Our current VIP load balancing solution [Eis16] uses packet encapsulation. A network load balancer puts the forwarded packet into another IP packet with Generic Routing Encapsulation (GRE) [Han94], and uses a backend’s address as the destination. A backend receiving the packet strips off the outer IP+GRE layer and processes the inner IP packet as if it were delivered directly to its network interface. The network load balancer and the backend no longer need to exist in the same broadcast domain; they can even be on separate continents as long as a route between the two exists. Packet
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