Subject: [Mip4] draft-ietf-dhc-mipadvert-opt-01.txt

From: Pete McCann <[email-masked]>
Date: Tue, 2 Dec 2003 14:34:01 -0600

One more late comment on this draft (I don't have an opinion at this
time on whether it should be advanced):

Is it required that all mobility agents configured by this option be
on-link?  That seems to be implied by text like the following:

>   H
>      Home agent.  This agent offers service as a home agent on the link
>      on which this mobility agent announcement is sent.
>
>   F
>      Foreign agent.  This agent offers service as a foreign agent on
>      the link on which this mobility agent announcement is sent.

But is it really necessary?  For example, you should be able to
configure a home agent that is on a remote link, right?  Then your
DHCP-configured address could be used like a co-located CoA for a MIP
registration, and you could keep the HA for subsequent handoffs.

This might be a good way to, for example, configure an HA in the local
network while roaming, but when you haven't deployed Mobile IP FAs,
and you want to centralize the HAs on links other than the access
links.

I assume this sort of functionality would be supported by the existing
Mobile IP Home Agent option specified in RFC 2132.

-Pete

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From: Henrik Levkowetz <[email-masked]>
Date: Tue, 2 Dec 2003 22:24:27 +0100

Hi Pete

> time on whether it should be advanced):

Ok

> registration, and you could keep the HA for subsequent handoffs.

Yes. Quite right.  The text implies it, but unnecessarily. 

> and you want to centralize the HAs on links other than the access

Not sure I see exactly what you mean here. Are you thinking in terms
of virtual home networks / never-at-home mobiles?

> Mobile IP Home Agent option specified in RFC 2132.

Yes; if you only want to configure an HA the Home Agent option should
be sufficient. 

I originally wrote a draft defining only an FA option, (as that's what
we needed) but as the numbers of fields grew, and I included almost all
of the regular advertisement fields, I thought I might just as well make
it general. Also, as the number of available dhcp option codes are quite
limited, I thought I'd define this as a more general option with
sub-options so as to make room for possible future mobility-related
options without depleting the option space further.

	Henrik

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From: Pete McCann <[email-masked]>
Date: Tue, 2 Dec 2003 16:40:10 -0600

Hi, Henrik,

 > of virtual home networks / never-at-home mobiles?

That's a possible use case but not the only one.  MNs wouldn't be
prevented from going home, it is just that when they initially attach
to the network and start a session, they may not be on the same link
as the one on which the operator has deployed HAs.  The HAs would be
in the same network (same administrative domain) but could be on
another link.  If that link does not provide access, then the MNs
would never go home.

 > Yes; if you only want to configure an HA the Home Agent option should

Ok.

 > it general.

Yeah, that's the impression I got while reading it.

 > Also, as the number of available dhcp option codes are quite

Ok, but maybe the language describing the H bit (at least) should be
touched up a bit.

-Pete

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From: Henrik Levkowetz <[email-masked]>
Date: Wed, 3 Dec 2003 00:17:05 +0100

Hi Pete,

> another link.  If that link does not provide access, then the MNs

Ok, so you're here thinking of the dhcp assignment of HA as a
provisioning mechanism, I guess. In combination with the dynamic HA
assignment draft it would be a way of provisioning the first HA to
contact (now called the Requested HA in that draft), for instance.

> Yeah, that's the impression I got while reading it.

Right :-)

> Ok, but maybe the language describing the H bit (at least) should be

Yes, I'll take care of that.

	Henrik