Getting started with software-defined networking

At the same time, enterprises have serious concerns about how they can isolate security and networking for multiple application containers across many different data centers and cloud services. The Container Network Interface (CNI) is a library definition and a set of tools to configure network interfaces in Linux containers through many supported plugins. A lot of popular container runtimes, such Foundry, and Apache Mesos, are using the CNI to define a common interface between the network plugins and container execution for application containers on Linux.

Source: www.redhat.com