On Mon, Feb 23, 2015 at 1:33 PM, Randy Bush <randy@psg.com> wrote:
you might find http://www.route-aggregation.net/ interesting
Hi Randy, I found it very interesting. Wish I'd noticed when it was fresh. I don't fully understand the math yet but the algorithm doesn't smell right. As near as I can figure it may only be correct in a static system. If after convergence the disaggregate ceases to be reachable from the aggregate, there doesn't appear to be either enough information in the system or enough triggers traveling between routers for it to reconverge to a correct state. Deriving only from the information available to each router at each step, look at page 58 in the presentation and see if you can figure out what happens to the network in that start state when the link between u7 and u9 drops. Remember that all the slashed half-moons mean that the router in that position does not relay the disaggregate and, in most cases, does not know that the disaggregate exists. I've emailed the authors and asked them to clarify. I hope I'm wrong. I'm tried of being a killjoy on this sort of thing and it would be truly cool if it turns out they've cracked the problem. Regardless, if we could presume (with support from the registries) that disaggregates are always reachable from the aggregate (always TE, never downstream customers or discrete sites) and everybody with an address block was courteous enough to advertise an aggregate then it might be usable to control IPv6 deagg. Actually, as long as we could assume the first part we could probably have routers synthesize aggregates to cover the second. But without the first assumption it looks dysfunctional. I discussed the cutouts problem in my 2010 presentation to ARIN XXVI in Atlanta: https://bill.herrin.us/network/201010-cutouts.pdf Regards, Bill Herrin -- William Herrin ................ herrin@dirtside.com bill@herrin.us Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>