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Re: Multi-6 [WAS: OT - Vint Cerf joins Google]
On Sun, 11 Sep 2005, Richard A Steenbergen wrote:
Actually, you've missed two crucial lines from the report:On Sun, Sep 11, 2005 at 06:32:58AM +0200, Mikael Abrahamsson wrote:Giving each entity who wants to multihome an AS of their own and own address block, doesn't scale. Think this in the way of each home in the world being multihomed, it just doesn't scale.To quote some stats from the latest weekly routing table report to hit nanog: BGP routing table entries examined: 169983 Total ASes present in the Internet Routing Table: 20445 Origin-only ASes present in the Internet Routing Table: 17787 Origin ASes announcing only one prefix: 8431 This says that although there are 170k prefixes on the Internet, there are only 20k entities who actually need to announce IP space. There is only one explanation for such a large difference (8.5x) between these two numbers, namely that people who are announcing IP space need multiple blocks in order to accomodate their needs.
Prefixes after maximum aggregation: 97203
Unique aggregates announced to Internet: 82000
That implies that 73k (170k - 97k) worth of announcements are related to traffic engineering tricks, multihoming, poor education or simply 'because'. ( A decade on and there are still books/routers/courses/people which don't grok CIDR )
A further 15k (97k - 82k) worth of announcements seem to be duplicates;
multiple paths being naturally seen or intentionally announced.
Of the 82k worth of possibly unique prefixes, 8k worth of those are from ASes announcing solely one route. The remaining 74k prefixes are announced by 9k ASes; 8 each.
An interesting question to ask, before you point at IP rationing being the main cause, is how many entities that have received IP allocations also have ASes? In other words, these ASes having 8+ prefixes each may in some cases be a single ISP announcing the routes of 5 seperate customer entities.the majority of these prefixes are due to IP rationing, which forces growth into multiple blocks.
A further question to ask would be, considering that issuing IPs is the RIR's business, why haven't the RIRs noticed a tendency for certain entities to keep coming back for more IP space, and thus why haven't the RIRs been putting aside aggregatable IP space for these entities or been notifying their membership on the possible need for a change in addressing policies to avoid such problems ?
Certainly, I'll agree that IP rationing (via RIR policies) is responsible for a certain, hopefully small, percentage of non-aggregatable prefixes. But I don't think that IP rationing is responsible for the majority of such prefixes.
Then again, I may be biased ;)