Subject: RE: [seamoby] draft-ietf-seamoby-paging-problem-statement-01.txt

From: "Karim El-Malki (ERA)" <[email-masked]>
Date: Tue, 20 Feb 2001 18:24:26 +0100

Hello James

Thanks for the explanation, it did clarify some things for me.
If some of this thinking was included in the draft it could help
understand the reasoning better.

>The paging area update could
> contain mobile IP registrations, as you propose, no assumptions are
> made about the content of the signalling in the following discussion.

I didn't propose to replace L2 functionality with Mobile IP.
My thoughts were along these lines: if you can track MN movement
between FAs using MIP then it would make sense to leave paging to the
L2 network if the L2 network supports it.

> 
> 	1) Requiring operators to make paging areas and subnets conform
> 	to a subset relationship that would allow mobile IP signalling
> 	to do double duty as paging area updates. This is completely
> 	unrealistic. Paging areas are much larger than subnets 
> typically, 
> 	they often overlap and have other topological oddities 
> that do not 
> 	lend themselves to a uniform mapping.

I would imagine this depends on network design.
I don't think that it would be so unrealistic to have a one-to-one
(or one-to-n) mapping between FA router and paging area. It depends
on how the L2-L3 systems are engineered and could well be different
for different wireless systems. It also depends on how paging areas
are defined in that system. So I still think that it is possible
to do without L3 paging in an L2-paging-capable network.

> Finally, there is the intertechnology case which also would 
> be simplified
> by an L3 paging solution, as outlined in the draft. 		

Haven't looked at this really, but I would guess that if paging
is needed in an inter-technology case (you may have discussed the
need already but there's not much reasoning in the draft) then L3 is
the way to do it.

One other point which I think was made already. A lot of the reasoning in
the Homogeneous Technology section is based on the network-assisted handoff
technique. I believe that, given our discussion so far, that's
not the only option and it is possible for the MN to communicate and
participate in the L3 handoff.

Regards
/Karim

---

From: Madhavi Subbarao <[email-masked]>
Date: Tue, 20 Feb 2001 18:00:40 -0500

Hello,

> L2 network if the L2 network supports it.

L3 Paging can also be used to support MNs that 
are 'roaming' but don't have/need an IP address...

MN 'roams' but is not in communication with
any nodes and thus, doesn't need an IP address.  
As it moves, it MIP registers with new FA but does not
request an IP address (but to make its whereabouts known).  This
propagates to HA, so HA knows that MN can be reached via this FA.
Later when a CN wants to send to the MN, the CN does a DNS lookup
which points to the HA.  HA sends a L3 page message to FA, which
triggers L2 page to MN to prompt it to send a MIP registration and
obtain an IP address to receive communication from CN.

This support is not explicitly stated in the draft, although it
may be helpful to include.

Regards,
Madhavi