Re: [Int-area] Review of draft-narten-ipv6-3177bis-48boundary-05

[Brian E Carpenter <brian.e.carpenter@gmail.com>]

On 2010-08-21 08:47, Joel M. Halpern wrote:
> There does seem to be one significant benefit for being able to get the
> same size block from different providers.
> If you have used one size, and change providers, if the prefix length
> gets longer, you have to rework your plan.  And if it gets shorter, but
> you don't rework your plan, you are wasting a LOT of space.

Yes. That's why there is a strong recommendation to people
developing site addressing plans to use only the longest
possible sub-prefix of their PA prefix, in case they later
change to another ISP who gives them less PA space.

> This does not mean that there should be one size for all cases.On the
> other hand, telling operators that they must offer four different sizes
> to all their customers (/48, /52, /56 and /60) makes the operator
> bookkeeping harder, at the very least.

There certainly should not be a MUST. In any case, the RIRs and ISPs would
ignore it. The /48 doctrine crashed and burned among the RIRs and ISPs
some years ago; 3177bis recognizes this reality.

    Brian

> 
> Yours,
> Joel
> 
> Brian E Carpenter wrote:
>> On 2010-08-21 08:23, Fred Baker wrote:
>>> On Aug 20, 2010, at 12:49 PM, Eric Gray wrote:
>>>
>>>>     Having multiple chunk sizes seems to me to be a recipe for in-
>>>> efficient use of address space in general.  
>>> speaking for myself, I think a one-size-fits-all model has the same
>>> effect. In my home, today, I have two LANs; I could easily imagine
>>> expanding that to half a dozen or even a dozen in various scenarios.
>>> Giving me a /48 is a waste of address space - it's at least 4096
>>> times as much as I need, and would give my upstream the ability to
>>> address 4095 more homes like mine if they were to allocate /60's. To
>>> the extent that they are paying their RIR for address space, er,
>>> membership, it wastes their money and increases my monthly payment.
>>> I think there is a great reason to suggest that access and transit
>>> networks to offer their downstreams /48, /52, /56, and /60 options at
>>> various costs. It makes business sense for them, allows them to
>>> reasonably recover their costs without burdening the downstreams,
>>> allows for downstreams to number their networks in ways they like and
>>> reasonably move up to shorter prefixes when they need to, and (since
>>> I didn't mention /64) ensures that the smallest users -
>>> residential/SOHO - have options for routing within the home as
>>> appropriate.
>>
>> Another +1 to Fred. I was originally a strong advocate of Eric's view,
>> in fact I take credit/blame for a lot of RFC3177, but I believe that
>> experience, especially the remarkable success of CIDR in controlling
>> the growth of PA routes for IPv4, and the acquired wisdom of the RIRs
>> in administering CIDR, have shown that there is no efficiency benefit
>> in fixed chunks.
>>
>>     Brian
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>