WillJ: Are existing Internet routers capable of handling the millions of IPv6 networks/routes? Can/will the carriers work together to summarize each others' networks to reduce the number of IPv6 networks on the Internet?

Jeff_Doyle: Right now only the most expensive core routers can handle scales of a million or more entries; that's a big concern. On the one hand the big vendors like Cisco and Juniper express confidence that they can keep up with demand, and past history has proven that out pretty well. But on the other hand at some point you hit the limitations of physics; different kinds of hardware, different kinds of protocols, and different kinds of algorithms are going to be needed. I think it was Tony Li that made the very good point that Moore's Law doesn't apply to the silicon used in routers: The commoditization necessary to control costs as capacities grow does not exist in the core router industry. If you're interested, some of the more forward-thinking IRTF working groups like the Routing Research Group (RRG) are worth your time to check out.

WillJ: If you were building a new regional network (multiple states) would you be using IPv6 out of the box? Which vendors have the best core routers for a regional network?

Jeff_Dolye: I would insure that IPv6 capability is there, by all means, and if there is a compelling reason I would enable it along with IPv4. But if you're asking would I build an IPv6-only network, the answer is no. With apologies to other router vendors, Cisco and Juniper pretty much own the core market.

Moderator-Keith: PRE-SUBMITTED QUESTION: I understand what you are saying about enterprises not being interested in IPv6 yet, but even with service providers, what do you see as obstacles to IPv6?

Jeff_Doyle: SPs are quickly moving beyond questioning whether IPv6 is going to be needed and toward practical, reality-based implementation. The big challenge here is that there remains a tremendous number of holes in IPv6 support: Network management, security (try finding an IPv6-capable IDS!), most backoffice applications. What vendors claim and what they can actually deliver is, in a very many cases, two different things. But that's changing. SPs are pressuring their vendors because their IPv6 operations need to be completely equitable with their IPv4 operations, with as few "paradigm shifts" as possible, and that capability just isn't there yet.

Silvia: How many organizations do you know that have implemented IPv6 at least partially or gone dual-stack?

Jeff_Doyle: Most ISPs now have implementation plans in the works, although few are at the point of being able to offer IPv6 access on a wide scale (as in IPv6 to the home or small office). On the enterprise side, very few are implementing IPv6 but don't have any practical need to.

Moderator-Keith: PRE-SUBMITTED QUESTION: You say that IPv4 addresses will run out in 2010 or 2011. What happens then, to all those people who aren't ready for it?

Jeff_Doyle: Not much, really. Keep in mind that nothing is going to stop working when the last IPv4 address is given out. A bit like Y2K (but with far less potential for catastrophe), the network operators whose business depends on having a steady supply of public IP addresses already recognize the threat and are preparing for it.

Moderator-Keith: PRE-SUBMITTED QUESTION: You have written about IPv4 depletion and predictions about when that will happen. When do you think we will see an "IPv6 only" world?

Jeff_Doyle: There is, and always has been, a focus on v4/v6 interoperability and coexistence. But the reality is that no one wants the complications of running two protocols in their network. As a result, I think that as IPv6 takes off there will be a substantial OPEX incentive to get rid of IPv4. Saying that is still a bit controversial, but my opinion is that IPv4 will cease to exist in most networks somewhere between 2015 and 2020. Let's schedule another chat on March 3, 2020 and see whether I was right :-)