Concentrate N inputs into L outputs. Typically L<<N

Knockout switch uses simple low speed devices and a concept from an "elimination tournament".

Examples of an elimination tournament:

• Tennis open.

• NCAA Basketball Championship.

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  The Basic Building Block--The 2x2 Beta Element

  

  Rules of the "game":

  1. If only one wired input, then it is just a delay. This keeps things synchronized. In sports this is called a "bye".
  2. If two wired inputs, but a cell on only one, this is the "winner by default".
  3. If two cells at the inputs, then select the winner according to one of the following options:
     1. Top is winner (virtue of position)
     2. Randomly choose a winner.

  Example:

  N = 4, L = 3. A full elimination tournament.

  
  

  Example 2:

  

  Note that in each case, we went from N inputs to L outputs. L<<N

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  How do we now feed L (or fewer) cells into 1 output line?

  The outputs of the L-selector (concentrator) always end up at the left-most inputs of the shifter:

  
  

  The function of the shifter is to have the cells come out on its L output lines in a sequential round robin order.

  Consider the following example in which there are 3 active inputs (i.e. inputs that have cells on them) in time slot 1. The 3 active inputs start at the leftmost input port of the shifter and are placed on output ports 1,2 and 3 of the shifter. At time slot 2, there are 4 active inputs,so the shifter places the left-most of those active cells on the (L1 + 1) output and the second active input on the (L1 + 2) output, etc. The shifter puts the actual cells in order on the output lines, then starts over or wraps around.

  

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  BBN Notes From Lecture 9 on 2/12/97
  

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  Created by Russ Ford from notes from Professor Vastola's Broadband Networks lecture given on 02/12/97 at RPI in Troy, NY.