BGP TTL

[Chris Whyte]

> 
> 'course, in this world of closest-exit inter-domain routing,
> one can with certainty assign new community values on ingress 
> and get a reasonable idea of geographic distribution of data 
> sources on the peers network.  Of course, this is assuming 
> MED brokenness or other policy isn't skewing "good ole 
> closest-exit" path selection.
> 
> Not only would conflicting assignments be an issue, but I'm
> guessing that with the number of available paths impacting 
> Adj-RIB-In size today, a default "additive" community policy 
> would result in a notable impact in memory utilization.  

Yes, but not all of us are tier-1s, and probably (hopefully?) never will
be, so keep in mind that there are some of us out there who don't have
>1.5M paths and 'additive' is a perfectly fine thing to do in our
network today and the foreseeable future.

> 
> The work we're seeing from lots of folks is attempting to scope 
> advertisement of "distant" policy for this and other reasons, 
> not multiply it.

I don't think a peer advertising someone like me communities multiplies
the problem but then maybe I don't thoroughly understand the problem.
Again, there are many of us out there who aren't transit free and,
therefore, have slightly different requirements for traffic and
performance analysis. I believe communities can help us in gathering
that information.

Thanks,

Chris

> 
> -danny
> 
> 
> > This is very true of course but I can see value in 
> receiving communities
> > from peers too. For example, one might want to use a tool that can
> > provide you with the amount of traffic destined for a 
> specific community
> > that represents a geography in your peer's network. As 
> tools develop in
> > this area, which they are, I can see communities being useful to get
> > other traffic or performance-related data.
> 
>