Mobile telephone operators are not the only candidates for the Layer 3 mobility solution provided by Mobile IP. The following sidebar illustrates an example of the current plight of nomadic laptop users, and while Mobile IP isn't advantageous to dial-up users, it is useful to the average laptop user. Numerous public and private radio access technologies are well within the means of enterprise deployment, but none of these technologies can provide the ideal combination of ubiquitous coverage, high speed, and low cost. With Mobile IP, a device that has access to multiple radio networks can easily make use of the optimal link without user interaction.
Current Plight of Nomadic Laptop Users: Example
Most laptop users are familiar with the Nomadic laptop mobility protocol. It does not support full mobility, but it does allow limited mobile access, described as follows:
Location discovery Handled at Layer 8, the user layer. Users look for wired or wireless access each time they need to connect to the network, searching for Ethernet jacks and phone jacks, scanning for WLAN signals, and attaching cellular modems.
Move detection Handled at Layer 8, the user layer. When the cables are too short, the user must locate a new access link and manually reestablish a connection.
Update signaling Protocols like Dynamic Host Configuration Protocol (DHCP) and the IP Control Protocol (IPCP) part of Point-to-Point Protocol (PPP) provide a new IP address to users. Sometimes these assignments can trigger a dynamic Domain Name System (DNS) update, allowing inbound reachablity.
Path (re)establishment Applications must detect the connectivity changes and be restarted, or in some cases, the entire device must be rebooted.
While calling this a mobility protocol is a bit of an exaggeration, it clearly represents how mobility is accomplished in many cases. Throughout the rest of this book, we show that this is less than ideal and that real options exist to provide a better end-user experience in many cases.
Looking back at the ambulance example, it is easy to see that a solution that requires user interaction is not a viable option. Constant connectivity across a network enables new applications for a connected ambulance. Public safety applications like the connected ambulance are just the beginning. From fleet management in the transportation industry to sales force automation, the benefits of seamless mobility are endless.