v6 & DSL / Cable modems [was: Private use of non-RFC1918 IP space (IPv6-MW)]

Matthew Moyle-Croft mmc at internode.com.au
Fri Feb 6 10:42:54 UTC 2009

My comment was regarding customers believing that they were going to,  
by default, get a statically allocated range, whatever the length.

If most customers get dynamically assigned (via PD or other means)  
then the issue is not a major one.


On 06/02/2009, at 8:56 PM, Paul Jakma wrote:

> On Thu, 5 Feb 2009, Matthew Moyle-Croft wrote:
>> DHCP(v6).  Setting the idea in people's heads that a /64 IS going  
>> to be their own statically is insane and will blow out provider's  
>> own routing tables more than is rational.
> Routing table size will be a function of the number of customers -  
> *not* the prefix length assigned to them (for so long as address  
> space is sufficiently sparsely allocated that there's a 1:1 mapping  
> from customer to prefix - which should be "for a long time" with  
> IPv6).
> So (within that longer term constraint) it doesn't matter if you're  
> allocating your customer a /48, /56 or /64.
> Indeed, what you're suggesting - smaller-than-64 allocations -  
> *would* increase routing table sizes. With your proposal those  
> indexes would increase greatly in depth (and possibly other space  
> increases due to not being able to optimise for "hierarchical  
> routing of bits past 64 is highly rare").
> Think of IPv6 as a 64bit network address + host address. At least  
> for now.
> regards,
> -- 
> Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
> Fortune:
> If you don't have a nasty obituary you probably didn't matter.
> 		-- Freeman Dyson

Matthew Moyle-Croft Internode/Agile Peering and Core Networks
Level 5, 162 Grenfell Street, Adelaide, SA 5000 Australia
Email: mmc at internode.com.au    Web: http://www.on.net
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