Subject: RE: [seamoby] L2/L3 Paging

From: "Martin, David P" <[email-masked]>
Date: Mon, 26 Mar 2001 12:40:30 -0500

<Snipping my question on whether we should assume L2 know the location of
the MN>

>    I don't see why we should assume that. If a mobile
>    is dormant, we probably know its last attachment 
>    point, but that doesn't mean that the L2 must 
>    track its movement accurately.

OK, I agree so far, as long as the L2 tracking granularity is finer than L3.

>    In fact, I'd say
>    that that should be an explicit *non-goal* as it
>    would allow the MN to sleep for longer periods.

<snipping more of my comments concerning level of difficutly>

>    This doesn't seem to hard: suppose you have a
>    beacon which all dormant nodes listen too. To
>    find a node, the last attachment point performs
>    a search in the local paging area. When the mobile
>    wakes up, it establishes a link to its current AP,
>    and a tunnel to the old AP to scoop up the
>    packet(s).

I agree that a paging system can be designed that can work with a technology
that does not continually track a MN location.

However, a (working) paging system *cannot* be designed without a
registration mechanism.  The purpose of a registration mechanism is to
provide rough location state information on where a MN is located in a
network topology.  This location state can be of several forms, specific
access point, specific paging zone, specific network (scalability issues),
last known access point, last known access zone, etc.  But the network has
to have some type of location information to even begin to guess on how to
start paging.  In your example above, the mobile in effect registers upon
wake up, giving the network location state to work with.  Of course a
mechanism must exist (at one or more layers) to deal with stale location
information.

So, I'm trying to say that there must be some location state maintained
somewhere at layer 2, otherwise the entire network would behave as one big
LAN segment.

---

From: Michael Thomas <[email-masked]>
Date: Mon, 26 Mar 2001 10:20:24 -0800 (PST)

Martin, David P writes:
 > registration mechanism.

   Sure.

 > The purpose of a registration mechanism is to
 > start paging.

   Correct.

 > In your example above, the mobile in effect registers upon

   Yup.
 
 > somewhere at layer 2, otherwise the entire network would behave as one big

   I don't see this as having much to do with L2. If
   I can route an IP packet to the last known point
   of attachment, it could put out the dragnet by
   sending out IP packets which eventually (or not)
   find the mobile node. L2 location information may
   or may not be involved. At a base level, I don't
   think we should count on them being there though.

	    Mike