Re: [v6ops] DHCPv6/SLAAC Make Hosts Confusing-//RE: new draft: draft-liu-bonica-v6ops-dhcpv6-slaac-problem

Andrew Yourtchenko <ayourtch@cisco.com> Tue, 29 October 2013 19:34 UTC

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Date: Tue, 29 Oct 2013 20:33:30 +0100
From: Andrew Yourtchenko <ayourtch@cisco.com>
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To: Mark ZZZ Smith <markzzzsmith@yahoo.com.au>
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Cc: "v6ops@ietf.org" <v6ops@ietf.org>, Ted Lemon <mellon@fugue.com>, "Ole Troan \(otroan\)" <otroan@cisco.com>, Dave Thaler <dthaler@microsoft.com>, "draft-liu-bonica-v6ops-dhcpv6-slaac-problem@tools.ietf.org" <draft-liu-bonica-v6ops-dhcpv6-slaac-problem@tools.ietf.org>
Subject: Re: [v6ops] DHCPv6/SLAAC Make Hosts Confusing-//RE: new draft: draft-liu-bonica-v6ops-dhcpv6-slaac-problem
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On Tue, 29 Oct 2013, Mark ZZZ Smith wrote:

> So I'm afraid I'm still confused by this.
>
> The reason why you need VRRP/HSRP etc. is because ND NUD isn't acceptably fast enough to detect that a default gateway has gone away. It might be possible to lower the NUD timers such that they detect default gateway death much quicker, however you then have all of the hosts actively probing the default gateway very quickly, creating load on its control plane.
>
> VRRP/HSRP avoids this control plane load by making the the switch between routers transparent or nearly transparent to the hosts, without the need to lower NUD timers. It could be viewed as a NUD special case and optimisation.
>
> This all has nothing to do with RAs or DHCPv6 - the need for VRRP is to overcome a performance limit in ND NUD, and that limitation would still exist in a DHCPv6 only model without VRRP/HSRP. So I don't understand why DHCPv6 is or woud be "better" and RAs are "worse" in this scenario.

Essence of that section: RA deals with routing [not always very 
efficently]. DHCPv6 does not do it at all.

--a

>
>
> Regards,
> Mark.
>