[ppml] IPv4 "Up For Grabs" proposal

[Kevin Kargel]

 Thanks Bill, I do agree with everything you have said, with the
exception of the danger of route proliferation with some of the proposed
"ULA" schemes.  In the interest of not muddying the waters I will leave
it at that and not explore tangents.

BTW, I am a DFZ provider.  I do agree that many small to medium networks
will need to conserve route processor resources and pick a protocol and
stick to it.  

My humble forecast is certainly that IPv4 will be predominantly replaced
by something else, which at the moment looks like IPv6.  I just don't
see it happening in the accelerated time frame (within a couple/few
years) that many are propounding.  

Kevin

:$s/worry/happy/g 



> -----Original Message-----
> From: wherrin at gmail.com [mailto:wherrin at gmail.com] On Behalf 
> Of William Herrin
> Sent: Wednesday, July 11, 2007 6:45 PM
> To: Kevin Kargel; ARIN Address Policy
> Subject: Re: [ppml] IPv4 "Up For Grabs" proposal
> 
> On 7/11/07, Kevin Kargel <kkargel at polartel.com> wrote:
> > Why is there such a big push to drop IPv4?  Is there a 
> reason that v4 
> > and v6 can't operate concurrently in perpetuity?  Won't the 
> customers 
> > go where the content is and the content go where the money is?
> 
> Kevin,
> 
> Others have offered excellent and concise answers to your 
> three questions. I'll attempt a longer one that hopefully 
> clarifies more than it muddies.
> 
> IPv4 causes a lot of grief for the operators of the 
> "default-free zone" or DFZ. The DFZ is the part of the 
> Internet which has authoritative knowledge of the direction 
> in which to route any packet legitimately on the Internet. It 
> has no "default" route, no path to "everything else."
> 
> Right now there are about 220,000 routes in the IPv4 DFZ. 
> This puts a good deal of strain on the system.
> 
> For one thing, every subprocessor on every router in the DFZ 
> has to have enough memory and horsepower to manage 220,000 routes.
> 
> For another, every time one link in the DFZ comes up or goes 
> down, routers potentially across the entire DFZ have to 
> rearrange all 220,000 routes so that they follow the new best 
> paths. While this process completes there can be routing 
> loops and dead zones where the Internet is just plain broken. 
> The more routes there are, the longer it takes to complete.
> 
> As the crunch for IPv4 addresses starts to tighten, its 
> likely that large service providers will receive more small 
> allocations instead of fewer large ones. This exacerbates the 
> problem: each allocation consumes yet another route in the DFZ.
> 
> To address this, DFZ providers spend vast sums of money on 
> routing hardware and high-reliability core network links that 
> rarely go down yet they are still only able to do an adequate 
> job of keeping the Internet stable.
> 
> Because of the change in how IP addresses are justified and 
> assigned, the IPv6 DFZ has only a couple thousand routes and 
> is expected to have fewer than 100,000 routes at full 
> deployment. This will make it possible for folks on the DFZ 
> to both spend less money -and- do a better job of keeping the 
> Internet stable.
> 
> The hitch is: until IPv4 goes away, you're not talking about 
> 100,000 routes. You're talking about 100,000 IPv6 routes PLUS 
> 220,000 IPv4 routes. So it gets worse before it gets better 
> and until IPv4 goes away, it doesn't get better.
> 
> 
> So, how does end come? Surely companies don't just up and 
> refuse to provide IPv4! Right?
> 
> Right. But you don't have to be in the DFZ to provide IPv4 service.
> You can use a default route to someone who is. That's the 
> path to IPv4's decline.
> 
> In addition to the redundancy/reliability advantage to 
> participating in the IPv4 DFZ, there is an economic 
> advantage: DFZ participants can peer with each other. Peering 
> means you charge your customers to send you packets but then 
> trade them off to the destination network for free. The 
> destination accepts your packets for free. He'll charge his 
> customer to deliver them and would rather receive them for 
> free than pay someone for the privilege. Today, this cost 
> advantage strongly outweighs the costs associated with 
> managing 220,000 routes.
> 
> As IPv6 use increases and IPv4 use correspondingly declines, 
> these advantages shrink until provider by provider, 
> participation in the
> IPv4 DFZ costs more than a default route would. Exit stage left.
> They'll still announce their prefixes into the IPv4 DFZ but 
> they'll discard the routing table in favor of a default route.
> 
> Its the beginning of the end. As folks drop out of the IPv4 
> DFZ, the reliability and efficiency of the IPv4 Internet will 
> decline. Static default routes break easily in non-trivial 
> networks. That creates a feedback loop encouraging more 
> service migration to IPv6 which in turn encourages more folks 
> to drop out of the IPv4 DFZ.
> 
> Eventually, this destabilizes IPv4 enough that folks start to deploy
> IPv6 tunnels to get the IPv4 packets where they need to go. 
> With that tunnelling in place and IPv4 traffic much lighter 
> than it is today, its suddenly very advantageous for folks 
> still in the IPv4 DFZ to drop the zone back to a single 
> router inside the AS so that the IPv6 border routers don't 
> have to contend with IPv4 at all. IPv4 regains stability, but 
> the routing becomes opaque and very ineffecient.
> 
> IPv4 probably hangs on for quite a while in this marginalized 
> state but for all intents and purposes its no longer the 
> protocol on the Internet.
> 
> RIP.
> 
> Regards,
> Bill Herrin
> 
> 
> 
> -- 
> William D. Herrin                  herrin at dirtside.com  bill at herrin.us
> 3005 Crane Dr.                        Web: <http://bill.herrin.us/>
> Falls Church, VA 22042-3004
>