[DNA-BOF] DAD Optimization Problem Statement

[Youn-Hee Han <yhhan@sait.samsung.co.kr>]

Hi all,

I and Soohong have been writing a problem statement draft 
for DAD optimization. Although we seems to need a more 
discussion about the exact definition of 'DAD optimization',
we hope that our works will help us discuss about it.

You can see an incomplete version of the draft in the following link;
http://myhome.personaldb.net/bluebibi/dadopti/draft-han-dna-dadopti-problem-statement-00.txt

As Soohong said in the previous mail, we do not assure that
DNA wg just try to reduce time delays of the current DAD.

The current problem statement document handles mostly 
the time delay problem. And, we included another problem as follows:


*******
[Link local scope of DAD]

The current DAD scheme can guarantee the uniqueness of an address
only inside a link. It uses the Neighbor Solicitation/Neighbor
Advertisement message exchange to detect duplicate address. Because
the messages can't go over a router, DAD may not detect a duplicate
address in an another link.

Here is an example. Assume a router has two interface attached to two
separate links. It assigns the same prefix A:: to them and advertises
the Router Advertisement messages with the prefix A:: with L bit
(on-link flag) off and A bit (autonomous address-configuration flag)
on.
                              ________
              A::            |              |                A::
_______________|  Router  |__________________
              |               |_______|                  |
              |  A::1                                        |  A::1 
       ___ |____                                  ___|___
      |               |                                  |            |
      |   Host     |                                  |   MN   |
      |____ ___|                                  |______|

Assume there is a host with address A::1 in the first link. Then
another host arrives at the second link and forms an address with
stateless address autoconfiguration. The second host happens to have
1 as its interface id and picks A::1 as its address. Then, even
though the second host performs DAD, it can not detect the duplicate
address at the first link. If the second host moves to the first link
(or the first host moves to the second link), hence, the address
collision occurs, because the moving host considers the new link as
the same link as the previous one and does not create a new address
at the new link.
********

What do you think about this? If you have any comments, please send me.
Currently, we consider this as a DAD problem related to DNA wg.

And, we can think another problems as follows.
The followings are not contained in the current document.

  [Possible subjects 1] 

    The basic DAD procedure is very vulnerable to a simple Denial-
    of-Service attack.  Basically, an attacker simply prevents a 
    node from getting a link local address by claiming to have that 
    particular address. 

  [Possible subjects 2]   

   In order to process DAD, all nodes have to send solicited-node 
   multicast address using NS message, whenever IPv6 addresses are 
   composed of its interface identifier.  This procedure may reduce 
   the network performance especially within the low bandwidth 
   networks.

   [Possible subjects 3] 
 
   IPv6 node in 802.11 environments will never be able 
   to receive the DAD packets if its MAC address is same as another 
   node, because of the frame filtering based on the source MAC 
   address.  In this case the DAD always succeeds even though the 
   addresses are duplicate.

Do you have any comments about these?
Should we include these problems in DAD optimization problem statements?

Thanks for reading long mail.

Youn-Hee Han