Overview

As the convergence of voice and data continues, a more discreet change is also coming into play. Although data is considered fixed to a location, the end user is now more mobile. This opens a new set of challenges for the industry and manufacturers alike because of the need for mobility. What once was a simple procedure of connecting the user's modem to a land line now poses the need to connect that same user to a device while mobile. Protocols need to be more flexible, accommodating the mobile user as the device is moved from location to location. Moreover, the physical devices (for example, the modems) must be moved often. In a dial-up, circuit-switched communications arrangement, this is not a major problem. The user can unplug a modem, reconnect it to a landline elsewhere, and dial from anywhere.

However, when we use Internet Protocol (IP) as our network protocol, data is routed based on a network/subnetwork address. Routing tables keep track of where the user is located and route the datagrams (packets) to that subnetwork (see Figure 23-1). When a mobile user logs on and attempts to dial in to the network, the IP address is checked against a routing table and routed accordingly. Updating the tables can be extremely overhead intensive, and it can produce significant amounts of latency in the Internet or intranet. Using an ICMP Route Discovery Protocol (IRDP), which is part of the Transmission Control Protocol/IP (TCP/IP) protocol suite, helps. However,...