Waste will kill ipv6 too

Owen DeLong owen at delong.com
Fri Dec 29 02:05:33 CST 2017


> [snip... I hate slash, I hate android, blah balh]
> 
> Back to the main theme... artificially cutting the address space in half, just makes the point even stronger. IPv6 address space is, in fact, half as big as people think it is, because we've drawn a line at /64 -- and the catastrophic part is people *ARE*

Incorrect...

If you want to make that argument, that we shouldn’t have SLAAC and we should use /96 prefixes, that wouldn’t double the space, it would multiply it by roughly 4 billion. 

However, I have to wonder why you think we will burn through 18 quintillion /64s, even with the current scheme? Put another way, that’s roughly 281 trillion /48 end sites. 

> wiring that into hardware. Every example I've seen people bat around about just how big 2^128 is, ignores the reality of Real World Networking(tm). They ignore infrastructure. The ignore route table size. They ignore the sparse nature of hierarchical address assignment. In the "10B people === 10B /48's" example, that's a dense PI allocation scheme that will lead to a global routing table approaching 10B routes -- you can't aggregate a random selection of /48s -- with zero consideration for how those 10B networks will interconnect.

Most of the time, I use the 10B people = 200B /48s, or less than 1/1000th of the total address space. (2.5x for sparse and infrastructure and 8x for provider free pools). 

The routing problem might be real if everyone goes to PI, but I think that’s an unlikely scenario. 
> 
> The simple truth is, we're doing the exact same thing with IPv6 that we did with IPv4: "The address space is so mind alteringly large we'll never use even a fraction of it." *pause* "Umm, wait a minute, we're carving this turkey up alarmingly fast." Will we use up the entire thing? Of course we will; it's not, in fact, *infinite*, so we *will* eventually assign all of it. It's going to happen a lot faster than most people think, as we're so cavalier with handing out vast amounts of space for which most people will never use more than (a) one LAN, and (b) a few dozen addresses within that single LAN. Will it happen in 5, 10, 100 years? The later is a safer bet. (not that I'll be around to collect) But just like IPv4, some decades down the road, people will see how stupid our allocation scheme really is, and begin a new "classless" era for IPv6. The short of it is, we got here first, so we don't have to give a shit about being efficient or frugal.

Your definition of “amazingly fast is pretty odd... we’ve allocated tiny fractions of 2 /3 prefixes to special uses (multicast, ULA, loopback, unknown, etc.). Beyond that, there’s a /3 delegated to IANA as unicast space for distribution to the RIRs. Of that /3, IANA has delegated a little more than 5 /12s to RIRs. That’s the total of 20 years worth of turkey carving and constitutes well under 1/8th of the address space. Issued. By that measure, we’ve got well over 160 years to worry about runout. 

I’m not saying we won’t ever run out, but I am saying that nobody alive today is likely to see it. 

Owen




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