4

Mobility and Routing

This chapter considers IP mobility and routing issues related to 6LoWPAN. There are several causes of mobility in embedded systems utilizing low-power wireless technology. Many systems require support for node mobility of wireless devices. Often devices may be integrated into moving machines, carried by people or animals, or tagged on equipment or supplies. In other applications the edge routers themselves may be mobile, changing their point of attachment on the Internet, thus requiring us to deal with network mobility. While this kind of physical mobility of edge routers or nodes is easy to comprehend, there are also other more subtle causes of topology change in which nodes don’t actually move. In wireless networks, the radio channel is continually changing due to fading effects, where changes in the environmentcan drastically affect radio connectivity between nodes. These radio changes often force nodes to make use of alternative routes and even to change LoWPANs without physically moving. Furthermore, autonomous embedded devices may run out of battery, fail or make use of long sleep cycles, all of which may cause changes in network topology. These basic causes of mobility along with core IPv6 and 6LoWPAN solutions for dealing with them, are covered first in Section 4.1.

Although IPv6 and 6LoWPAN have techniques to be able to prevent mobility within a LoWPAN from affecting network operation, to deal with address changes caused by nodes moving between ...

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