The Ip Micro Mobility Approach

Mobile IP is a powerful protocol which supports Internet mobility and scales reasonably with the number of users within a system. Due to the high roundtrip delay of the Internet and due to Mobile IP’s control overhead, Mobile IP causes connections of a mobile node to be interrupted for up to 5 seconds for each change of its attachment point to the Internet. This interruption induces TCP to run into its slowstart procedure or disturbs real-time multimedia transmissions in a significant way. Thus Mobile IP is more applicable for nomadic computing than for mobile computing. Resulting from this weakness recently some micro mobility approaches have been proposed within the IETF, which support mobility in a well defined area, e.g. in an access network, and interact with Mobile IP in a hierarchical way. Those protocols do not scale as well with the number of users as Mobile IP does but behave much better for handovers. In the near future those micro mobility protocols will gain much attention, especially for the "All-IP Approach" of future mobile cellular networks where everything (data traffic, signalling and circuit switched services) shall be transported in IP packets. This survey introduces two very similar micro mobility protocols called Cellular IP and HAWAII and presents their mechanisms to support mobility.