Both orchestration systems use an Overlay Network between host nodes to emulate the presence of managed units in a single local network space. This type of network is a logical type that uses ordinary TCP / IP networks for transport and is designed to emulate the presence of cluster nodes in a single network to manage the cluster and exchange information between its nodes, while at the TCP / IP level they cannot be connected. The fact is that when a developer develops a cluster, he can describe a network for only one node, and when a cluster is deployed, several of its instances are created, and their number can change dynamically, and in one network there cannot be three nodes with one IP address and subnets (for example, 10.0.0.1), and it is wrong to require the developer to specify IP addresses, since it is not known which addresses are free and how many will be required. This network takes over tracking the real IP addresses of nodes, which can be allocated randomly from the free ones and change as the nodes in the cluster are re-created, and provides the ability to access them via container IDs / PODs. With this approach, the user refers to specific entities, rather than the dynamics of changing IP addresses. Interaction is carried out using a balancer, which is not logically allocated for Docker Swarm, but in Kubernetes it is created by a separate entity to select a specific implementation, like other services. Such a balancer must be present in every cluster and, but within the Kubernetes ecosystem, is called a Service. It can be declared either separately as a Service or in a description with a cluster, for example, as a Deployment. The service can be accessed by its IP address (see its description) or by its name, which is registered as a first-level domain in the built-in DNS server, for example, if the name of the service specified in the my_service metadata , then the cluster can be accessed through it like this: curl my_service; … This is a fairly standard solution, when the components of the system, along with their IP addresses, change over time (re-created, new ones are added, old ones are deleted) – send traffic through a proxy server, IP or DNS addresses for the external network remain constant, while internal ones can change, leaving taking care of their approval on the proxy server.

Both orchestration systems use the Ingress overlay network to provide access to themselves from the external network through the balancer, which matches the internal network with the external one based on the Linux kernel IP address mapping tables (iptalbes), separating them and allowing information to be exchanged even if there are identical IP addresses in internal and external network. And, here, to maintain the connection between these potentially conflicting networks at the IP level, an overlay Ingress network is used. Kubernetes provides the ability to create a logical entity – an Ingress controller, which will allow you to configure the LoadBalancer or NodePort service depending on the traffic content at a level above HTTP, for example, routing based on address paths (application router) or encrypting TSL / HTTPS traffic, like GCP does and AWS.

Kubernetes is the result of evolution through internal Google projects through Borg, then through Omega, based on the experience gained from experiments, a fairly scalable architecture has developed. Let's highlight the main types of components:

* POD – regular POD;

* ReplicaSet, Deployment – scalable PODs;