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27 lines
3.2 KiB
Plaintext
:_mod-docs-content-type: CONCEPT
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[id="ovn-kubernetes-architecture-con"]
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= Introduction to OVN-Kubernetes architecture
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The following diagram shows the OVN-Kubernetes architecture.
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.OVK-Kubernetes architecture
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image::299_OpenShift_OVN_Kubernetes_arch_1_0725.png[OVN-Kubernetes architecture]
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The key components are:
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* **Cloud Management System (CMS)** - A platform specific client for OVN that provides a CMS specific plugin for OVN integration. The plugin translates the cloud management system's concept of the logical network configuration, stored in the CMS configuration database in a CMS-specific format, into an intermediate representation understood by OVN.
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* **OVN Northbound database (`nbdb`) container** - Stores the logical network configuration passed by the CMS plugin.
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* **OVN Southbound database (`sbdb`) container** - Stores the physical and logical network configuration state for Open vSwitch (OVS) system on each node, including tables that bind them.
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* **OVN north daemon (`ovn-northd`)** - This is the intermediary client between `nbdb` container and `sbdb` container. It translates the logical network configuration in terms of conventional network concepts, taken from the `nbdb` container, into logical data path flows in the `sbdb` container. The container name for `ovn-northd` daemon is `northd` and it runs in the `ovnkube-node` pods.
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* **ovn-controller** - This is the OVN agent that interacts with OVS and hypervisors, for any information or update that is needed for `sbdb` container. The `ovn-controller` reads logical flows from the `sbdb` container, translates them into `OpenFlow` flows and sends them to the node’s OVS daemon. The container name is `ovn-controller` and it runs in the `ovnkube-node` pods.
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The OVN northd, northbound database, and southbound database run on each node in the cluster and mostly contain and process information that is local to that node.
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The OVN northbound database has the logical network configuration passed down to it by the cloud management system (CMS).
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The OVN northbound database contains the current desired state of the network, presented as a collection of logical ports, logical switches, logical routers, and more.
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The `ovn-northd` (`northd` container) connects to the OVN northbound database and the OVN southbound database.
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It translates the logical network configuration in terms of conventional network concepts, taken from the OVN northbound database, into logical data path flows in the OVN southbound database.
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The OVN southbound database has physical and logical representations of the network and binding tables that link them together. It contains the chassis information of the node and other constructs like remote transit switch ports that are required to connect to the other nodes in the cluster. The OVN southbound database also contains all the logic flows. The logic flows are shared with the `ovn-controller` process that runs on each node and the `ovn-controller` turns those into `OpenFlow` rules to program `Open vSwitch`(OVS).
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The Kubernetes control plane nodes contain two `ovnkube-control-plane` pods on separate nodes, which perform the central IP address management (IPAM) allocation for each node in the cluster. At any given time, a single `ovnkube-control-plane` pod is the leader. |