Scaling Bloom filter-based multicast via filter switching

Stateless multicast forwarding with in-packet Bloom filters (iBF) has recently been proposed as a highly scalable way for supporting a large number of multicast groups. However, iBF multicast generates redundant traffic due to false positive forwarding decisions and it also scales poorly with multicast group size. In this paper we investigate scaling iBF multicast to arbitrary multicast group sizes, by partially sacrificing the network's fully stateless operation. We propose a switched-iBF multicast scheme that places multicast forwarding state at a few network nodes, so as to minimize redundant traffic regardless of the group size. We evaluate the scheme through simulations and find that switched-iBF multicast can scale to any group size while keeping redundant traffic below 1%-4% at the (minimal) cost of placing state at no more than 0.5%-2.5% of network nodes. We also compare the state requirements of switched-iBF multicast against other multicast schemes. Our evaluation shows that switched-iBF multicast achieves a tremendous reduction of multicast state in the range of 87%-99.6%. Hence, even though the system is no more fully stateless, it remains far more scalable than other approaches.