Patent ID: 7400619

Claim:
A method for sub-port multicasting in an Asynchronous Transfer Mode (ATM) switching system, comprising: providing multicast fan-out port information for sub-ports of each of a plurality of switch ports into a multicast cell at an ingress port card, wherein the providing includes: determining that a cell received at the ingress port card is the multicast cell, obtaining a connection identifier (ID) corresponding to the cell received by the ingress post card using Virtual Path Identifier (VPI)/Virtual Channel Identifier (VCI) information and multiple physical device (MPHY) information associated with the received cell, obtaining the fan-out switch port information and the fan-out sub-port information by referencing the connection ID in a virtual connection parameter table of the ingress port card, and providing the multicast fan-out sub-port information into a local header of the multicast cell in a bitmap format while the cell is at the ingress port card; transmitting the multicast cell having the multicast fan-out sub-port information from the ingress port card to an egress port card; reading the multicast fan-out port information from the multicast cell at the egress port card; and performing multicasting for the sub-ports corresponding to the multicast fan-out port information using a corresponding switch port number connected to the egress port card and without using an egress translation table.