[ppml] IPv4 address and routing slot markets

Stephen Sprunk stephen at sprunk.org
Mon Oct 29 14:40:50 EDT 2007

Thus spake "Scott Leibrand" <sleibrand at internap.com>
> The only thing that will make that theory true is $$$.  Today, the $$$ 
> favors accepting all prefixes.  If routing table growth accelerates to the 
> point where the cost of upgrading hardware gets much higher
> than it is today, then some ISPs will consider filtering, perhaps in
> the manner I outlined at the start of this thread, because the benefits
> of doing so would outweigh the costs.  If that happens, then
> organizations wishing to announce deaggregates smaller than the
> minimum prefix size will need to also announce their covering
> aggregate to maintain full reachability.

What if the /24 I bought is in space ARIN has marked as having a minimum 
allocation of /20?

> I disagree with Stephen's characterization that this would make 
> deaggregates pointless for anything but private use. I still see a
> role for deaggregates, but would expect (in a world of widespread
> filtering) that they would only be announced as far as the business
> relationship extends: to one's upstreams and possibly a few
> peers.  That would preserve the ability to use deaggregates to
> do inbound TE, while ensuring that only networks wishing to
> receive the deaggregates need do so.

If buyers had to purchase transit from the seller to get useful 
reachability, it's no longer a sale/transfer of PI address space but rather 
a SWIP of PA space to a (possibly multihomed) transit customer.  That isn't 
what I thought we were discussing when we talk about a black/gray/white 
market for addresses, since a mechanism for _renting_ address space already 

If I'm going to go to the hassle of _buying_ address space, I want it to be 
completely PI and have full reachability without any requirement for the 
seller to continue providing me transit service.  That is, AIUI, what people 
are afraid of because it necessitates the buyer getting a slot in the DFZ 
for each purchased block.

Even if we don't allow chopping up /8s into anything longer than a /20, 
that's still a heck of a lot of routes added to the DFZ vs. today.  OTOH, 
there's only ~900k /20s, and router vendors swear they'll be able to handle 
that (for a price).  Given that's a hard limit if people filter at that 
boundary, and a lot of big folks (you know, the ones with 80% of the address 
space) have big blocks they won't deaggregate that far, is the apparent lack 
of backpressure really a problem?


Stephen Sprunk         "God does not play dice."  --Albert Einstein
CCIE #3723         "God is an inveterate gambler, and He throws the
K5SSS        dice at every possible opportunity." --Stephen Hawking 

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