Communities

Mon Oct 15 16:34:24 UTC 2001

On Mon, Oct 15, 2001 at 11:55:27AM +0200, Iljitsch van Beijnum wrote:
> How many networks are there that use communities to indicate where (which
> interconnect point) a route was learned? 

How feasible is it for me to provide this information in any
meaningful way if I have tens or even hundreds of interconnect
points in my network?  Obviously I can assign a unique community
to each such point on my network, and tag all routes I learn there
with that community, but is the benefit of my doing so?  Unless
you have some way of knowing whether interconnect point A is "better"
than interconnect point B, how would you use that information?

This isn't to say that there isn't a reason to do this.  I can think
of several *internal* uses for such a scheme, including distance-
sensitive billing applications, traffic engineering, etc.  But is
there a benefit to revealing this information to customers or peers?

> And how many networks use this information if their upstream provides it?

Without having a clear understanding of each upstream's network
topology and routing policy, how would you use such information to
label one route as "better" than another? 

What problem(s) are you trying to solve, and are you sure that 
BGP communities are the right tool for the job?

--Jeff