On Mar 24, 2011, at 3:17 PM, Michael Hallgren wrote: > Le jeudi 24 mars 2011 à 14:26 -0700, Bill Woodcock a écrit : >> On Mar 24, 2011, at 1:47 PM, Patrick W. Gilmore wrote: >>> On Mar 24, 2011, at 3:40 PM, Owen DeLong wrote: >>>> On Mar 24, 2011, at 12:42 PM, Zaid Ali <z...@zaidali.com> wrote: >>>> >>>>> I have seen age old discussions on single AS vs multiple AS for backbone >>>>> and datacenter design. I am particularly interested in operational >>>>> challenges for running AS per region e.g. one AS for US, one EU etc or I >>>>> have heard folks do one AS per DC. I particularly don't see any advantage >>>>> in doing one AS per region or datacenter since most of the reasons I hear >>>>> is to reduce the iBGP mesh. I generally prefer one AS and making use of >>>>> confederation. >>>> >>>> If you have good backbone between the locations, then, it's mostly a >>>> matter of personal preference. If you have discreet autonomous sites that >>>> are not connected by internal circuits (not VPNs), then, AS per site is >>>> greatly preferable. >>> >>> We disagree. >>> Single AS worldwide is fine with or without a backbone. >>> Which is "preferable" is up to you, your situation, and your personal >>> tastes. >> >> >> We're with Patrick on this one. We operate a single AS across >> seventy-some-odd locations in dozens of countries, with very little of what >> an eyeball operator would call "backbone" between them, and we've never seen >> any potential benefit from splitting them. I think the management headache >> alone would be sufficient to make it unattractive to us. >> >> -Bill >> >> > > Right. I think that a single AS is most often quite fine. I think our > problem space is rather about how you organise the routing in your AS. > Flat, route-reflection, confederations? How much policing between > regions do you feel that you need? In some scenarios, I think > confederations may be a pretty sound replacement of the multiple-AS > approach. Policing iBGP sessions in a route-reflector topology? Limits? > Thoughts?
I always look at confederations as a longer term plan because you have some idea how your backbone is going to shape out. Knowing where you are going makes confederation planning easier. Start with RR's and then see if confeds make sense. Zaid
