Re: [MEXT] Subject: Multiple CoA draft 10 -- two proposals and some comments

On 12/12/08 1:08 AM, "Christian.Kaas-Petersen@tieto.com"
<Christian.Kaas-Petersen@tieto.com> wrote:

> Assume a mobile node with home address HoA has two interfaces,
> both attached to foreign links.  After exchange of binding update
> and binding acknowledgement, the home agent's binding cache (at
> least the snip of it related to HoA) will look like this
> 
>     HoA, BID= 7, CoA1, other parameters like period of validity...
>     HoA, BID=10, CoA2, other parameters ...
> 
> The draft uses HoA=2001:db8::EUI.
> 
> Draft 10, section 5.1 states, that a BID value must be unique for a
> home address and care-of address pair.  This is satisfied above, but
> it means, that the mobile station is not allowed to change the
> second entry such that it also uses CoA1 as care-of address.

=> But why would the MN want to do that? The scenario you're suggesting
means that there is effectively one binding, so why do we need to allocated
two BIDs to the same CoA? If there is a reason then I think your proposal is
fine, although it will be tricky to implement. But I'd like to see a
plausible scenario first.

> Draft 10, section 4.2 (and other places) defines the H flag, which when
> set means the mobile node wants to use both its home link and one or
> more of its foreign links.  The H flag is really an instruction to the
> home agent, that in addition to all the bidings currently defined
> is shall have an extra binding where packets shall not be tunneled.
> 
> Proposal:  The mobile node should be able to define a binding saying
> 
>     HoA BID=0 HoA
> 
> This is a kind of default binding to be used when any of the other HoA-
> bindings cannot be used.  I think the H flag is an indirect way of
> saying there is an extra binding, whereas the binding above is direct.
> It also avoids continuously setting the H flag when both home link
> and foreign links are active.

=> This is basically asking for a permanent binding. Again, I'd like to
understand why this is needed, compared to what the draft says now.

Hesham

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