On Wed, 30 Mar 2005 21:30:38 +0200, Hans Petter Holen wrote:
I agree that IPv6 needs multi-homing to fly - but I was hoping there would be other technical implementations of multi-homing than PI. It seems we need a thing called "wonder".
Call it PI, Prefix or whatever, here is what we have: - A *arbitrarily* connected set of nodes - called AS'es- in a graph, called "Internet". - A set of destinations, called "prefixes". - Things called "packets", which should be routed thru the graph on a short (best: the shortest) path. If one can find a way to route these packets on the shortest path in any topology without telling the nodes something about each destination, - even a source route is such information and requires knowledge about the structure of the graph - he will probably receive the Fields medal and/or a Nobel price ;-/ The original idea behind the IPv6 TLA, NLA, SLA was a geographical and administrative hierachical design, in the century of *competitive* operators this concept is *broken by design*. In this competitive network world, where operator A charges B for transit, the only chance to implement *true* multihoming is to pass information about the destination to all relevant nodes. But I don't see why we should have a problem doing so. Memory is cheap. However there *are* possible technical improvements, example given: - Use a two level address distribution concept: Level 1 : Pass path information about ISP AS'es only* Level 2 : Flood address origination information separate. ( Example: Multihoming Customer 1 is using AS1 and AS2 for prefix X, Customer 2 is using AS2 and AS3 for prefix Y, then a far AS would see Level 1 : Paths : (AS5 AS4 AS1), (AS5 AS6 AS7 AS2), (AS3) This is sufficient to avoid loops and build policies. Level 2 : Offers: AS1:(X), AS2(X,Y), AS3(Y) No path information is required in these floods. ) - Pass information on demand ( However this should only be done in a two level concept for stability reasons, think of "bad weather" DDoS Flood conditions. ) *However* all this solutions have one impact: - New BGP protocol, new routers, new budget ... Ceterum Censeo: Either there is way to *route* the IPv6 address space, *at least* *with the IPv4 quality* - which means serving the customer demand "true multihoming", or IPv6 is dead. If a large address space is offered, it must be *usable*, which means *routable*, at least with the capabilities of the good old IPv4. No one needs a 40 digit ZIP code for letters for a human postman, a 5 digit code is suffiicient. And a postal service offering 40 digits ZIP codes as "premium service" for standard letters will probably economically fail ;-/ Best Regards Oliver P.s.: Think of UMTS. Design driven by comissions and managers. Today: Billions spend. >270ms ping time. B.t.d.t. Same for IPv6 ?! Oliver Bartels F+E + Bartels System GmbH + 85435 Erding, Germany oliver@bartels.de + http://www.bartels.de + Tel. +49-8122-9729-0