Label space reduction in multipoint-to-point LSPs for traffic engineering

Many ISPs use MPLS for traffic engineering to account for and utilize their resources properly. A fundamental problem in MPLS is to reduce the label space usage by label switched paths (LSPs), while meeting the flow requirements. While routing mechanisms have been proposed in the context of minimizing point-to-point LSPs, the problem has not gained sufficient attention with respect to multipoint-to-point LSP trees. We propose two mechanisms to reduce the label space usage of multipoint-to-point LSPs. First, given a set of LSPs to meet flow demands, we propose a simple algorithm to merge these LSPs into a minimal number of egress rooted multipoint-to-point trees. Then we show a mechanism where we try to fit a maximal number of flows in a single egress rooted multipoint-to-point LSP. We evaluate our methods on real world topologies and traffic patterns and show their effectiveness.