Real-time processing for virtual circuits in ATM switching

We propose adding real-time hardware primitives to packet switches, ATM in particular, to provide efficient support for inward multicasting similar to some of today's switches that support real-time multicast in the switch hardware. To implement this, we propose extending the lookup table used for routing by adding additional opcode and operand fields (or pointers to those fields) into the routing table and by including ALU circuitry to process these fields and corresponding fields in the arriving cells. With the rapid capacity growth of today's RAM and the modest gate count required for ALUs, memory word widths can be extended with minimal additional chip count and the ALU can be a small addition in a header processing VLSI, thereby giving only a modest increase in complexity. The benefit of including real-time processing in the switch is that it is now possible to solve the ACK implosion problem associated with high-speed reliable multicasting transport protocols. By keeping the primitives as general as possible, other applications can benefit from these real-time primitives.