It is desirable for an organization to have a fairly large campus with
a single IP address prefix, a rich physical topology, where the network
elements do not need to be configured, where endnodes can move around
without changing their IP addresses, and where ARP and Neighbor 
Discovery
traffic can be confined.

This functionality is often provided by bridges.
However, bridges have disadvantages: routing is confined to a spanning
tree (precluding pair-wise shortest paths), ARP and Neighbor Discovery
packets must be carried across all the links, the header on which the
spanning tree forwards has no hop count, spanning tree forwarding in the
presence of temporary loops spawns exponential copies of packets, nodes
can have only a single point of attachment, the spanning tree, in order
to avoid temporary loops, is slow to start forwarding on new ports, and
it is not possible to take advantage of the rich physical topology for
capacity since the packet flows are restricted to following the spanning
tree.

Routers on the other hand avoid those disadvatages but have their own
disadvantages: IP addresses are link specific so a host that moves must
change its IP address, the routers must be configured with unique link
prefixes for each of the attached links, and the block of IP address
space can not be fully utilized because it must be partitioned across
the different links.

The BoF will explore combining the benefits of bridges and routers
without requiring any changes on any of the hosts, IP routers, or
bridges.  The design should support both IPv4 and IPv6.