4. [Scenario] For “NO EXPORT” scenario, it's a misconfiguration of the network to set “no export”, or “no advertise”, as opposed to using some other traffic engineering community. This is not an improper block, because you don't have the full forward and reverse path visibility to understand. From: Jared Mauch. #4
[Lancheng Qin] We cannot prevent networks from using “NO EXPORT”. Therefore, once a network uses “NO EXPORT” in BGP, which can lead to asymmetric routing, existing inter-domain SAV mechanisms may block legal traffic. We call it “improper block” because we believe that legal traffic must be properly permitted.
[Lancheng Qin] We cannot prevent networks from using “NO EXPORT”. Therefore, once a network uses “NO EXPORT” in BGP, which can lead to asymmetric routing, existing inter-domain SAV mechanisms may block legal traffic. We call it “improper block” because we believe that legal traffic must be properly permitted.