1. Utilizing Home and Away Interfaces Simultaneously
66th IETF at Montreal, Quebec, Canada
Benjamin Koh
Keigo Aso

2. Contents Problem Possible Operations Conclusion Network based solution
Mobile Node based solution
Conclusion

3. Problem
When a MN IF returns home, it cannot use both of its interfaces for flows.
If it uses home link, the mobile node MUST de-register all the bindings
The preferences in HA set by the MN before the movement is not available any more.
If it uses interfaces attached to foreign links, the mobile node disables the interface attached to the home link
draft-ietf-monami6-multiplecoa-00.txt
To use home and foreign links simultaneously, the “home agent can set up another link other than home link and uses the link for the mobile node to return virtually to home network. The detail can be found in Figure 7.”
No emulation details given (Just a figure)
Contradiction with earlier text in Section 3.3
When the mobile node returns home, there are two situations, since the Home Agent defends the mobile node's Home Address by using the proxy neighbor advertisement. It is impossible to utilize all the interfaces when one interface is attached to the home link and the others are attached to foreign links.

4. Network based solution
Operation 1
HA advertises prefix to make the home link appear to be the foreign link.
MCoA-MN considers HA Link to be a foreign link
MIPv6-MN and MCoA-MN can never perform the returning home procedure (always away)
Operation 2
HA advertises 2 prefixes.
Home Link prefix
Foreign Link prefix
MCoA-MN can choose prefix to configure
MIPv6-MN should always select Home Link prefix
Default behaviour?

5. Mobile Node based solution
+----+
| CN |
+--+-+ |
Internet | HA | |
CoA2| | | Home Link |
| MCoA MN +======== | |
CoA | | MN |
Home Link | |
CoA
Operation
MCoA-MN uses a CoA formed by the home prefix in the home network.
MIPv6-MN performs the returning home procedure.
Advantage
No changes to operation of MIPv6-MN (can use own home address).
MCoA-MN can select to return home or not.

6. Conclusion
Both solutions keep backward compatibility with Mobile IPv6.
Network based solution may hinder normal operations of a Mobile IPv6 node
Recommendation for changes to MCoA draft:
Slight text changes to section 3.3 (for simultaneous usage of both home and foreign interfaces)
Add supplementary text to Figure 7 describing detailed operation of solution(s)