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

[Eric Gray <[e-mail]>]

Brian,

	This puts us on the horns of an interesting dilemma.

	Service providers can (and probably will) allocate different sized 
address spaces.  There are two differentiation points (at least) that may
be associated with this - one mostly good and one mostly bad.

	The first is that the efficiency with which a service provider uses
the address space they are allocated, combined with the way that they do
this, can reduce their operating costs, while allowing them to attract 
more (and different) customers.  This is probably a good thing.

	The second is that they can differentiate themselves by offering
address allocation sizes that do not align well with other providers, in
an attempt to lock-in customers who will find that they can anticipate
administrative head-aches and extra costs if they ever decide they want 
to go with a different service provider.  This is probably a bad thing.

	Over the long run, the good, bad and just plain ugly will be sorted
out - but it might be a good idea to consider starting with at least some
recommendations...

--
Eric

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Brian E Carpenter
Sent: Friday, August 20, 2010 4:57 PM
To: Joel M. Halpern
Cc: IPv6 Operations; [e-mail]
Subject: Re: [Int-area] Review of draft-narten-ipv6-3177bis-48boundary-05

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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> 
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