IPv6 - real vs theoretical problems

Jeff Wheeler jsw at inconcepts.biz
Fri Jan 7 02:01:12 UTC 2011


On Thu, Jan 6, 2011 at 8:04 PM, Jimmy Hess <mysidia at gmail.com> wrote:
> It is advisable to look for much stronger reasons than "With
> IPv4 we did it"  or   With IPv4 we ran into such and such
> problem"   due to unique characteristics of IPv4 addressing
> or other IPv4 conventions that had to continue to exist for
> compatibility reasons, etc, etc.

I certainly agree that there are many advantages to the greater
address space offered by IPv6.  I don't mean to advocate that we do
things the same way as was necessary to conserve v4 address space, and
I'm sure we all realize that RIR policies necessarily contributed to
routing table growth in trade for extending the life of the available
address space.

I'm not blindly deploying /64 networks, either.  Doing so with the
current set of problems, and lack of knobs, is very foolish.  My
transit providers offer a mix of /126 and /124 demarc subnets so far,
and /124 is what I choose to standardize on for my BGP customers and
private peering, for simplicity and convenience.  As I mentioned
before, I currently allocate a /64 and configure a /124, so I am not
painting myself into a corner either way.

How many of us with an appreciable level of expertise remain concerned
that our approach may need significant adjustment?  How many think we
know what those potential adjustments may be, and have planned to make
them easy (or transparent) for ourselves and customers if they become
necessary?  This is what is IMO most important to a responsible IPv6
deployment.  To do otherwise is inviting unpredictable future pain.

I am comforted by the fact that Level3 is deploying customer demarc
subnets as /126 and is NOT allocating a /64 for each, but are instead
packing them densely in an IPv4 /30 fashion.  They recognize problems
with the /64 approach, choose not to follow the "standard" to the
letter, and implement their dual-stack network in a way they
presumably believe is safe and scalable.  Large networks like Level3
choosing to insist that equipment vendors support this configuration,
rather than have problems with densely packed subnets smaller than
/64, will mean that anyone who wants to sell a router to Level3 had
better make it work correctly this way, which is good for the small
guy like me who thinks he will eventually transition to that
configuration.  Right now, I am still hedging my bet.

Are there any large transit networks doing /64 on point-to-point
networks to BGP customers?  Who are they?  What steps have they taken
to eliminate problems, if any?

-- 
Jeff S Wheeler <jsw at inconcepts.biz>
Sr Network Operator  /  Innovative Network Concepts




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