North American Network Operators Group

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Re: Upstreams blocking /24s? (was Re: How Not to Multihome)

  • From: Patrick W. Gilmore
  • Date: Mon Oct 08 23:20:22 2007

On Oct 8, 2007, at 10:28 PM, David Conrad wrote:

The argument, as I understand it (and those who argue this direction feel free to correct me if I misstate), is that as the IPv4 free pool exhausts, there will be a natural pressure to increase address utilization efficiency. This will likely mean longer prefixes will begin to be put (back) into use, either from assignments and allocations that were "rediscovered" or from unused portions of shorter prefixes. Customers will approach ISPs to get these long prefixes routed, shopping through ISPs until they find one that will accept their money and propagate the long prefix.

Now, of course announcing a route doesn't mean anyone will accept it, but as I understand the theory, larger ISPs will agree to accept and propagate longer prefixes from other larger ISPs if those other ISPs will be willing to accept and propagate transmitted long prefixes ("scratch my back and I'll scratch yours"), particularly if this encourages the smaller ISPs to 'look for other employment opportunities' when they can't afford the router upgrades.

We know this is not the case from history. For instance, look at Sprint & ACL112.

Also, we know from history that smaller ISPs sometimes are better able to do router upgrades than large ones.

Personally, I fully expect the first part to happen. Where I'm having trouble is the second part (the accepting longer prefixes part). However, a few prominent members of the Internet operations community whom I respect have argued strongly that this is going to happen. I thought I'd ask around to see what other folk think...

I'd bet against the first part happening, so the second part is moot.