Skupper overview
Hybrid clouds enable organizations to combine on-premises, private cloud, and public cloud resources. While such a solution provides many benefits, it also presents a unique challenge: enabling these resources to communicate with each other.
Skupper provides a solution to this challenge with a Virtual Application Network that simply and securely connects applications running in different network locations.
Virtual Application Networks
Skupper solves multi-cluster communication challenges through something called a Virtual Application Network (VAN). To understand the value of Skupper, it is helpful to first understand what a VAN is.
A VAN connects the applications and services in your hybrid cloud into a virtual network so that they can communicate with each other as if they were all running in the same site. In this diagram, a VAN connects three services, each of which is running in a different cloud:
In essence, the VAN connects the services in a distributed application with a microservice architecture.
VANs are able to provide connectivity across the hybrid cloud because they operate at Layer 7 (the application layer). They use Layer 7 application routers to route communication between Layer 7 application addresses.
Layer 7 application routers
Layer 7 application routers form the backbone of a VAN in the same way that conventional network routers form the backbone of a VPN. However, instead of routing IP packets between network endpoints, Layer 7 application routers route messages between application endpoints (called Layer 7 application addresses).
Layer 7 application addresses
A Layer 7 application address represents an endpoint, or destination in the VAN. When an application sends a communication to an address, the Layer 7 application routers distribute the communication to any other application in the VAN that has the same address.
For example, in this diagram, Service B sends a message with an application address to its local application router. Service A and Service C are subscribed to the same address, so the application router routes copies of the message through the VAN until they arrive at each destination.
VANs provide multiple routing patterns, so communications can be distributed in anycast (balanced or closest) or multicast patterns.
Skupper
Skupper is an open source tool for creating VANs in Kubernetes. By using Skupper, you can create a distributed application consisting of microservices running in different Kubernetes clusters.
This diagram illustrates a Skupper network that connects three services running in three different Kubernetes clusters:
In a Skupper network, each namespace contains a Skupper instance. When these Skupper instances connect, they continually share information about the services that each instance exposes. This means that each Skupper instance is always aware of every service that has been exposed to the Skupper network, regardless of the namespace in which each service resides.
Once a Skupper network is formed across Kubernetes namespaces, any of the services in those namespaces can be exposed (through annotation) to the Skupper network. When a service is exposed, Skupper creates proxy endpoints to make that service available on each namespace in the Skupper network.