TABLE OF CONTENTS One of the major headaches in using Mobile IP is long handoff latency. Also, the global update signaling overhead could be a problem as the use of Mobile IP increases. Among the most prominent solutions, based on reducing the network latency of updates, are the micromobility schemes. Conceptually, these schemes break up the roaming regions into micromobility zones (although they may not actually use the term "micromobility zones"). The key characteristics of micromobility zones are: (1) they are larger than "normal" coverage areas of wireless IP subnets (for example, a region where there might have been a number of subnets each covered by a FA, might be replaced by one micromobility zone, as shown in Figure 6.15), (2) Mobile IP global registration is not needed for movement within the micromobility zone; only local updates are needed, and (3) Mobile IP global registration is needed only for movement between micromobility zones. The idea is that most of the handoffs of the MH would occur within micromobility zones (with only a few between micromobility zones). Only local updates would be needed for these, and not the normal Mobile IP registration (which is global in scope). Hence, the expected handoff latency would be very low. Global signaling overhead is also significantly reduced.
We note that because of certain shared characteristics, Layer 2 mobility schemes often can be thought of as micromobility schemes. However, micromobility schemes...
