Re: Regional AS model

[Owen DeLong <owen () delong com>]

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 <zaid () 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