Re: [MEXT] Alt-CoA and PMIP6 (was RE: [netlmm] FW: comment ondraft-ietf-mext-binding-revocation-01)

[Vijay Devarapalli <vijay at wichorus.com>]

Alper Yegin wrote:
> Vijay,
>
> > In MIPv6, if the binding update is successful, the binding ack is always
> > sent to the CoA and not to the source address of the BU. If the AltCoA
> > option is used, then the binding ack would go back to the address that
> > appeared in the AltCoA option.
>
> That's interesting. Is there a technical reason why BA cannot be sent back
> to the source address of the BU (other than not being specified so in RFC
> 3775)?
>
> Mirroring the src/dst IP addresses between BU/BA appears logical, simple,
> and useful. Not sure why it is not explicitly allowed in the RFC 3775.
>
> > In PMIPv6, I don't believe there is a scenario where you would want to
> > use the AltCoA option. (if someone has a valid scenario, please let me
> > know).
>
> Sending and receiving PMIP signaling using Alt-CoA provides the ability to
> separate control plane and data plane. And that's useful for relocating the
> PMIP6 tunnel while keeping the PMIP6 signaling anchored on a fixed MAG
> (because moving that requires re-negotiation of security-related
> parameters). 
>
> This scenario is being examined by WiMAX Forum and use of Alt-CoA appears to
> fit (module some wrinkles and clarifications).

IMO, a clean solution for this would to define a new mobility option 
called the Data Plane Address option. When the LMA encounters the Data 
Plane Address option, it uses the address stored in that as the tunnel 
end point for data packets. The source address of the Proxy Binding 
Update would still be considered as the Proxy CoA and used for all 
control plane packets (Proxy Binding Ack, HA/LMA Switch Message and 
Binding Revocation Indication Message).

I think such an extension would be simple enough that we can standardize 
it quickly.

Trying to do the above with the AltCoA option, IMO, is a misuse of the 
AltCoA option. AltCoA option by definition is supposed to over ride the 
source address of the BU/PBU and be treated as the CoA/Proxy CoA.

Vijay

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