Re: FW: more specific routes in today reality

[Gert Doering <]

Hi,

On Wed, Nov 07, 2001 at 03:48:20PM +0100, Koepp, Karsten wrote:
> All I am saying is, regardless of whether we want this type of multi-homing 
> or not, networks originating from different AS should use PI space. It does 
> neither save a route nor address space to make pieces of a PA block 
> multi-homed. It only binds the network to the provider assigning the PAs.
> That's why I was up-set.

Whether or not an announcement is PI or PA has no influence on the number
of routes visible in the global table.

Using a sub-block from PA space has two advantages:

 - more flexible in block size (what if the customer comes back later
   and needs twice the space?)

 - more robust concerning filtering / dampening (the ISPs PA space will
   most likely be still visible, even if the sub-network is filtered
   somewhere)

 - if the customer goes away, the network can be given back and the
   route will disappear -> good for conservation *and* aggregation.

The only benefit of PI is "you can keep your network if you change ISPs",
which is convenient for the end customer but very expensive on the global 
routing system.  

This is why people actually ask for "stop handing out PI at all" (which
I am *not* advocating here, but think about it).

- and due to this pros and cons, which most people agree upon, the RIPE 
recommendations make sense.

Gert Doering
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