Junos® OS For Dummies®, 2nd Edition

Functions of a Network OS

Networks consist of specialized devices that pass along traffic from one to another. Each device must know what to do with each arriving bundle of traffic, or packet, so that the packet can continue its journey to its destination. The devices perform three primary functions to process each packet:

• Controls where the device sends the packets.
• Applies services such as prioritization or security.
• Forwards the packet to the next connecting device.

These actions are the primary functions of the network operating system that runs on the device. In simplest terms, the control plane of the network operating system is the brain of the device with the forwarding plane providing the brawn to quickly move packets through the system. Depending on the type of packet, the services plane may also provide packet services such as address translation, prioritization, and security.

Control functions

This essential map for connectivity, security, and other orchestrating processes is the function of the network operating system's control plane. The processes and information of the control plane must provide answers to two essential questions:

• How does the network direct the delivery of packets from one place to another? In other words, what are the routes or paths to establish, how do they change, and how does each device know which route to use for each packet?
• What does the network do with each of the packets along its journey? In other words, what are the handling rules, ...