comment on draft-tsirtsis-dsmip-problem-03.txt

[Ryuji Wakikawa <ryuji@sfc.wide.ad.jp>]

Hello 

Thanks authors for this draft. 

This draft assumes the case where a mobile node possibly needs both
v4 and v6 reachability with mobility support.
But if mobile just wants IPv6 communication, IPv4 reachability is not
necessary. IPv6 reachability at IPv4 network is important. 
For these mobiles, what we need is just extends MIP binding to bind
IPv6 HoA and IPv4 CoA or vice versa.

The draft lists the following work
   - it should be possible to create IPv4 extensions to Mobile IPv6 so
   that a dual stack mobile node can register its IPv4 and IPv6 HoAs to
   a dual stack Home Agent using MIPv6 signaling only.
   - it should be possible to create IPv6 extensions to MIPv4 so that a
   dual stack mobile node can register its IPv4 and IPv6 HoAs to a dual
   stack Home Agent using MIPv4 signaling only.
   - it should also be possible to extend MIPv4 and MIPv6 so that a
   mobile can register a single CoA (IPv4 or IPv6) to which IPv4 and/or
   IPv6 packets can be diverted to.

I am not sure whether a mobile nodev6 always needs IPv4 HoA. 
Assignment of both v4 and v6 HoA limits deployment scenario, too.  It
requires that a mobile node have to subscribe to one service provider
for v4 and v6 mobility.

Therefore, I believe MIP4 and MIP6 should support movement to both
v4/v6 network, but not delivering both v4/v6 packets.
If a mobile node needs IPv4 reachability with mobility support, it
should supports MIPv4 that is capable to move to IPv6 network.  The
same for IPv6 reachability. 

Unless we will decide to re-design single mobility protocol (super
MIP:-)) for IPv4 and IPv6, it is better to use both protocols on a
mobile node that needs both IPv4 and IPv6 reachability. Then, a mobile
node can have IPv4/v6 HoA after all.

regards,
ryuji