Compression of multicast labels in large IP routers

In small cell-based Internet protocol routers, multicast traffic is generally handled by appending to each cell a local multicast label (LML) containing a bitmap with as many bits as switch ports, so as to identify the ports to which a copy of the cell has to be transferred. This approach is not feasible for switches having 128 ports or more, because the LML length would rise above 16 bytes, thus representing an intolerable overhead, given the small size of cells (typically 64 bytes). We discuss both static and adaptive lossy compression algorithms to reduce the size of LMLs to be attached to multicast cells, at the price of the delivery of cells to a larger set of outputs than necessary, and we compare the compression algorithms performance in terms of switch bandwidth waste, using both analytical and simulation models.