further comprising:

receiving at the one port to which said one link-level facility is attached, said TIN frame;

transmitting from said one port to said one link-level facility, a reject (RJT) frame when said one port is in a port intervention or port malfunction state, or a port-busy (port-BSY) frame when said one port is busy.

21. The method of claim 20 further comprising transmitting from said specific link-level facility, one of a test initiation response (TIR) frame or a BSY frame to the source of said TIN frame upon receipt of said TIN frame.

22. The method of claim 21 further comprising transmitting from said one link-level facility, an additional TIN frame to said specific link-level facility upon receipt by said one link-level facility of said port-BSY frame from said one port or said BSY frame from said specific link-level facility.

23. The method of claim 21 further comprising deleting the identification of said specific link-level facility upon receipt of said RJT frame, and wherein the receipt of said TIR frame indicates communication between said one link-level facility and said specific link-level facility.