[arin-ppml] IPv6 /32 minimum for extra-small ISP

William Herrin bill at herrin.us
Wed Apr 14 18:50:55 EDT 2010

On Wed, Apr 14, 2010 at 3:58 PM, Milton L Mueller <mueller at syr.edu> wrote:
>> -----Original Message-----
>> The problem is that even if you got an extremely small allocation
>> that as soon as you advertise it, you consume the same amount of
>> routing resources on everyone else's BGP router on the Internet,
>> that someone with a larger allocation has who is advertising theirs.
>> Thus it is not fair to base pricing solely on the amount of numbering.
> Just curious. Has this assertion ever been tested, examined, modeled?
> There are two logical components to this statement that I am
> interested in verifying:
> A small allocation:
> a) "consumes the same amount of resources"
> b) on "everyone else's" BGP router
> The latter is an especially strong claim.

Hi Milton,

One prefix has the same routing table cost regardless of whether it's
the whole Internet ( or a single address (e.g. To be effective each prefix must be carried in every
"DFZ" router.* Worse, routing table costs are overhead for which no
mechanism presently exists to recover the cost from the folks
announcing the prefix.

Packet forwarding costs vary by traffic instead of by route count, but
packet forwarding costs are directly recovered from the customers
generating and/or consuming the packets.

See http://bill.herrin.us/network/bgpcost.html for an analysis of
routing table costs.

* I talk about routers in the "default-free zone" (DFZ) instead of BGP
routers because it's possible to run partial BGP at the edge of the
network that replaces some or all routes with a default route. Such
routers are not part of the DFZ since they need a default route to
someone else who does carry the whole table in order to reach everyone

A more subtle question is the degree to which an organization's size
tends to impact their disaggregation (tendency to announce each
address block as multiple prefixes).

Bill Herrin

William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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