Subject: Re: [MOBILE-IP] [SIP] Applicability of IP Mobility to CDMA Soft Handoff

From: Ashutosh Dutta <[email-masked]>
Date: Wed, 3 May 2000 13:52:15 -0400

HI James & co,  I have few questions after my first reading of the draft
Page 7:
             When you talk about RAN-RAN interconnection (closley coupled way),
what is your assumption? Does each neighboring  RAN (RAN-GW) belong to a
different IP subnet? or these RAN-GWs belong to the same subnet but are just
distributed along.

Page 6:

               Client listening to multiple base stations (3 or 6) at the same
time: Do you assume multiple interfaces on the client or just one?
In cases where the neighboring BSs for a mobile client are part of RANs
belonging to different subnets ( and controlled by different RAN-GW), how does
the RAN-GWs interact with each other to take care of soft-handoff, probably some
sort of IP-mobility solution like IP multicast can be helpful here.

Thanks
Ashutosh

---

From: James Kempf <[email-masked]>
Date: Thu, 4 May 2000 08:22:07 -0700

>different IP subnet? or these RAN-GWs belong to the same subnet but are just

Whether or not they belong to a different subnet is not important from the
point of view of a moving terminal, since the terminal's IP packets
are not routed through the RAN based on the terminal's IP address.
The termimal's packets are processed into radio frames, in which
the IP packets are encoded. If the RAN is IP based (it may not be and, in fact,
in current 2G and 3G designs is not), then the links are typically point to
point or at most one hop, due to the stringent timing constraints. The
radio frames in an IP-based RAN would run on top of IP (maybe UDP) directly, and
the terminal's IP packets would not be identifiable in the RAN as
such, except by performing the same processing the terminal's CDMA
hardware performs to decode the radio frames.

>sort of IP-mobility solution like IP multicast can be helpful here.

The client has only one "interface" in the IP sense. A mobile CDMA
phone uses a signal processing technique to combine the incoming
signals to produce a single packet. This process proceeds at
the physical layer, i.e. L1, and therefore the upper layers never
see more than a single packet as was incoming to the frame selector/
distributor from the corresponding node. So the phone can have only a single IP
address for the CDMA connection, even though at the physical layer there are
multiple signals coming in with the same (modulo errors) octet stream.

This characteristic is the single largest deterrent to using IP
mobility in CDMA RANs.

                jak

---

From: James Kempf <[email-masked]>
Date: Fri, 5 May 2000 10:46:05 -0700

>James,
>
>> ATM is already packet (well, cell) switched. There is a potential opportunity
>> for replacing ATM with IP, provided the stringent timing and jitter
>> constraints can be met, but I don't think that existing IP mobility solutions
>> will have a role to play in CDMA RAN networks for soft handoff purposes.
>
>You claim that IP is not able to guarantee delay and jitter
>requirements, while ATM is able to do it. This is not proven. If this
>is the central point of the draft, you will have to back it with data,
>otherwise we are not on solid ground. Personally I would be very
>interested in arguments in favor of ATM regarding QoS guarantees, and
>for a complete and satifying draft, you should probably consider
>extending the draft in this direction.
>

No, what I said was that IP *MAY* have a role to play in the RAN, but it
has not been proven yet.

Personally, I think it does have a big role to play, but, as an engineer,
I'm not willing to say "yes" until I see the numbers.

>If it is not QoS which differentiates an ATM based RAN and an IP based
>RAN, then it the mobility protocol which is used. I think THIS FITS
>the charter of this WG, and we should focus on whether MIP and
>the micomobility proposals (CIP, RMIP, HAWAII) are able to support
>the needs of ANY radio technology. The MIP in its current form
>is not able to "penetrate" the WCDMA RAN, it has to stop at the
>edges.
>

As we tried to point out in the paper, given current understanding of
IP routing protocols and RAN designs, our belief is that soft handoff
is not a candidate for replacement with current IP mobility, but
hard handoff is. A hierarchical model of mobility management, with
soft handoff being highest performance and mobile IP for hard
handoff, seems like the most logical model to me.

Personally, I'd like to see the fast handoff discussion in this group confined to
replacing hard handoff, and confined to the context of current mobile IP
and IP routing protocols. If there is interest in looking at new
routing protocols and mobility management for networks that operate
like CDMA RANs, I think it should be taken up in a separate working
group. The model here is MANET, which discusses a mobility model
which is orthogonal to the model presented by mobile IP.  I am skeptical
that a mobility model will cover all wireless networks, simply because, given
the MANET work, we already know that there will be some that
don't fall under the mobile IP model. On the other hand, mobile IP
has proved its usefulness in the 3GPP2 packet data service. It seems likely that any
replacement to current soft handoff that uses IP mobility would
require a separate protocol because the CDMA network is very different.

                        jak

---

From: Roberts Phil-QA3445 <[email-masked]>
Date: Mon, 8 May 2000 10:29:11 -0500

OK.  ATM v. IP is definitely off topic on this list.  Take it offline.

-----Original Message-----
From: Arek Dadej [mailto:[email-masked]]
Sent: Friday, May 05, 2000 10:32 AM
To: [email-masked]
Subject: Re: [MOBILE-IP] Applicability of IP Mobility to CDMA Soft
Handoff

Andrew,
I tend to agree with the first statement (even if it applies to fixed access
networks). However, your second statement is rather far going, if you
consider
switching of high volume, aggregated traffic. Why is it that truly high
capacity, gigabit IP routers somehow cannot do without underlying ATM
switching?
--Arek

-----Original Message-----
From: Andrew T. Campbell
To: [email-masked]
Sent: 5/6/00 3:56 AM
Subject: Re: [MOBILE-IP] Applicability of IP Mobility to CDMA Soft Handoff

My personal view is ATM and virtual cicuits complicate
the design of the access network and are not needed.

Packet based link layers will win - ATM is dead.

---

From: "Alan O'Neill" <[email-masked]>
Date: Tue, 9 May 2000 17:13:23 +0100

James said in

> From: James Kempf [SMTP:[email-masked]]
> Sent: Saturday, May 06, 2000 3:16 AM
>hard handoff is.

James, the authors of <draft-oneill-ema-01.txt > absolutely agree with you
(and for the same reasons). We rewrote the .00 draft  after similar comments
from our UMTS people end of last year, and converted the edge nodes from
basestations (BS) to access routers (AR) so that situations in which the
radio interface were both local and remote to the AR could be encompassed.
Your draft has made this issue clear to everyone which is good.

>A hierarchical model of mobility management, with

But the above does not necessarily follow from the first para...Why not
native (routed) instead of tunnelled forwarding in hard hand-over?

>which is orthogonal to the model presented by mobile IP.

Clearly, the routing piece can sit in MANET if those chairs
are happy, but the signalling hand-over for EMA in support of the routing
has no home if not here.....
And that leads to the risk that we develop (at least) two non-interworking
signalling solutions to the same (or similar) problem, where the only
difference in the solution should be the mode of data -forwarding (native v
tunnelled) which can be selected through policy, AAA, and/or cellular
signalling. In addition, because all the routed solutions require Mobile IP
inter-domain, not including them at all in the work effectively blocks them
to some extent. Hope you can see the problem...

>I am skeptical that a mobility model will cover all wireless networks,
>simply because, given the MANET work, we already know that there
>will be some that don't fall under the mobile IP model. On the other
>hand, mobile IP has proved its usefulness in the 3GPP2 packet data
>service. It seems likely that any replacement to current soft handoff
>that uses IP mobility would require a separate protocol because the
>CDMA network is very different.

You are right to be sceptical but that doesn't mean we should not try,
especially when others believe from their work that a generic (or at least
broader) model is both possible and useful.

Regards,  Alan.

---

From: James Kempf <[email-masked]>
Date: Tue, 9 May 2000 15:21:48 -0700

>native (routed) instead of tunnelled forwarding in hard hand-over?

My understanding from talking with people who have worked on routers
(I'm not a router expert myself) is that the convergence of routing
tables is too slow for handoff of realtime applications. Now, it's
possible that a new routing algorithm that converges faster could
be invented, but interdomain handover is likely to involve different
carriers or ISPs, which means that they will probably want to use
standard Internet routing algorithms between them.

As far as tunneling goes, if IPv6 is used, tunneling may be avoided
in certain cases.

>has no home if not here.....

I'm confused. If the singalling is in support of the routing, then
shouldn't the two activites be co-located?

>to some extent. Hope you can see the problem...

I guess I don't. If you are talking about MANET and mobile IP, clearly
there is a need to look at their interaction, and there would be the
same need for a new protocol for CDMA RAN networks. But why is this
any different than the current IS-95 based network, where soft handoff
runs in the IS-634 based RAN and hard handoff runs over IS-41? Not
to say that this situation is ideal, just that it indicates a data
point of where such work was necessary. And the interaction between
Internet and intradomain routing protocols in wired networks is the
same case.

>broader) model is both possible and useful.

Sure, it's always possible that somebody will come up with a generic
solution. My skepticism is, however, based on experience. Different
routing protocols are used for inter- v.s. intradomain routing for
current fixed, wired networks (BGP v.s. RIP), so I see no reason why the same
shouldn't be the case for wireless networks and their wired access
networks.

                jak

---

From: "Alan O'Neill" <[email-masked]>
Date: Wed, 10 May 2000 10:17:39 +0100

James,

To clarify....

> ----------
> From:         James Kempf
> Reply To:     James Kempf
> Sent:         Tuesday, May 9, 2000 11:21 pm
> To:   [email-masked]; [email-masked];
> [email-masked]
> Subject:      RE: [MOBILE-IP] Applicability of IP Mobility to CDMA Soft
> Handoff
>
>
> tables is too slow for handoff of realtime applications.
>
Yes - deployed algorithms are way to slow.

> Now, it's
> be invented,
That is what MANET has been working on for a while now, and at least one of
these, TORA, looks like it can scale to be commercially important. That is
neither to say that others can't be made to scale, nor does it suggest that
the work is complete. Our hand-over times in simulation are more than
sufficient for real-time apps...one of our primary drivers in doing this is
support of such apps. We have been working on this problem for two years and
are presently coding the algorithm into FreeBSD3.2 for testing and release,
and may also release the OPNET sim code. None of us are in anyway
underestimating the timescales required for the community to understand,
evolve, standardise and deploy a new routing algorithm though, so MIP in the
short-medium term is also important (ie I am therefore really keen that MIP
does this work as well).

> but interdomain handover is likely to involve different
Inter-domain requires mobileIP in our work which is clearly stated in our
drafts. We are not trying to change the Internet routing architecture.
However, with a scalable mobile enabled routing algorithm, inter-domain
hand-over = inter-operator hand-over IN-SESSION which we think will be rare
due to obvious commercial barriers. Roaming is in contrast pretty important.

> As far as tunneling goes, if IPv6 is used, tunneling may be avoided
But not all cases, and nowhere close to majority of cases. But be aware that
tunnelling is also required in our model to support remote access, so
co-existence of native and tunelled forwarding is critical for us.

> shouldn't the two activites be co-located?
The signalling is not in support of routing, it is in support of hand-over
and associated AAA. Hand-over causes injection of messages into the routing
protocol to enable it to track the mobile (mech is routing protocol specific
triggered through the EMA<->routing API). The signalling is common to a
range of possible routing algorithms, and also common in many ways to MIP.

> Internet and intradomain routing protocols in wired networks is the
This seems orthogonal to me - as I agree with it :-)

> shouldn't be the case for wireless networks and their wired access
Not trying to change the routing architecture in anyway...TORA (or whatever)
intra-domain. BGP inter-domain with MIP supporting inter-domain hand-over
(which we all agree technically if not commercially)