This might indicate a Denial of Service (DoS) attack or a spike in server load. The Inbound Rate Limit Discarded IPv6 IPsec ...

This might indicate a Denial of Service (DoS) attack or a spike in server load. 
The Inbound Rate Limit Discarded IPv6 IPsec Authenticated Packets/sec counter has exceeded a defined threshold. View this counter under IPsec DOS Protection in Performance Monitor. The counter specifiesthe rate at which authenticated IKEv1, IKEv2, AuthIP, or ESP IPv6 packets are received on a public adapter and discarded because they exceed the rate limit for IPv6 IPsec authenticated packets per second. An authenticated packet is an IPsec packet with an associated state entry. A state entry is a pair of IPv6 addresses that is authorized to pass through from a public to an internal adapter.