IP4 Space

Tim Durack tdurack at gmail.com
Tue Mar 23 13:25:29 UTC 2010


On Tue, Mar 23, 2010 at 8:17 AM, William Herrin <bill at herrin.us> wrote:
> On Tue, Mar 23, 2010 at 3:40 AM, Owen DeLong <owen at delong.com> wrote:
>> On Mar 22, 2010, at 10:27 PM, Mark Newton wrote:
>>> On 23/03/2010, at 3:43 PM, Owen DeLong wrote:
>>>> With the smaller routing table afforded by IPv6, this will be less expensive. As a result, I suspect there will be more IPv6 small multihomers.
>>>> That's generally a good thing.
>>>
>>> Puzzled:  How does the IPv6 routing table get smaller?
>>>
>> Compared to IPv4?  Because we don't do slow start, so, major providers won't be
>> advertising 50-5,000 prefixes for a single autonomous system.
>
> On the other hand, smaller ASes still announce the same number, the
> hardware resource consumption for an IPv6 route is at least double
> that of an IPv4 entry, RIR policy implies more bits for TE
> disaggregation than is often possible in IPv4 and dual-stack means
> that the IPv6 routing table is strictly additive to the IPv4 routing
> table for the foreseeable future. Your thesis has some weaknesses.

Plus the RIRs are currently applying pressure to assign only the bare
minimum IPv6 address space to PI multi-homers (at least, the RIR I
deal with.) I can see this quickly leading to non-contiguous
assignments in the not to distant future.

Today I have enough address space to easily allocate /48s per site,
assuming a /64 per VLAN. But I can see the need to assign /56s per
switch port for dhcp-pd. If I were to assign a /48 per switch stack
(seems like a reasonable engineering decision), I'm quickly going to
burn through lots of /48s. I'm sure I could come up with clever ways
to save address space, but I'm wondering why when one of the promises
of IPv6 is to avoid having to think too hard about individual
assignments.

-- 
Tim:>




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