Re: [address-policy-wg] 200 customer requirements for IPv6

[Sebastian Abt <]

Hi,

* Thomas Narten wrote:
> It is not immediately clear to me what the policies are (or should be)
> for an ISP doing transit. Clearly, the don't need a full /32, since
> they aren't really assigning (directly, or via delegation) lots of
> addresses. But shouldn't they be able to get space?

I think one should hand out /32s to transit ISPs even if they don't need
as much addresses as others may because that makes deploying sane
filters a lot easier.  

An ISP doing transit has mostly many POPs where it has to address own
equipment and customer routers.  Following the recommendations on IPv6
addressing one would assign /64s per transfer networks and some /128s
per loopback.  In order to achieve internal aggregation one would also
want to allocate a bigger chunk per POP - following the recommendations,
a /48.

So you can see that a typically ISP doing transit needs n*/48, with n
depending on the numbers of POPs they have.  With handing out a /32 one
can be sure that there are enough /48s available to cover the ISPs POPs
(hence, this ISP will never use more than one routing table slot) and on
the other hand there is no additional prefix length one has to make
exceptions for when deploying filters.

But, is it really a problem for an ISP doing transit to get an own
allocation?

regards,
sebstian

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