Method of adding stages to a scalable switching network

An in-service method of adding stages comprising:

• designating a multistage switching network for adding stages, where the multistage switching network comprises a plurality of stages comprising a plurality of switching elements comprising a plurality of top ports and a plurality of bottom ports and the multistage switching network further comprises a plurality of connections each providing communications between two adjacent stages of switching elements and coupled to a bottom port of a switching element of the upper adjacent stage and a top port of a switching element of the lower adjacent stage;
• providing an insertable unit comprising at least one stages each comprising a plurality of switching elements comprising a plurality of top ports and a plurality of bottom ports, having an uppermost stage and lowermost stage;
• providing a desired topology having a first desired interconnection pattern above the uppermost stage of the insertable unit and a second desired interconnection pattern below the lowermost stage of the insertable unit;
• making sacrificial connections prior to the insertion to provide better connectivity between switching elements within the same stage in the insertable unit;
• selecting a first stage of switching elements from the plurality of stages of the multistage switching network and a second stage of the multistage switching network of switching elements from the plurality of stages, where the second stage is adjacent to and below the first stage, and where the multistage switching network has a set of connections interconnecting the first stage and the second stage;
• and
• inserting the insertable unit by:
• a) selecting a bottom port, bottom_port, from ports of a switching element in the first stage which is connected to a top port, top_port, of a switching element in the second stage;
• b) breaking the connection between top_port and bottom_port;
• c) determining a top port, mid_top_port, of a switching element in the uppermost stage of the insertable unit corresponding to bottom_port in accordance with the first desired interconnection network;
• d) determining a bottom port, mid_bottom_port, of a switching element in the lowermost stage of the insertable unit corresponding to bottom_port in accordance with the second desired interconnection network;
• e) breaking any connection connected to mid_top_port;
• f) breaking any connection connected to mid_bottom_port;
• g) making a connection between bottom_port and mid_top_port;
• h) making a connection between top_port and mid_bottom_port;
• i) repeating steps (a)-(h) until there are no bottom ports of ports of a switching element in the first stage which are connected to any top port of a switching element in the second stage.