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

[bmanning at vacation.karoshi.com]

On Mon, May 17, 2010 at 03:42:44PM +0800, Shane Kerr wrote:
> Bill,
> 
> On Mon, 2010-05-17 at 06:32 +0000, bmanning at vacation.karoshi.com wrote:
> > On Mon, May 17, 2010 at 08:05:00AM +0200, Mikael Abrahamsson wrote:
> > > On Mon, 17 May 2010, bmanning at vacation.karoshi.com wrote:
> > > 
> > > >	DHCP to hand out DNS servers, NTP servers on request, and do
> > > >	dynamic update for the forward and reverse DNS maps.
> > > 
> > > And the new feature you were looking for was to hand out a default-gw, 
> > > right? That's the "this" feature you were referring to and IETF didn't 
> > > want to do?
> > 
> > 	-and- hand out DNS servers and NTP servers w/o pulling new
> > 	option codes - basically rework DHCP internals to remove the
> > 	IPv4 specific formats and use an adressing abstraction to 
> > 	allow the existing options (that code addresses) to become
> > 	address agnostic. For me, it was the more intuitive way to 
> > 	slice the DHCP problem - now we have -two- things called 
> > 	DHCP, one for IPv4 and one for IPv6 - and they are functionally
> > 	different.  This seemed nutz to me, we don't have a DNS for 
> > 	IPv4 and a slightly different and incompatible DNS for IPv6. **
> 
> There are a lot of differences, in all ways better for IPv6.
> 
> For example, in IPv6 you always have link-local addresses to use, even
> before you get any "real" IPv6 addresses. For DHCP in IPv4 you have to
> "cheat" a bit on all operating systems to do things like "send to an IP
> without using ARP" or "send a packet without having a IP on the
> interface". You actually need OS-specific code for this in most cases.
> 
> Another fundamental difference is how addresses are managed. In IPv6 you
> have multiple addresses per interface. A proper address management
> protocol, like DHCPv6, needs to know how to hand out multiple addresses
> to a client. Also, in addition to lease timers, each address has
> different timers to allow things like renumbering and privacy-preserving
> addresses.

	you -could- support that in DHCPv6, i don't think its -required-
	or just take the degenerate case (which is what I did) and just
	hand out one - the others get assigned in the usual v6majik.

> A huge amount of protocol hackery would have been required to include
> even just the address management bits in something compatible with DHCP
> for IPv4. Since DHCP for IPv4 is itself a hack on BOOTP, which Google
> informs me evolved from RARP, it was already quite crufty. Having
> implemented DHCPv6, I assure you it is a joy to work with, compared to
> most other IETF protocols. :)

	Damming w/ faint praise! I built a bootp server to work w/ RARP
	and was in on the first DHCP WG mtgs - I thought Ralph was nutz too.
	As for a joy... maybe.  Its a royal PITA to have to run both a
	DHCP and DHCPv6 daemon.  

> > 	But what do I know.  I'm just a code hobbiest - no corporate
> > 	or vendor backing here.  I am not going to try and change the
> > 	vectors on this code/base/spec - the inertia is just too large.
> 
> That's one way to look at it. I tend to think the DHCPv6 specification
> is pretty good, and not in need of changing. In 5 years maybe I can
> finally start using computers without this legacy DHCP crap on it, and
> then I'll be very glad for the changes.

	5 years?  We could just dump RA/ND et.al. and DHCP and just 
	use Bonjour ...  :)  Just like it was promised in 1997.

> 
> --
> Shane

--bill (the cynic)