Available SDN plug-ins

The Cisco ACI CNI plug-in for OKD provides integration between the Cisco Application Policy Infrastructure Controller (Cisco APIC) controller and one or more OKD clusters connected to a Cisco ACI fabric.

This integration is implemented across two main functional areas:

The Cisco ACI CNI plug-in is designed to be transparent for OKD developers and administrators and to integrate seamlessly from an operational standpoint.

For more information, see Cisco ACI CNI Plugin for Red Hat OpenShift Container Platform Architecture and Design Guide.

flannel is a virtual networking layer designed specifically for containers. OKD can use it for networking containers instead of the default software-defined networking (SDN) components. This is useful if running OKD within a cloud provider platform that also relies on SDN, such as OpenStack, and you want to avoid encapsulating packets twice through both platforms.

Architecture

OKD runs flannel in host-gw mode, which maps routes from container to container. Each host within the network runs an agent called flanneld, which is responsible for:

Each flanneld agent provides this information to a centralized etcd store so other agents on hosts can route packets to other containers within the flannel network.

The following diagram illustrates the architecture and data flow from one container to another using a flannel network:

Node 1 would contain the following routes:

Node 2 would contain the following routes:

Contiv is an open-source networking plug-in module for container infrastructure. Contiv provides an infrastructure for application-oriented network policies and support for a range of multiple networking modes. These include:

OKD can use Contiv for networking containers instead of the default OpenShift SDN.

Architecture

Each node within the cluster runs a Contiv agent called netplugin while the master hosts run the Contiv controller (called netmaster), along with supporting control plane components (such as etcd).

Together the components of Contiv (netmaster and netplugin) handle key networking functions for OKD including:

Contiv uses the Container Network Interface (CNI) to interface with OKD and Kubernetes. A key value store based on etcd is used to store Contiv-specific state information. This is in addition to and separate from the instance of etcd used by other components in the system, including OKD itself.

The VMware NSX-T ™ Data Center provides a policy-based overlay network reproducing the complete set of Layer 2 through Layer 7 networking services (such as switching, routing, access control, fire-walling, and QoS) in software for native OKD networking capabilities.

The NSX-T components can be installed and configured as part of the Ansible installation procedure, which integrates an OKD SDN into a data-center-wide NSX-T virtualised network connecting bare metal, virtual machines, and OKD pods. See the Installation section for information on how to install and deploy OKD with VMware NSX-T.

The NSX-T Container Plug-In (NCP) integrates OKD into an NSX-T Manager, which is typically configured for the entire data center.

For information on the NSX-T Data Center architecture and administration, see the VMware NSX-T Data Center v2.4 documentation and the NSX-T NCP configuration guides.

Nuage Networks' SDN solution delivers highly scalable, policy-based overlay networking for pods in an OKD cluster. Nuage SDN can be installed and configured as a part of the Ansible-based installation procedure. See the Advanced Installation section for information on how to install and deploy OKD with Nuage SDN.

Nuage Networks provides a highly scalable, policy-based SDN platform called Virtualized Services Platform (VSP). Nuage VSP uses an SDN Controller, along with the open source Open vSwitch for the data plane.

Nuage uses overlays to provide policy-based networking between OKD and other environments consisting of VMs and bare metal servers. The platform’s real-time analytics engine enables visibility and security monitoring for OKD applications.

Nuage VSP integrates with OKD to allows business applications to be quickly turned up and updated by removing the network lag faced by DevOps teams.

There are two specific components responsible for the integration.

Nuage Virtual Routing and Switching software (VRS) is based on open source Open vSwitch and is responsible for the datapath forwarding. The VRS runs on each node and gets policy configuration from the controller.

Nuage VSP Terminology

Mapping of Constructs

Many OKD concepts have a direct mapping to Nuage VSP constructs:

A Nuage subnet is not mapped to an OKD node, but a subnet for a particular project can span multiple nodes in OKD.

A pod spawning in OKD translates to a virtual port being created in VSP. The vsp-openshift plug-in interacts with the VRS and gets a policy for that virtual port from the VSD via the VSC. Policy Groups are supported to group multiple pods together that must have the same set of policies applied to them. Currently, pods can only be assigned to policy groups using the operations workflow where a policy group is created by the administrative user in VSD. The pod being a part of the policy group is specified by means of nuage.io/policy-group label in the specification of the pod.

Integration Components

Nuage VSP integrates with OKD using two main components:

nuage-openshift-monitor

nuage-openshift-monitor is a service that monitors the OKD API server for creation of projects, services, users, user-groups, etc.

For the developer workflow, nuage-openshift-monitor also auto-creates VSD objects by exercising the VSD REST API to map OKD constructs to VSP constructs. Each cluster instance maps to a single domain in Nuage VSP. This allows a given enterprise to potentially have multiple cluster installations - one per domain instance for that Enterprise in Nuage. Each OKD project is mapped to a zone in the domain of the cluster on the Nuage VSP. Whenever nuage-openshift-monitor sees an addition or deletion of the project, it instantiates a zone using the VSDK APIs corresponding to that project and allocates a block of subnet for that zone. Additionally, the nuage-openshift-monitor also creates a network macro group for this project. Likewise, whenever nuage-openshift-monitor sees an addition ordeletion of a service, it creates a network macro corresponding to the service IP and assigns that network macro to the network macro group for that project (user provided network macro group using labels is also supported) to enable communication to that service.

For the developer workflow, all pods that are created within the zone get IPs from that subnet pool. The subnet pool allocation and management is done by nuage-openshift-monitor based on a couple of plug-in specific parameters in the master-config file. However the actual IP address resolution and vport policy resolution is still done by VSD based on the domain/zone that gets instantiated when the project is created. If the initial subnet pool is exhausted, nuage-openshift-monitor carves out an additional subnet from the cluster CIDR to assign to a given project.

For the operations workflow, the users specify Nuage recognized labels on their application or pod specification to resolve the pods into specific user-defined zones and subnets. However, this cannot be used to resolve pods in the zones or subnets created via the developer workflow by nuage-openshift-monitor.

vsp-openshift Plug-in

The vsp-openshift networking plug-in is called by the OKD runtime on each OKD node. It implements the network plug-in init and pod setup, teardown, and status hooks. The vsp-openshift plug-in is also responsible for allocating the IP address for the pods. In particular, it communicates with the VRS (the forwarding engine) and configures the IP information onto the pod.

Kuryr SDN has some requirements regarding configuration of OpenStack it will be using. In particular:

kuryr-controller is a service responsible for watching OKD API for new pods being spawned and creating Neutron resources for them. For example, when a pod gets created, kuryr-controller will notice that and call OpenStack Neutron to create a new port. Then, information about that port (or VIF) is saved into the pod’s annotations. kuryr-controller is also able to use precreated port pools for faster pod creation.

Currently, kuryr-controller must be run as a single service instance, so it is modeled in OKD as Deployment with replicas=1. It requires access to the underlying OpenStack service APIs.

kuryr-cni container serves two roles in Kuryr-Kubernetes deployment. It is responsible for installing and configuring Kuryr CNI script on OKD nodes and running kuryr-daemon service that is networking the Pods on the host. This means that kuryr-cni container needs to run on every OKD node, so it is modeled as DaemonSet.

OKD CNI will call the Kuryr CNI script every time a new pod is spawned on or deleted from an OKD host. The script fetches the container ID of the local kuryr-cni from Docker API and executes Kuryr CNI plug-in binary through docker exec passing all the CNI call arguments. The plug-in then calls kuryr-daemon over local HTTP socket, again passing all the parameters.

kuryr-daemon service is responsible for watching for Pod’s annotations about Neutron VIFs created for them. When CNI request for given Pod is received daemon either has VIF information in memory already or waits for the annotation to appear on Pod definition. Once VIF info in known all the networking operations happen.