Subject: [Mipshop] RE: I-D ACTION:draft-hancock-mipshop-gist-for-mih-00.txt

From: "Hepworth, Eleanor" <[email-masked]>
Date: Thu, 6 Jul 2006 17:08:46 +0100

Hi Akbar,

> I read your Internet Draft with some interest as I am also 
> interested in the topic of Media Independent Handover.  I had 
> the following questions:
> 
> 1) We had written an Internet Draft
> that suggested some MIH application timers and application 
> retry mechanism using UDP.  As far as I can see this is 
> complementary to the GIST approach that you are advocating as 
> GIST assumes that the applications take care of this type of 
> functionality.  Is my interpretation correct?

Not quite.  The assumption we make in the GIST case is that the retry
mechanisms, and associated timer and other control related mechanisms,
which are needed to handle network layer imperfections such as
congestion and message loss, are handled by GIST.  However, retries to
handle MIH application error conditions are handled within the
application.  The reason for this division is explained in the design
considerations draft
(http://www.ietf.org/internet-drafts/draft-hepworth-mipshop-mih-design-c
onsiderations-00.txt).

In that sense, both approaches require MIH application intelligence to
recover from error conditions.  The difference is that in the GIST
approach this intelligence can be tuned purely to cover typical
application performance rather than having to take into account and
adapt to network conditions as well.
 
> 2) I was not clear on how GIST would take care of the MIH 
> proxy situation (e.g. MIH L2 function in network that acts as 
> proxy for terminal when communicating with MIH network 
> server).  Can you please explain?

We don't see that this is necessarily a special case; GIST would be used
between the access point/base station and the interior of the network.
There are problems with providing meaningful security protection between
the terminal and the MIH server (the network node providing the peer MIH
service) in this scenario, however, those problems are fundamentally
caused by the decision to use mixed L2/L3 transport.
 
> 3) Do you have a view of MIH interactions with other mobility 
> protocols such as Mobile IP?

So far as MIH being used to support mobility protocols e.g. triggering a
MIP handover, this is more a matter of the MIH application themselves
and hence in the scope of 802.21 rather than this topic in MIPSHOP.  In
that sense, I think we're pretty aligned with the views in section 7 of
your draft.

Thanks

Ele

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