As a host moves around, it may be assigned different IP addresses based on its location. When this happens, the host acquires a new IP address and continues to operate, but the previous TCP connections are invalid and torn down.
Normally this process takes just a second or two, and presents no problem to most applications (watch Outlook as you roam and you will see what I mean; the connection will drop but then reconnect on its own)
The problem is applications that cannot handle a 1-2 second drop. What applications can you think of that fall into this category? I can think of VoIP and streaming media as about the only two right now.
Mobile IPv6 was designed to eliminate this 1-2 second drop by creating a "Home Address" that doesn't change, regardless of location. The changes necessary to implement Mobile IPv6 are not insignificant, and for the limited number of applications that truly need the fast failover time, we just weren't able to get MIPv6 included into Windows Vista.
Do you have a killer scenario where you think only MIPv6 will work? Leave a comment and let me know!
By the way, check out http://www.microsoft.com/technet/community/columns/cableguy/cg0904.mspx for a terrific summary of Mobile IPv6.
Even in non VOIP applications, node movement cannot be always transparent because TCP reconnection may force the user to go through a lengthy logon and authentication procedure.
In addition to unloading the application from processing events outside its scope, MIPv6 handles this movement more gracefully as there is no reconnection.
The home agent in MIPv6 has another role which is keeping a mobile node always reachable; without this feature, a node (being mobile or nomad) can be connected in a foreign network without being visible, this in my opinion the killing scenario mainly in a P2P networking application.
If you are uploading a large file via FTP, a 1-2 second drop would be bad.
is that Windows XP is not supporting it.
(plz, avoid the "yes, it support CN" answer, CN is usefull as long as MIPv6 is mainstream, but it is not)
Vista also have limited support of latest mobile IPv6 specifications (see NEMO).
This means MS customer only have one solution : go to linux to get a complete end-to-end mobile IPv6 solution (desktop to server).
Another fun is to see that almost none of the MS servers are IPv6 enabled, which shows also the MS "internal support" to the IPv6 technology.