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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Communities BCP [was: RE: BGP Path Filtering]
> Spank me if I'm wrong here, but you don't pass MEDs on transitively > anyway. Correct. As a matter of fact, even advertising MEDs to IBGP is left as "an implementation issue", not a protocol requirement. > And if you strip communities off, you limit your peers/customers/ > providers from being able to use the same control that you are > asking for. As everyone has different policies, they're likely stripped or ignored on ingress (or somewhere across the world) anyways. Given, you'd accept them on ingress from transit peers for RFC1998ish stuff, and perhaps under special circumstances from bilateral peers, but that doesn't mean you ever need to carry them past the ingress BGP router into your own network. The effects of propagating what's essentially garbage needlessly have real impacts on the convergence and stability characteristics of the global routing system. It essentially falls back Postel's robustness principle with "[...] be conservative in what you send". Though I've never put anything formal together (for general consumption), I have performed testing and seen the effects the presence of needless attributes have on efficiencies of BGP update packing (and all things subsequent), and they are very real. -danny
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