The previous chapters addressed mobility within a single private network. However, during the course of a business day, most mobile workers move beyond the confines of a single private network. These workers traverse multiple public and private networks and thereby exhibit metro mobility. For example, delivery personnel, service workers, and public safety officers spend their days traveling across a metropolitan market and would benefit greatly from a seamless "always on" mobility solution. Imagine how productivity would increase if employees could access just-in-time training, real-time work order systems, procurement systems, and other job-related systems while on the go.
The proliferation of in-vehicle computers with multiple wireless links makes metro mobility and access to these capabilities a reality. However, placing the burden of managing metro mobility on the end user is not cost effective and is almost counterproductive. For example, service technicians or sales personnel should not need extensive information technology training to do their jobs, but should be able to leverage on-the-go capability outside their private networks. Deploying Mobile IP in the network easily accomplishes this.
Mobile IPenabled systems do not require an end user to be aware of the networking capabilities of his or her computer. Rather, the Mobile IP client automatically selects the most cost-effective link and provides the user with the most appropriate level of connectivity while enabling real-time applications such as voice, video, and data.
Metro mobility adds a new set of challenges to Mobile IP deployment, most of which are easily overcome. Many of the challenges stem from the security implications of Internet routing. Although the basic requirements of roaming remain the same, the challenges of traversing multiple autonomous systems require a greater integration effort than roaming in a private intranet.
Figure 6-1 shows the different environments that a Mobile Node might encounter in a metro mobility deployment. This chapter explores Mobile IP features that can be used in these different environments. When roaming on a public network, Mobile Nodess can encounter asymmetric routing problems because of firewalls and ingress filtering that can be addressed with reverse tunneling. Network Address Translation (NAT) traversal, as seen in the public hot spot at the coffee shop, also presents a problem and requires a new type of tunneling. Virtual private network (VPN) integration and public and private roaming is also explored. Finally, the chapter discusses the Registration Revocation mechanism that efficiently manages mobility bindings.
Figure 6-1. High-Level Metro Roaming Topology