An overview of the pipelined common buffer architecture (PCBA) for memory based packet/cell switching systems

A pipelined common buffer architecture (PCBA) is proposed for memory based switching systems. Unlike previously proposed shared-memory switching system, the PCBA is suitable for prioritized and multicast (without multiple memory write) traffic for both fixed length and variable length cell/packet. Therefore, switching among ATM traffic and existing LAN can be accomplished. The PCBA can route both fixed-sized cell data and variable-sized packet data. It separates switching system control and packet/cell data streams (the dichotomy) inside the switching system to simplify the design process for identifying VLSI chips implementation. The PCBA also uses pipelining for both system control and data movement, to achieve the highest possible system throughput, i.e. one system buffer per system clock cycle. A system buffer in PCBA has fixed size N×W bits where N is the number of switch ports and W is the width of data path (number of bits transmitted/received to/from system buffer at one clock cycle by a switch port). Furthermore, the usage of external memory modules for both data and control memory takes full advantage of advances in commercial RAM technology. It can be seen that the PCBA not only can easily expand its queue size for different networking environments, but can also support future traffic types without modification to the architecture