Re: Regionally aggregatable address space for multihoming

[Jim Bound <seamus@bit-net.com>]

also for inter-planetary networks too. seriously I have people asking. 

/jim

On Tue, 5 Jun 2001, Brian E Carpenter wrote:

> How would this work for intercontinental private networks,
> whose multiple connection points are in several different
> continents?
> 
>    Brian
> 
> Iljitsch van Beijnum wrote:
> > 
> > Hi.
> > 
> > I guess I'll jump right in.
> > 
> > After reading "IAB/IESG Recommendations on IPv6 Address Allocations to
> > Sites" it occurred to me that a way to keep the number of routes in the
> > routing tables down could be to use regionally aggregatable address space for
> > multihoming.
> > 
> > The idea is that routers on one end of the globe have little need to know
> > very specific routes to multihomed networks in some another part of the
> > world. For instance, a router on the US west coast doesn't need to know how a
> > network in Europe is connected. It should just send the packet to the
> > east. At some point, the packet would end up in the destination region, or as
> > close to the destination region as the originating network extends, and only
> > there the originating network would have to know where to send the packet
> > next.
> > 
> > Individual networks could implement filters in strategic places to keep the
> > specific routes for multihomed networks inside the proper region. There is no
> > requirement that networks use the same regional subdivision: a European
> > network may use regions that map to two countries, while another network that
> > has only a few points of presence in Europe may see the entire continent as a
> > region. Some networks may prefer to keep carrying all routes everywhere.
> > 
> > All networks announce their customer's routes everywhere, but peers simply
> > filter out these announcements on exchange points that do not fall within
> > their idea of the region. So our European network would normally only accept
> > routes to Dutch addresses in Amsterdam and Brussels (for backup) but the
> > other network only connects to the exchanges in London and Paris so it would
> > pick up the announcements for the Dutch multihomed address range there.
> > 
> > A further reduction of the routing tables could be possible by installing
> > exchange routers for regions at internet exchanges. The exchange router would
> > announce an aggregate for the region and all networks may send traffic to
> > that router. The exchange router holds all the more specific routes for the
> > aggregate and forwards the packets to one of the providers for the
> > destination network.
> > 
> > A problem with this is that all networks that have multihomed customers in a
> > region must connect to all the exchanges where the aggregate is announced.
> > All other default free networks have to connect to at least two of the
> > exchanges for that region. Exchange routers should be present outside as well
> > as within the region they service, for reasons of redundancy and because not
> > all networks are present in all regions.
> > 
> > The granularity of the address assignments has to be fairly fine, so that it
> > doesn't conflict with the hierarchical structure of any existing network. A
> > granularity of 1 to 10 million people to a region seems reasonable. (This
> > would mean large cities or small countries/states/provinces.) With
> > potentially 1% of the population being multihomed that would make for about
> > 100k routes per region, so today's routers would be able to handle several of
> > those regions.
> > 
> > Iljitsch van Beijnum
>