An ATM Routing and Concentration Chip for a Scalable Multicast ATM Switch

We have proposed a new architecture for building a scalable multicast ATM switch from a few tens to a few thousands of input/output ports. The switch, called the Abacus switch, employs input and output buffering schemes. Cell replication, cell routing, and output contention resolution are all performed in a distributed way so that the switch can be scaled up to a large size. The Abacus switch adopts a novel algorithm to resolve the contention of both multicast and unicast cells destined for the same output port (or output module). The switch can also handle multiple priority traffic by routing cells according to their priority levels. This paper describes a key ASIC chip for building the Abacus switch. The chip, called the ATM routing and concentration (ARC) chip, contains a two-dimensional array (3 32) of switch elements that are arranged in a cross-bar structure. It provides the flexibility of configuring the chip into different group sizes to accommodate different ATM switch sizes. The ARC chip has been designed and fabricated using 0.8m CMOS technology and tested to operate correctly at 240 MHz. Although the ARC chip was designed to handle the line rate at OC-3 (155 Mb/s), the Abacus switch can accommodate a much higher line rate at OC-12 (622 Mb/s) or OC-48 (2.5 Gb/s) by using a bit-sliced technique or distributing cells in a cyclic order to different inputs of the ARC chip. When the latter scheme is used, the cell sequence is retained at the output of the Abacus switch.