[arin-ppml] CIDR v2.0

Kevin Kargel kkargel at polartel.com
Tue Sep 16 09:11:51 EDT 2008

The difficulty with this is that we already have problems of hardware
that is insufficient to support the routing tables.  ISP's are already
filtering long CIDR routes (>24bit) because there isn't sufficient
memory or processor in the hardware to support the number of routes it
would require.  

Your idea would work, but only if we got rid of PI space and forced
everyone to use IP space from their ISP so that there could be efficient
route aggregation.  If you search through threads you will see that
there is violent opposition by end users who want to be provider

> -----Original Message-----
> From: arin-ppml-bounces at arin.net 
> [mailto:arin-ppml-bounces at arin.net] On Behalf Of Iljitsch van Beijnum
> Sent: Tuesday, September 16, 2008 5:37 AM
> Subject: [arin-ppml] CIDR v2.0
> In the early 1990s IPv4 address space was running out. They 
> fixed this by changing routing protocols. Maybe we should try 
> to do that again.
> <history>
> In the early days of the internet you could only use IPv4 
> addresses as blocks of 16777216, 65536 or 256 addresses. 256 
> was too small for most people so 65536 was a popular choice, 
> but there are only some 16000 of these class B blocks and it 
> was looking like those would be exhausted by the mid-1990s. 
> So they started giving people a bunch of class C blocks (256 
> addresses each) but now the routing tables started to explode 
> because a university that needed a single class B block 
> before now used something like 16 class C blocks, which had 
> to appear in routing tables individually. To fix this, 
> routing protocols, especially BGP, were changed to be able to 
> work with address blocks of arbitrary power of two sizes so 
> address space and routing table slots could be managed much 
> more efficiently. (This is "classless interdomain routing".)
> </history>
> Now that IPv4 address space is becoming scarce again, why not 
> do the same thing again? But now rather than arbitrary powers 
> of 2, we modify the protocols to work with arbitrary address 
> ranges. I.e.,
> -
> To accommodate legacy routers that can't do lookups based on 
> ranges we can put in backward compatibility mechanisms from 
> BGP5 to BGP4 similar to the ones from BGP4 (with CIDR) to 
> BGP3 (no CIDR).
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