Switching system comprising distributed elements allowing attachment to line adapters, and having multicasting capabilities

摘要

A switching system comprising a switching structure (1130) for routing cells from a set of M input ports towards a set of M output ports. Each cell comprises a routing header defining to which of said M output ports the cell is to be routed. The system further includes a set of distributed individual Switch Core Access Layer elements (S.C.A.L.) ( 1000), each distributed SCAL element communicating through one communication link (1400, 1600) to the input and output port of the centralized switching structure (1130). Each SCAL element allows the attachment to at least one Protocol Adapter (Protocol Engine 1600- 1900) and comprises a set of corresponding PINT circuits which further includes a receive part receiving the data cells from the attached Protocol Adapter (Protocol Engine 1600). The receive part includes means for introducing at least one extra byte to every cell that will be reserved for carrying a routing header used for controlling the switching structure in a first step, then a second header that will be used for the PINT circuit when the cell will be received by the transmit part of the PINT element, in a second step. The transmit part of each PINT circuit comprises a control module that receives all the cells that are routed and generated at the considered output port. In accordance with the value carried by the extrabytes, the control means controls whether to discard or not the cell being presented at the input of the PINT circuit. While the receive part of the PINT circuit performs the introduction of the extrabytes needed for controlling the routing and multicasting operations, the accurate values that are needed for doing this are generated into the switching system by means of two successive table read operations. These two successive read operation achieves a two-level multicast feature that provides wide multicasting capabilities, even when the SCAL elements are distributed at different physical areas of the switching system.