1. Mobile IP and Upper Layer Interaction
MOBOPTS WG, IETF 66
Vijay Devarapalli
Rajeev Koodli

2. Problem
Mobile node wants to change its home address or start using a different home address
e.g. for privacy reasons
What happens to existing sessions using the old home address?
How does Mobile IP know if there are existing sessions on the old home address?
How is the correspondent node informed?
Is it ok to expect sessions to break when the home address changes?

3. Reachability and change in HoA
Once MN starts using the new HoA how is it reachable at the new HoA?

4. Possible solutions Existence of a binding cache entry at the CN
Check if the CN has a binding cache entry for the MN’s old home address
If there is no binding cache entry, then there is no session with the CN
If there is a binding cache entry, then need to inform the CN
But the existence/lack of a binding cache entry does not imply there is/isn’t a session
BCE exists but no active traffic
Traffic reverse tunneled through the home agent

5. Possible solutions Use old HoA and new HoA simultaneously for a while
The MN shouldn’t change the HoA abruptly
Let existing sessions continue with the old HoA
Start new sessions with the new HoA
But how does Mobile IP know there are existing sessions?

6. Detecting existing sessions
The mobile node records the timestamp of the last packet sent using a particular binding update list entry
But this doesn’t accurately say if there is an existing session
The mobile node keeps track of all the sockets that were opened with a particular home address
May need to formalize an interface for this

7. Detecting existing sessions
Look through all the Protocol Control Blocks (PCB) for active sessions with the old home address
Does not work for UDP connections on some operating systems. Works only for TCP

8. Reachability at the new HoA
MN wants to be reachable at the new HoA
FQDN is used to reach the mobile node
The MN can use the DNS update mechanism described in the bootstrapping work
If some other identifier is used to reach the mobile node, we need to figure out how to update the identifier to HoA mapping

9. Changing a psuedo-HoA
There are solutions that describe using a psuedo-HoA instead of the real HoA in route optimized traffic
Changing the psuedo-HoA is easy
HoA to psuedo-HoA mapping is stored in the binding update list at the MN and the binding cache entry at the CN
Need to update these mappings

10. Run Shim6 over MIPv6
Shim6 allows one to use multiple HoAs at the same time
Not suitable for changing home addresses
All HoAs not known initially
Can still be done with shim6
But requires shim6 support on the CN