Subject: Registration (was RE: [seamoby] L2/L3 Paging)

From: James Kempf <[email-masked]>
Date: Mon, 26 Mar 2001 10:12:40 -0800 (PST)

Dave,

>>    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.
>

I think the whole point of paging is that the location is tracked somewhat
less accurately in dormant mode than in active mode. Otherwise, why
bother with paging? The mobile node could simply continue to do
active mode location tracking. Making it less accurate requires less
signalling, allowing the dormant mode mobile more sleep time, saving
battery.

>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 it sounds like a requirement for the mobile node to register with
the network at some point prior to going into dormant mode? The exact
point at which the registration is made may depend on whether a timeout based 
mechanism or an explicit notification mechanism is used at L2 to determine
whether the mobile node has gone into dormant mode.

>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.

I don't necessarily think this needs to be at L2. MIP registration, for
example, would fill the bill.

		jak

---

From: Kulwinder Atwal <[email-masked]>
Date: Mon, 26 Mar 2001 18:37:46 -0500

> -----Original Message-----
> From: Michael Thomas [mailto:[email-masked]]
> Sent: Monday, March 26, 2001 4:15 PM
> To: Casati, Alessio (Alessio)
> Cc: 'Michael Thomas'; [email-masked]
> Subject: RE: Registration (was RE: [seamoby] L2/L3 Paging)
> 
> 
> Casati, Alessio (Alessio) writes:
>  > 
>  >  > 
>  >  > Exactly. But when there is no link we may have 2 cases:
>  >  > the link can be re-established via L2 paging, or the 
> packets (when they
>  > do 
>  >  > need to be delivered) get dropped
>  >  > for a while, and then timers will do the rest.
>  >  
>  >    I believe that there is a third possibility:
>  >    The paging interface allows delivery of IP 
>  >    datagrams. None of these exist, as far as I 
>  >    know, but that doesn't preclude some clever
>  >    radio-heads from doing so :-)
>  > 
>  > 		   Mike
>  > 
>  > 
>  > The 2 I mentioned (packet drop or link re-establishments) do exist.
>  > I agree the third way may not exist (ever).
> 

Not only can it exist.  It does exist.  Take a look at how Piconet Broadcast
works for dormant devices (parked) in Bluetooth.  Further, a device may
power down everything but a small portion of the reciever.  The reciever can
trigger on the L2 address to wake up the rest of the chip/device.

It is clear that a paging protocol is only useful for Commercial Cellular
technologies that:

1. Use Paging as a substitute for routing.

2. Use Paging as a substitute for a power efficient hardware design.

Bluetooth transmissions are timer driven and based on QoS policy.  An
asynchronous paging protocol has no value.  

What is the compelling reason to link a WAN Cellular Paging protocol to a
general IP Context Transfer 'toolkit'?

- Kulwinder.

>    _Ever_? That's a pretty strong statement.
>    That implies that shipping IP packets down
>    some sort of paging interface is just a
>    generally bad idea. I haven't heard anybody
>    give any reasoning of why that might be.
> 
> 	Mike
>

---

From: "Casati, Alessio (Alessio)" <[email-masked]>
Date: Tue, 27 Mar 2001 12:47:48 +0100

The process of paging a mobile, and sending one packet to it over the paging
channel, is called SMS...

Point to point SMS is not sent over the paging channel in GSM/UMTS.
Paging can be used to trigger the reception of the ptp SMS data over other
channels.
Besides, SMSCB (Cell Broadcast) is sent over the CBCH channel in GSM
and over the CTCH in UMTS (TS 25.041 ; TS 24.012 ; TS 25.324; TS 25.301).

Using the paging mechanism to piggyback IP packets seems a bit stretched.
Using
a broadcast or common transport channel, when available, is more feasible,
instead.
On whether this is useful for the things the WG want to do, I'm agnostic...

alessio