Subject: [mobile-ip] Mipv6 issue #176: HAO accessible for upper layers

From: Jari Arkko <[email-masked]>
Date: Fri, 29 Nov 2002 13:57:48 +0200

Section 9.3.1 says

 > After all IPv6 options have been processed, it
 > MUST be possible to process the packet without the knowledge that it
 > came originally from a care-of address or that a Home Address option
 > was used.

Thomas commented this with the following:

 > Add, that the information that a HAO must still be accessible to
 > higher layers that want it, as there are upper layers that will need
 > access to that information?

The basic idea of HAO is that upper layers do not in general need this
information. The contents of the HAO conceptually replace the source
address of the packet. However, I can see an analogy with the API discussion,
where some applications wish to be able to use care-of address as
a source address. Even if I can't think of any specific example, there
may be some future applications that wish to know if the peer is communicating
from a care-of address, and what that address is.

It seems that support for this, if needed, should be developed as the
API work progresses. Mobile IPv6 base compliant stacks should be able to
support such APIs once they have been specified.

Jari

---

From: "Charles E. Perkins" <[email-masked]>
Date: Fri, 29 Nov 2002 17:07:56 -0800

Hello Jari,

> from a care-of address, and what that address is.

I do not think that there is a close analogy to the case where
a mobile node would choose a care-of address as its source
address instead of its home address.  It would be a closer
analogy to allowing applications to know about all decapsulations
that were done by the mobile node.

I understand that there may be future APIs that expose the
structure of the network-layer packet to higher-level protocols.
However, I believe that, in general, the point is to remove any
need for applications to maintain this visibility.

> support such APIs once they have been specified.

I agree.  Furthermore, I think that we should not get too far
into the realm of specifying what higher level protocols,
or applications, are supposed to do.  The current specification
stops by specifying what the network-layer interface is, and
I reckon that's pretty reasonable.  Perhaps, if we succeed,
there will not be any need to develop API support for HAO visibility.

Regards,
Charlie P.