evolution of the 6-bone

[Alain Durand]

At the last G6 meeting, we talked about some evolutions about the routing
issues in the 6-bone. We came up with some propositions.  I'd like to discuss
them here.

Few points first:
-----------------
- we'd like to ease routing
- statics routes are going to be used for quite a long time
  (we do not believe in RIPng at the scale of the growing 6-bone)
- we should automaticaly derived them from a routing registry
- some sites are willing to work hard to achive a good routing,
  some others jsut need a 6-bone access.
- tunnel informations is of little use to compute routes. Tunnels
  are somehow point to point link, i.e. layer 2. Current informations
  in the ripe database about tunnels are only relevant to set up
  tunnels. We need layer 3  informations, i.e. reachable prefixes,
  not links, to build routes.

Our proposal:
-------------
we'd like to define 2 kinds of 6-bone nodes:
	- core nodes
	- leaf nodes

Core node:
----------
  - has a router that knows most (if not all) 6-bone routes
  - should not have a default route (not quite sure about that)
  - is willing to provide 6-bone access to any other node
  - cooperate with other core nodes

Leaf node:
----------
  - any other node with a default route to a core node

Note: Core nodes might be fully inter-connected with tunnels. This is not
mandatory, but might prove usefull. not sure, to be discussed


RIPE database:
--------------
To compute all the 6-bone routes, we only need the following
informations for each core node:
  - IPv6 address of the tunneling router
  - Prefixes directly reachable from this node

  NB1: the IPv6 address is only used to build the string of routers
  NB2: somehow, this is the same kind of informations that a dynamic
       routing algorithm carries.


Interesting points of this proposal:
------------------------------------
  - easy to implement
  - simplify the computation of the routes
  - sites might use several prefixes.
  - sites might set up experimental tunnels with other sites and only route
    selected prefixes through this tunnel. The rest of the traffic will be
    routed through the regular routes.
  - only core nodes willing to cooperated should add few new entries in
    the ripe database.
  - only few core nodes are needed. Currently I use less than 10 different
    routers in my routing table.
  - nodes might become core at any time: they just need to add the extra
    informations about the prefixes they can reach.

What I call core nodes are somehow what we see as transit nodes on the map...


	- Alain.