  A well known drawback of IP-multicast is that it requires per-group state to
be stored in the routers. Bloom-filter based source-routed multicast remedies
this problem by moving the state from the routers to the packets. However, a
fixed sized Bloom-filter can only store a limited number of items before the
false positive ratio grows too high implying scalability issues. Several
proposals have tried to address these scalability issues in Bloom-filter
forwarding. These proposals, however, unnecessarily increase the forwarding
complexity.
  In this paper, we present Extensible-Bloom-filter (XBF), a new framing and
forwarding solution which effectively circumvents the aforementioned drawbacks.
XBF partitions a network into sub-networks that reflect the network topology
and traffic patterns, and uses a separate fixed-length Bloom-filter in each of
these. We formulate this partition assignment problem into a balanced edge
partitioning problem, and evaluate it with simulations on realistic topologies.
Our results show that XBF scales to very large networks with minimal overhead
and completely eliminates the false-positives that have plagued the traditional
Bloom-filter-based forwarding protocols. It furthermore integrates with SDN
environments, making it highly suitable for deployments in off-the-shelf
SDN-based networks.
