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Re: IPv6 RA vs DHCPv6 - The chosen one?
From: Ray Soucy <rps () maine edu>
Date: Wed, 21 Dec 2011 11:25:53 -0500

Agree that in the long term support for more flexibility is good.

Acknowledge that change is slow, and we're just at a point now where
popular host systems even include mature DHCPv6 (but without route

Both of the features discussed would be useful in specific
applications, but more often than not what get's used is what most
host implementations support, so the horse may have already left the
barn on that one, at least for the next 5 years or so.

RA + SLAAC is great for residential environments and automatic discovery.

For a more controlled environment, RA + DHCPv6 is increasingly
attractive, especially in a dual-stack environment where having a
similar operational model for both protocols can simplify operations
and support, and allow for a phased deployment.

Remember, an RFC is just an idea on how things should work; it's not a
standard until most people choose to implement it.

"The nice thing about standards is that you have so many to choose from."

On Tue, Dec 20, 2011 at 1:27 AM, Ravi Duggal <raviduggal2906 () gmail com> wrote:

IPv6 devices (routers and hosts) can obtain configuration information
about default routers, on-link prefixes and addresses from Router
Advertisements as defined in   Neighbor Discovery.  I have been told
that in some deployments, there is a strong desire not to use Router
Advertisements at all and to perform all configuration via DHCPv6.
There are thus similar IETF standards to get everything that you can
get from RAs, by using DHCPv6 instead.

As a result of this we see new proposals in IETF that try to do
similar things by either extending RA mechanisms or by introducing new
options in DHCPv6.

We thus have draft-droms-dhc-dhcpv6-default-router-00 that extends
DHCPv6 to do what RA does. And now, we have
draft-bcd-6man-ntp-server-ra-opt-00.txt that extends RA to advertise
the NTP information that is currently done via DHCPv6.

My question is, that which then is the more preferred option for the
operators? Do they prefer extending RA so that the new information
loaded on top of the RA messages gets known in the single shot when
routers do neighbor discovery. Or do they prefer all the extra
information to be learnt via DHCPv6? What are the pros and cons in
each approach and when would people favor one over the other?

I can see some advantages with the loading information to RA since
then one is not dependent on the DHCPv6 server. However, the latter
provides its own benefits.

Ravi D.

Ray Soucy

Epic Communications Specialist

Phone: +1 (207) 561-3526

Networkmaine, a Unit of the University of Maine System

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