Design and Analysis of a Large-Scale Multicast Output Buffered ATM Switch

We propose and analyze a recursive modular architecture for implementing a large-scale multicast output buffered ATM switch (MOBAS). A multicast knockout principle, an extension of the generalized knockout principle, is applied in constructing the MOBAS in order to reduce the hardware complexity (e.g., the number of switch elements and interconnection wires) by almost one order of magnitude. In our proposed switch architecture, four major functions of designing a multicast switch: cell replication, cell routing, cell contention resolution, and cell addressing, are all performed distributively so that a large switch size is achievable. The architecture of the MOBAS 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 VLSI implementation, 3) relaxed synchronization for data and clock signals, and 4) building the center switch fabric (i.e., the multicast grouping network) with a single type of chip. A two-stage structure of the multicast output buffered ATM switch (MOBAS) is described. The performance of the switch fabric in cell loss probability is analyzed, and the numerical results are shown. We show that a switch designed to meet the performance requirement for unicast calls will also satisfy multicast calls' performance. A 16 x 16 ATM crosspoint switch chip based on the proposed architecture has been implemented using CMOS 2-μm technology and tested to operate correctly.