Deploying Bidirectional Multicast Shared Trees in MPLS Networks

Multicast over MPLS networks can merge the their advantages, but is still accompanied many problems mainly on scalability. In this paper, we propose an architecture for deploying bidirectional multicast shared trees in MPLS networks (BIDIR-MMST). Tree manager server (TMS) collects the positions of all multicast group members and computes the topology of BIDIR-MMST, then sends messages to routers constructing the tree. The multicast group uses the BIDIR-MMST to forward MPLS packets when their close degree is more than the specific threshold delta. Flows are bidirectional in the share tree. Label spaces are spared by aggregating most of multicast groups on BIDIR-MMSTs. Packets are discard in the edge routers that belong to BIDIR-MMST but are not part of the multicast group. The experiments show that the trees are able to aggregate more than 50% of multicast groups when deltales0.75 and BIDIR-MMSTs are near links within domain in terms of number. Its ability of aggregation can be more 6 times than unidirectional MMST. Forwarding processes of core routers are simplified and forwarding states of MPLS domain are reduced in the architecture. Deploying BIDIR-MMST will enhance the scalability of MPLS multicast.