Security boundaries in the network layer

A Kubernetes network policy defines the rules for different groups of Pods that are allowed to communicate with each other. In the previous chapter, we briefly talked about the egress rule of a Kubernetes network policy, which can be leveraged to enforce the principle of least privilege for microservices. In this section, we will go through a little more on the Kubernetes network policy and will focus on the ingress rule. We will show how the ingress rules of network policies can help to establish the trust boundaries among microservices.

Network policies

As mentioned in the previous chapter, as per the network model requirement, Pods inside a cluster can communicate with each other. But still, from a security perspective, you may want to restrict your microservice to being accessed by only a few services. How can we achieve that in Kubernetes? Let's take a quick look at the following Kubernetes network policy example:

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