Subject: Re: [MOBILE-IP] A practical question...

From: "Hesham Soliman (EPA)" <[email-masked]>
Date: Tue, 10 Oct 2000 10:42:57 +1100

Hi Thierry,

I believe your solution is perfect for one case :
The devices connected to the MR do not have a MIPv6 implementation. 
Some people might argue that if you do not have a MIPv6 implementation
then you should not be mobile. But that is also debatable I think.

If the devices have MIPv6 in them (ie. MN's) then they can manage their 
own mobility. There is a chapter on this in the HMIPv6 draft. In this case 
the MR advertises itself as a MAP upon entering a foreign network.
As a result the MN's attached to it would register with the HA with an 
alt-CoA which is the MR's (MAP) address. 

It would be good to get your comments on this solution. 

Cheers,
Hesham

> -----Original Message-----
> From: Thierry Ernst [SMTP:[email-masked]]
> Sent: Tuesday, 10 October 2000 2:57
> To:   [email-masked]
> Subject:      Re: [MOBILE-IP] A practical question...
> 
> Matteo Berioli wrote:
> > PROBLEM: Let' s assume we have a Mobile Router, to which a Mobile Host
> > attaches. We know how the matters work with IPv4 and Mobile IP (see
> > RFC 2002 par: 4.5 page 61-62). The problem is here that we have a
> > double re-direction of each packet directed to the Mobile Host. As a
> > matter of fact, each packet has to pass through the Home Agent of the
> > Mobile Host and then through the Home Agent of the Mobile Router.
> > Let's assume, now, that the mobile network is an IPv6 network. In IPv6
> > could be this double re-direction avoided?
> 
> Hi Matteo,
> 
> I have also been doing some thinking about mobile networks.  This issue
> has not really been addressed nor even raised though there are many
> interesting problems to be dealt with.   
> 
> At the time being, Mobile IPv6 does not support mobile networks at all.  
> The Home Agent of the Mobile Router is unable to redirect packets sent
> to a node attached to the Mobile Router (call it MNN - Mobile Network
> Node), and no optimal routing is possible between the CN and the MNN.   
> See my Internet Draft for the problem description on the IETF web site
> or on my web page:
> http://www.inrialpes.fr/planete/people/ernst/Documents/draft-ernst-mobilei
> p-v6-network
> 
> 
> > 1° possibility
> > A pool of IPv6 addresses is assigned to the Mobile Router when it
> > desires to connect to the Internet; so the Mobile Router can assigned
> > an its own Care-of Address to each Mobile Host asking for one. This
> > allows the Mobile Host to inform by itself its Correspondent Nodes and
> > its Home Agent of this new Care-of Address, and this avoids the double
> > re-direction...
> 
> You need a protocol to enquire and distribute the care-of address
> between the Mobile Host and the Mobile Router.   
> 
> > 2° possibility
> > A single IPv4 address is assigned to the Mobile Router as its Care-of
> > Address, because, for example, the Edge Router to which the Mobile
> > Router attaches doesn't support IPv6. Now the problem comes!
> 
> Are you dealing with Mobile IPv4 or with Mobile IPv6 ?  
> 
> > It could be solved in this way (I wonder if it is possible and
> > realistic...):
> > when a Mobile Host attaches to the Mobile Router, it asks to the DHCP
> > server, which is in the Mobile Router, for a Care-of Address, and
> > sends its Home Address to it;
> 
> The DHCP server is not necessarily on the Mobile Router.   The Mobile
> Network may be composed of several routers (i.e. subnets).  What if the
> Mobile Host does not attach directly to the Mobile Router ?
> 
> > the Mobile Router could use Stateful Address Autoconfiguration
> > (setting M=1 in the Router Advertisement packets), and it could oblige
> > all the hosts in the mobile network, to acquire the same Care-of
> > Address, that is the one it got from the Edge Router!!
> 
> > So all the hosts, both fixed and mobile hosts, share one Care-of
> > Address; but they don't care about this, because the Mobile Router set
> > M=1 in the Router Advertisement packets, so avoiding Stateless Address
> > Autoconfiguration and Duplicate Address Detection.
> > So each host on the mobile network can inform by itself its
> > Correspondent Nodes and its Home Agent of this new Care-of Address.
> 
> As a result, all hosts have to take active part in the mobility
> management of the mobile router.     I don't find this solution
> reasonable.   My solution is that all the mobility management is done by
> the Mobile Router (MR) ; the MR advertises its CoA together with its
> prefix asking all CNs of nodes located in the mobile network to use the
> MR's CoA when they want to send a packet holding a destination address
> matching the prefix of the MR.
> 
> > Now when a packet arrives to the Mobile Router, obviously it will be
> > encapsulated in an IPv4 packet (see figure in the attachment), so
> > first of all the Mobile Router has to decapsulate it.
> > Then if the packet comes from a Correspondent Node it will have, as
> > Destination IP Address, the Care-of Address of the Mobile Router and
> > in the Routing Header it will have the Home Address of the Mobile Host
> > that is on the mobile network, and with which the Correspondent Node
> > is communicating.
> 
> > The Mobile Router knows the Home Addresses of the Mobile Hosts it has
> > in charge and knows to which link-layer addresses they are related; so
> > the Mobile Router has to recognize this address in the Routing Header
> > and it has to forward the packet directly in the local network to the
> > Mobile Host.
> 
> Same comment as before, if the MN does not attach directly to the MR.
> 
> 
> Cheers,
> Thierry.
> 
> --
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---

From: Thierry Ernst <[email-masked]>
Date: Tue, 10 Oct 2000 12:36:55 +0200

Hi Hesham,

See my comments below.

> "Hesham Soliman (EPA)" wrote:
>
> Hi Thierry,
>

> It would be good to get your comments on this solution.

As I understand your draft
http://ietf.org/internet-drafts/draft-ietf-mobileip-hmipv6-00.txt, the
MN enters the mobile network and listens to router advertisements.   It
gets a LCOA and registers with the MAP, i.e the mobile router MR.   It
adversites the MAP's address to its HA and its CNs.   Fine.

How packets get routed from the CN to the MN ?  I understand that the
MAP's address is the home address of the MR.    The MR also gets a
care-of address at each of its Access Router.    Then, the packets sent
from CN to MN is sent to the MAP's address and the routing header
contains the home address of the MN.  The packet gets routed to the HA
of the MR where it is encapulated to the current care-of address of the
MR as if the final destination was the MR itself.   The final
destination is transparent to the HA.   The packet is received and
decapsulated by MR and the desitnation address is switched with the one
contained in the routing header.  The packet is then forwarded to the
MN.

Your proposition therefore works for mobile nodes MNs visiting a mobile
network.  (However, there is no optimal routing between CN and MN, but
this not the present subject of the discussion)

What about FIXED nodes located in the mobile network ?  This was the
topic of my draft
http://www.inrialpes.fr/planete/people/ernst/Documents/draft-ernst-mobileip-v6-network.
For the same reasons as outlined in my draft, the packet sent from a CN
to a FIXED host located in the mobile network can not reach its final
destination.   Packets are routed to the HA of the MR and then the HA
does not know what to do with them.  Those enters in a loop until the
TTL expires.   See the explanation in my draft.  As a result, FIXED
nodes in the mobile network never see the packets sent from CNs. From
what I understand, your solution does address this issue.

I agree that your solution is fine for MNs that visit the mobile
network, but one shouldn't forget about those FIXED host located in the
mobile network.  To me, the issue of routing packet from CNs to the
FIXED host is more important as this is more likely to happen.

Cheers,
Thierry.