Subject: [Mip4] another perspective on the use of multiple interfaces

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 17 Mar 2010 20:54:08 +0100

Hello MIP4 group,

I would like to propose a different perspective on the use of multiple
interfaces on the Mobile Router connected on a cell network.

Currently draft-gundavelli-mip4-multiple-tunnel-support proposes
Mobile IP extensions to manage several [EVDO] egress interfaces on a
Mobile Node, presumably the egress interfaces of a Mobile Router too:

           Managed by Mobile IP
            ---^---
           /       \

             /= = = -ppp0               vif0: virtual iface
            / = = = -ppp1               ppp0: cell network iface
      vif0-=       .
            \      .
             \     .
              = = = -pppn

I would like to propose an alternative where Mobile IP _is_ used but
only for heterogeneous handovers; and let the homogeneous simultaneous
multiple interface management be managed by something else.  The two
(Mobile IP and something else) should be compatible:

                    Managed by something else, less frequent IP updates
                     ---^---
                    /       \
                      /= = = -ppp0
                     / = = = -ppp1
             / vif0-=       .
             |       \      .
             |        \     .
    Managed  |         = = = -pppn
    by      <
    Mobile IP|
             | wifi0-                  wifi0: WiFi interface
             |
             \ bt0-                    bt0: Bluetooth interface
                                       all are egress.

This perspective takes advantage of the fact that the ppp interfaces
hold stable addresses over long periods of time (during the vehicle
route) whereas the wifi0 and bt0 IP addresses change much more often.

Mobile IP is very good at managing one interface at a time, switching a
unique default route, and dealing with heterogeneous handovers.  I
believe Mobile IP less appropriate for managing multiple default routes
or for very slow changes of the IP address (where the handovers are
managed by the link layer).

What do you think?

Alex