Mobile Inter-networking with IPv6 : Concepts, Principles and Practices

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Mobility on the Internet: Introduction

The best way to predict the future is to invent it.    –Alan Kay

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In order to understand what mobility on the Internet means, let us consider Figure 1.1. Bob, a user connected to the Internet by means of an access network (such as a cable modem or a DSL or a dial-up network), is "talking" to Alice, who is another user connected to the Internet by a different access network (e.g., WLAN). We do not show Bob and Alice themselves, but only their devices. Now, consider that Alice "moves" from her current access network to another access network (e.g., the Code Division Multiple Access (CDMA) cellular network). There are two basic problems we can see. First, how can Bob continue the existing conversation with Alice? Second, how can Bob reliably reach Alice once she has moved? The first problem can be broadly considered to be the handover problem. It is quite similar to that of users continuing their calls on their cell phones in spite of movement (such as in a moving train). The second is the reachability problem. It is quite similar to being able to reach users on their cell phones even when they are out of town (i.e., roaming). These two problems, which appear to be very straightforward, create many technical challenges associated with mobility on the Internet.

Perhaps it is tempting to assume that Mobile Internet is a given. Even so, it might ...