The OKD cluster uses a virtualized network for pod and service networks.
Part of Red Hat OpenShift Networking, the OVN-Kubernetes network plugin is the default network provider for OKD.
OVN-Kubernetes is based on Open Virtual Network (OVN) and provides an overlay-based networking implementation.
A cluster that uses the OVN-Kubernetes plugin also runs Open vSwitch (OVS) on each node.
OVN configures OVS on each node to implement the declared network configuration.
OVN-Kubernetes is the default networking solution for OKD and single-node OpenShift deployments.
OVN-Kubernetes, which arose from the OVS project, uses many of the same constructs, such as open flow rules, to determine how packets travel through the network.
For more information, see the Open Virtual Network website.
OVN-Kubernetes is a series of daemons for OVS that translate virtual network configurations into
OpenFlow is a protocol for communicating with network switches and routers, providing a means for remotely controlling the flow of network traffic on a network device, allowing network administrators to configure, manage, and monitor the flow of network traffic.
OVN-Kubernetes provides more of the advanced functionality not available with
OVN supports distributed virtual routing, distributed logical switches, access control, DHCP and DNS.
OVN implements distributed virtual routing within logic flows which equate to open flows.
So for example if you have a pod that sends out a DHCP request on the network, it sends out that broadcast looking for DHCP address there will be a logic flow rule that matches that packet, and it responds giving it a gateway, a DNS server an IP address and so on.
OVN-Kubernetes runs a daemon on each node. There are daemon sets for the databases and for the OVN controller that run on every node.
The OVN controller programs the Open vSwitch daemon on the nodes to support the network provider features; egress IPs, firewalls, routers, hybrid networking, IPSEC encryption, IPv6, network policy, network policy logs, hardware offloading and multicast.