1. Inter-technology handoff support in mobile mode for Proxy Mobile IPv6 Hidetoshi Yokota KDDI Lab Sri Gundavelli Cisco Kent Leung Cisco IETF #76 Hiroshima

2. Implementation issue and a common practice Some host implementations do not allow migration of IP session(s) between interfaces  Some do, others don’t: the bottom line is there is no strict rule… Use of “virtual interface” is a common practice to make it work without a big hack  The scope of the work is to document this known practice NetExt WG should create a guideline for inter- technology handoff  Virtual interface approach can be one reference implementation 2

3. 3 Relationship between IP session and the interface Tight coupling IP address is bound to a physical address IP session could be disconnected even if the same address is assigned Datalink layer Physical layer IP layer Transport layer Application layer [Socket I/F] I/F “ppp0” WiMAX IP stack (IPv4/IPv6) TCP/UDP Application EVDO I/F “wmx1” IP1 I/F “ppp0” WiMAX IP stack (IPv4/IPv6) TCP/UDP Application EVDO I/F “wmx1” IP1 Loose coupling IP address does not have one-to-one mapping with a physical interface IP session may be maintained even if the interface is changed

4. 4 Virtual interface approach for interworking I/F WiMAX Virtual interface IP stack (IPv4/IPv6) TCP/UDP Application Communication Manager Datalink layer Physical layer IP layer Transport layer Application layer (1) (2) EVDO I/F (3) additional software for interwork (1): Controls the switching of physical devices (2): Retrieves wireless conditions (e.g. signal strength) and turns the devices on and off (3): Configures the threshold of the signal strength or preferred interface

5. 5 Summary and proposal Clarification of necessary functionalities for interworking  Showed how virtual interface can be involved with the physical interfaces and applications through the IP stack Documentation of guidelines  NetExt WG should capture the aspect of inter-technology handoff and identify the virtual interface approach as a workable solution