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Users of portable computers would like to carry their laptops with them whenever they move from one place to another and yet maintain transparent network access through the wireless link. The existing set of network protocols do not meet this requirement since they were designed under the assumption of a stationary network topology in which hosts do not change their location over time. The authors' approach, which is based on the use of a natural model and an existing IP option, does not introduce any new protocol and achieves optimal routing. The solution is transparent to transport and higher layers, and does not require any changes to stationary hosts and routers. The model is natural, because the authors coordinate a collection of mobile hosts (MHs) as a new IP network. They route packets to the MHs by using a router. The router is special because once it receives a packet, it does special things to ensure its safe delivery to its destination (the MH). This special operation is invisible to existing hosts and routers, so all the routing difference due to movement of the hosts can be hidden and effected by mechanisms under the control of the special entities. The other part of the model, which is a very natural part of a physical wireless data communications system, is the transceiver (access point), which collects wireless packets from a MH for delivery to existing hosts along existing wired networks. This transceiver provides the reference point by which the location of the MH is known.