Why are Geneve encapsulations used for host overlay tunnels?

The Geneve header is extensible (consisting of an 8-byte fixed header plus 0 to 252 bytes of variable TLV), enabling the tunnel to carry rich information such as logical datapath fields, input/output ports, conntrack zones, and more. OVN (Open Virtual Network) constructs virtual networks using logical routers and logical switches. For cross-Hypervisor (CVK) communication, such additional metadata is required to achieve precise forwarding and control logic for distributed gateways.