What is the Control Plane? Explained by Wallarm

Control Plane - Everything you Must Know

This plane is the network-routing component that take care of data packet flow and forwarding. At the very basic level, it’s accountable for the right network traffic routing on a specific network and ensures the application provides a request response.

You can also consider it as the fundamental framework to refer to while you intend to grasp how information can be controlled between multiple networks.

Need a more simple explanation? Consider it like an air traffic control system that decides which routes aircraft have to take to reach their destination. In network routing, the control panel does the same for incoming traffic.

Functions 

• Constructing network topology
• Identifying the network path
• Routing table formation
• Storing path details in routing tables
• Instructing data plane on how to forward the data packet 
• Routing algorithm management
• Storing networking-related configurations
• Routing protocol participations
• Ensuring around-the-clock service delivery

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How Does It Work?

By now, you must have understood that the data and control planes co-exists to decide the future of a traffic and data packet. Now, let’s move to another crucial aspect; how does the control plane work.

• At the network-routing level, it takes the help of routing protocols to decide the traffic destination. By closely referring to the traffic IP address, it prepares the routing table that is later referred to by the data plane to divert the traffic to the suitable destination.
• It also decides whether the data packet is worth forwarding or should be discarded. It also sets the priorities for them. In addition, it works as a fully optimized framework handling policies, data forwarding, and customization.
• Its penetration is more in organizations relying more on cloud services as it’s essential to do effective data packet forwarding inside closed-knit distributed network systems.

Control & Data Plane - How do They Differ?

Data Plane

A sub-part of the control plane, it takes the packet-forwarding related instructions from the control plane. Because it forwards a packet in question to its respective destination, so you may also hear its another name, i.e. forwarding plane, often.

They both are part of networking infrastructure and deal in data packet forwarding. They even co-exist. Hence, it’s obvious to get confused and consider these two as the same. In reality, they are poles apart.

A control plane is a decision-maker while the data plane is where implementation is taken care of. But the former does a lot of jobs as data packets are constructed here. 

The Control plane is a fully independent entity while the data plane can’t exist alone.

In fact, the data plane has no significance alone. It needs a control plane to decide what to do. 

The router also plays different roles for these two. It forwards a data packet for the data plane. 

Short of time?

Kubernetes Control Plane

Adopted by many, Kubernetes is a globally recognized open-source software used in development scenarios where containers are used. With this system, it’s easy to scale containers quickly. At the very basic level, Kubernetes features a Kubernetes cluster that will consist of a unified worker machine.

The worker machine or node will further feature a pod that is responsible for running containers seamlessly.

For a more complicated system, various dozen clusters featuring hundreds of nodes will co-exist. It would be too difficult to manage all those nodes and pods, as it is not easy to spot the incident of pod falling or non-functional containers. 

Kubernetes or k8s control plane will show up as a remedy here. 

It is different from the customary control plane. Here, it represents a collection of components responsible to take crucial cluster decisions.

In addition, it will also take care of cluster events’ response and detection. The constructing entities of the Kubernetes control plane are the etcd key-value store, multiple controllers, API server, and scheduler. These components communicate frankly with the API server.

Service Mesh Control Plane

When Service Mesh is concerned, the control plane has a different meaning. Here, it’s also a part of policy enforcement and establishment. Let’s try to understand how this happens. In a Service Mesh, multiple disconnected services come together to form a whole application and make internal & external communication. 

As all these applications are located in different geographical locations, their management becomes more difficult. It’s very tough to achieve standardized security, authorization, connectivity, and service discovery. 

The use of proxies is a great way to reduce these complexities. Service mesh uses proxies whose partnered containers have sidecars as resources. Sidecar proxy will be a part of every service replica responsible for incoming and outgoing request handling.

The service mesh control plane makes things further sorted by acting like a unified source of truth that will feature every updated configuration update. Service control mesh will ensure that these configurations reach the correct proxy.

Those who are working with service meshes and Kubernetes mostly use the control plane as a resource to deploy the configurations while massive scalability is the aim. 

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Control Planes and APIs

In general, when APIs are not used, the control plane constructs the configuration files and has to share them over the network to proceed with communication. This one task will be repeated 1000 or more times. To avoid the tardiness involved, APIs are used.

The proxy server will feature an API-defining protocol that will lead to seamless and efficient communication between data and the control plane. In case of modifications in proxy server configuration, control will automatically forward the required changes details to every related proxy server.

Once a proxy server receives the changed configuration details, it will validate, adopt, and implement said changes. When the changes are implemented as per the suggested changes, the interaction between data and the control plane will be seamless. 

Such change-bringing API is often known as data plane API and is used by many leading proxy servers. Some of the key examples of data plane APIs are Nginx Controller API and Envoy xDS API.

Control plane API is another concerning concept to get familiar with here. It’s a type of API, used by a control plane, to consider getting familiar with the permitted configurations acceptable for a data plane. Now, data plane APIs and control plane APIs have different meanings.

For instance, data plane API is mostly needed while control plane API is not always required. Still, control plane API has great importance because it’s a great resource to maintain a standard operational flow between different layers of the software. 

Both kinds of APIs are part of Service Mesh. Before one thinks of enjoying these APIs, it’s important to understand the availability status. For instance, are they offered as an open-source resource or a proprietary asset? 

Proprietary control APIs will allow you to use facilities/features of particular brands. You will have to use a proprietary control plane to manage the proxy server. For instance, if you use Nginx Controller API then you have to use Nginx’s control plane for your control plane management. 

This isn’t going to happen with Open APIs as they won’t tie you with specific implementations. Open control plane APIs are easy to modify and grant full customization abilities. This happens with Envoy xDS control plane APIs.

You can easily configure the Traffic Director with free services like backend services and forwarding rules. It comes with a pre-defined implementation configuration file but also provides flexibility to bring desired changes. Control planes like Consul and GCP Traffic Director are already using such great flexibility.

Make sure that if you’re using control plane API and seeking better API security, apply security practices on control plane API as well. 

A Quick Recap

It was a long post, right? Considering the importance of the control plane, we have to present crucial facts and aspects. Let’s have a quick recap of everything.

• The control plane works as the mind dictating everything about the data packet. It constructs the configuration files that will decide the future of the data packets.
• Even though the data plane is tucked with the control plane, these two are not the same. They have considerable differences.
• It acts differently in Kubernetes and Service mesh. The service mesh control plane collects every related configuration file while the Kubernetes control plane features components responsible for cluster decisions.
• Control plane APIs are offered as open and proprietary resources and are responsible for seamless communication.

Hope this helps. The better clarity one will have over networking components, the flawless would be data transfer.