[ppml] Suggestion for ARIN to deligate smaller IP blocks

Jon Lewis jlewis at lewis.org
Wed Jun 6 22:33:37 EDT 2007

On Wed, 6 Jun 2007, Leroy Ladyzhensky wrote:

> the last time I checked, a full BGB routing table had about 130,000
> routes.... and lets say that ARIN ended up passing out 10,000 /24 address

Been a while, has it?  The global table is closer to 218,000 routes now.

> spaces to companies that requested the smaller block... this would only be a
> 7.5% increase in the routing table size. And if my memory serves me... the
> current routing table uses about 65megs of router memory for each upstream
> connection... so this would require about 4 megs of addition router DRAM to
> handle 10,000 additional routes per upstream. Do core routers like the "Big
> Iron" not have 12 or 16 megs free of DRAM to hold additional routes?

That totally ignores a large installed base of switch based routers (Cisco 
6500/7600, many versions of which crap out at somewhat less than 256k 
routes regardless of the amount of free memory.  i.e. on a 6509 with sup2 
and 512mb RAM, I have 135MB free.  But I'm less than 20k routes away from 
"really bad things" happening if I don't have several tens of thousands of 
dollars of hardware upgrades (per router) for new supervisor cards, new 
power supplies, and new fan trays.

> This discussion is to not ONLY hand out 24's... but to give /24's or even
> /23's to companies who provide internet based services like MSP's and ASP's
> who would like to own an address space to have the ability to change
> upstream providers as needed.

I haven't been paying full attention.  Are we talking about handing out a 
/24 or shorter prefix to any network that wants one, just to multihomed 
networks, or just to multihomed service provider networks?

If just the multihomed ones, then there's perhaps an argument to be made 
that doing so doesn't really change the size of the global table...those 
networks are already announcing PA /24s or shorter networks.  Other than 
the fact that if you really wanted, you could selectively filter such that 
you ignored those routes (only accepting the parent route), does it really 
matter if those nets announce PA vs PI /24's?  One could even argue that 
this would conserve IP space...as contrary to ARIN regulations, in my 
experience it's fairly common for an ISP to automatically assign a 
multihomed customer a /24 if they want it, even if they already have other 
PA /24 assignments.  I've seen multihomed networks that couldn't get PI 
space have 3 or more PA /24s...and sometimes even announce them all into 
the global table.

If you're suggesting any ARIN end user who wants ISP independence (not 
just multihomed networks) get a PI allocation, I'd be very worried about 
explosive global table growth.

  Jon Lewis                   |  I route
  Senior Network Engineer     |  therefore you are
  Atlantic Net                |
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