Subject: [16ng] For your comments: "Duplicate Address Detection Optimization Using Enhanced Neighbor"

From: xia yangsong <[email-masked]>
Date: Wed, 14 Jun 2006 11:42:52 -0500

Hi all,
  
   I have submitted the draft as follow,
   http://www.ietf.org/internet-drafts/draft-xia-16ng-end-00.txt.

   Please review. 
   Your comments will be appreciated.

Best Regards
Frank

---

From: JinHyeock Choi <[email-masked]>
Date: Fri, 28 Jul 2006 16:25:13 +0900

Dear Frank and Behcet

I finally went over the eND draft and here are my belated comments.

I think it is useful to explicitly notify a host the uniqueness of an
address in case there is a reliable and trustworthy omniscient entity,
whether a router or a server, which knows all the address currently in
use on a link. Then DAD can be performed without multicast. Also it
can be done more quickly.

However I have a few concerns on the draft.

First, I understand that a router indicate the address uniqueness by
sending an RA with P bit. But it will be difficult to secure a bit 
in RA message format for this purpose. As you may know in DNA discussion, 
there hardly left a bit in reserved filed of RA.

Second, it's not clear how that RA can carry the address whose
uniqueness it guarantees.

In the RA message, there is no field to carry Target address.

Also I assume that the (DAD probe) NA has
- unspecified source address,
- solicited node multicast destination address,
- tentative address as Targent Address
- NO source link-layer address.

So the router doesn't know the host's link-layer address and can't
send the RA to the host in unicast.

Third, in Sec 4.4., I wish the draft describes how the host behave
upon receiving an RA in more detail. I have difficulty understanding
the operation.

I wish the above helps.

Thanks for your kind consideration.

Best Regards

JinHyeock
>From [email-masked] Sat Jul 29 00:38:22 2006
From: Pars Mutaf <[email-masked]>
To: [email-masked]
Organization: INT Evry
Date: Fri, 28 Jul 2006 15:49:59 +0200
Subject: [16ng] is access router an oracle
Reply-To: [email-masked]

Hello, 

I have a question about the centralized DAD approach (i.e. with AR
acting as oracle as currently being discussed in 16ng). I would be 
more than happy if you send me a reply. Please help me understand
(seriously).

The IPv6 interface ID has 64-2=62 bits that can be used for stateless
address autoconfiguration. With a reasonable random number generator, we
can generate IPv6 addresses with ~0 address collision probability (or,
am I overly optimistic ;-).

But no. We don't feel comfortable. Computers are not reliable. There may
be a bug or another problem and a collision may occur. Hence, we need a
duplicate address detection mechanism. Then (in 16ng) we rely on the
access router knowing all addresses to detect the address collisions.

We don't trust computers, but we trust the access router acting as an
oracle i.e. knowing all addresses. Isn't that strange? There is no bug
in the access router? What if one, or more, or all addresses were lost
by the AR? 

If the AR is not error-prone (it isn't), its contribution is really
important? In addition, please don't forget that it is not easy for the
AR to learn ALL addresses (please see my reply/question to Erik).

This makes sense? Or, is there an error in my thinking.

Thank you.

Best regards, 

Pars Mutaf

==========

A psychological test:

There is an incoming packet (ok?) The AR (knowing all addresses in the
subnet) checks whether or not the destination address exists in its
cache. No it does not exist. 

What the AR should do?

a) Drop the packet
b) Perform neighbor discovery 

If you choose (b), then you don't think the AR reliably knows all
addresses.