From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Sat Aug 07 2004 - 01:43:14 GMT-3
At 4:57 PM -0700 8/6/04, nikolai wrote:
>Any thoughts regarding choosing one versus the other in order to collapse
>several ASs into a single one?
Well, it depends on the problem you want to solve. I find that in
complex enterprises, where there may be very involved inter-region
policies, confederations give a nice degree of control. Of course,
this results in multiple AS, admittedly with only one seen by the
outside world.
RRs tend to be more useful in a homogeneous service provider
environment, although you may run into IGP scalability issues. A key
document to read here is http://www.ietf.org/rfc/rfc3345.txt, which
examines stability issues with respect to, among other things,
hierarchical reflectors and possibly multiple IGP domains.
>
>The single AS consists of about 100 BGP speakers, no possibility for full
>mesh, of course. IGP is OSPF, and the AS is used as a Transitive area.
>
>I personally do not like multi-tier RRs and lots of Clusters.
They tend to be used by service providers that don't have much
internal policy to implement, but need to keep their iBGP peerings at
a reasonable number. Again, see RFC 3345. You also may want to look
at whether you can improve scalability in the core by using MPLS
rather than BGP speakers.
>In addition, I
>have the feeling that implementing routing policy would be easier with
>Confederations, where we can see clearly the sub-AS PATH of the routes.
>Having multiple geographical areas looks to me as a good argument in favor
>of Confederations, since they all would require some local authority, and
>common IGP with the backbone routers is not desired. And the BGP design
>looks much prettier...
>
>Your input would be appreciated,
>
>Nikolai Tsankov
>niko@4ovek.com
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