Le vendredi 25 mars 2011 à 02:09 -0700, Zaid Ali a écrit : > 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. >
Yes, I agree. Confed's is a choice, in particular if you need elaborate policies between regions of your network. Police sessions between sub-ASes, keep iBGP simple... Say, you start with RR... If or once your network is large, and having customers connected to it, migrating to conferedrations may be a challenge. Right? Thoughts? Experiences? mh > Zaid
