What is a control plane?

As computer networks have become an essential part of modern business, connecting people and devices around the globe, the importance of network architecture and the components they rely on has increased as well. 

The control plane is primarily responsible for controlling the processes and functions that govern how data travels through a network. To do this, it follows routing protocols or rules, informed by algorithms, to determine the best route for data to take between devices (also known as "nodes").  

Networks are usually depicted as a series of planes (or layers) connecting the various nodes that make up the network. The data plane, control plane and management plane each perform different roles and have different security requirements for how they conduct data.

• Control plane: The control plane defines how the network is laid out and how data will be handled, especially the path that data will travel on as it is routed through the network. 

• Data plane: Also known as the forwarding plane, the data plane enables data to be sent around the network through devices such as routers and switches. 

• Management plane: The management plane is where the network’s operations are coordinated, including the configuration of the network and the administration of policies that define its functionality. 

Before diving into the benefits of control planes and how they work, there are a few terms it will help to understand:

• Computer network: A computer network is 2 or more connected computing devices—such as desktop computers, mobile devices, routers or applications—for the purpose of transmitting and sharing resources and information. The setting up of devices and systems on a network is a process known as network orchestration. Networked devices rely on communications protocols—rules that describe how to transmit or exchange data across a network—to share information over physical or wireless connections. For example, the Border Gateway Protocol (BGP) manages how data gets routed from network to network on the internet. 

• Software-defined networking: Software-defined networking (SDN) is a software-controlled approach to computer network architecture that relies heavily on application programming interfaces (APIs)—sets of rules that enable applications to communicate with each other and exchange data and features. 

• Router: A router is a physical or virtual device that sends data “packets” between networks. A data packet is a unit of routing information that's been properly formatted to be transmitted over a network. Control planes, either physical or virtual, enable routers to analyze data packets and determine the best path to send them through the network. Most control planes and routers use highly sophisticated routing algorithms to forward data packets.

• Switch: A switch is a component that enables multiple devices to be connected through the forwarding of data. Switches are a core component used in modern computer networks, including the Internet. Switches use Ethernet cables to move data packets between devices, allowing data and resources to be shared between users and nodes. 

The control plane performs 4 critical functions that enable modern computer networks to operate: Routing, managing traffic, maintaining topology and load balancing.

One of the most important roles that control planes perform in a computer network is routing, which means determining the path that data travels on in the network. Routing depends on data collections, known as routing tables, that list the various routes information could take. In some cases, each of these routes will have a specific metric associated with it that the router and control plane will consider when routing the data. 

In addition to routing tables, routers use a set of rules or protocols with which to choose the correct routes. One example is the popular Open Shortest Path First (OSPF) protocol used to control network configuration. Another is Domain Name System (DNS), a protocol that translates domain names into IP addresses to help browsers load websites.

While the routing process defines the routes data will take through a network, the traffic management function prioritizes and shapes network traffic to ensure the high availability of applications that devices on the network are running. The control plane enforces network policies that have been set by administrators, such as access control lists (ACLs) that help optimize network performance and security. Additionally, prioritizing and controlling traffic throughout the network minimizes the likelihood of network failure or the failure of connected devices on the network. 

In addition to managing and routing network traffic, the control plane also maintains a network topology, typically represented as a graph, that shows the arrangement of computers and other devices on the network. These complex connections are established and maintained through a combination of physical and virtual components, such as routers and software. The control plane manages the network topology by maintaining detailed routing tables that show how data should be transmitted across a network for optimal results.

Load balancing is the process of distributing network traffic efficiently across many different servers to increase system availability and enhance user experience. It is performed in the control plane. Most popular websites and apps receive millions of user requests a day, making load balancing (and the control planes that enable it) critical to app and site functionality. In the control plane, the scheduler is a process that assigns workloads to nodes and ensures that compute resources are used efficiently. 

To balance traffic and workflow, the control plane is constantly moving data between nodes on a network. Typically, this involves clustering, which is connecting a group of computers so their resources can be combined into a single functional unit. Control plane load balancing (CPLB) contributes to the high availability of the control plane and can be used to balance both internal traffic, data that originates inside a network, and external traffic, data that originates from an external source.  

Control planes work differently depending on how the computer network they are installed on is configured. In a conventional or traditional computer network, fixed hardware devices such as routers and switches control network traffic. In a conventional network, control plane, management planes and data planes are all installed in the firmware of routers and switches. However, this approach is becoming less practical as modern enterprises increasingly move to SDN architectures which give them more scalability.

As computer networking has become more essential to business, the SDN has emerged as the most efficient way to enable many business applications. The SDN market is growing quickly; in 2023, it was estimated at USD 24 billion and is expected to grow by a compound annual growth rate of over 19% (USD 60 billion) in the next 4 years.¹

The SDN depends on a centralized platform used to communicate with the overall IT infrastructure of a business. That platform is used to direct data and network traffic between devices. 

In an SDN, the control plane uses a specialized component called an API server to manage and control data exchanged between nodes. Using control planes and API functionality, SDNs can operate business application environments as computer code, minimizing developer time and helping modern enterprises operate more efficiently. 

Control planes have many benefits when it comes to network management. Here are some of the most common:

• Efficiency: The control plane provides a single point from which every device or node on a network can be managed. For example, network administrators use the control plane to configure security settings, such as access control, and automate the delivery of critical software updates. 

• Adaptability: The control plane allows devices on a network to react dynamically to changes in network functionality, such as a link failure or power outage. For example, when it comes to routing data across a network, the control plane can adjust when a node fails and reroute data accordingly. 

• Scalability: Control planes are considered highly scalable because additional resources can be added easily without increasing the complexity of the network. Some control planes are even configured to be automatically scalable, a feature known as autoscaling. When user traffic on a network reaches a certain threshold, autoscaling triggers the provisioning of additional compute resources.

• Resiliency: Control planes are highly resilient because of certain aspects of their architecture. First, they are usually kept separate from the data plane, meaning that a failure on the control plane—for example, a load balancer malfunctioning—won’t affect the data plane.

• Low latency: Control planes monitor latency and other performance metrics for connected systems and devices on a network (such as computers, mobile devices and graphics cards) so they can be kept below certain levels. In particular, CPU latency is important to monitor as it reflects the amount of time it takes data to move through a system. 

• Security: Control planes with additional security features—known as endpoint control planes—give network administrators the ability to monitor devices connected to a network, identify threats and enforce additional security policies. 

Control planes are a vital part of computer networks and are essential to many valuable enterprise applications.  

Cloud computing, the on-demand access of computing resources over the internet, is highly dependent on the computer networks that control planes underpin. In fact, control planes have become so essential to cloud architectures that there are now specific cloud control planes designed to be deployed exclusively in cloud environments. Cloud control planes provide management, routing and other essential features that connect devices on cloud networks. 

The cloud computing market is one of the fastest-growing technology sectors in the world. In 2021, it was estimated to be USD 551.8 billion. By 2031, it is estimated to have grown to USD 2.5 trillion.² All the largest cloud providers in the world use control planes as part of their network architecture. These include Google Cloud, Microsoft Azure and Amazon Web Services (AWS.) 

Perhaps the most popular cluster, the Kubernetes cluster specifically runs containerized applications, managing nodes from the control plane and allowing software code to run in any computing environment. Through specialized components known as Kube-Proxies, network administrators can monitor changes that happen to individual nodes in a Kubernetes cluster and adjust network rules inside each individual node to adapt to them. 

Analytics as a Service (AaaS) is a type of capability delivery model that gives companies data analytics functionality without having to build their own data platform or hire a team to manage it. Control planes help data analysts and cloud architects provision the necessary infrastructure to analyze data and execute critical analytics tasks. Cloud control planes enable many cloud-based data storage and processing capabilities that are critical to AaaS.

Multi-factor authentication (MFA) is a type of identity verification that requires a user to supply more than 1 piece of evidence that proves who they are claiming to be. MFA is used widely by many popular applications like personal banking apps, healthcare providers, email providers and social media sites. Control planes manage the setup and configurations of all MFA tasks; for example, the issuing and validation of 1-time passwords (OTPs) that help make user accounts more secure.