RE: New Version Notification for draft-chakrabarti-nordmark-6man-efficient-nd-05.txt

"Pascal Thubert (pthubert)" <pthubert@cisco.com> Sat, 01 March 2014 18:09 UTC

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From: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
To: 神明�_哉 <jinmei@wide.ad.jp>, Erik Nordmark <nordmark@acm.org>
Subject: RE: New Version Notification for draft-chakrabarti-nordmark-6man-efficient-nd-05.txt
Thread-Topic: New Version Notification for draft-chakrabarti-nordmark-6man-efficient-nd-05.txt
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Date: Sat, 01 Mar 2014 18:09:03 +0000
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Hello Jinmei:

You are correct, that would be a chicken and an egg problem.
In fact, the draft clarifies that the initial RS will have to be multicasted on the link. In section 2:

      Remove the use of multicast for DAD and Address Resolution (no
      multicast NS messages), and remove periodic multicast RAs.  Some
      multicast RS and RA are needed to handle the arrival of new hosts
      and routers on the link since they need to bootstrap to find each
      other.


The multicast is to all routers as opposed to all hosts, and we can expect to improve at least the support of that multicast group.
In practice, a number of WiFi APs out there just block RS towards the wireless side. 

We'll note also that the multicast is of linklocal scope. IOW, for a multilink Subnet, only one link will be impacted. 
This property is leveraged in RFC 6775 for LLNs with the expectation that every device can reach a router over its link, which in route-over is one radio hop.

Cheers,

Pascal


> -----Original Message-----
> From: ipv6 [mailto:ipv6-bounces@ietf.org] On Behalf Of ????
> Sent: vendredi 28 février 2014 23:54
> To: Erik Nordmark
> Cc: IETF IPv6
> Subject: Re: New Version Notification for draft-chakrabarti-nordmark-6man-
> efficient-nd-05.txt
> 
> At Thu, 27 Feb 2014 22:08:27 +0100,
> Erik Nordmark <nordmark@acm.org> wrote:
> 
> > But we seemed to not have edited the rest of the draft correctly
> > around DAD, including the bootstrapping section.
> > As the draft currently stands DAD for link-locals is (or "can be"
> > given the lack of editorial clarity) replaced by NS/ARO. But address
> > resolution for link-local targets needs to be done for using multicast NS.
> 
> I don't understand how it works in the bootstrap stage.  To send the NS/ARO for
> a link-local address (on bootstrap), the host should first know the registrar's
> address.  But the host can't get the information by unicast RS-RA exchange since
> the source address of the RS would need to be the link-local address to prove
> unique.  Or am I misunderstanding your intent?
> 
> --
> JINMEI, Tatuya
> 
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