Subject: RE: [mobile-ip] Multi-homing MIPv6???

From: "Hesham Soliman (EPA)" <[email-masked]>
Date: Thu, 11 Oct 2001 12:08:39 +1000

> I have a non-security related question! 
> 
	=> How dare you com on this list :) 

> I don't recall seeing any
> discussion of mult-homing and its relation to MIPv6 HO.  Perhaps
> I missed something.  
> 
	=> Well there is a couple  of issues here: 
	1. How well does ND handle multihoming
	2. How can MIPv6 implementations handle 
	    multihomed hosts for outbound traffic
	3. How can MIPv6 handle inbound traffic 
	    for multihomed hosts

	We had problems with the KAME implementation 
	last year but Mattias can explain that much better 
	than I can. 
	 
	For the second point, there are some implementations
	out there that allow attaching the Home address to 
	a "virtual" interface, hence giving hosts the flexibility
	of splitting their flows on different interfaces. 

	We tried to address the third point in
	
http://standards.ericsson.net/hesham/draft-soliman-mobileip-flow-move-00.txt

	People have commented on it but we haven't added the 
	comments yet. 

> Also, I don't recall seeing much discussion
> of SCTP and MIPv6. 
> 
	=> What kinds of issues do you see ?

	Other useful (related) drafts:

http://www.ietf.org/internet-drafts/draft-ietf-ipngwg-default-addr-select-06
.txt
	
http://www.ietf.org/internet-drafts/draft-ietf-ipngwg-router-selection-00.tx
t

	Also Homeless MIPv6 made a nice attempt but I can't find 
	the link to the draft. Perhaps you could do a serach for 
	it. 

	Cheers,
	Hesham

---

From: Mattias Pettersson <[email-masked]>
Date: Thu, 11 Oct 2001 12:41:08 +0200

>      last year but Mattias can explain that much better

I don't know if we had problems, just too many possibilies... :)

Seriously, multihoming comes in two flavors:
 - One interface that is connected to a multihomed site
 - Multiple interfaces connected to different sites

In the first case the MN has one default router (could be multiple
routers too), and receives RAs with multiple prefixes in them. The MN
would have to choose the correct source and destination address
according to draft-ietf-ipngwg-default-addr-select-06.txt.

In the second case the MN for sure has more than one default router. It
will have a hard time choosing an appropriate next hop just following
RFC2461. Mobile IPv6 gives the implementer free hands, while
draft-ietf-ipngwg-router-selection-00.txt provides some useful
guidelines.

The problems we had were related to that regular ND is not defined for
multiple interfaces.

>      of splitting their flows on different interfaces.

Using different care-of addresses on different interfaces is one aspect
of multihoming with MIPv6.

Another is when the home subnet is multihomed and you will have multiple
home addresses.

Yet another is when you have multiple home networks (because you have
multiple interfaces or for some other reason) and each is generating a
set of home addresses.

>      http://www.ietf.org/internet-drafts/draft-ietf-ipngwg-default-addr-select-06.txt
> 
>      http://www.ietf.org/internet-drafts/draft-ietf-ipngwg-router-selection-00.txt
> 

Homeless MIPv6 is interesting because it targets both mobility and
multihoming. In that draft all addresses are valid for communication.
There is no such thing as home addresses and care-of addresses (although
they are mentioned for backwards compatibility), and renumbering,
mobility and multihoming is hopefully covered by this protocol. The
upper layers are somewhat aware of all addresses used.

I figure SCTP could be made to do similar things, but it is not designed
for mobility.

Mobile IPv6 is very different because it focuses on a static home
address that is visible to the upper layers while the actual addresses
used are hidden.

BTW, has anyone tried Mobile IPv6 together with home network multihoming
or renumbering?

/Mattias

---

From: Francis Dupont <[email-masked]>
Date: Fri, 19 Oct 2001 18:12:02 +0200

=> I proposed to use mobility mechanisms for this case (the idea
is mobility provides a way to use an alternate address when an
uplink of the multihomed site fails: resilience for already opened
connections).

=> my purpose when I implemented mobile IPv6 was to support switch
between different link technologies, for instance (my favourite :-)
replace my expensive 9600bits/s GSM data by a free 100Mbits/s Ethernet.
So not only there is an issue in the choice of the best interface,
but the availability is highly dynamic. BTW simultaneous usage is
even more complex (I know some research works about this).

   routers too)                                              ^^^^^^^^

=> likely (i.e. if you have need/money to get many uplinks you should
duplicate internal routers too :-).

   and receives RAs with multiple prefixes in them. The MN
   would have to choose the correct source and destination address
   according to draft-ietf-ipngwg-default-addr-select-06.txt.

=> this is not enough because the issue is the choice of the
"default link" (which drives the whole thing) between independent sites.
For instance if an interface is connected to the home link you should
prefer it (a simple rule but this has to be explicitely in a policy).

=> I disagree: ND is defined for routers which have commonly multiple
interfaces. The problem is for hosts with multiple interfaces.
And for instance (not a criticism) the router selection draft doesn't
help when a host is attached to independent sites, i.e. an extra policy
is needed (but there already are a lot of multi-interface hosts so
the problem is more no-spec/no-common-solution than no good solution
is known).
   
   >      of splitting their flows on different interfaces.
   
=> I believe this is the best way (i.e. I advice all new implementors
to do that).

=> this is the defaut in the second case.

=> i.e. when can get second and first cases together.

=> you don't need multiple home networks in order to get a very complex
situation (:-).

=> I didn't read last address management in SCTP drafts but if SCTP has
(or shall have) address list management it has no fallback (e.g.
home agent) mechanism so mobile to mobile is not fully supported.

=> Mobile IPv6 is more a two level (identifier/routing) beast than SCTP.

=> yes, a colleague of mine seems to believe more prefixes you have,
better it is (:-).

   or renumbering?
   
=> my first answer describes something that you should like (PS:
real life renumbering takes days so has no fun :-).

Thanks

[email-masked]

PS: Mattias, you should come or send someone to the ETSI IPv6 plugtest
in order to test codes in these interesting cases (BTW there will be
a lot of IEEE 802.11b for cellular addicts too).