Mobile IPv6 233
methods ensure that packets destined for the Mobile Node are received by the Home Agent,
which tunnels them to the Mobile Node.
In Mobile IPv6, these Home Agent functions are provided by the IPv6 neighbor discovery
mechanism. ARP is an Ethernet-based protocol, whereas neighbor discovery is an IP-based
protocol. Both mechanisms provide the same end functionality.
Transition to Mobile IPv6
Mobile IPv4 deployments are not switching over to Mobile IPv6 overnight. Is there a need to
leverage existing Mobile IPv4 infrastructure to support IPv6 clients? Or would it be better to
build a future-proof Mobile IPv6 infrastructure for IPv6 clients and legacy IPv4 clients? Should
there be coexisting Mobile IPv4 and Mobile IPv6 infrastructures?
As a reference point, cdma2000 is expected to support both Mobile IPv4 and Mobile IPv6.
IETF has proposals that support each of these cases. The answer will depend on the network
that is used for IPv6 services. If an existing Mobile IPv4 network is already in place, an overlay
of the IPv6 data trafﬁc would sufﬁce. Most likely, we will see new Mobile IPv6 networks built
for these new services. The following section explains how the Mobile IPv4 clients can upgrade
to Mobile IPv6 to reap the beneﬁts.
Mobile IPv6 has a clear advantage in that it is the successor to Mobile IPv4. This might be
stating the obvious, but because Mobile IPv4 has been deployed and tested in the ﬁeld, much
can be learn from the experience. So, what was learned from Mobile IPv4 that can be applied
to Mobile IPv6?
A major eyeopener was that service-provider deployments use the AAA infrastructure.
Although the Mobile IPv6 protocol deﬁned in RFC 3775 is designed using a security
association between a Mobile Node and a Home Agent, the relationship between the Mobile
Node and AAA is mandatory in these deployments. And, the NAI is the common identiﬁer for
the AAA infrastructure. Thus, it seems that using an authentication mechanism for the NAI is
prudent, because the standard IPSec is between the IP endpoints. Another point to consider is
that the network would like to use the same security key with the Mobile Node, regardless of
whether it is using Mobile IPv4 or Mobile IPv6.
Deployment of Mobile IPv4 struggled because of the conﬁguration needed on the client. It was
then easy to realize that Mobile IPv6 needed a method to bootstrap the Mobile Node
conﬁgurations, such as the Home Agent address, security association with the Home Agent, and
so on, using the AAA infrastructure.
Not all lessons learned need to stem from deployment experience. Just analyzing the situation
and behavior that would ensue gives rise to clever solutions. To this end, Hierarchical Mobile