On Mar 24, 2011, at 2:26 PM, Bill Woodcock wrote: > > 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 > > > > > To be clear, when I said backbone, I meant that if a packet arrives at site A destined for site B, it goes across some form of internal path and not back out to the internet. That Site A and Site B learn each other's routes via iBGP and not via third-party ASNs.
If A learns B's addresses from a third party ASN, then, it is highly desirable (IMHO) to have A and B in separate ASNs. Owen
