> >Considering the case of a mobile node initiating a TCP
> connection to a
> >global address, with a choice of a global home address and a
> global care-of
> >address, I think the desirable default behavior to use the
> global home
> >address for the TCP endpoint and insert the home address
> option (and a
> >binding-update option in the SYN). I think this is the
> desirable default
> >even if the care-of address and the destination address appear to be
> >topologically closer than the home address and the
> destination address.
>
> I agree. That way the TCP won't break if and when the mobile moves,
> which is one of the main reasons for doing mobile IP in the
> first place.
>
> It would also be good if common apps made it very easy for the user to
> override the default behavior and force use of the COA address as the
> source, for those cases when the user (a) knows that the
> destination is
> "close" and (b) doesn't plan to move before the session ends
> or doesn't
> care if a move breaks the session.
I can imagine having a "this is short-lived" socket option, and if the app
sets the option then the stack would prefer care-of addresses over home
addresses instead of the other way around. This is the app telling the stack
that your condition (b) holds. I don't see the importance of condition (a).
Assuming you send a binding-update in the SYN, then communication using the
home address will be relatively efficient - just a little more overhead in
the packets, but no extra packets and no packets going through the home
agent.
The main exception would be when you are dealing with a server that handles
lots of short-lived connections - it's binding cache might not work well. So
for your short-lived connections to such a server, you'd want to use your
care-of address instead of your home address.
If this option is going to be useful, it needs to be something that the app
can decide - having UI for this would not be good.
Rich
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