Regional AS model

[owen at delong.com (Owen DeLong)]

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 at 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