v6 & DSL / Cable modems

David W. Hankins David_Hankins at isc.org
Fri Feb 6 15:29:54 CST 2009


On Fri, Feb 06, 2009 at 02:37:00PM -0600, Jack Bates wrote:
> I agree, and I have done this in the past. However, I am very happy with 
> the support of IPv6 to do away with requiring VRRP.

I can respect that.  I don't agree with it, mostly I don't think
IPv6 really has obviated that need, but it's a reasonable position to
have.

> This is a nice method as well, though limited by the half life of the DHCP 
> lease. It also doesn't address the fact that you might be handing out IP 
> addresses from *both* DHCP relay agents with cross redundancy for gateways.

Minor note; the redundancy problem isn't.  :)  It's solved trivially
usually without any changes in config or design.  DHCP just works that
way.

> Dumb hosts is exactly what makes life infuriating. I want smart hosts. The 
> network should be relatively dumb. Perhaps I'm mistaken, but the premise of 
> IP was that hosts are smart and networks are dumb. Then we started making 
> smart networks to break things.

It is issues like this that we so often find polarizing.  I'm not for
a 'smart internet core', but rather for intelligent 'assist services'
for simple/dumb clients to use to cross a simple/dumb network.

I think expanding the behaviour of IP end hosts is going to create a
real mess in terms of emergent behaviours.

> I want built in multiple IP bindings on my hosts. I'd like (Windows 7 

I suppose you can individually configure every host to get itself
temporary addresses from RA announcements.  This isn't usually a
good default configuration, but OS implementation already seems to
be inconsistent on the default configuration here.  So we're back to
the IPv4 dark ages where you have to walk around to all the devices to
effect changes in policy (beyond prefix field contents).

I prefer the model where I configure one (1) DHCPv6 server that does
that for me.

DHCPv6 and RA have all the same multiple-address features, and share
the same semantics in terms of preferred and valid lifetimes.

It gets back to the original philosophical question of design; should
the algorithm run on the clients or on the network's assist services?

Here we may never agree, but my position is that placing the burden on
the assist services simplifies mandatory client implementation, and
centralizes configuration management and control.

Or put another way, it fulfills a larger set of requirements, while
still keeping the rest as a subset of its offering.

-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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