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

Jack Bates jbates at brightok.net
Fri Feb 6 13:38:25 UTC 2009

Matthew Moyle-Croft wrote:
> 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.

Dynamic or static; how does this alter the state of the routing table? A 
network assigned is a network assigned. In addition, IPv6 has some 
decent support for mobile IP, which my limited understanding of says 
they enjoy routing tables the rest of us never get to see.

IPv6 is designed to be renumbered. Not all implementations support this 
extremely well, but it is there. I believe the mobile technologies 
support renumber on the fly better than traditional aggregation networks 
who have no expectation of mobility.


> 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

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