Service communications between services hosted in Service Fabric can be categorized as internal or external. Internal communication between services hosted on Service Fabric is easily achieved using the Naming Service. External communication, originated from an application or a user outside the boundaries of Service Fabric, will need some extra work. To understand how this works, let's dive deeper into the logical network layout of a typical Service Fabric cluster.

A Service Fabric cluster is usually placed behind an Azure load balancer. The load balancer acts like a gateway to all traffic which needs to pass to the Service Fabric cluster. The load balancer is aware of every post open on every node of a cluster. When a request hits the load balancer, it identifies the port the request is looking for and randomly routes the request to one of the nodes which has the requested port open. The load balancer is not aware of the services running on the nodes or the ports associated with the services.

The following figure illustrates request routing in action: