Scalable multistage interconnection network architecture and method for performing in-service upgrade thereof

For use in a scalable switch fabric architecture comprising an input switching stage having N inputs and N outputs operable to connect selected ones of said N inputs to selected ones of said N outputs, an output switching stage having N inputs and N outputs operable to connect selected ones of said N output switching stage inputs to selected ones of said N output switching stage outputs, and a removable core switching stage having N inputs adapted for coupling to said N input switching stage outputs and having N outputs adapted for coupling to said N output switching stage inputs, a replacement core switching stage for replacing said removable core switching stage, said replacement core switching stage comprising:

• an input switching sub-stage having R inputs and R outputs operable to connect selected ones of said R inputs to selected ones of said R outputs, wherein N of said R inputs are adapted for coupling to said N input switching stage outputs;
• an output switching sub-stage having R inputs and R outputs operable to connect selected ones of said R output switching sub-stage inputs to selected ones of said R output switching sub-stage outputs, wherein N of said R output switching sub-stage outputs are adapted for coupling to said N output switching stage inputs;
• and
• a removable core switching sub-stage having R inputs adapted for coupling to said R input switching sub-stage outputs and having R outputs adapted for coupling to said R output switching sub-stage inputs.

For use in a scalable switch fabric architecture comprising an input switching stage having N inputs and N outputs operable to connect selected ones of the N inputs to selected ones of the N outputs, an output switching stage having N inputs and N outputs operable to connect selected ones of the N output switching stage inputs to selected ones of the N output switching stage outputs, and a removable core switching stage having N inputs adapted for coupling to the N input switching stage outputs and having N outputs adapted for coupling to the N output switching stage inputs, a method of replacing the removable core switching stage comprising the steps of:

• connecting a replacement core switching stage in parallel with the removable core switching stage, the replacement core switching stage comprising:
• an input switching sub-stage having R inputs and R outputs operable to connect selected ones of the R inputs to selected ones of the R outputs, wherein N of the R inputs are adapted for coupling to the N input switching stage outputs;
• an output switching sub-stage having R inputs and R outputs operable to connect selected ones of the R output switching sub-stage inputs to selected ones of the R output switching sub-stage outputs, wherein N of the R output switching sub-stage outputs are adapted for coupling to the N output switching stage inputs;
• and
• a removable core switching sub-stage having R inputs adapted for coupling to the R input switching sub-stage outputs and having R outputs adapted for coupling to the R output switching sub-stage inputs;
• and switching data traffic to the replacement core switching
• stage from the removable core switching stage;
• and removing the removable core switching stage.