turning on comcast v6

Tony Hain alh-ietf at tndh.net
Tue Dec 31 20:16:06 UTC 2013

Ryan Harden wrote:
> IMO, being able to hand out gateway information based on $criteria via
> DHCPv6 is a logical feature to ask for. Anyone asking for that isn't
trying to tell
> you that RA is broken, that you're doing things wrong, or that their way
> thinking is more important that yours. They're asking for it because they
> a business need that would make their deployment of IPv6 easier. Which,
> IMO, should be the goal of these discussions. How do we make it so
> deploying IPv6 isn't a pain in the butt? No one is asking to change the
> they're asking for the ability to manage their IPv6 systems the same way
> do IPv4.

As I said in the response to Leo, this issue has been raised before and
couldn't get traction because the combination of a one-size-fits-all mantra
from the leadership with concession such that the dhcp model would be
self-contained, would have led to the end of the RA model. You are correct,
neither way is better, and both need to operate independently or in
combination, but getting there requires a clear use case, or many similar
cases, to make progress. 

I believe you are correct in that many people do use the dhcp option to
assign the router, but quantifying that is a very difficult task because
that community rarely worries about driving standards to get their way. I
find that most of this community finds innovative ways to reuse tools
defined for a different purpose, but its close enough to accomplish the task
at hand while avoiding the cost of getting a vendor to build something
specific. That is all fine until the original backer of the tool goes a
different direction, and ongoing evolution requires someone to justify its
continued support. The scattered community has so many different corner-case
uses it is hard to make a clear and quantified need for what the tool should

The primary reason that this is even a discussion is that the decision was
made long ago in the DHCP WG to avoid bringing forward unused baggage from
the evolution of IPv4 and dhcp by not bringing any options forward until
someone documented an ongoing use for it. That remains the only real
requirement I am aware of for getting a dhcp option copied forward from IPv4
to IPv6; document a widespread use case. This one has had an artificial
requirement of getting past the dhcp vs. RA model wars, but that would have
been, and still is easy enough to beat down with sufficiently documented
use. Documented use is where things fail, because we loop back to the point
about the people using it don't participate in driving the process to
demonstrate how widespread the use actually is, and what specific
functionality is being used to make sure the new definition is sufficient. 

Lee asked the question about use cases, and you were the only one that
offered one with substance. Compound that with the point that nobody else
jumped in with a 'me too', and the case could be made that you are looking
for a standard to be defined around your local deployment choices. Not to
say your deployment is isolated, wrong, or shouldn't be considered
best-practice, rather that it is hard to demonstrate consensus from a single
voice. Besides documenting the use case, it will help to fight off
objections by also documenting why this innovative use is deployed rather
than another widely deployed choice (in the case you present, why not
802.1X?, not that it is better, just 'why not' ; and I personally consider
pre-dated or inconsistent implementations at deployment as a perfect
justification, but that is just my take).  At the end of the day, if
operators don't actively participate in the standards process, the outcome
will not match their expectations. 


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