Dual stack IPv6 for IPv4 depletion

Mike Hammett nanog at ics-il.net
Thu Jul 9 00:57:29 UTC 2015


Isn't /56 the standard end-user allocation? 




----- 
Mike Hammett 
Intelligent Computing Solutions 
http://www.ics-il.com 



Midwest Internet Exchange 
http://www.midwest-ix.com 


----- Original Message -----

From: "Israel G. Lugo" <israel.lugo at lugosys.com> 
To: "Mark Andrews" <marka at isc.org> 
Cc: "NANOG" <nanog at nanog.org> 
Sent: Wednesday, July 8, 2015 7:45:50 PM 
Subject: Re: Dual stack IPv6 for IPv4 depletion 


On 07/09/2015 12:59 AM, Mark Andrews wrote: 
> In message <559DB604.8060901 at lugosys.com>, "Israel G. Lugo" writes: 
>> Doesn't seem to make sense at all for the ISP side, though. Standard 
>> allocation /32. Giving out /48s. Even if we leave out proper subnet 
>> organization and allocate fully densely, that's at most 65,536 subnets. 
>> Not a very large ISP. 
> /32 is not the standard allocation. It is the *minimum* allocation 
> for a ISP. ISPs are expected to ask for *more* addresses to meet their 
> actual requirements. 

Thank you for pointing that out. When speaking of /32 I was referring 
specifically to RIPE policy, with which I am more familiar: "Initial 
allocation size" for a LIR is /32, extensive to a /29 with minimal 
bureaucracy. Perhaps I should have said "default allocation". 

I understand ISPs should ask for more addresses; however, even e.g. a 
/24 (8x /32) seems to me like it could be "roomier". 


>> People usually look at IPv6 and focus on the vast numbers of individual 
>> addresses. Naysayers usually get shot down with some quote mentioning 
>> the number of atoms in the universe or some such. Personally, I think 
>> that's a red herring; the real problem is subnets. At this rate I 
>> believe subnets will become the scarce resource sooner or later. 
> No. People look at /48's for sites. 35,184,372,088,832 /48 sites out of the 
> 1/8th of the total IPv6 space currently in use. That is 35 trillion sites 
> and if we use that up we can look at using a different default size in the 
> next 1/8th. 
Yes, if we look at end sites individually. My hypothesis is that these 
astronomic numbers are in fact misleading. There isn't, after all, one 
single ISP-Of-The-World, with The-One-Big-Router. 

We must divide the addresses by ISPs/LIRs, and so on. Several bits in 
the prefix must be used for subaddressing. A larger ISP will probably 
want to further subdivide its addressing by region, and so on. With 
subdivisions comes "waste". Which is something we don't need to worry 
about at the LAN level, but it would be nice to have that level of 
comfort at the subaddressing level as well. 

Let's say I'm a national ISP, using 2001:db8::/32. I divide it like so: 

- I reserve 1 bit for future allocation schemes, leaving me a /33; 
- 2 bits for network type (infrastructure, residential, business, LTE): /35 
- 3 bits for geographic region, state, whatever: /38 
- 5 bits for PoP, or city: /43 

This leaves me 5 bits for end sites: no joy. 

Granted, this is just a silly example, and I don't have to divide my 
address space like this. In fact, I really can't, unless I want to have 
more than 32 customers per city. But I don't think it's a very 
far-fetched example. 

Perhaps I'm missing something obvious here, but it seems to me that it 
would've been nice to have these kinds of possibilities, and more. It 
seems counterintuitive, especially given the "IPv6 way of thinking" 
which is normally encouraged: "stop counting beans, this isn't IPv4". 

Regards, 
Israel G. Lugo 




More information about the NANOG mailing list