Re: [RRG] Thoughts on the RRG/Routing Space Problem

[Kevin Loch <kloch@kl.net>]

Tony Li wrote:
> One way would be to split them in such a way that they jointly remained 
> syntactically similar to the original address space.  This is one of the 
> cuter things about GSE.  Then new generation systems could recognize 
> them as split (via a compatibility bit someplace) and to legacy systems, 
> it would appear to be a legacy address.

I've been thinking about how a new address format definition would help
a scenario like this.

Scalable Address Format (SAF):

0001[ASN 5-15]:[ASN 16-31]:[inter-ASN topology 0-31]:[routing hint 0-63]

inter-ASN topology allows variable length subnetting between /32 and
/63.

ASN bits 0-4 are not used
ASNs 4096.0 - 65535.65535 must not be used with this format

Higher network layers must ignore and/or set bits 64-127
to zero.  For compatibility border routers may set these
to zero if necessary.

For example ASN 6.3:

1006:3:100:1:: saf host address with no hint
1006:3:100:1:2001:4810:0:100 saf host addr with global uni subnet hint

Forwarding routers that understand and act on SAF addresses space
only need to have a route for the hint network.   The hinted network
needs to know how to get to the end site but nobody else does.

The hint could be set by originating host, forward dns or reverse dns
lookups.  ASN tricks might also work as the end site ASN is encoded.
Routers may need to dump packets to lookup servers for setting hints.
All dns servers should be located on addresses covered by conventional
global unicast routes if DNS is used for hint resolution.

There are many ways to define who is allowed or not allowed to set the
hint bits and how lookups are done.  You could also do lookups by
ASN as it is encoded in the address as a last resort.

A side effect of this is that RIR's only need to manage ASN's, not
address blocks.  Each ASN allows for 32 bits of inter-ASN topology,
which the site can divide between subnet/host bits as desired.

- Kevin

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