A Recursive Modular Terabit/Second ATM Switch

This paper proposes a recursive modular architecture for a very large scale ATM switch. By extending the concept of the original Knockout switch, the cell filtering and contention resolution functions are distributed over many small switch elements, which are arranged in a crossbar structure. The output ports of a switch fabric are partitioned into a number of groups by a novel grouping network to permit sharing of the routing paths in the same group. This partitioning and sharing concept is applied recursively to construct the entire switch, which results in close to one order of magnitude fewer switch elements. The proposed ATM switch has a regular and uniform structure and, thus, has the advantages of: (1) easy expansion due to the modular structure; (2) high integration density for the VLSI implementation; (3) relaxed synchronization for data and clock signals; and (4) building the center swtch fabric with a single type of chip. Furthermore, peripheral line concentrators (or ATM statistical multiplexers) can be implemented with the grouping networks and be tightly coupled with the switch fabric. This permits buffers in the multiplexer to be eliminated at the cost of more switch elements required in the switch fabric. The technique of channel grouping for trunk circuits can also be incorporated in the proposed ATM switch to improve the cell loss/delay performance while the cells’ sequences are retained. An experimental prototype circuit for the key switch element has been designed, and it has been shown that more than 4000 of the switch elements can be integrated into a VLSI chip with the existing CMOS l-μm technology.