Mobility and the IP

In a book such as this one dealing with aspects relative to synergies between
the IP world and wireless networks, it would be incomplete to deal with IP
without discussing aspects related to mobility in the Internet.
Mobile personal computing devices are becoming ubiquitous as their
prices drop and their capabilities increase. With the growing dependence of day-to-day computing on the distributed information base, providing network
attachment to these devices is an essential requirement. Using wireless
network interfaces, mobile devices can be connected to the Internet in the
same way as desktop machines are connected using Ethernet or any other
infrastructure. The major difference, however, is that mobile devices can
move while in operation, which means that their point of attachment to the
network can change from time to time. From a network’s viewpoint, host
movement constitutes a change in the network topology. It is natural that
mobile users desire uninterrupted access to all networking services even while
moving. However, host mobility introduces several new addressing and routing
problems at the IP layer. The Internet routing system routes a datagram
to a host based on the network number contained in the host’s Internet
address. If a host changes its point of attachment and moves to a new subnetwork,
IP datagrams destined for it can no longer be delivered correctly.
It is useful to distinguish between two types of mobility in the Internet
context:
• Macro-mobility, which implies the movement of a node among
administrative domains. This implies a complete change of IP
address and network settings (i.e., moving from your company in
Europe to an airport in the United States).
• Micro-mobility, which is defined as mobility between access points
within one administrative domain (i.e., one campus). IP addresses
and administration are the same, however location and routing to
mobile nodes is the problem.