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OVN-Kubernetes: A Robust Kubernetes Networking Provider

OVN-Kubernetes (Open Virtual Networking - Kubernetes) is an open-source project that provides a robust networking solution for Kubernetes clusters with OVN (Open Virtual Networking) and Open vSwitch (Open Virtual Switch) at its core. It is a Kubernetes networking conformant plugin written according to the CNI (Container Network Interface) specifications.

Challenges for Cluster Networking in Kubernetes Ecosystem

  • Kubernetes at its core is a bunch of powerful APIs like Pods, Services, EndpointSlices and NetworkPolicies.
    • If we look at The Kubernetes Network Model it imposes a set of fundamental requirements for how networking is expected to behave for pods in a cluster.
    • At the end of the day we need a robust networking platform to fulfill those requirements.
  • Handling complicated telco and enterprise networking scenarios.
    • Kubernetes Cluster Networking Model addresses the basic set of problems such as communication between containers in a pod, communication between pods, allowing external (outside the cluster) entities to talk to pods via services, ingress and gateway-api on a primary network level using clusterCIDRs and serviceCIDRs.
    • However when we start talking about more powerful networking abstractions like secondary networks, multi-homing and more fine grained cluster egress controls outside the normal node SNATing the Kubernetes Networking Model falls short
  • Lifecycle management of networking infrastructure.
    • In addition to having an implementation that fulfills the basic requirements of the Kubernetes Networking model, we also need a level driven controller that automatically takes care of the lifecycle and health of the critical networking aspects.
  • Networking on Kubernetes is not simple.
    • There are complicated features such as service traffic policies, terminating endpoints, topology aware hints which involve multiple moving pieces and components that needs a "driver" that ensures they work as expected.

What is OVN-Kubernetes?

OVN-Kubernetes was designed to precisely solve the above problems in a Kubernetes cluster. The OVN-Kubernetes plugin watches the Kubernetes API. It acts on the generated Kubernetes cluster events by creating and configuring the corresponding OVN logical constructs in the OVN database for those events. OVN (which is an abstraction on top of Open vSwitch) converts these logical constructs into logical flows in its database and programs the OpenFlow flows on the node, which enables networking on a Kubernetes cluster.


The key functionalities and features that OVN-Kubernetes provides include:

  • Kubernetes Core Networking Conformance
    • Creates pod networking including IP Address Management (IPAM) allocation and virtual ethernet (veth) interface for the pod.
    • Programs overlay based networking implementation for Kubernetes clusters using Generic Network Virtualization Encapsulation GENEVE tunnels that enables pod-to-pod communication.
    • Implements Kubernetes Services & EndpointSlices through OVN Load Balancers.
    • Implements Kubernetes NetworkPolicies and AdminNetworkPolicies through OVN Access Control Lists (ACLs).
    • Supports IPv4/IPv6 Dual-Stack clusters.
  • Fine grained Cluster Egress Traffic Controls
    • Multiple External Gateways (MEG) allows for multiple dynamically or statically assigned egress next-hop gateways by utilizing OVN ECMP routing features.
    • Implements Quality of Service (QoS) Differentiated Services Code Point (DSCP) for traffic egressing the cluster through OVN QoS.
    • Provides ability to send egress traffic from cluster workloads using an admin-configured source IP (EgressIP) to outside the cluster using OVN Logical Router Policies and Network Address Translations.
    • Provides ability to send egress traffic from cluster workloads using the service load balancer IP (EgressService) to outside the cluster using OVN Logical Router Policies and Network Address Translations.
    • Provides the ability to restrict egress traffic from cluster workloads (Egress Firewall) using OVN Access Control Lists.
  • Advanced Networking Features
    • Implements Hybrid Networking to provide support for mixed Windows/Linux clusters using VXLAN tunnels.
    • Provides IP Multicast using OVN IGMP snooping and relays.
    • Provides ability to offload networking tasks from CPU to NIC using OVS Hardware Offload thus providing increased data-plane performance.
    • Adds support for creating secondary and local networks in addition to the default primary networks

Why choose OVN-Kubernetes in Kubernetes ecosystem?

Networking is the backbone for any Kubernetes cluster. Kubernetes at its core provides an extensive set of Networking APIs and features that need to be implemented in a Kubernetes conformant manner for networking to work properly in a Kubernetes cluster. The aim of OVN-Kubernetes project is to be able to provide a pluggable and seamless networking platform for Kubernetes end users. The project focuses strictly on enhancing networking for the Kubernetes platform and includes a wide variety of features that are critical to enterprise and telco users. OVN-Kubernetes community members are active in upstream Kubernetes (particularly in SIG Network) to create new features and then realize them in OVN-Kubernetes. In addition to a feature rich platform, the project also aims to be a highly scalable and performant Networking Platform.

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