[ppml] NANOG IPv4 Exhaustion BoF
gih at apnic.net
Fri Mar 7 03:17:53 EST 2008
John Curran wrote:
> At 5:39 PM +1100 3/7/08, Geoff Huston wrote:
>> Yes, the situation the this industry has driven itself into is messy, but
>> I'm pretty sure that global collapse is not exactly on the agenda.
>> What I would claim is that this transition is just another risk factor
>> in an industry that has its fair share already and doubtless will
>> continue to have its fair share in the future.
> I'd agree with you if there were anything resembling a useful
> feedback mechanism on the global routing table.
The sad fact is that the global routing table has been under
concentrated assault by the legions of /24s for many years now.
Since 2001 50% of the routing table is more specifics - and now there
are 135,208 of them. My supposition is that TE is the major factor -
when you look at highly deaggregated prefixes you tend to see a
collection of upstreams and load spreading across the upstreams.
So in many ways the routing system is already under this "fragmentation"
pressure and will remain so whether its IPv4 or IPv6 (and I suspect at a
more meta level, efforts to reintroduce aggregation into the routing
system, if adopted would not have much impact in changing the current
numbers by very much simply because of these TE pressures). What we
route across is the cross product of the number of distinct entites, the
level of interconnection between entities and the desired/imposed level
of diversity of path. And as the network expands the value of this cross
product will rise, transfers, minimum size limits, or any other factor
nowithstanding, and the routing table will continue to inflate at a rate
that is higher than the number of distinct routing entities.
So what I'm saying is that the routing system is an expression of a more
basic metric of the network's interconnection, and that this value will
be expressed in the routing system irregardless of the particular
routing technology and irrespective of the varioous address policies
that we may state.
As I understand your argument here John its that fragmented address
supply won't make it any better, but it could make it worse, and that
could trigger responses such as selective filtering, threatening global
connectivity. Yes, thats a valid concern. Without much data to quantify
the risk its hard to assess how critical this factor will be.
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