  IP mobility addresses the problem of changing the network point-of-attachment
transparently during movement. Mobile IP is the proposed standard by IETF.
Several studies, however, have shown that Mobile IP has several drawbacks, such
as triangle routing and poor handoff performance. Multicast-based mobility has
been proposed as a promising solution to the above problems, incurring less
end-to-end delays and fast smooth handoff. Nonetheless, such architecture
suffers from multicast state scalability problems with the growth in number of
mobile nodes. This architecture also requires ubiquitous multicast deployment
and more complex security measures. To alleviate these problems, we propose an
intra-domain multicast-based mobility solution. A mobility proxy allocates a
multicast address for each mobile that moves to its domain. The mobile uses
this multicast address within a domain for micro mobility. Also, aggregation is
considered to reduce the multicast state. We conduct multicast state analysis
to study the efficiency of several aggregation techniques. We use extensive
simulation to evaluate our protocol's performance over a variety of real and
generated topologies. We take aggregation gain as metric for our evaluation.
  Our simulation results show that in general leaky aggregation obtains better
gains than perfect aggregation. Also, we notice that aggregation gain increases
with the increase in number of visiting mobile nodes and with the decrease in
number of mobility proxies within a domain.
