Re: IPv6 day and tunnels

[Owen DeLong <owen () delong com>]

On Jun 4, 2012, at 6:11 PM, Jeroen Massar wrote:

> On 2012-06-04 17:57, Owen DeLong wrote:
> [..]
> > If you're going to redesign the header, I'd be much more interested
> > in having 32 bits for the destination ASN so that IDR can ignore IP
> > prefixes altogether.
>
> One can already do that: route your IPv6 over IPv4.... IPv4 has 32bit
> destination addresses remember? :)
>
> It is also why it is fun if somebody uses a 32-bit ASN to route IPv4, as
> one is not making the problem smaller that way. ASNs are more used as
> identifiers to avoid routing loops than as actual routing parameters.
>
> Greets,
> Jeroen

While this is true today (to some extent), it doesn't have to always be true.

If we provided a reliable scaleable mechanism to distribute and cache prefix->ASN mappings and could reliably populate 
a DEST-AS field in the packet header, stub networks would no longer need separate ASNs to multihome and IDR routing 
could be based solely on best path to the applicable DEST-AS and we wouldn't even need to carry prefixes beyond the 
local AS border.

While I don't think DNS is up to the task of reliable distribution and caching (though something somewhat similar to 
DNS could do the job rather well), DNS-style resource records could be used. For example, instead of using my own 
AS1734 as I do today, my multi-homed household could be placed in the database with pointers to my two upstream ASNs as 
follows:


2620:0:930::/48                 AS              10      6939
                                                AS              10      8121
192.124.40.0/23                 AS              10      6939
                                                AS              10      8121
192.159.10.0/24                 AS              10      6939
                                                AS              10      8121

Or, if I wanted to do some traffic engineering, I could tweak the preferences to be non-equal values.

The router doing the DEST-AS insertion into the packet would grab the most preferred AS to which it has a valid 
feasible successor.

I believe that the number of transit autonomous systems on the planet is much smaller than the minimum number of 
prefixes to represent all multi-homed organizations with independent routing policies. As such, I believe this could 
produce much more scalable routing with relatively little additional overhead.

Owen