For communications devices, users expect mobility to be more than just the ability to move. The goal of communications mobility is for a device to be fully operable while it is moving. Mobile telephony has set a standard that mobile computing devices need to live up to. These devices need to be fully functional whenever and wherever they are operated.
To achieve full mobility, a protocol must support location discovery, move detection, update signaling and path (re)establishment. These requirements can be met in different ways at any layer of the OSI model. Chapter 2 shows how these requirements are met at Layer 3 with the Mobile IP protocol. The chapter also discusses how Mobile IP interacts with different layers to achieve better mobility.