Host mobility for IP networks: a comparison

The growth of wireless networking is enabling many Internet hosts to become mobile. This article describes and compares three alternatives for providing host mobility managment in IP-based networks. We first summarize the operation and behavior of Mobile IP, on which the Internet Engineering Task Force has focused as a host mobility solution. We next describe two alternative architectures (Migrate and host identity protocol) for providing mobility management. Our qualitative comparison focuses on contrasting the different performance, security, deployment, scalability, and robustness properties of each approach.

Requirements for Mobility Management

For small networks, dynamic routing protocols can handle mobility. Routing protocols for such mobile networks are being researched intensively and are summarized elsewhere (e.g., [4]); much of the emphasis in mobile ad hoc routing has been on routing for small subnets of tens to hundreds of nodes. However, as networks grow larger, full host-based routing makes routing table sizes unmanageable, and it becomes attractive to introduce addressing and routing hierarchy to reduce routing overhead. Once addressing becomes hierarchical and mobile hosts are capable of moving from one network prefix to another, it becomes necessary to support additional mobility management mechanisms. The most general requirements include: •

Location-independent identifier. Mobile nodes must have or obtain an identifier that remains static across location changes.

•

Compatibility with IP routing. Mobility management must interwork successfully with IP routing, such as acquiring a new topologically correct IP address upon moving, since full host routes are not propagated in the Internet.

•

Location management. If a mobile node offers services to other nodes, it must be able to be located by clients or peers as it changes its location.

•

Transparency. Mobility management mechanisms should offer some level of transparency to higher-layer protocols and applications. For example, the act of readdressing should not normally cause a TCP connection to break.

•

Security. Mobility management mechanisms should not introduce additional security vulnerabilities into the network.