Re: Regional AS model

[Owen DeLong <owen () delong com>]

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. 
> > >
> > > Zaid
> >
> > 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.
Only if you want to make use of ugly ugly BGP hacks on your routers, or, you don't care about Site A being
able to hear announcements from Site B.

> Which is "preferable" is up to you, your situation, and your personal tastes.  (I guess one could argue that wasting 
> AS numbers, or polluting the table with lots of AS numbers is bad or un-ashetically pleasing, but I think you should 
> do whatever fits your situation anyway.)
I don't see any significant downside to AS number consumption given a 32-bit AS Number space.
I do see significant downsides to disabling BGP loop detection.

Owen