This is not what you were asking about in your original post on this topic - you were talking about BGP sessions inside GRE tunnels, which is not how most (any?) DDoS mitigation services operate, to my knowledge. GRE is used over the Internet for many different applications, including post-DDoS-mitigation re-injection of legitimate traffic onwards to the server/services under protection. Hardware-based GRE processing is required on both ends for anything other than trivial speeds; in general, the day of software-based Internet routers is long gone, and any organization still running software-based routers on their transit/peering edge is at risk. DDoS mitigation providers using GRE for re-injection should set the MTU on their mitigation center diversion interfaces to 1476, and MSS-clamping on those same interfaces to 1436, as a matter of course. This is not a new model; it has been extant for many years. There are a variety of overlay and transit-focused DDoS mitigation service providers who utilize this model. In your original post on this topic, you also made the assertion that these issues had not been addressed by DDoS mitigation service operators; that assertion is incorrect. Hello Roland, You are still missing the main point, the main question is what Dennis highlighted "Perf implications when cloud security providers time to

detect/mitigate is X minutes. How stable can GRE transports and BGP sessions be when under load?"

I mean, during the X minutes (between detection and mitigation), the scrubbing center will be sending both legitimate and illegitimate traffic to the customer, and here is the exact period I am worried about the GRE control traffic -which will be much more vulnerable to be dropped than the relaxed three minutes of BGP hold time. All of the top 5 DDoS cloud scrubbing centers are using BGP over GRE, and even if the BGP is only used for signalling the victim subnet, the GRE control traffic will still suffer from the congestion during the X time. Thank you for your clarification about the MTU consideration and GRE HW acceleration. Ramy