Mysterious missing DHCPv6 feature, was Re: How does one obtain an IPv6 DNS server when VPNing to an ASA?

[Benedikt Stockebrand]

Hi Doug and list (again),

Doug Barton <dougb at dougbarton.us> writes:

>>> You still haven't answered the question, "Why should RA be _required_
>>> in IPv6 when DHCP is perfectly capable of doing everything that RA can
>>> do and more?"
>>
>> Because RA is way easier to develop embedded devices for than DHCP.
>
> A) This may have been true 15 years ago, but as it has already been
> pointed out numerous times the marginal coast of stateless DHCP
                                                   ^^^^^^^^^
Do you mean stateless or stateful here?

> vs. RA on today's devices is well into the noise.

That may be true down to the ARM class of embedded systems used for
smart phones, PDAs and similar gear.  But check the specs for any of
the smaller Atmel AVR microcontrollers (for starters, try "Atmel_AVR"
on Wikipedia).  These are roughly in the Commodore VC-20 class of 30
years ago, and they are actually used for embedded systems.  Beyond
that, think of RFID devices.

Add to that the extra cost of implementing both Autoconf and stateful
DHCP for address management, at a total resale price of less than
maybe Euro 20 (USD 30) for an entire product, then it does make a
significant difference.

I've done a few IPv6 training workshops with people building these
kinds of devices.  The simplifications IPv6 brings for them *are*
significant as much as making their products dual-stacked is a serious
pain for them.

> And B) even if it were
> true, I don't have these theoretical micro-devices on my network, so I
> ask again, why MUST I configure RA in order to have IPv6?

Why must they implement both Autoconf and stateful DHCP?

Implementing the same feature, i.e. network layer configuration, in
several independent ways, increases the overall complexity and cost of
networks.  In the SIP telephony world this non-orthogonality provides
a rather convenient customer lock-in to the vendors, but it doesn't
really help anyone else.


Cheers,

    Benedikt

-- 
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Benedikt Stockebrand, Dipl.-Inform.   http://www.benedikt-stockebrand.de/