OpenShift Network Plugins
External
- https://docs.openshift.com/container-platform/3.5/architecture/additional_concepts/sdn.html
- https://docs.openshift.com/container-platform/3.5/install_config/configuring_sdn.html
Internal
Overview
TODO: unify with the upper layer OpenShift_Concepts#SDN.2C_Overlay_Network
Pods get IP addresses from the cluster network, and the address allocation and packet routing is provided by a software-defined network (SDN), implemented using Open vSwitch (OVS). A specific behavior is provided by the SDN plug-in chosen at installation: subnet, multitenant and networkpolicy.
TODO: network architecture, parse and incorporate: https://docs.openshift.com/container-platform/3.5/architecture/additional_concepts/sdn.html#sdn-design-on-masters
SDN Plug-Ins
subnet
The "ovs-subnet" plug-in provides a "flat" network: every pod in the cluster can communicate with every other pod and service, regardless of the project (namespace).
Ansible configuration file:
os_sdn_network_plugin_name='redhat/openshift-ovs-subnet'
multitenant
The "ovs-multitenant" is a plug-in that provides project-level network isolation for pods and services. Each project gets a unique Virtual Network ID (VNID)
Virtual Network ID (VNID)
The Virtual Network ID (VNID) identifies traffic as being initiated by pods associated with a specific project. Pods from different projects cannot send or receive packets to/from pods and services of a different project, except for those that have VNID 0. VNID 0 allows the pods of the project to communicate with all other pods, and all other pods can communicate with them.
The "default" project has VNID 0. This allows the router service to route packets between projects.
The VNID are managed by the masters, which allocate them to projects when the projects are created.
Network Isolation
Network isolation with ovs-multitenant is implemented as follows
Configuration
Ansible configuration file:
os_sdn_network_plugin_name='redhat/openshift-ovs-multitenant'
networkpolicy
Projects may configure their own isolation policies using NetworkPolicy objects.