Subject: Re: [MOBILE-IP] Some comments on draft-kempf-cdma-appl-00.txt

From: Arek Dadej <[email-masked]>
Date: Fri, 5 May 2000 06:02:07 +0930

Andras,

The "horror" stack you describe below is nothing really horrofic, and nothing
new. Telecom networks have seen this many times already, and the operators were
not only happy, but also knew how to manage all this. The answer is, as I
already pointed out, in the stratified view of stacks.

If you want examples, here are a few:

1) a very basic and old one: IP-level interconnection between a number of
geographically distributed LANs using switched PSTN or ISDN connections. You
have the PSTN or ISDN stratum first (with its own L1 transmission, L2 link
control and L3 routing), and this is used by the IP stack (with "null" L2 in
most cases)without the IP really knowing what's underneath. The same goes for
old X.25 networks that were often run in a similar way.

2) TCP/IP over ATM over satellite network - first you have the satellite
stratum (complete with layer 3 if we are talking network of satellites), ten
there goes the ATM infrastructure, and finally the TCP/IP network.

3) Most of the "IP switching" schemes - you have the complete ATM (up to the
ATM layer) underneath the TCP/IP network with IP-based routing decisions, then
you have to see ATM stratum first, and the IP on top of it. Note that ATM,
since it involves switching of cells between multiple points, is in fact a
complete NETWORK infrastructure.

It should not be too difficult to find a few more tricky, more complex existing
systems that resemble your horror stack, yet are happily used by te operators.

Regards
--Arek

-----Original Message-----
From: veres
To: [email-masked]
Sent: 5/4/00 10:22 PM
Subject: Re: [MOBILE-IP] Some comments on draft-kempf-cdma-appl-00.txt

Pete,

> AV> What do you mean by 'end-to-end'? It is a message between the
> AV> control unit (typically in the RNC) and the BTS or MH. In this
> AV> respect it IS e2e, as it involves two (possibly IP layer) nodes.
>
> What I meant by "end-to-end" was an IP stack on an MT communicating
> with another IP stack somewhere in the network to convey power control
> information.  As Chip correctly pointed out, power control is a link
> layer issue, not an IP layer issue.  We should not use end-to-end
> IP packets to do power control.
>
> -Pete

If you consider the RAN to be L2, then it is a L2 issue. If, on the
other
hand,
RAN is a L3 network, which means that there are several L3 routers
between
the
BTS and the RNC, then signaling between the two nodes is to be done on
L3.

In my view the major problem with current RAN is that it tries to
reinvent

a networking layer on - what it calls - L2, i.e., L2/L1 radio frames are
routed
in the RAN network (consisting of hundreds of nodes!) - which requires
fundamentally L3 funcions e.g., routing protocols.
And do not forget, that on top of this we still need IP with its own
solution
for routing etc.,  even in the current WCDMA solutions, for all data and
management traffic.

Now, IF on top of this pile, we want to place MIP to interwork with all
of
this,
well, where do we end up? Who will be able to manage it? I am not sure
operators
would be happy...

Andras

---

From: James Kempf <[email-masked]>
Date: Mon, 8 May 2000 09:57:43 -0700

>it is easy to understand and appreciate its conclusion, in short this
>draft is not a bombshell
>trying to invalidate Mobile IP in cellular networks.
>

That wasn't the intention. The intention was to question the applicability
of Mobile IP in radio *access* networks. There are other places
in cellular networks where mobile IP has a very big role to play (namely
hard handoff). The draft says something to that effect, but maybe it
should be more strongly worded.

>The typos are:
>1. base station should be replaced by base transceiver station or BTS
>everywhere.

BTS is 3GPP2 terminology. The equivalent 3GPP terminology is Node B.
We were trying to be agnostic, hence, we used terminology that was different
from both.

>2. RAN should probably be replaced by base station controller or BSC in
>most places.

Again, BSC is 3GPP2 terminiology. And RAN implies the entire radio
access network, including (in 3GPP2 terminology) the BSC, BTS, the
wires or optical fiber connecting them, and the connection
between one BSC and another, not simply the BSC.

>3. that soft handoff is an application layer mechanism should be
>replaced by L2 mechanism in at least two places.
>

This is debatable. If you look at the current 3GPP design (for example),
the protocol that does soft handoff (NBAP) runs on top of SCCS-UNI/SCCOP which
is (I presume) the transport layer and network layer, and that runs on top of
AAL5, which is L2. So in the current networks, soft handoff is being
done above L2. I suppose to be technically congruent with the
OSI model, we should have said "session layer" instead of "application
layer". The 3GPP protocol stack actually has a couple places in
the control plane where SCTP over IP over ATM is a supported option for
L4/L3/L2.

We should probably include this example to support our claim about soft
handoff.

                jak