DHCPv6-4.1.mumble

[David W. Hankins]

On Thu, Jun 12, 2008 at 06:22:18PM +0000, Evan Hunt wrote:
> > again: i think there are at least two advantages to IETF DHCP's
> > approach of segregating IPv6 and IPv4 configuration state betwixt
> > the two protocols - DHCPv4 and DHCPv6.
> 
> Out of curiosity, what are these advatages?

i mentioned fate-sharing; if your DHCPv4 server runs out of leases,
the client is unlikely to receive the configuration (it is unlikely
to try DHCPINFORM since that would actually be illegal without a
valid IP address, and rather continue trying DHCPDISCOVER).  in this
case, the client probably does have an ipv6 address, and so could
easily speak to the IPv6 addresses of the nameservers were it so
capable.  this fate-sharing is an advantage of the system, and it
produces a clean symmetry in implementation for single-stack
networks; no cross-dependancies to tear down later.

i also mentioned simplicity.  if you additionally have 6-in-4 and/or
4-in-6 options, then you have doubled the complexity to implement a
client.  it is hard enough to answer the question of what a client
should do if it gets conflicting config from v4 and v6 (like domain
search), you now also have to answer the question of what to do if the
6-in-4 config also conflicts with the 6-in-6, and prepare yourself for
inconsistent choices among the vendors.  this seems like a linear
doubling on the surface, but the effort to maintain and debug the
software feels more exponential to me.

-- 
Ash bugud-gul durbatuluk agh burzum-ishi krimpatul.
Why settle for the lesser evil?	 https://secure.isc.org/store/t-shirt/
-- 
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