Scalable datacenter multicast using in-packet bitmaps

Scalability is a key issue in datacenter multicast as it needs to support a large number of groups in commodity switches with limited fast memory. Previous in-packet Bloom filter-based datacenter multicast schemes have been proposed to address the scalability issue. They encode a multicast tree in a Bloom filter carried in each packet. However, these schemes induce high bandwidth overhead due to the false positives inherent in Bloom filters, and cannot scale well to the increasing variety of group sizes. In this paper, we propose an in-packet bitmap-based approach towards scalable datacenter multicast, improving the bandwidth efficiency. We use a bitmap to encode switch ports of a multicast tree in the packet header, eliminating false positive forwarding. In addition, we use a clustered Golomb coding method to compress in-packet bitmaps for further reducing the bandwidth overhead. Experimental results on simulations and a Click-based switch prototype demonstrate that our scheme achieves up to several orders of magnitude reductions in bandwidth overhead compared to previous schemes.