Subject: RE: multi-interfaced vs multi-addressed [Re: [Mip6] Draft Agenda for WG meeting at IETF58]

From: Soliman Hesham <[email-masked]>
Date: Tue, 4 Nov 2003 05:55:05 -0500

> > MIPv6 needs
 > > to allow for more than one coa to be associated with a single
 > > hoa. 
 > 
 > Correct as well.. (but see more below)
 > 
 > But you seem to be neglecting the case where a single interface, but
 > multi-addressed host would act as a Mobile Node.  It needs MIPv6
 > mechanisms as well.  Just using multi6/ipv6 for recognizing 
 > attributes of
 > a prefix is not enough!

=> Of course, I didn't intend to neglect it, I meant that
it requires more work than just MIPv6. But MIPv6 needs to support
multiple CoAs per HoA anyway.

 > Exactly -- which is why solving the generic problem in MIPv6 
 > (the coa-hoa
 > bindings) is probably necessary.  I'm not sure if we've spelled out 
 > whether it's absolutely necessary -- e.g., could it be 
 > possible to use 
 > different HoA's for different CoA's?

=> That's possible, but:
1. Not all MNs will have more than one HoA. 
2. Even if they do, this does not help because the 
CN might pick any of those addresses to communicate
with. E.g. 
- CN first picks the MN's HoA_1. 
- MN binds HoA_1 --> CoA_1 
- CN then picks HoA_1 again for another connection. 
Now the MN wants to bind HoA_1 --> CoA_2 for that
connection (?). 

 > But I fail to see anything relating to interfaces in the 
 > actual problem
 > statement -- which was the point.

=> Perhaps the authors of draft-montavont-pb can take this 
comment into account. 

 > 
 > -- 
 > Pekka Savola                 "You each name yourselves king, yet the
 > Netcore Oy                    kingdom bleeds."
 > Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
 > 
 > 

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From: Pekka Savola <[email-masked]>
Date: Tue, 4 Nov 2003 13:55:00 +0200 (EET)

On Tue, 4 Nov 2003, Soliman Hesham wrote:
[multi-addressed, single-interface scenario]
>  I meant that it requires more work than just MIPv6. But MIPv6 needs to
> support multiple CoAs per HoA anyway.

No, I disagree here.  You're implying that MN with two interfaces would
not need more work.  This does not seem to be correct: clearly, the user
(or someone) must specify the attributes/preferences for the
prefixes/interfaces being used.  The same with just one interface but
multiple addresses.

Perhaps you're assuming that the implementation (or the user) could just
have default values like, "WLAN interface is preferred over GPRS", based
on some characteristics and knowledge, and try to avoid having to have
more fine-grained control for example on the ISPs being used (one could
offer QoS service, other might not)?

My point is that I don't believe it is really possible to have these kinds
of coarse preferences without user interaction -- so the situation should
be pretty close to having to pick between service from ISP X and ISP Y.

(These will probably be even more natural if you put this kind of solution 
in a network where the network access control is already being done -- the 
user would need to authenticate somehow to get service anyway, which would 
yield the information about ISP<->prefix relationships..)

> 1. Not all MNs will have more than one HoA. 

We might be able to mandate it (not sure if that's feasible, but that
might be an option).

> Now the MN wants to bind HoA_1 --> CoA_2 for that

I take it you mean the problems occur because we can't signal to CN which
HoA it should be using, and we couldn't control which path
("cheap/expensive") between the HoA and the CoA is chosen?

There might be ways to work around this problem, but it might be that 
multiple CoA's per HaO would be needed.