Multistage Switching Network Interconnection
The basic component of a multistage network is a two-input, two-on interchange switch interchange switch.
Figure: Operation of a 2 x 2 interchange switch
- As shown in the figure the 2 X 2 switch has two input labeled A and B, and two outputs labeled 0 and 1.
- There is control sign (not shown) associated with the switch that establishes the interconnection between the input and output terminals.
- The switch has the capability connecting input A to either of the outputs. Terminal B of the switch behaves in a similar fashion.
- The switch also has the capability to arbitrate between conflicting requests.
- If inputs A and B both request the same output terminal only one of them will connected; the other will blocked.
- Also, Using the 2 X 2 switch as a building block, it possible to build the multistage network to control the communication between a number of source and destinations.
- Moreover, To see how this done, consider the binary tree shown the figure.
Figure: Binary tree with 2 x 2 switches
- The two processors P1 and P2 connected through switches to eight memory modules marked in binary from 000 through 111.
- The path from source to a destination determined from the binary bits of the destination number.
- Moreover, The first bit of the destination number determines the switch output in the first level.
- Generally, The second bit specifies the output of the switch in the third level.
- Also, Example to connect P1 to memory 101, it is necessary to form a path from P1 to output 1 in the first level switch, output 0 in a second level switch and output 1 in the third level switch.