Alternative path control system and method

• US 6,397,356 B1
• Filed: 06/01/1999
• Issued: 05/28/2002
• Est. Priority Date: 06/02/1998
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yonezawa, Naomichi
• Primary Examiner(s): Iqbal, Nadeem
• Application Number:
  US09/323,120
• Time in Patent Office: 1,092 Days
• Field of Search: 714/43,44,47,56,6,25,37 710/15,17,20,36,65,38,40
• US Class Current: 714/43
• CPC Class Codes: G06F 11/2007 using redundant communication media

Abstract

An information processing system of the invention includes a first system to which a first device is connected, that produces a request for the first device; a second system which is independent from the first system. The first system includes a first element which outputs the request to the second system. The second system has a second element which receives the request from the first element and outputs the request to the first system. The first system also has a third element which receives the request from the second element and outputs the request to the first device. A method for providing an alternative path for an information processing system which includes a first system, to which a first device is connected, that produces a request for the first device and a second system which is independent from the first system, wherein the first system includes a first element and a third element which is provided between the first element and the first device, wherein the second system includes a second element, includes first outputting the request from the first element to the second element; second outputting the request from the second element to the third element; and third outputting the request from the third element to the first device.

Claims

1. An information processing system comprising:

a first system, in which a first device is provided, that produces a request for said first device, wherein said first system includes a first element which is connected to said first device and has at least two inputs, a second element which receives said request and outputs said request to one of said inputs of said first element, and a third element which outputs said request to said second element; and

a second system, in which a second device is provided, that has a fourth element which is connected to said second device and has at least two inputs, a fifth element which receives said request and outputs said request to one of said inputs of said fourth element, and a sixth element which outputs said request to said fifth element;

wherein said third element outputs said request to said sixth element when there is a failure on the path from said third element to said first element; and

wherein said fifth element outputs said request to one of said inputs of said first element.

2. The information processing system as claimed in claim 1, wherein said third element determines whether said request is to be sent in said first system or to said second system based on an address of said request and whether or not there is a failure on the path from said third element to said first element.

3. The information processing system as claimed in claim 1, wherein said third element includes a first register which stores information indicating said second system as an alternative path.

4. The information processing system as claimed in claim 1, wherein said third element includes a second register which stores information indicating that there is a failure on the path from said third element to said first element.

5. The information processing system as claimed in claim 1, wherein said fifth element determines whether said request is to be sent to said first element or to said fourth element based on an address of said request.

6. The information processing system as claimed in claim 1, wherein said third element includes an element which adds information to said request,

wherein said information designates said sixth element to unconditionally transfer said request to said fifth element.

7. An information processing system comprising:

a first system, connected to a first device, and which produces a request for said first device;

a second system which is independent from said first system;

a first element, which is provided in said first system, that sends said request to said second system;

a second element, which is provided in said second system, that receives said request from said first element and outputs said request to said first system; and

a third element, which is provided in said first system, that receives said request from said second element and outputs said request to said first device.

8. The information processing system as claimed in claim 7, wherein said first element outputs said request to said second system when there is a failure on the path from said first element to said third element.

9. The information processing system as claimed in claim 7, wherein said first element outputs said request to said third element when there is not a failure on the path from said first element to said third element.

10. The information processing system as claimed in claim 7, wherein said first element determines whether said request is to be sent in said first system or to said second system based on an address of said request and whether or not there is a failure on the path from said first element to said third element.

11. The information processing system as claimed in claim 7, wherein said first element includes a first register which stores information indicating said second system as an alternative path.

12. The information processing system as claimed in claim 7, wherein said first element includes a second register which stores information indicating that there is a failure on the path from said first element to said third element.

13. A method for providing an alternative path for an information processing system which includes a first system, to which a first device is connected, that produces a request for said first device and a second system which is independent from said first system, wherein said first system includes a first element and a third element which is provided between said first element and said first device, wherein said second system includes a second element, comprising:

first, outputting said request from said first element to said second element;

second, outputting said request from said second element to said third element; and

third, outputting said request from said third element to said first device.

14. The method as claimed in claim 13, wherein said first element outputs said request to said second element when there is a failure on the path from said first element to said third element.

15. The method as claimed in claim 13, wherein said first element outputs said request to said third element when there is not a failure on the path from said first element to said third element.

16. The method as claimed in claim 13,

wherein said first element includes a first register which stores information indicating said second system as an alternative path;

wherein said first register is accessed during said first outputting step.

17. The method as claimed in claim 13, further comprising:

determining whether said request is to be sent in said first system or to said second system based on an address of said request and whether or not there is a failure on the path from said first element to said third element.

18. The method as claimed in claim 17,

wherein said first element includes a second register which stores information indicating that there is a failure on the path from said first element to said third element

wherein said first register is accessed during said determining step.